Perspectives in (human) ecology

New Paper on Human Uniqueness

2009-11-09T18:34:00.001-08:00

A new paper in Evolutionary Anthropology reviews the causes of the global expansion of homo sapiens and argues that it was our propensities for cooperation and social learning that made this ecological dominance possible. The paper initially takes a distinctly macroecological perspective on the evolution of human culture, by commenting on some general facts reflecting the evolutionary success of humans.

The emergence of human uniqueness: Characters underlying behavioral modernity

Kim Hill, Michael Barton, A. Magdalena Hurtado

email: Kim Hill (kim.hill@asu.edu) Michael Barton (Michael.Barton@asu.edu) A. Magdalena Hurtado (A.Magdalena.Hurtado@asu.edu)

ABSTRACT

Although scientists are aware that humans share the same biological heritage as do all other organisms on the planet, the reliance of Homo sapiens on culture and cooperation has resulted in what can best be described as a spectacular evolutionary anomaly.^1:11 The extra-somatic adaptations, technological dominance, and success of our species in colonizing every terrestrial habitat have no parallel.² Moreover, Homo sapiens accounts for about eight times as much biomass as do all other terrestrial wild vertebrates combined,³ an amount equivalent to the biomass of all 14,000+ species of ants,⁴ the most successful terrestrial invertebrates. Human societies are complex, with more specialized economic niches in the United States than the total number of mammalian species on the planet.⁵ While some might suggest that only post-industrial humans achieved stunning biological success, data suggest that humans living as hunter-gatherers would have attained a world population of more than 70 million individuals⁶ and a total biomass greater than that of any other large vertebrate on the planet if agriculture had not been repeatedly invented as they spread.

"we outline a series of preadaptations that may help explain why later Homo evolved unique traits that chimpanzee, elephant, and porpoise lineages did not. Other apes have large brains, regularly engage in social learning, and exhibit theory of mind. Moreover, those ape species also passed through the Pleistocene without evolving the combination of characters that make humans biological outliers. We must, therefore consider important preadaptations in the genus Homo that led to human uniqueness.”

This is an excellent review paper that I'm sure will get a lot of attention. Its interesting to see human behavioral ecologists paying progressively more attention to cultural evolution and group level dynamics as major driving forces in the expansion of homo sapiens. I might add that this topic general, that is asking the big 'why questions' about what factors made humans such an expansive force as Pleistocene hunter-gatherers, receives strikingly little attention from evolutionary ecologists.

First Americans Paper in PNAS

2009-01-29T06:46:00.000-08:00

PNAS published a review paper on the peopling of the Americas authored by Tom Dillehay.
I have to say it strikes me as kind of an odd paper to appear in a journal like PNAS. Its title is 'Probing Deeper into First American Studies' and yet it really doesn't report anything new and as a review paper goes the synthesis of existing data is just sort of... so so. Also interesting is that even though it explicitly addresses different ideas about how the New World was colonized, it does not cite a paper written on this very topic that was published in this very journal within the last year. Is that odd? I think so. Especially since its a novel and interdisciplinary approach to understanding migrations and that is exactly what Dillehay says we need more of...
Here's a quote from the paper:

"Places of origin, dates of entry, routes of dispersion, and types of early cultural lifestyles lie at the heart of the debate over the initial peopling of the Americas. Fresh thinking about these and other issues has occurred because of the recent demise of the Clovis-first paradigm to explain the initial peopling of the Americas (2, 6, 7, 8) and because of new and more flexible interdisciplinary research directions."

I have to admit I'm also a bit tired of the Monte Verde crowd claiming that the 'Clovis-first paradigm' has been defeated because of sites like, well... Monte Verde, which is much more problematic than we're aloud to acknowledge. If you do question it, prepare to be berated by Dillehay and his friends. (Also, 'paradigm' ? really? clearly Clovis-first is nothing like an actual paradigm as defined by Thomas Kuhn. Just a pet peeve...)

Just the same, this will continue to be a hot topic in archaeology and hopefully the issues raised in this short reivew will be resolved with new data and research in the future.

Water bears: just because everyone should know about these

2009-01-25T09:11:00.000-08:00

This doesn't come from an obscure source or anything like. Just NPR's Science Friday, but here's a very cool video they posted on their website. Enjoy it.

An idea worth spreading

2008-06-09T17:05:00.000-07:00

Here's a video of a lecture by Ron Eglash about fractals in Africa. its quite interesting in terms of the small bit of history of fractals you get as well as in terms of those he discovers in African settlements and art. I don't know if its true that fractals are not just as present outside of Africa but this is cool. I thank Chris Millington for sending this.
The video is part of the TED series - I posted one before. Its just shy of 17 minutes long.

Hiatus

2008-04-07T09:49:00.000-07:00

The semester got away from me a bit and I've been terrible about getting anything posted for a while now. I was at the Society for American Archaeology meetings in Vancouver last week, which were great fun and I should blog about them. That is why I missed a week in the series on Foraging. I hope to get rolling again soon. The other big event is of course the SWARM meetings, which are later this week - lots to get together for those...

Humans and extinctions: the flightess sea duck

2008-03-20T07:33:00.000-07:00

A paper just published in PNAS argues that since the flightless sea duck didn't got extinct until well into the Holocene humans probably didn't hunt megafauna to extinction. No, seriously.

Here's the title, and abstract:
****
The protracted Holocene extinction of California's flightless sea duck (Chendytes lawi) and its implications for the Pleistocene overkill hypothesis

T. L. Jones, J. F. Porcasi, J. M. Erlandson, H. Dallas, Jr., T. A. Wake, an R. Schwaderer

Bones of the flightless sea duck (Chendytes lawi) from 14 archaeologicalsites along the California coast indicate that humans huntedthe species for at least 8,000 years before it was driven toextinction. Direct ¹⁴C dates on Chendytes bones show that theduck was exploited on the southern California islands as earlyas 11,150–10,280 calendar years B.P., and on the mainlandby at least 8,500 calendar years B.P. The youngest direct dateof 2,720–2,350 calendar years B.P., combined with theabsence of Chendytes bones from hundreds of late Holocene sites,suggests that the species was extinct by 2,400 years ago. Althoughthe extinction of Chendytes clearly resulted from human overhunting,its demise raises questions about the Pleistocene overkill model,which suggests that megafauna were driven to extinction in ablitzkrieg fashion by Native Americans 13,000 years ago. Thatthe extermination of Chendytes was so protracted and archaeologicallyvisible suggests that, if the terminal Pleistocene megafaunaextinctions were primarily the result of human exploitation,there should also be a long and readily detectable archaeologicalrecord of their demise. The brief window now attributed to theClovis culture (13,300–12,900 B.P.) seems inconsistentwith an overhunting event.

****

There is also an accompanying commentary by Donald Grayson.

The authors have thoroughly documented an interesting relationship between human predation and this species of flightless duck. There seems little doubt that the duck was periodically or frequently preyed upon for millennia before it went extinct. They argue that the early inhabitants of the California coast were more technologically sophisticated than is generally acknowledged - they had some boats/canoes from which to hunt. What I don't understand is the lack of attention to ecology when they try to make the leap of connecting the relationship they document to Pleistocene extinctions in general. So maybe people had boats 12,000 years ago but I think its worth considering that there are some pretty fundamental differences between mammoths and ducks... (!!) and the particular island environments where most island extinctions took place are also different from the California coast. The colonists didn't bring rats, the environment was not as circumscribed as many islands and may have provided more natural refugia from human predation, the people may have had their main populations on the coast rather than on islands (in the california case), and they may have been at lower population densities.

Grayson's commentary is surprisingly even-handed. He seems more conservative with regard to the suggestion that this particular history of this particular species of flightless bird has general implications for our thinking of the loss of megafauna. But rather suggests that understanding the processes of extinction on a species by species basis tells us that there some important nuances that are often overlooked and that in many cases direct predation may not be the mechanism of extinction. Humans alter environments in lots of ways and it may be these indirect effects that are often detrimental. Rats and dogs and pigs all likely accelerated the rate of extinction in the case of Polynesian colonists.

Grayson and Jones et al (and lots of other archaeologists) frequently point out that the evidence for association between unambiguous signs of human activity and the remains of the extinct megafauna are rare in North America. And that is part of the point Jones et al are making. That this species has loads of direct associations with people and hence the extinction process is very visible. So why isn't it more visible for sloths and other really large critters that went extinct and should be very visible? If people were butchering these animals in a more expedient manner and not transporting bones to caves and rock shelters very often, then that could explain the lack of well preserved evidence. (I suppose). They also point out that the process of human mediated extinction seems to take a really long time in some cases, even islands, and yet for 35 genera across the entire continent of North America it was very rapid.

Good points in the article and in the commentary... would have liked to see more discussion of the ecological variables that alter the probability of extinction.

Best,
O

SWARM schedule posted

2008-03-17T08:57:00.000-07:00

The blog post for the upcoming SWARM meetings has been updated with more detailed scheduling information. The Human Macroecology symposium will be on Thursday April 10, 2008. Read more about it here.

More very small humans found

2008-03-11T11:59:00.000-07:00

An exciting discovery was recently made and just reported on in PLoS One. Several (25ish) individuals of very small and potentially insularly dwarfed humans were found on the island of Palau, which is within spitting distance (relatively speaking of course) of the well known and hotly debated finds from Flores.

title and authors are:

Small-Bodied Humans from Palau, Micronesia

Lee R. Berger, Steven E. Churchill, Bonita De Klerk, Rhonda L. Quinn

Its an open access article so you can get it here.
A blog written about the find has been posted on Anthropolog.net, which you can read here.
These finds are much more recent, dating to the last 3000 years than the ones from Flores, which are 18,000 years old or so. They were found in cave sites which appear to be burial locations as very few artifacts and no other fauna are associated.
The authors interpret the findings as dwarfed homo sapiens rather than some genetic abnormality as has been argued for the Flores finds (and contests as well of course).
There are some similarities between these Paluan finds and the ones from Flores.

Here is the final paragraph of the paper to offer their conclusions:

"Based on the evidence from Palau, we hypothesize that reduction in the size of the face and chin, large dental size and other features noted here may in some cases be correlates of extreme body size reduction in H. sapiens. These features when seen in Flores may be best explained as correlates of small body size in an island adaptation, regardless of taxonomic affinity. Under any circumstances the Palauan sample supports at least the possibility that the Flores hominins are simply an island adapted population of H. sapiens, perhaps with some individuals expressing congenital abnormalities."

It will be interesting to see how the different sides of the Flores arguments react to these findings.
Great stuff. exciting to think about. human biogeography.

cheers,
O

A little primate biogeography

2008-03-08T12:56:00.000-08:00

A fairly recent PNAS paper makes some interesting claims about the first primates to arrive in the New World. These little mouse sized guys, called Teilhardina magnoliana may have arrived by crossing the landbridge between Siberia and the New World way before people did (like 60 million years ago or so). They tip the scales at around 28 grams.

A good popular news piece based on the article can be found here.

Here's the stuff on the PNAS paper:

The oldest North American primate and mammalian biogeography during the Paleocene–Eocene Thermal Maximum

K. Christopher Beard

Section of Vertebrate Paleontology, Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, PA 15213

Edited by Alan Walker, Pennsylvania State University, University Park, PA, and approved January 10, 2008 (received for review October 25, 2007)

Abstract

Undoubted primates first appear almost synchronously in thefossil records of Asia, Europe, and North America. This temporalpattern has complicated efforts to reconstruct the early dispersalhistory of primates in relation to global climate change andeustatic fluctuations in sea level. Here, I describe fossilsfrom the Tuscahoma Formation on the Gulf Coastal Plain of Mississippidocumenting an anatomically primitive species of Teilhardinathat is older than other North American and European primates.Consistent with its antiquity, a phylogenetic analysis of dentalcharacters recognizes Teilhardina magnoliana, sp. nov., as themost basal member of this genus currently known from eitherNorth America or Europe. Its stratigraphic provenance demonstratesthat primates originally colonized North America near the baseof the Paleocene–Eocene Thermal Maximum (PETM), but beforean important fall in eustatic sea level. Correlation based oncarbon isotope stratigraphy and sequence stratigraphy indicatesthat the earliest North American primates inhabited coastalregions of the continent for thousands of years before theywere able to colonize the Rocky Mountain Interior. The transientprovincialism displayed by early North American primates correspondsto similar biogeographic patterns noted among fossil plants.Decreased precipitation in the Rocky Mountain Interior duringthe early part of the PETM may have been an important factorin maintaining biotic provincialism within North America atthis time. These results underscore the need to obtain multiple,geographically dispersed records bearing on significant macroevolutionaryevents such as the PETM.

Cosmic impacts and the end-Pleistocene extinction: idea seems not to hold up

2008-03-08T11:59:00.000-08:00

A while back I posted a blog on a paper published in PNAS arguing that a comet impact was responsible for the extinction of the megafauna in North America. They also argue that the impact was responsible for the disappearance of the Clovis culture - the earliest recognized archaeological culture in the New World known for large well made and very distinctive fluted spear points.
I was skeptical of their ability to link the proposed impact to the strongly size biased nature of the extinctions and wondered about how it extended to the similar patterns in extinction that we see on other continents. There was a lot missing in terms of how to link the impact to mammals - but aside from that it seemed like they may have demonstrated that lots of stratigraphic layers around the United States contain minerals of extra-terrestrial origin. or maybe not...

A news focus just published in Science (authored by Science writer Richard Kerr) reviews the evidence and points out that many of the claims by the authors of the comet study are not holding up. This is probably not surprising on the whole but it is amazing how many of the claims seem to be really thoroughly refuted and experts in the study of cosmic impacts suggest that the hole's in the study were evident long before it was published - that can happen when papers go to non-specialized audiences. Also note that the paper was published in PNAS...

Magnetic spherules believed to be diagnostic of the impact were a key line of evidence for the study by Firestone et al. (the authors of the PNAS paper) but it turns out that such spherules may be regularly introduced to our atmosphere from space and are not useful markers for a specific impact.

Excerpt from the article:
"One problem is that no one has "any of the classic evidence of an impact," says impact specialist David Kring of the Lunar and Planetary Institute in Houston, Texas. Spurred by the 1980s debate over what killed off the dinosaurs, "the community learned a lot about what the threshold of evidence is" for confirming an impact, he explains. But taking all the evidence offered by the group proposing the mammoth-killer impact, "you end up with [markers] that are not diagnostic of impact," says impact specialist Bevan French of the National Museum of Natural History in Washington, D.C. Proponents, meanwhile, are defending some of their published claims and giving ground on others but promising ultimate vindication.

ET? An impactor (top) may have produced magnetic spherules (lower right), but similar spherules (lower left) continually fall from space.
CREDIT: STOCKTREK IMAGES/GETTY IMAGES; L. FRANZÉN, N. PINTER, AND S. ISHMAN, GSA TODAY (2008); FIRESTONE ET AL., PNAS 104, 41 (2007)

Diamonds not forever
Everyone agrees on one point at least. "Obviously, something really interesting happened 13,000 years ago," as Kring puts it. It was 12,900 years ago, to be precise, that a world staggering out of the last Ice Age suddenly plunged back into a millennium of near-glacial climate before emerging into the current warmth. It was also about then--emphasis on the uncertainties summed up by "about"--that the mammoths and other great beasts disappeared from North America. And the Paleo-Indian Clovis culture vanished from the archaeological record around then, too."
Science 7 March 2008:
Vol. 319. no. 5868, pp. 1331 - 1332
DOI: 10.1126/science.319.5868.1331

Experts question the existence of the nanodiamonds that are thought to be traced to the impact and other lines of evidence, such as the iridium spike in the stratigraphic layers in question, have been fairly extensively criticized and questioned as well.

These criticisms really don't sound like the nay-saying that goes with old stodgy types not like their conventional wisdoms being questioned. They seem pretty solid. Perhaps the debate will continue to play out in the literature.

later
O

Human Macroecology at AAAS/SWARM

2008-03-04T16:21:00.000-08:00

We at human macroecology are proud to announce that we have organized a symposium for this year's SWARM meetings, which will be held here in Albuquerque, New Mexico from the 9th to 12th of April 2008. SWARM is the southwest and rocky mountain regional division of the AAAS, the publishers of the journal Science. The symposium features the work of several authors whose work represents the backbone of the approach we conveyed in our class last semester. They also provide the exemplary examples of what this style of social science research will strive to emulate in the future. We hope that anyone who can travel to the event considers stopping in and enjoying the papers, which will prove to be diverse, exciting, and novel in their perspectives and analyses. Information about registration can be found here and lodging info is here.

The keyword for this year's SWARM meeting is collaboration, thus human macroecology fits the theme very well.

The abstracts for the symposium and each of the papers are presented below. We'll periodically add information about the symposium to this blog so check back in from time to time if you're interested.

The symposium will be held on Thursday April 10th, 2008. Papers should start at 9:00 am but the official schedule has not yet been completed. I'll post new information as it becomes available.

Cheers,
Oskar

*************************************************************************************
Symposium Schedule:

Thursday, April 10, 2008.

Order	time	Speaker	Affiliation
1	9:00 - 9:20	Oskar Burger and Bill Burnside	University of New Mexico
2	9:20 - 9:40	James H. Brown	University of New Mexico
3	9:40 - 10:00	Bill Burnside and Jordan Okie	University of New Mexico
4	10:00 - 10:20	Larry Todd	Colorado State University
5	10:20 - 10:40	Mary Stiner	University of Arizona
	10:40 - 11:00	break	break
6	11:00 - 11:20	Peter Turchin	University of Connecticut
7	11:20 - 11:40	Alison Boyer	University of New Mexico
8	11:40 - 12:00	Helen Davis et al.	University of New Mexico
	12:00 - 1:00	lunch	lunch
9	1:00 - 1:20	Robert Walker et al.	Max Planck Institute
10	1:20 - 1:40	Paul Hooper	University of New Mexico
11	1:40 - 2:00	Marcus Hamilton	University of New Mexico
12	2:00 - 2:20	Melanie Moses	University of New Mexico
13	2:20 - 2:40	Louis Bettencourt	Los Alamos National Laboratory
	2:40 - 3:00	break	break
	3:00 - 4:00	round table discussion

Each presentation is allotted 20 minutes, 15 for the talk with 5 for questions.

Symposium Title:

Human Macroecology: Emergent Patterns and Processes in Large-Scale Human Ecology

Symposium Abstract:

Through a multidisciplinary team of speakers and a panel discussion, this symposium explores the developing field of human macroecology, the study of emergent patterns in human-environment interactions across scales. This collaborative approach to social science emphasizes law-like generalizations of human dynamics that occur at scales larger than what can be observed in a single study, survey, or field site. Within this framework, we borrow from a diverse range of fields, including evolutionary ecology, statistical mechanics, complex systems, biogeography, and others. The talks are connected by the spirit of the analyses and the nature of the questions asked, and provide examples of studies that human macroecology will strive to emulate in the future. These include studies of life history variation in primates and humans that emphasize emergent features of human evolution and energetic tradeoffs among essential demographic variables. Other presentations explore biogeographic trends and large-scale human-environment interactions. To this end, archaeological and paleobiological perspectives are utilized to explore the dynamic feedbacks of demographic trends, dietary shifts, adaptations and their impacts on the environment. We examine the form and structure of human settlements by analyzing how properties of cities and road networks change with population size and geography. Explicitly considering the flow of energy, materials, and information that power human societies highlights the importance of a metabolic framework for human ecology. In many instances, analogies with biological systems are employed to gain novel insights into human dynamics. By encompassing a wide range of topics and datasets we take a macroscopic view of the complexity and diversity of human systems, identifying underlying regularities, mechanisms, and organizing principles. Our approach bridges historic disciplinary divides while building a perspective that is needed to confront many of our most pressing issues of population growth, energy use, and sustainability.

Organized by Oskar Burger and Bill Burnside

9:00 - 9:20 am

Title: Orientation to the Goals, Motives, and Definition of Human Macroecology

Authors: Oskar Burger¹ and Bill Burnside²

1 Department of Anthropology, University of New Mexico

2 Department of Biology, University of New Mexico

Abstract: We present the definition and rationale behind the developing field of human macroecology. We emphasize the interdisciplinary and collaborative nature of this approach to social science by outlining its connections to a wide range of other areas of research that also focus on big picture dynamics in human systems. In doing so, we present some of the more salient emergent patterns that have been examined empirically and discuss some of their likely underlying mechanisms. Additionally, we provide framework for the symposium by highlighting commonalities in theme and approach among the papers which follow.

9:20 - 9:40 am

Title: Toward a Metabolic Theory of Human Ecology

Author: James H. Brown

Department of Biology University of New Mexico

Abstract: The developing metabolic theory of ecology (MTE) uses metabolism – the uptake, transformation, and allocation of energy and materials by organisms – to conceptualize, synthesize, and unify diverse environmental sciences. Since ecological interactions involve exchanges of energy, matter, and information, it is possible to use first principles (e.g., conservation of mass and energy, second law of thermodynamics, chemical stoichiometry) and biological processes (e.g., scaling of metabolic rate with body size and temperature, and dependence of resource use, life history, demography, and species diversity on metabolic rate) to build models and test their predictions. The principles, models, and approaches of MTE are directly applicable to human ecology. In collaborations among colleagues and students in biology and anthropology, we have begun to compile ‘macroecological’ data and to apply MTE. Our goal is to understand how energy and material resources are acquired, transformed, and allocated by aboriginal hunter–gatherers and modern technological societies. Preliminary results highlight the potential to use metabolism as well as genetics to cross the interdisciplinary interfaces between the natural and social sciences.

9:40 - 10:00 am

Title: Ecology of Range Size among Traditional Human Foragers: Macroecological Implications for Cultural Diversity Patterns

Authors: Bill Burnside and Jordan Okie

Department of Biology, University of New Mexico

Abstract: Indigenous human cultures display consistent geographic patterns of ethnic and linguistic diversity and group and territory size. As with biological species, cultural groups are more concentrated in the tropics. In species and populations generally, the geographic range reflects foraging ecology and energy requirements. We hypothesize that similar forces constrain range sizes of human societies: 1) environmental productivity will decrease territory size by supporting given populations with less land, while 2) reliance on hunting will increase territory size because energy is lost ascending food chains. Using a database of 339 traditional foraging societies, we used OLS regressions to test correlations between range size and climate; range size and mobility; and range size and foraging mode (gathering, hunting, fishing). We develop mathematical theory to explain the resulting macroecological patterns, guided by the effects of temperature on productivity and kinetics, or the rates of biological reactions and ecological interactions. Analyses of datasets on both traditional foraging societies and global indigenous cultural diversity support our theory. Combining macroecological analyses of ethnographic data with mechanistic ecological theory helps explain general patterns of human foraging ecology and cultural diversity.

10:00 - 10:20 am

Title: Scale, Boundaries, and Bridges: Human Dimensions in Paleoecology

Author: Lawrence C. Todd

Colorado State University

Abstract: One of the more difficult hurdles for research that examines multi-scale, transdisciplinary ecological processes can be the widespread perception that human actions and cultural transmission of information preclude inclusion of our species. One approach that makes this partition more permeable uses human paleoecology and archaeology as a basis for placing human behaviors within a framework of macroecological analysis. Fundamental to this approach is the effort to refocus archaeological research toward an integrated study of landscapes in which human actions are approached in ways that can be investigated in concert with other biological and physical processes. This approach emphasizes that only the most reductionist of research programs can investigate ecological relationships that do not consider aspects of all three domains of landscape formation and evolution (i.e., the cultural, the biological, and the physical). Examples for the Greybull River Sustainable Landscape Ecology project (GRSLE) in northwester Wyoming’s Greater Yellowstone Ecosystem are used to illustrate the basic components of this approach, which is referred to as “landscape taphonomy.” Investigations of this sort help bridge the unfortunate gap between research in the social and natural sciences.

10:20 - 10:40 am

Title: Changes in the ‘Connectedness’ and Resilience of Paleolithic Societies in Mediterranean Ecosystems

Author: Mary C. Stiner

Department of Anthropology, University of Arizona

Abstract: Human predator-prey relationships changed dramatically in the Mediterranean Basin between 250,000 to 9,000 years ago. Many of these changes can be linked to increases in Paleolithic human population densities. Small game species are particularly diagnostic of increases in human hunting pressure and are a major source of evidence for demographic change after 40-45,000 years ago. Biomass-corrected data on prey choice also indicate increasing use of those species that possess higher reproductive efficiencies. Step-wise, apparently irreversible shifts in human predatory niche are apparent in the Mediterranean Basin, beginning with the earliest Upper Paleolithic in the east and spreading westward. Evidence of demographic pressure and greater use of resiliant prey populations is followed by technological innovations to exploit these animals more efficiently. The zooarchaeological findings suggest that Middle and Lower Paleolithic reproductive units probably were not robust at the micropopulation scale, due to the rather narrow set of behavioral responses that characterized social groups at the time, and that localized extinctions at the micropopulation level were likely to have been common. Upper Paleolithic groups were the quintessential colonizers and, in addition, uniquely good at holding on to habitat gained. Upper Paleolithic archaeological “cultures” have shorter histories of existence than those of earlier periods, but they were even more widespread geographically. The demographic robustness of the Upper Paleolithic systems may stem from wholesale strategies for evening-out or sharing risk and volatility in technology. Micropopulations were larger and often denser on landscapes, more connected via cooperative ties, and thus more robust.

11:00 - 11:20 am

Title: Dynamical Feedbacks between Population Growth and Sociopolitical Instability

Author: Peter Turchin

Department of Ecology and Evolutionary Biology, University of Connecticut

Abstract: Most preindustrial states experienced recurrent waves of political collapse and internal warfare. One possible explanation of this pattern, the demographic-structural theory, suggests that population growth beyond the means of subsistence leads to state instability and breakdown, which in turn causes population decline. In several cases (e.g., early modern England and ancient China) we have data on both population dynamics and sociopolitical instability that can be analyzed using standard time-series approaches. Such analyses confirm that periods of sustained and vigorous population growth are followed, with a time lag, by waves of instability. Industrialization was made possible by rapid gains of agricultural productivity, and the general expectation is that the Malthusian component of the demographic-structural theory should lose relevance. Nevertheless, a survey of industrializing states (Western Europe, the U.S., Russia, and Japan) shows that periods of popular immiseration (proxied by declines in the average body height) were also followed, after a time lag, by waves of instability.

11:20 - 11:40 am

Title: Human Colonization and Pacific Island Biodiversity

Author: Alison G. Boyer

Department of Biology, University of New Mexico

Abstract: Human arrival on every landmass around the world has been associated with elevated extinction probability in the native fauna, which has been a major contributor to biodiversity loss and global change. Human impacts, through direct predation, habitat change and the introduction of exotic species, have been implicated as extinction drivers, but aside from one or two well-analyzed locations, the relative roles of these environmental impacts are much debated. Regression trees built on zooarcheological data from over 40 islands were used to assess the relative importance of these extinction drivers in island bird extinctions across the tropical Pacific. Prehistoric extinctions showed a strong bias toward larger body sizes and flightless, ground-nesting species, even after accounting for preservation bias, indicating a significant human predation component. In many cases endemism was also associated with extinction, possibly through impacts of exotic predators and habitat destruction. Human societies on small, isolated islands can be thought of as replicated microcosms which provide crucial information on the dynamic interplay between humans and biodiversity in natural communities.

11:40 am - 12:00 pm

Title: People as Islands: The Theory of Island Biogeography and Patterns of Disease across Human Populations.

Authors: Helen Elizabeth Davis¹, Oskar Burger¹, and Michael Gurven², and Hillard Kaplan¹.

1Department of Anthropology, University of New Mexico,

2Department of Anthropology, University of California- Santa Barbara,

Abstract: Infectious disease plays a major role in human population dynamics. Here we investigate host-parasite interactions across space and time using data collected among the Tsimane, a traditional forager-horticulturalist society in lowland Bolivia. Community ecology and human macroecology models are used to address the co-evolution of hosts and disease with respect to parasite virulence and spread, and human infection and re-infection rates. GIS mapping provides a spatial distribution pattern for 17 helminth and protozoa infections across the population (n=3,000). Application of MacArthur and Wilson’s (1967) theory of island biogeography allows us to identify disease reservoirs and analyze their contribution to population dynamics and disease spread. Counter-intuitively, higher population density (nodes) did not correlate with parasite density, suggesting that other factors such as wealth and immune system integrity are important. Particular attention is given to children’s health, with cognitive performance correlating significantly with parasitic burden and a measure of immune system integrity (IgE). Finally, we discuss the relationship of pathogen load across human populations and how these patterns have global significance.

1:00 - 1:20 pm

Title: The Tradeoff between Number and Size of Offspring in Humans and other Primates

Authors: Robert Walker¹, Michael Gurven², Oskar Burger³, Marcus Hamilton³

1 Max Planck Institute for Evolutionary Anthropology

2 Department of Anthropology, University of California- Santa Barbara,

3 Department of Anthropology, University of New Mexico

Abstract: Life-history theory posits a fundamental trade-off between number and size of offspring that structures the variability in parental investment across and within species. We investigate this ‘quantity–quality’ trade-off across primates and present evidence that a similar trade-off is also found across natural-fertility human societies. Restating the classic Smith–Fretwell model in terms of allometric scaling of resource supply and offspring investment predicts an inverse scaling relation between birthrate and offspring size and a -1/4 power scaling between birth rate and body size. We show that these theoretically predicted relationships, in particular the inverse scaling between number and size of offspring, tend to hold across increasingly finer scales of analyses (i.e. from mammals to primates to apes to humans). The advantage of this approach is that the quantity–quality trade-off in humans is placed into a general framework of parental investment that follows directly from first principles of energetic allocation.

A .pdf of a paper that this talk is based on can be found here.

1:20 - 1:40 pm

Title: Understanding the Effects of Braininess on Primate and Human Lifespan Evolution

Author: Paul Hooper

Department of Anthropology, University of New Mexico

Abstract: Explaining variation in animal lifespans is a central goal in life history theory and the metabolic theory of ecology. Understanding why primates in general, and humans in particular, are especially long-lived for their body size is a particularly relevant problem in this area. While previous life history approaches have taken adult mortality rates (and thus adult lifespan) as given, it has become apparent that lifespan should be treated as a partially endogenous decision variable, mediated by investments in mortality reduction throughout life (e.g. cellular maintenance and repair). The goal of this paper is to evaluate the conceptual continuity between two life history models—Kaplan & Robson 2002 and Charnov 2001—in which investment in survival is an endogenous decision variable. I show that Kaplan & Robson's result—that a more learning-intensive niche leads to greater investment in longevity—can be replicated within Charnov's framework using a numerical example. I then briefly discuss these results with respect to the allometry of mammalian and primate life history variables.

1:40 - 2:00 pm

Title: Scaling the Metabolism of Human Socio-Economies from Hunter-Gatherers to Nation States

Author: Marcus J. Hamilton

Department of Anthropology, University of New Mexico

Abstract: Like all biological species, human socio-economies are embedded within complex ecosystems that are structured by the fluxes and flows of energy and information between organisms and their environments. To meet energy demands, humans harvest resources from their environments by tapping into these flows thus creating nonlinear feedbacks between human and ecological systems. In this paper I use scaling theory to quantify the rate at which humans extract, distribute, and expend energy and information within different socio-economies, from hunter-gatherers to nation states. Preliminary data from over 1,030 human cultures show that human energy use scales at approximately the same sublinear rate across the range of human socio-economies. These results suggest a potential scaling law for human energy use, and the implications for understanding human evolution and ecology are discussed.

2:00 - 2:20 pm

Title: Cities as Organisms: Allometric Scaling of Urban Road Networks
Authors: Melanie E. Moses and Horacio Samaniego

Computer Science Department, University of New Mexico

Abstract: Just as the cardiovascular network distributes energy and materials to cells in an organism, urban road networks distribute energy, materials and people to locations in cities. Understanding the topology of urban networks that connect people and places leads to insights into how cities are organized. We study statistics of road networks and traffic patterns across 425 US cities and show that urban road networks are much less centralized than biological vascular networks. As a result, per capita road capacity is independent of the spatial extent of cities. In contrast, driving distances depend on city area, although not as much as is predicted by a completely centralized model. This intermediate pattern between centralized and decentralized extremes may reflect a mixture of different travel behaviors. The approach presented here offers a novel macroscopic perspective on the differences between small and large cities and on how road infrastructure and traffic might change as cities grow.

2:20 - 2:40 pm

Title: Urbanization, Social Adaptation and Sustainable Development

Author: Luís Bettencourt

Theoretical Division, Los Alamos National Laboratory

Abstract: The problem of creating solutions for sustainable development is increasingly predicated on the management of the resource demands of social economic life in cities. Urbanization is the most conspicuous social force at play worldwide today. Developing countries such as China and India are less that 50% urban, but are expected to reach the levels observed in developed nations (80-90%) in the next 3-4 decades. The consequences of urbanization for human demands on natural ecosystems is somewhat ambivalent. While certain forms of consumption (energy, changes in diet) per capita certainly increase on average, urbanization can partially liberate land from human occupation while increasing the efficiency with which a dense population can be serviced. Quantifying these potentially contradictory trends has been a challenge in the past. We show however that scaling, i.e. the analysis of the systematic variation of urban properties with population size reveals scale invariant statistical regularities that capture systematically and predict the course of cities as their population sizes change. We use these insights to frame the discussion of a transition to sustainability in terms of the consumption of several resources used to quantify human footprint, and show how urbanization may be compatible, and even accelerate, the achievement of continued economic growth that is compatible with the preservation of the Earth's support systems.

Natural selection and culture

2008-03-04T13:39:00.000-08:00

A paper was published this week in PNAS on rates of culture change and has an interesting commentary by Stephen Schennan. As its open access you can get it here.

Here's the basics on the paper:

Natural selection and cultural rates of change

Deborah S. Rogers and Paul R. Ehrlich^*

Department of Biological Sciences, Gilbert Building, 371 Serra Mall, Stanford University, Stanford, CA 94305

Contributed by Paul R. Ehrlich, December 17, 2007 (received for review November 5, 2007)

It has been claimed that a meaningful theory of cultural evolutionis not possible because human beliefs and behaviors do not followpredictable patterns. However, theoretical models of culturaltransmission and observations of the development of societiessuggest that patterns in cultural evolution do occur. Here,we analyze whether two sets of related cultural traits, onetested against the environment and the other not, evolve atdifferent rates in the same populations. Using functional andsymbolic design features for Polynesian canoes, we show thatnatural selection apparently slows the evolution of functionalstructures, whereas symbolic designs differentiate more rapidly.This finding indicates that cultural change, like genetic evolution,can follow theoretically derived patterns.

********

I like papers that suggest that we shouldn't just assume that certain features of culture are immune to scientific inquiry.

Cultural evolution is one of those areas of anthropology/social science with lots of baggage - both in terms of misguided criticisms and in terms of misused analytical techniques and models - but its an area that is rapidly growing and seems to consistently make provocative findings - as this paper does.

So they study boats from Polynesia:
"Finding cultural traits with which to test such ideas proveddifficult. The traits we settled on were the design elementsof canoe building across Polynesian societies. We have sincelearned that the French philosopher Alain (Émile-AugusteChartier) in 1908 proposed that boat design would be subjectto natural selection (26). "Tout bateau est copié surun autre bateau... Raisonnons là-dessus à la manièrede Darwin. Il est clair qu'un bateau très mal fait s'enira par le fond après une ou deux campagnes, et ainsine sera jamais copié... On peut donc dire, en toute rigueur,que c'est la mer elle-même qui façonne les bateaux,choisit ceux qui conviennent et détruit les autres" (pp41–42). [Every boat is copied from another boat... Let'sreason as follows in the manner of Darwin. It is clear thata very badly made boat will end up at the bottom after one ortwo voyages, and thus never be copied... One could then say,with complete rigor, that it is the sea herself who fashionsthe boats, choosing those which function and destroying theothers. (Translated by D.S.R.)]"

They divide traits of the canoes into those that seem likely to directly impact the canoe's performance (functional or design characteristics) from those that do not (stylistic), so you need to be comfortable with that dichotomy.

that state: "Our expectation was that the functional traits would changeat a significantly different rate from that of symbolic traits."

They statistically evaluated what the differences in rates of change were between the stylistic and functional groups across the islands through time. The statistical technique was interesting - they compared a randomized assignments of functional vs. stylistic to a Wilcoxon signed rank frequency distribution for the recalculated Jaccard distances. I don't know if there were better ways to conduct this test or not. They found that the rates were different, with functional traits changing at a slower rate.

They conclude that: 1) such evolutionary perspectives are indeed good for the study of culture change (a rah rah team conclusion); 2) this identifies the different mechanisms that might act on culture change, and; 3) design features don't change randomly or 'mutations' indicating the link between canoe design and actual survival characteristics. Changes must be conservative and thought out... etc.

enjoy,
O

Levy Walks in the Ocean

2008-02-28T21:01:00.000-08:00

A paper published this week in Nature about Levy Walks among marine predators.

Reference info, title, and abstract follow:

Nature 451, 1098-1102 (28 February 2008) | doi:10.1038/nature06518; Received 17 October 2007; Accepted 29 November 2007

Scaling laws of marine predator search behaviour

David W. Sims, Emily J. Southall, Nicolas E. Humphries, Graeme C. Hays, Corey J. A. Bradshaw, Jonathan W. Pitchford, Alex James, Mohammed Z. Ahmed, Andrew S. Brierley, Mark A. Hindell, David Morritt, Michael K. Musyl, David Righton, Emily L. C. Shepard, Victoria J. Wearmouth, Rory P. Wilson, Matthew J. Witt & Julian D. Metcalfe

Many free-ranging predators have to make foraging decisions with little, if any, knowledge of present resource distribution and availability¹. The optimal search strategy they should use to maximize encounter rates with prey in heterogeneous natural environments remains a largely unresolved issue in ecology^1,^2,³. Lévy walks⁴ are specialized random walks giving rise to fractal movement trajectories that may represent an optimal solution for searching complex landscapes⁵. However, the adaptive significance of this putative strategy in response to natural prey distributions remains untested^6,⁷. Here we analyse over a million movement displacements recorded from animal-attached electronic tags to show that diverse marine predators—sharks, bony fishes, sea turtles and penguins—exhibit Lévy-walk-like behaviour close to a theoretical optimum². Prey density distributions also display Lévy-like fractal patterns, suggesting response movements by predators to prey distributions. Simulations show that predators have higher encounter rates when adopting Lévy-type foraging in natural-like prey fields compared with purely random landscapes. This is consistent with the hypothesis that observed search patterns are adapted to observed statistical patterns of the landscape. This may explain why Lévy-like behaviour seems to be widespread among diverse organisms³, from microbes⁸ to humans⁹, as a 'rule' that evolved in response to patchy resource distributions.

*****

So there has been a lot of attention to this Levy Walk stuff in recent years. Do animal movements form power law distributions in terms of the length of each 'flight' they take? If you track an animal as it moves, it goes in a straight line for a while and then turns. These straight line lengths between turns are called paths or flights. A Levy Flight distribution is one where the histogram of these flights has a really long tail toward long flights and the probability of finding a flight of any given length is a power law distribution with an exponent between about 1 and 3 (around 2 being typical). This means there are a lot of small lengths and a few really long ones and that as length increases by some factor the probability decreases by a constant factor (the exponent). Some folks think the importance of these Levy Flights is way overblown and some people think its a big deal. If its a big deal its because we are learning something fundamental about how foraging behavior is organized and presumably how that organization reflects something about the underlying ecology or prey distribution. Are these things adaptive? To get a visual, imagine taking 'flights' while foraging that were all the same length. You might deplete all the resources in your immediate surroundings efficiently but what happens when you have to move a long way? So lots of small steps and a few long ones might be the way to go to efficiently search in your foraging habitat - and that is more or less what the Levy Flight is about.

Here they argue that Levy Flights are optimal foraging strategies that reflect the underlying distribution of prey. Hopefully we'll know more about the mechanistic links between path length distributions and prey distributions in the future. Also note that the book on Foraging that I have been blogging about does not cover this new work on Levy Flights even though this would certainly be a hot topic to some. Of course I don't blame the editors of the book as you can't fit in everything.

Anyway, its an interesting paper that is worth checking out.

Best,
Oskar

Reproducing in Cities: recent paper by R. Mace

2008-02-19T16:34:00.000-08:00

A recent perspective by Ruth Mace published in Science (subscription required) gives a perspective on the demographic transition - the transition to reduced fertility rates among wealthy nations and economic classes. The argument is based on the costs of childrearing that seem to increase with urbanization and the lowered rates of infant and child mortality that can accompany city life in contexts where sufficient health care and sanitation are available.

Here's the paper's abstract:

"Reproducing in cities has always been costly, leading to lowerfertility (that is, lower birth rates) in urban than in ruralareas. Historically, although cities provided job opportunities,initially residents incurred the penalty of higher infant mortality,but as mortality rates fell at the end of the 19th century,European birth rates began to plummet. Fertility decline inAfrica only started recently and has been dramatic in some cities.Here it is argued that both historical and evolutionary demographersare interpreting fertility declines across the globe in termsof the relative costs of child rearing, which increase to allowchildren to out compete their peers. Now largely free from thefear of early death, postindustrial societies may create anenvironment that generates runaway parental investment, whichwill continue to drive fertility ever lower."

The paper provides an interesting perspective on fertility in urban life and of course on the demographic transition in general. Mace essentially argues that the demographic transition is the result of the quantity quality tradeoff.

"Industrialization and urban living enable new professions toemerge, some of which are only available to those invested withconsiderable capital or training." .... "Whether perceived relative costs are equivalentto actual costs is a moot point; but, in essence, historicaland evolutionary demographers are converging on similar explanationsfor demographic change. The cost of raising a child includesenabling it to compete with its peers—for marriage partners,for jobs, or for the means to support a family—and ifthat competition increases costs, then basic evolutionary ecologypredicts that optimal fertility will decline (16). Educationintroduced a new mechanism through which children could competefor future employment opportunities. School also adds pressureon parents to present adequately fed and dressed offspring forpublic scrutiny."

Figure 2, pasted in below, represents the basic schematic for the argument. Mace says that in many instances wealth and fertility are often positively correlated within these 'homogenous subpopulations'. While this may indeed be true (I think that it is and would argue in favor of that point), the data supporting it are really not that good and the source Mace cites as proving
that wealth and family size are usually positively correlated really provides only weak support and is based on little data.

Fig. 2. Schematic diagram of how different levels of parental investment per child can generate positive relationships between fertility and wealth in subpopulations (where each of the diagonals represents a different subpopulation within a larger society) but a negative relationship between wealth and fertility over a large heterogeneous population. Levels of parental investment per child may be highest in urban areas.

Mace is skeptical the opinion that these trends in fertility decline simply represent shifts in cultural values that have rapidly swept over the globe and I think for good reason. Clearly the pattern is consistent in very different cultural contexts (Europe, Americas, and Africa have all gone through similar demographic transitions following broadly similar correlations between economic diversification and urbanization). Instead, there is good evidence for a general evolutionary mechanism at work. So the general trend of having "few higher quality offspring" started as initially advantageous, accelerated with lower levels of child mortality and the increased importance of inherited wealth and status, and then became subject to runaway selection.

"Transfers of resources from parents to offspring are key tounderstanding human life-history evolution (23). In wealth-owningsocieties, siblings compete with each other for their parents'material and intellectual resources (24–26). If parentalinvestment is a key influence on children's future success,and the ability to invest effectively in children is heritable(and cultural traits such as wealth and status are usually highlyheritable), then it is possible that runaway cultural selectionhas occurred in preferred levels of investment in each child(27), driving the quantity/quality trade-off further in thedirection of offspring quality. Hence, I argue that the emergenceof postindustrial life, now largely free from the fear of earlymortality, seems to have generated conditions under which arunaway process of ever-escalating levels of investment in ourchildren continues to drive fertility ever lower."

The link to 'cultural selection' could be a bit more clear in order to differentiate it from the widely spreading cultural shift idea of some cultural demographers which she criticizes earlier in the paper. Readers who are not already on Mace's side of the argument may not see the difference, and its not entirely clear. However, I am on Mace's side of the argument and think that evolutionary mechanisms do indeed underly fertility decisions of this sort. The runaway selection idea is one that deserves more attention. I'd like to see some modeling or analytical work showing exactly how it could lead to below replacement fertility. Perhaps some of the references in the paper accomplish this. On the whole, its good to see this sort of approach being applied in human demography. Being a UNM graduate student though, I couldn't help but notice that some of the highly relevant work done by some faculty and/0r grad students here was not cited or included in the paper (e.g., Moses and Brown 2003; Kaplan 1996), but that is clearly only a gripe driven by hometown bias.

**********************
Kaplan H. (1996) A Theory of Fertility and Parental Investment in Traditional and Modern Human Societies. Yearbook of Physical Anthropology, 39, 91 - 135

Moses M.E. & Brown J.H. (2003) Allometry of human fertility and energy use. Ecology Letters, 6, 295-300

Some Mac Links

2008-02-16T16:23:00.000-08:00

A paper has recently been published in Plos one about the peopling of the new world that uses a large sample of mtDNA from Native Americans to assess population history. They argue for a three stage model that essentially supports the idea that the new world was colonized by northeast Asian groups who crossed Beringia and an ice-free corridor through northwest North America. They do argue that the origin of Clovis culture may go back to 16,000 years or more, which is a bit older than generally thought.
Blogs on this paper can be found here (Anthropology.net) and here (Dienekes).

Also of potential interest is a recent proposal to start an institute of human origins at the University of California San Diego. The news article explains that:
"The Center for Academic Research and Training in Anthropogeny will be “trans-disciplinary,” said Varki, who will be co-director with Gage and Schoeninger. (Anthropogeny is the study of human evolution.)

“It will be more than multidisciplinary,” he said. “CARTA will transcend disciplines, bringing together biologists, social scientists, neuroscientists, chemists, medical specialists – anybody who can bring insight into the question of where we come from.”

Said Schoeninger: “The center will allow us to move well beyond the bounds of any given field of study. Looking at the biological and cognitive links between humans and other primates or other animals – and doing so not only with the breadth afforded by different disciplines, but also with the depth offered by an evolutionary perspective – will give us a richer picture of the past and of today.”"

Sounds pretty cool. We need more work on figuring out what makes humans human.

Human macroecology is interested in underlying mechanisms of the growth and form of human institutions/groups/populations at multiple scales. A recent study in Science magazine covered geometric principles of the growth and form of cities that is covered by Science Daily and worth a quick read.

Cheers,

Quantity/quality offspring tradeoff in humans and other primates

2008-02-05T09:21:00.000-08:00

The following article is available online in firstcite with the Proceedings of the Royal Society B.

Title: The tradeoff between number and size of offspring in humans and other primates

Abstract: Life-history theory posits a fundamental trade-off between number and size of offspring that structures the variability in parental investment across and within species. We investigate this ‘quantity–quality’ trade-off across primates and present evidence that a similar trade-off is also found across natural-fertility human societies. Restating the classic Smith–Fretwell model in terms of allometric scaling of resource supply and offspring investment predicts an inverse scaling relation between birth rate and offspring size and a −¼ power scaling between birth rate and body size. We show that these theoretically predicted relationships, in particular the inverse scaling between number and size of offspring, tend to hold across increasingly finer scales of analyses (i.e. from mammals to primates to apes to humans). The advantage of this approach is that the quantity–quality trade-off in humans is placed into a general framework of parental investment that follows directly from first principles of energetic allocation.

Authors: Robert Walker, Michael Gurven, Oskar Burger, Marcus Hamilton

I have a biased perspective but I think this is a really good paper. It combines the classic model of the quantity/quality tradeoff in life history theory developed by Smith and Fretwell with a recent model by Charnov and Ernest (citations below).
The Smith-Fretwell model basically says that the relative cost of a kid C is the total energy budget mom has to put toward making kids R divided by the number of kids she has N. so C = R/N. This also means that the number of kids then is given by N = R/C. This is a pretty straight forward model that works well. So the higher the cost of an average kid to an average mother in a species or population the fewer kids the average mom will have. We know from life history theory that mom's energy budget R is a function of her mass and that a 3/4 power allometry of body mass is a pretty reasonable estimate for this energy budget. We also know that a reasonable estimate of the cost of a kid seems to be mass at weaning, which is a linear function of mom's mass - about .3M among mammals where M is mom's mass. This means that on average mammal offspring are dependent on their moms for energy until they are about 1/3 her size (Charnov 1993 and others). Anyway, these two observations can be placed into the Smith-Fretwell model to predict another well-known allometric relationship, the -1/4 power scaling of fertility rate with body mass. This happens because R is proportional to M^3/4 and C is proportional to M^1 so we get that N can be predicted by M^3/4 divided by M^1 which gives us M^-1/4. Or we can use these same expressions to look at the relationship between the number and size of offspring, which is predicted to be an inverse relationship (N/R = 1/C ~ M^-1). Our analysis demonstrates that the theory predicts the actual empirical trends in humans and primates.

If this is kind of thing is new to you just realize that when we look for patterns across large numbers of species - like all mammals or all birds - we find these really consistent relationships where a lot of important traits seem to be largely constrained (or at least well-predicted) by the average adult mass of the species. Three of these traits used here are metabolic rate, which is taken to be energy budget, the size of the offspring when its independent from its mom (important because that's when the mom can start making new kids if she wants so its a key constraint on fertility), and these two predict another - that fertility rate is slower with larger animals than with smaller ones.

We need to keep in mind that mass at weaning is generally a good proxy for the measure we are really interested in which the energetic cost of the offspring to the mother. For primates and in humans in particular, however, this may not be a good approximation. Human mothers invest much more in their offspring as human kids are often dependent long after they are weaned.
We take this into account by looking at mass of the offspring at ages older than the typical age at weaning and find that the model works better as a result. So this basic prediction of life history theory, that a tradeoff exists between the number and size of offspring, is met with data on human groups (natural fertility, small-scale populations) and among primates. There are some other points to the paper as well and we hope people find it interesting and that it provokes further research in this area. comments welcome of course.

I'll post a stable link to the pdf of the paper as soon as I can but something is wacky with UNM's server so I can't right now. [Ok, here's a link to a pdf of the paper.] If you are on a computer that has access to the proceedings of the royal society then you should be able to get it here.

best,
Oskar

***********************************
Charnov, E.L. & Ernest, S.K.M. 2006 The offspring-size/clutch-size trade-off in mammals. Am. Nat. 167, 578–582, (doi:10.1086/501141).

Charnov, E.L. 1993 Life history invariants: some explorations of symmetry in evolutionary ecology. Oxford, UK: Oxford University Press.

Smith, C.C. & Fretwell, S.D. 1974 The optimal balance between number and size of offspring. Am. Nat. 108, 499–506, (doi:10.1086/282929).

"Evidence for declines in human population densities during the early Upper Paleolithic in Western Europe"

2008-01-28T11:00:00.000-08:00

In PNAS's first issue of the New Year, Eugene Morin elegantly combines a macroecological approach with archaeological data to investigate forager ecology and the evolution of modern humans. Amongst other things, Eugene Morin finds a strong correlation between hunter-gatherer population density and mammalian species richness (see Morin's figure pasted on the right). Please post any comments you have of this paper on the blog.

"Evidence for declines in human population densities during the early Upper Paleolithic in Western Europe", 2008, PNAS, 105, pp. 48-53.

Abstract

"In western Europe, the Middle to Upper Paleolithic (M/UP) transition, dated between 35,000 and 40,000 radiocarbon years, corresponded to a period of major human biological and cultural changes. However, information on human population densities is scarce for that period. New faunal data from the high-resolution record of Saint-Ce´ saire, France, indicate an episode of significant climatic deterioration during the early Upper Paleolithic (EUP), which also was associated with a reduction in mammalian species diversity. High correlations between ethnographic data and mammalian species diversity suggest that this shift decreased human population densities. Reliance on reindeer (Rangifer tarandus), a highly fluctuating resource, would also have promoted declines in human population densities. These data suggest that the EUP represented for humans a period of significant niche contraction in western Europe. In this context, the possibility that a modern human expansion occurred in this region seems low. Instead, it is suggested that population bottlenecks, genetic drift, and gene flow prevailed over human population replacement as mechanisms of evolution in humans during the EUP."

Darwin2009: The Beagle Project

2008-01-26T09:34:00.000-08:00

I just learned about the Beagle Project from John Hawkes' blog.
As the page for the Beagle Project explains:
"2009 is one of the most significant anniversary years in science: it marks the 200th anniversary of the birth of Charles Darwin (12 February 1809), and the 150th anniversary of the publication of his book On the Origin of Species by Means of Natural Selection."

and then,

"Our contribution to this [celebration of this great anniversary] will be to build a sailing replica of HMS Beagle, the ship on which Darwin circumnavigated the globe between 1831 and 1836. It was during the shore expeditions he made from the Beagle that he collected the specimens which would later inspire the theory of Natural Selection and the Origin of Species.

The replica HMS Beagle will be launched in 2009 and will spend the year opening its decks to the public, teachers and scientists and supporting the Darwin200 celebrations."

So they are going to build a replica Beagle and then sail over the same ground that Darwin covered when he participated on this epic voyage. They are going to bring modern equipment and do a number of inspired projects along the way.

What a phenomenal sounding adventure. All I can say is 'take me take me!!'. Don't you think they need an archaeologist? Especially one that is interested in things like island biogeography, primate life history variation, foraging behavior, conservation biology, scaling/metabolic theory, natural history in general, and oh of course -human macroecology- and who is tons of fun to work with? Sign me up. Yeah, there's no way this is a complete voyage without a human macroecologist. Somebody please convince them for me.

Best,
Oskar

Special Feature: Foraging with Charnov

2008-01-25T09:41:00.000-08:00

This semester I'll be taking a 1 hour seminar from Dr. Ric Charnov that meets every Friday, in which we'll be going through a new book on Foraging theory that just came out a few months ago. (also available at Amazon).

Foraging: Behavior and Ecology (Paperback)
by David W. Stephens (Editor), Joel S. Brown (Editor), Ronald C. Ydenberg (Editor)

The book contains 14 chapters and we'll be going through each one sequentially, one per week.
Each week after class I'll write a short blog about the chapter and try to summarize any highlight's from our class discussion. I really hope some of you out there who are interested in foraging will read along and chime in on the blog. It should be a good way to get up to date on this challenging and always rapidly expanding field.

I probably wouldn't argue that all things foraging theory are necessarily part of what we call human macroecology but foraging behaviors and the models used to understand them are fundamental to a vast range of ecological and evolutionary questions. Moreover, foraging behaviors may often be part of the rule sets generating complex emergent social/group level/population patterns. That is, they may be part of the simple rules of interaction that generate emergent macroecological trends.

Anyway, starting next Friday for all weeks of the semester except springbreak there will hopefully be a blog about the chapter we discussed that week. Next week we start with chapter 1 ; Foraging: an overview, by R. C. Ydenberg, J. S. Brown, and D. W. Stephens.
see you then,
Oskar

"Wallace should hang" ?

2008-01-09T09:07:00.000-08:00

The New York Times has just published an interesting opinion piece called "Wallace should Hang" by evolutionary biologist and science writer Olivia Judson in recognition of Alfred Russel Wallace. Wallace was an independent 'discoverer' of the process of evolution by natural selection and a founding father of the field of biogeography. He often plays the role of an unsung hero and his contribution to the field seems to be misscharacterized in many settings. He anticipated many of the important issues of and processes of biogeography and was a great thinker although he had some nuances that the story does a good job of presenting. Check out this interesting read!

A couple hits from the blog ('osphere)

2008-01-04T10:36:00.000-08:00

Here's some fun reading:
Anthropology.net has this story about recent work regarding population declines in the Upper Paleolithic.

Freakonomics has an interesting post about the recent hubbub over California's emission reduction program getting blocked by the federal government. And it includes links/ref to a story that attempts to break down the economics behind California's plan. They argue that the costs of their plan have been severely under-estimated and that if California moved forward with it, it would contribute to the state's financial woes. I have to admit that I wish the study were wrong because I like the idea of the states taking the lead on a very lackluster federal government on issues like this. But it is of course a complex matter and we shouldn't endorse any plan that sounds good... We should pay close attention to this and other potential conflicts between state governments and the Feds/EPA on issues of sustainability, emission reduction/energy-use/recycling and the like.

And lastly - are you left or right brained? I see this thing going one way and one way only - I can't imagine it going counter-clockwise. See for yourself.

Oskar

Course wrap-up: its over now...

2008-01-03T11:45:00.001-08:00

Well, the semester is long done now. The papers are in, grades are out, and we've gone on to other things as far as the class goes. Overall, it was a great semester (er at least I thought so...) and we ventured over a lot of territory in the literature. The students were fantastic and taught the instructors a great deal. Thanks. We appreciate everyone's hard work.

The blog has been a bit slow lately but hopefully will pick up steam again here soon as I recover from my xmas break coma. This blog will change a little bit as it won't be specifically a course resource in the following semester, but it will remain active as a hotbed for information, news, and discussion on human macroecology (and other broadly related themes of course). And you all know I'd love to have a few more consistent contributors... I hope those of you who took the class and any who just stumbled onto this blog will continue to check in regularly.

We also really enjoyed doing the 'end oral dialogs.' (Each student met with the instructors for an hour long conversation about the semester during finals week). While a full day of these rendered Bill, Jordan, and I nearly brain dead and certainly less-able-than-usual to speak in complete sentences, we got a lot out of finding out what people really focused on during the semester - and what they retained as the salient themes. Pretty unanimously people liked the structure of the class - having a blog as a resource - focusing on discussion of recent papers.
Most folks really liked adopting the concepts of emergence and the theoretical toolkit of life history theory into human ecology. We did not get a clear consensus for things like the favorite paper but the content of Bettencourt et al (2007 in PNAS) and Moses and Brown (2003 in ecol letters(this link is to a pdf)) sure seemed to stay with people and leave them thinking. These papers are definitely thought provoking and provide theoretical frameworks and findings that should be widely contemplated and discussed. The classic paper by Leslie White (1943) also seemed to leave a lasting impression. Other frequently mentioned papers included those from the week on extinctions and the system dynamics approaches outlines in weeks 10 and 11 (especially papers by Tainter and Holling). Life history theory in general seemed widely appreciated as well.

We hope that as people move forward into different areas that they'll retain some of the approach to science we outlined and maintain a skeptical and analytical view when approaching claims of human uniqueness. We also hope they'll consider those very large-scale patterns and the mechanisms that underlie them - of course not to replace of microecological studies but to compliment them and extend their findings.

More soon.

Best wishes everyone. Thanks again for a great semester.

Happy New Year.

Oskar

Human Capital Vol. 1, N. 1: First issue of a new journal

2007-12-21T13:49:00.001-08:00

University of Chicago Journals has recently published the first issue of the new journal - Human Capital . This journal is based on a series of theoretical developments in economics beginning about 40 years ago leading to what today is called human capital theory. While it dates back to some classic theorists it is probably most closely associated with economists Gary Becker and Theodore Schultz. Students of human evolution should be familiar with the concept from its role in embodied capital theory, which has been used by Hilly Kaplan and colleagues to explain the coevolution of intelligence, long lifespan, dependent offspring, and complex foraging niche that has characterized primate diversification in general and especially the evolution of the human life course and adaptive niche (a pdf of one of the papers on this can be found here).

All of the articles in this inaugural issue look really interesting and blog worthy, so I'm just going to post titles and abstracts so that they are on your radar. It looks like it should be a really interesting journal to watch and I look forward to taking in some of these papers during vacation.
The first paper is by Isaac Ehrlich and Kevin M. Murphy and explains why a seperate journal of human capital is necessary. It gives a nice explanation for the rationale of human capital theory and its historical development.

The rest of the papers in the journal are as follows:

Education and Consumption: The Effects of Education in the Household Compared to the Marketplace

Gary S. Becker and

Kevin M. Murphy

University of Chicago and Hoover Institution

This article considers various differences between the effects of education in the marketplace and households. It shows that the household sector rewards skills that are useful at the many tasks that household members must execute, whereas the marketplace rewards skill at specialized tasks. In addition, increased supplies of more educated persons reduce returns to education in the marketplace, whereas if anything, increased supplies raise household returns to education. The greater demand over 40 years for household and market skills may have raised returns to education in households compared to those in the market sector.

***

The Changing Role of Family Income and Ability in Determining Educational Achievement

Philippe Belley

University of Western Ontario

Lance Lochner

University of Western Ontario and National Bureau of Economic Research

We use the National Longitudinal Survey of Youth 1979 and 1997 cohorts to estimate the effects of ability and family income on educational attainment in the early 1980s and early 2000s. The effects of family income on college attendance increase substantially over this period. Cognitive ability strongly affects schooling outcomes in both periods. We develop an educational choice model that incorporates both borrowing constraints and a “consumption value” of schooling. The model cannot explain the rising effects of family income on college attendance in response to rising costs and returns to college without appealing to borrowing constraints.

***

The Production of Cognitive Achievement in Children: Home, School, and Racial Test Score Gaps

Petra E. Todd and

Kenneth I. Wolpin

University of Pennsylvania

This paper studies the determinants of children’s scores on tests of cognitive achievement in math and reading. Using rich longitudinal data on test scores, home environments, and schools, we implement alternative specifications for the cognitive achievement production function that allow achievement to depend on the entire history of lagged home and school inputs as well as on parents’ ability and unobserved endowments. We use cross‐validation methods to select among competing specifications and find support for a variant of a value‐added model of the production function augmented to include information on lagged inputs. Using this specification, we study the sources of test score gaps between black, white, and Hispanic children. The estimated model captures key patterns in the data, such as the widening of minority‐white test score gaps with age and differences in the gap pattern between Hispanics and blacks. We find that differences in mother’s “ability,” as measured by AFQT, account for about half of the test score gap. Home inputs also account for a significant proportion. Equalizing home inputs at the average levels of white children would close the black‐white and the Hispanic‐white test score gaps in math and reading by about 10–20 percent.

***

The Evolution of Income and Fertility Inequalities over the Course of Economic Development: A Human Capital Perspective

Isaac Ehrlich

State University of New York at Buffalo and National Bureau of Economic Research

Jinyoung Kim

Korea University

Using an endogenous‐growth, overlapping‐generations framework in which human capital is the engine of growth, we trace the dynamic evolution of income and fertility distributions and their interdependencies over three endogenous phases of economic development. In our model, heterogeneous families determine fertility and children’s human capital, and generations are linked via parental altruism and social interactions. We derive and test discriminating propositions concerning the dynamic behavior of inequalities in fertility, educational attainments, and three endogenous income inequality measures—family‐income inequality, income‐group inequality, and the Gini coefficient. In this context, we also reexamine the “Kuznets hypothesis” concerning the relation between income growth and inequality.

***

Enjoy!

best wishes,

Oskar

Sociobiology revisited: a new paper by Wilson and Wilson

2007-12-17T15:11:00.000-08:00

An interesting review paper about multi-level selection was just made available (forthcomming) in the Quarterly Review of Biology by D S Wilson and E O Wilson. It's an interesting read. Here's the citation info and abstract:

RETHINKING THE THEORETICAL FOUNDATION OF SOCIOBIOLOGY

David Sloan Wilson

Departments of Biology and Anthropology, Binghamton University Binghamton, New York 13902 USA dwilson@binghamton.edu

Edward O. Wilson

Museum of Comparative Zoology, Harvard University Cambridge, Massachusetts 02138 USA

KEYWORDS

altruism, cooperation, eusociality, group selection, human evolution, inclusive fitness theory, kin selection, major transitions, multilevel selection, pluralism, sociobiology

ABSTRACT

Current sociobiology is in theoretical disarray, with a diversity of frameworks that are poorly related to each other. Part of the problem is a reluctance to revisit the pivotal events that took place during the 1960s, including the rejection of group selection and the development of alternative theoretical frameworks to explain the evolution of cooperative and altruistic behaviors. In this article, we take a “back to basics” approach, explaining what group selection is, why its rejection was regarded as so important, and how it has been revived based on a more careful formulation and subsequent research. Multilevel selection theory (including group selection) provides an elegant theoretical foundation for sociobiology in the future, once its turbulent past is appropriately understood.

The Quarterly Review of Biology, December 2007, vol. 82, no. 4

They are careful about defining their terms. Here are some useful definitions:

"sociobiology is the study of social behavior from a biological perspective, group selection is the evolution of traits based on the differential survival and reproduction of groups..."
"From an evolutionary perspective, a behavior can be regarded as social whenever it influences
the fitness of other individuals in addition to the actor."
"Group advantageous traits do increase the fitness of groups, relative to other groups, even if they are selectively neutral or disadvantageous within groups. Total evolutionary change in a
population can be regarded as a final vector made up of two component vectors, within and between-group selection, that often point in different directions."

They make a point that words like 'sociobiology' and 'evolutionary psychology' have become "tainted" due to their negative associations and bad reputations in many fields. This is of course especially true in the social sciences. I have almost never heard an anthropologist use sociobiology in a positive or even neutral context (only very negative - 'oh that stuff - we know better than that') but the vast majority of anthropologists would think of sociology as a field arguing that genes cause every observable trait we might observe - a much more extreme view than that used by its actual practitioners (above in the definitions).
In a similar vein, anything related to 'group selection' carries the connotation of being an automatically naieve argument even in fields where Darwinian analysis is accepted. I am mostly a behavioral ecologist (studying macroecological patterns) and I have been guilty of this. In many cases, arguments about group selection involve people speaking past each other and missing the point, this is why Wilson and Wilson often use the term 'multi-level selection' instead. We can show that altruism is costly to a perfectly self-interested actor but that a group of altruists out-competes a group of selfish social defectors. If we are comparing groups (populations) and focus only on individual-level benefits we may indeed miss part of the picture, but on the other hand the individual does a lot better in the group that doesn't get killed off by the more altruistic group. So the tension between the two views is not always necessary. Wilson and Wilson look at cases like the evolution of eukaryotic cells and argue that group selection must have been present to get the once autonomous entities (prob some form of early bacteria) to cooperate so closely in a tightly knit network of symbiotic mutualisms that they became organelles in the same cell.

So group selection must be common, they argue. Consider this view: "If a trait is locally disadvantageous wherever it occurs, then the only way for it to evolve in the total population is for it to be advantageous at a larger scale." Is altruism really locally disadvantageous though?

Getting back to relationships between groups, if we want to talk about why different populations spread at the expense of others then I think population level fitness measures are necessary and quite uncontroversially logical. George Williams himself proposed measures of population level fitness in his 1966 treatise against the brand of group selection proposed by Wynn-Edwards and others. [One of these measures was population density or size which he thought was not as good as the second measure, the numerical stability of the population through time, but this has much larger data requirements. These discussions are definitely relevant for our discussions of human evolution.] Wilson and Wilson also point out that there is room for multi-level selection in Williams' view, he only underestimated how frequently it could be important.

They are very careful to separate cogent arguments of multilevel selection from those they label naive group selection. The level of selection needs to be appropriate for the analysis being conducted. My feeling is that we can't categorically reject arguments of selection at the level of genes, individuals, families, other groups, maybe even species in some restricted geological cases like the study of mass extinction, and maybe higher levels like ecological network structures. Here's a nice quote they bring to this issue:
"In biological hierarchies that include more than two levels, the general rule is “adaptation at any level requires a process of natural selection at the same level and tends to be undermined by natural selection at lower levels.” All students of evolution need to learn this rule to avoid the errors of naı¨ve group selectionism. Notice that, so far, we are affirming key elements of the consensus that formed in the 1960s."

Humans are used as an example in many cases in the paper.
"The importance of genetic and cultural group selection in human evolution enables our groupish nature to be explained at face value. Of course, within-group selection has only been suppressed,
not entirely eliminated. Thus multilevel selection, not group selection alone, provides a comprehensive framework for understanding human sociality."

There seems little question that understanding how selection may play out at higher levels will be necessary for explaining how anatomically modern humans came to spread and conquer the globe. But we do need to be cautious with how such arguments are invoked.

This paper is extremely well written and thought provoking. I recommend checking it out.
Best,
Oskar

Complex Systems Summer School 2008

2007-12-15T15:07:00.000-08:00

The Santa Fe Institute is now looking for applications for next year's complex systems summer school. I attended the international school in Beijing 2005 and loved it (went back the next year as staff). I recommend it for folks interested in complex systems research from any perspective.

Here's the basic information on the school and how to apply (this is just the text of the email they send to alumni to help circulate the announcement):

_____

Complex Systems Summer Schools

Summer 2008

The annual Complex Systems Summer Schools provide an intensive introduction to complex behavior in mathematical, physical, living, and social systems for graduate students and postdoctoral fellows. Schools will be held in Santa Fe, New Mexico and Beijing, China. Applications are now available at http://www.santafe.edu/csss08.html.

Program Details

Santa Fe: June 1-28, 2008 at St John’s College in Santa Fe, New Mexico, USA. Directed by Dan Rockmore, Dartmouth College and Santa Fe Institute (SFI); administered by the Santa Fe Institute (SFI).

Beijing: June 30-July 25, 2008. Sponsored by SFI in cooperation with The Institute of Theoretical Physics, the Chinese Academy of Sciences (CAS). Co-directors: Dr. David P. Feldman, College of the Atlantic and SFI, and Dr. Chen Xiao-song, Institute for Theoretical Physics, CAS.

General Description

The Complex Systems Summer School offers an intensive four-week introduction to complex behavior in mathematical, physical, living, and social systems for graduate students and postdoctoral fellows in the sciences and social sciences. The schools are for participants who want background and hands-on experience to help prepare them to do interdisciplinary research in areas related to complex systems.

Each school consists of an intensive series of lectures, laboratories, and discussion sessions focusing on foundational ideas, tools, and current topics in complex systems research. These include nonlinear dynamics and pattern formation, scaling theory, information theory and computation theory, adaptation and evolution, network structure and dynamics, adaptive computation techniques, computer modeling tools, and specific applications of these core topics to various disciplines. In addition, participants will formulate and carry out team projects related to topics covered in the school.

Further details about topics and faculty at each school will be posted

as they become available.

Eligibility

Applications are welcome from all countries. Participants are expected to attend one school for the full four weeks. All activities will be conducted in English at both schools. No tuition is charged, and some support for housing and travel expenses is available. Enrollment is limited.

Applications are solicited from graduate students and postdoctoral fellows in any discipline. Some background in science and mathematics (including multi-variate calculus and linear algebra) is required. Proficiency in English is also required.

Students should indicate school location preference when applying. Placements may be influenced by restrictions in U.S. foreign visitor policies.

Application Requirements

1. Current resume or CV. Include a clear description of your current educational or professional status, and a list of publications, if any.

2. A statement of your current research interests and comments about why you want to attend the school (suggested length: one to two pages).

3. Two letters of recommendation from scholars who know your work.

How to Apply

Online: Our online application form allows you to submit all of your materials electronically (including a feature which allows your recommenders to upload letters of recommendation directly to your file). We strongly encourage you to apply online to expedite your application.

Postal Mail/Courier: Applications sent via postal mail will also be accepted. Include a cover letter providing your e-mail address and fax number, and specifying whether you wish to be considered for a travel scholarship. (This will not influence the review of your application.) Do not bind your application materials in any manner. Send application materials to:

Summer Schools

Santa Fe Institute

1399 Hyde Park Road

Santa Fe, NM 87501 USA

If applying via post, letters of recommendation may be sent separately to the address above, or included in your application package in sealed envelopes.

DEADLINE

All application materials, including letters of recommendation, must be received at SFI or electronically submitted no later than January 7, 2008.

Women, minorities, and students from developing countries are especially encouraged to apply.

If you have further questions about the Complex Systems Summer Schools, please e-mail goodwin@santafe.edu

Human Macroecology on Facebook

2007-12-13T16:33:00.000-08:00

I've created the "Human Macroecology" group on Facebook to help us keep in contact. Join if you dare.

Island Rule Paper

2007-12-07T09:39:00.000-08:00

Ok, I am admittedly way behind on this, as the paper I'm now blogging about came out over a week ago but given that we've posted about the Island Rule in here before, I'd feel remiss if we didn't cover a paper arguing that this well known rule from biogeography is a statistical artifact. If you are wondering why human ecologists should care about the Island Rule, that is also addressed in the previous post. So, this paper was published in the Proceedings of the Royal Society:

title: The island rule: made to be broken?

authors: Shai Meiri, Natalie Cooper, and Andy Purvis

abstract: The island rule is a hypothesis whereby small mammals evolve larger size on islands while large insular mammals dwarf. The rule is believed to emanate from small mammals growing larger to control more resources and enhance metabolic efficiency, while large mammals evolve smaller size to reduce resource requirements and increase reproductive output. We show that there is no evidence for the existence of the island rule when phylogenetic comparative methods are applied to a large, high-quality dataset. Rather, there are just a few clade-specific patterns: carnivores; heteromyid rodents; and artiodactyls typically evolve smaller size on islands whereas murid rodents usually grow larger. The island rule is probably an artefact of comparing distantly related groups showing clade-specific responses to insularity. Instead of a
rule, size evolution on islands is likely to be governed by the biotic and abiotic characteristics of different islands, the biology of the species in question and contingency.

So the issue in this and lots of studies that look at body size related trends is whether or not species can be treated as independent data points or whether adjustments have to be made for the phylogenetic relatedness of the species. That is, a bunch of species could exhibit a similar trend in something simply because they are closely related and if this is not adjusted for then we run the risk of identifying trends that we think are related to body size but are really just due to genetics/ancestry. Let's pretend that there are 3 camps on this issue - those that think you always have to adjust for phylogeny, those that think you have to sometimes, and those that think you never do. The authors of this paper would be in the first group, I would be in the second. Issues of statistical independence may indeed be under-appreicated in cross-species analysis of the sort common in biogeography and in studies of allometry. But as Jim Brown has pointed out (in informal lab-meeting type settings) it is not always clear exactly what things need to be controlled for in any given analysis. So, sure, for some things phylogeny might be the most important but in others it could be something like biome or some attribute of the niche that is occupied - or some general feature of ecology. There could potentially be a lot of uncontrolled confounds out there... How do we know which ones are most important, especially when we rarely have data on all of the potential variables we might want to examine?

So, this paper specifically argues that the trends that we think are behind the Island Rule are due to lineage specific responses to island colonization. That due to some issue of shared ancestry different but related species consistently respond similarly to island environments with respect to body mass change simply because they are related and not because of any general relationship between the mass of a colonizing organism and the island environment. The authors point out that none of the papers that have previously looked at the Island Rule have considered the role of phylogeny. After using methods that control for phylogeny, they state that:
"We did not find convincing evidence that larger size leads to insular size reduction within mammals in general (using independent contrasts) or within clades. Neither do we find that, as a rule, large mammals dwarf on islands nor that small mammals grow large..."

I'll also include a quote from their methods:
"We used only those studies that reported body size of mainland populations geographically closest to the island in question (Lawlor 1982). Some insular populations have their nearest
sister taxon on a mainland areawhich is a considerable distance away (e.g. Hafner et al. 2001). The paucity of good intraspecific phylogenetic data, however, precludes us from identifying the
closest relatives for most insular populations and we therefore use geographical distance to approximate phylogenetic affinity."

The issue of when we can and when we can't use species as data points won't be fully resolved any time soon. I'm sure that this paper will lead to some careful attention to this issue in the biogeographic community.

Cheers,
O

Next year's human ecology conference

2007-12-05T16:34:00.000-08:00

The call for participation in next year's human ecology conference has just recently been announced. The theme for this meeting seems quite relevant for a lot of the things we've discussed this semester (and is also on something we didn't spend much time on) and I encourage interested parties to think about attending or even presenting. The conference proposes to focus on "Integrative thinking for complex futures: creating resilience in human-nature systems." The conference is the official meeting of the Society for Human Ecology. Information about the call for papers and the theme of the conference are posted in .pdf format.
cheers,
O

New scaling paper: Organisms as 4 dimensional objects

2007-12-04T12:34:00.000-08:00

A new paper has just been released as forthcoming in American Naturalist that takes a novel and curious approach to scaling in ecology and evolution. I'll elaborate on the paper below but first a bit of context:

We've talked some about scaling relationships and why they emerge but haven't gotten too much into the details of the theories attempting to explain why certain scaling properties exist. These fall into two camps, life history models that usually take certain extrinsic properties as givens and more complicated physical models that attempt to explain why metabolic rate is body mass to the 3/4 power from first principles of energetics and geometry. Examples of life history models predicting the allometries for traits like birth rate, mortality rate, age at first reproduction, and life span are those of Charnov (1991, 1993, 2001). These tend to take factors like the production function (growth rate is some constant a*mass^(3/4)) as a given and predict the other allometries, which tend to be +1/4 powers for times (life span, generation length, etc) or -1/4 powers for rates (birth rate, mortality rate, intrinsic rate of increase r, etc.). These models often have mortality rate as an external environmental parameter, but not always, and often take size at independence as a given (which is a linear function of adult mass and this predicts the -1/4 power scaling of fertility rate). One very successful geometric model is presented in West et al. (1997, 1999) and demonstrates that the 3/4 scaling of metabolic rate results from an optimal solution to the problem of efficiently constructing biological resource distribution networks that must deliver resources to all the cells in an organism while satisfying certain design characteristics. That is, the network should efficiently fill space and deliver resources to cells as effectively as possible. This problem generates a fractal distribution network that optimally fills space and generates a predicted 3/4 power of metabolic rate with mass. The 'networks' we are referring to in this context are vascular systems in plants and circulatory systems in animals. (This treatment is shockingly rudimentary but hopefully good enough for present purposes).

This paper by Lev Ginzburg and John Damuth takes a different view on scaling relationships in ecology by looking at the dimensionality of organisms. First, here's the citation info and abstract. I'll continue to comnent below.

The Space‐Lifetime Hypothesis: Viewing Organisms in Four Dimensions, Literally

Lev Ginzburg^1, and

John Damuth^2,

1. Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794;

2. Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, California 93106

Abstract:

Much of the debate about alternative scaling exponents may result from unawareness of the dimensionality appropriate for different data and questions; in some cases, analysis has to include a fourth temporal dimension, and in others, it does not. Proportional scaling simultaneously applied to an organism and its generation time, treating the latter as a natural fourth dimension, produces a simple explanation for the 3/4 power in large‐scale interspecies comparisons. Analysis of data sets of reduced dimensionality (e.g., data sets constructed such that one or more of the four dimensions are fixed), results in predictably lower metabolic exponents of 2/3 and 1/2 under one and two constraints, respectively. Our space‐lifetime view offers a predictive framework that may be useful in developing a more complete mechanistic theory of metabolic scaling.

The authors argue that organisms can literally be viewed as four dimensional objects, three spatial and one temporal. While many traits scale with body size, they specifically focus on the well-known finding that metabolic rate scales as the +3/4 power of body mass whereas lifespan goes as the +1/4 power. This makes the product of the two an isometric relationship (m^3/4 x m^1/4 = m¹), such that a doubling in an organism’s size predicts a doubling in the energy it metabolizes in a lifetime. While many researchers take this as a consequence of other scaling relationships, it plays a fundamental role in the 4D view. As they state it, “these observations suggest instead that the scaling of lifetimes may reflect a fundamental manner in which organisms of all body masses are ecologically and evolutionarily functionally similar.” Thus the organism’s four dimensions, three spatial (length, area, volume) and one temporal (generation time) together give m¹. If these four dimensions are evenly divided into the isometric scaling of lifetime metabolic rate then each will be m^1/4. This predicts that metabolic rate should be m^3/4because energy is taken in through a 3D surface and then allocated to processes that take place in 4D (the dimension of time and within the 3 dimensional space of the organism). And if metabolic rate is m^3/4, the remaining dimension, generation time (or lifespan), should be m^1/4 to preserve the isometric scaling lifetime metabolic rate.

The role of generation time in ecology and evolution itself is another key component of the 4D argument: “Constructing one viable and reproductively capable daughter requires a certain duration (a “generation time”) that is conveniently viewed as an organism’s fourth dimension. So, on average, it takes a generation time of metabolism for a mother to guarantee the existence of her replacement.” This establishes the reasoning for why generation time is fundamentally an organism’s fourth dimension.

Where this argument becomes even less conventional is in the stated lack of a mechanism. In fact, my reading of the paper is that they intend the argument to predict the set of criteria to which any proposed mechanistic explanation of ¾ power scaling in biology must conform. For instance, they can predict that progressive reductions in dimensionality, by holding constant generation time, length, etc. should lead to predictable reductions in the exponent. So if generation time is held constant then they predict that metabolic rate should be a 2/3 power of mass, rather than ¾, and cite examples where within species metabolic rates have been shown to go as the 2/3 power of mass (if length and generation time are held constant, as with species of same size and lifetime, the scaling should be ½, etc.). They do this with multiple regressions. For instance, they predict that if height and generation length are controlled for, then metabolic rate should scale as the 1/2 power of mass and their data seem to conform to this prediction.

Because they do not suggest a mechanism, they are not necessarily at odds with any particular theory of metabolic scaling, such as that of the space-filling fractal geometry of supply networks in the circulatory and vascular systems of mammals and plants (e.g., West et al. 1999 - mentioned above). The explicitly non-mechanistic argument in the paper adds to its uniqueness but is also where some people may have the greatest trouble with the paper, as we are taught to focus on mechanisms and this nature of dimensional thinking is much more foreign to us (and maybe difficult to interpret at first). The theory makes simple and elegant predictions that should lead readily to either coherence or conflict with some of the existing takes on the topic (note that I'm saying the predictions are simple and elegant but am not saying anything about whether the empirical results are broadly accurate. Its of course too soon to see if how these predictions will weather the tests of time. They do give some good empirical support in the paper). Either way, dimensional thinking is a novel approach in this area that, when combined with the argument for the importance of generation time, makes a fundamental contribution to the literature and will certainly alter future approaches to the subject of scaling in ecology.

Well, something to think about anyway.

Oskar

New paper "Global climate change, war, and population decline in recent human history"

2007-11-28T21:43:00.000-08:00

(Published before print by Zhang et al. in PNAS, vol. 104, no. 49)

A successful example of macroscopic and interdisciplinary approaches to human ecology. Their abstract provides a nice appetizer:

"Although scientists have warned of possible social perils resulting
from climate change, the impacts of long-term climate change on
social unrest and population collapse have not been quantitatively
investigated. In this study, high-resolution paleo-climatic data
have been used to explore at a macroscale the effects of climate
change on the outbreak of war and population decline in the
preindustrial era. We show that long-term fluctuations of war
frequency and population changes followed the cycles of temperature
change. Further analyses show that cooling impeded agricultural
production, which brought about a series of serious social
problems, including price inflation, then successively war outbreak,
famine, and population decline successively. The findings
suggest that worldwide and synchronistic war–peace, population,
and price cycles in recent centuries have been driven mainly by
long-term climate change. The findings also imply that social
mechanisms that might mitigate the impact of climate change were
not significantly effective during the study period. Climate change
may thus have played a more important role and imposed a wider
ranging effect on human civilization than has so far been suggested.
Findings of this research may lend an additional dimension
to the classic concepts of Malthusianism and Darwinism."

Enjoy!
Jordan

Toward a human macroecology

2007-11-28T16:07:00.001-08:00

“Students will view human ecology from the complementary perspectives of biogeography and macroecology, showing patterns across space and time, and system dynamics, focusing on ways energy, materials, and information are processed and transformed in social systems.” From the Perspectives in Human Ecology course syllabus

In fact, we have looked at human ecology through several lenses: life history, biogeography, and systems theory. A glance through a photography magazine shows the power of different perspectives, often achieved using different lenses: magnifying, light-filtering, UV illuminating, and so on. Are the perspectives through which we’ve viewed human ecology truly complementary? Can we layer them to produce a distinct, penetrating vision of the human condition?

More specficially, do such seemingly disconnected patterns as the decrease in stature with population density (R. Walker), the latitudinal cultural diversity gradient (Collard & Foley), the organization of Balinese water temple networks (Lansing & Kremer), the demographic transition (Moses & Brown), and the scaling relations of cities (Bettencourt et al.) share a common currency? If so, what is the underlying economy of human nature?

In what ways is human macroecology, to name our overarching approach, a productive perspective, as Turchin would say? Does it clarify and reveal patterns and connections that other perspectives do not? What is its scope? What are its strengths and weaknesses? How might we improve it or alter it? And what are its evolving frontiers?

Finally, given Ginzberg’s caveats about natural laws—that we should not expect them to be exceptionless, inevitably predictive, and even explanatory or discerning of cause and effect—are there candidate “laws of human ecology?”

Contribute your thoughts to the blog, and come prepared to discuss them in class tomorrow.

Looking forward to our synthesis….

Bill

UNM Statistics Clinic

2007-11-27T12:02:00.000-08:00

This may be helpful to some of you doing empirical work for your papers. I just found out that Math&Stat department offers a statistics clinic that's free to UNM students, staff, and faculty.

Week 15: Human Macroecology and Historical Dynamics/Course Wrap-up

2007-11-23T10:41:00.000-08:00

Greetings All,
This week we are reading a chapter from Peter Turchin's book, War and Peace and War: The Rise and Fall of Empires (2006). The chapter, War and Peace and Particles, outlines Turchin's approach to the study of human history. We are not reading this to understand history or how it should be studied, although we will likely discuss this some, but rather to notice any similarities between human macroecology and the perspective on history that Turchin is trying to build and define. Turchin's arguments relate to some of the things we've discussed about laws and emergent phenomena and his approach to the relationship between individual actions and macroscopic patterns provides an excellent frame for some of our past discussions.
The Chapter we are reading is the beginning of part 3 of the book, which has the goal of defining this scientific approach to the study of history that he calls "cliodynamics." The book is written for a general audience and is generally very well written and easy to follow. However, two terms are mentioned briefly in this chapter, metaethnic frontier and asabiya, that are central to Turchin's theory of historical dynamics. I am elaborating on the definition of these terms and including two excerpts from earlier chapters of his book for the sake of clarity and context on how he uses them

Metaethnic frontiers are defined on pages 5 - 6 (of Turchin 2006) and this leads directly to the role of asabiya in historical dynamics.
The concept of metaethnic frontier emphasizes the importance of ethnicity as a marker of boundaries between groups, be they based on language, rituals, or symbols of dress and custom. Ethnicities are usually nested within each other and single empires may dominate multiple ethnicities, which then may or may not come to share a feeling of solidarity for the empire. Turchin further explains his use of the term as follows:
"The broadest groupings of people that unite many nations are usually called civilizations, but I prefer to call such entities metaethnic communities (from the Greek meta, 'beyond,' and ethnos, 'ethnic group' or 'nation'). My definition includes not only the usual civilizations - the Ester, Islamic, and Sinic, - but also such broad cultural groupings as the Celts and Turco-Mongolian steppe nomads. Typically, cultural difference is greatest between people belonging to different metaethnic communities; sometimes this gap is so extreme that people deny the very humanity of those who are on the other side of the metaethnic fault line.
Historical dynamics can be understood as a result of competition and conflict between groups, some of which dominate others. Domination, however, is made possible only because groups are integrated at the micro level by cooperation among their members. Within-group cooperation is the basis of inter-group conflict, including its extreme versions such as war and even genocide.
Different groups have different degrees of cooperation among their members, and therefore different degrees of cohesiveness and solidarity. Following the fourteenth-century Arab thinker Ibn Khaldun, I call this property of groups asabiya. Asabiya refers to the capacity of a social group for concerted collective action. Asabiya is a dynamic quantity; it can increase or decrease with time. Like many theoretical constructs, such as force in Newtonian physics, the capacity for collective action cannot be observed directly, but it can be measured from observable consequences."

[A metaethnic frontier is a frontier or border between different metaethnic communities.]

The concept of asabiya is "the capacity for social action." The propensity for a group to have asabiya is key to understanding the results of conflicts between empires. It is a central topic in this book and Turchin's earlier monograph on the topic of historical dynamics (Historical dynamics: why states rise and fall). Turchin finds the human potential to cooperate as a crucial social capacity, as it leads to a willingness to make huge sacrifices for the good of some broader social unit.
Asabiya as a concept is thoroughly defined on page 91 as follows:
"The concept of collective solidarity, or asabiya in Arabic, was Ibn Khaldun's most important contribution to our understanding of human history. The theory is described in his monumental The Muqaddimah: An Introduction to History. Asabiya of a group is the ability of its members to stick together, to cooperate: it allows a group to protect itself against the enemies, and to impose will on others. A group with high asabiya will generally win when pitched against a group of lesser asabiya. Moreover, 'royal authority and general dynastic power are attained only through a group and asabiya. This is because aggressive and defensive strength is obtained only through... mutual affection and willingness to fight and die for each other.' In other words, a state can be organized only around a core group with high asabiya. By acting in a solidary fashion, the members of the core group impose their collective will on other constituents of the state and thus prevent the state from falling apart.
But it is not enough to identify group solidarity as the main factor responsible for the strength of the state. Why do some groups have it in abundance, whereas others do not?"

So there's some background on Turchin's goals and use of these terms. We of course are focusing more on the nature of his perspective than specific understandings of history but both are certainly open for discussion.

Like last week there is no annotation for this week but please post a couple of questions and/or comments about War and Peace and Particles on this blog.

************************************************************************************
Some course-related details to keep in mind:
The next two class periods are the wrap-up for the content of the course. On Tuesday (11/27/07) we discuss Turchin and use it as a springboard for Thursday (11/29/07) when we define human macroecology, its goals, techniques, future prospects and limitations. On Thursday we will outline a blog entry and wikipedia article on human macroecology.
As a reminder, please also revisit the readings from the very first week. It may be the case that your take on this first assignment has changed a good deal and it will also be useful for discussion.

Next, we have student presentations. These are the last two class periods of the semester (12/04/07 and 12/06/07). These are informal presentations that have to be less than ten minutes each. Each presenter can get a max of 4 slides which must be emailed to us before hand. We'll have the slides ready for the order of the speakers. The order will be determined with a sign-up sheet on Tuesday of this week.

The presentations are of course about the content of your final papers. These are due on the Wednesday of finals week at 12:00 noon (that's 12/12/07 at 12!).

Another item is the final conversation or oral dialog. This is effectively a final exam where we will ask about your impressions of topics during the course as well as test your comprehension of the major themes of the semester and the arguments of the papers. These will be on the Monday, Tuesday, and Wednesday of finals week and we'll figure out specific exam times with a sign-up sheet in class.

As always, please let us know if you have any questions.

Cheers,
Oskar

Gapminder video

2007-11-20T10:26:00.000-08:00

Hey everyone,
Great discussion today. As always there was a lot more we could have talked about, both in terms of the scientific perspectives involved and the implications of the arguments in the papers. As the semester wraps up, spend some time thinking about what this class is all about and how you might apply what we've learned to your own interests. What were the main points, implications? We ended up going over sustainability some and how to manage human economies. But lets not forget about the macroscopic viewpoint and the mechanistic approach to understanding underlying rules that govern some of the complexity of human systems. Keep in mind that claims of absolute human uniqueness are abundant in many fields of study, yet in many cases human systems seem to exhibit behaviors that are extensions of other natural systems (but not always). Some of you will focus more on the applied aspects of the work we've covered and some on the macroecology of scaling, complexity, and life history we've gone over. Hopefully these themes come together and we are all simultaneously more responsible broad thinking scientists and students-at-large.
But this is all a digression that leads to the video below. I realize that many of you may not have spent a lot of time on the links I posted the other day. I really recommend visiting the gapminder site. Its informative and plays on a lot of themes that we've covered. I'm posting one particular speech by Hans Rosling but I could have chosen any of a number on his website. This one is particularly entertaining and information filled - and has some messages toward the applied end of big picture thinking. This speech is a bit long so set aside a few minutes (and I wouldn't try to watch it on a slow connection). Also note that all of the graphical stuff he does at the beginning of the talk is part of the interactive software on the website so you can all play with it.
Have a good break,
O

Week 14: Economics of energy in human systems

2007-11-15T12:16:00.000-08:00

Hey everyone,
Please read the following paper for next week:

Hall et al. 2001. The need to reintegrate the natural sciences with economics. Bioscience 51: 663-673.

(recommended) Smil, V. 2000. Energy in the twentieth century: Resources, conversions, costs, uses, and consequences. Annual Review of Energy & Environment 25: 21-51. (at least look at graphs and highlighted sections, for which will need latest version of Adobe reader)

Figures: Electricity use for night-time
lighting at global, national, and
local (Albuquerque) scales
(click on figures for larger view)

Note: No annotations due this week (Thanksgiving week), but please post your blog comments.

**********************************************
Like organisms, human societies run on energy, and their energy use and characteristics scale with their size. At a minimum, societies need enough energy to fuel the bodily metabolisms of its members. As traditional foragers aggregate into larger groups, they require proportionately less land, suggesting that larger societies, like larger animals, metabolize energy more efficiently (Hamilton et al., 2007b). As people aggregate further, forming large urban settlements, their per-capita infrastructure costs continue to fall with population size, while their gross productivity and creative output rise (Bettencourt et al., 2007). As the average energy use of people along this spectrum increases, they tend to invest more energy in fewer offspring (Moses & Brown, 2003). In essence, a metabolic view of societies illuminates modern changes in human life-history tradeoffs at an individual level and, arguably, at a societal level.

This week, we will examine the role of energetic resources in fueling social metabolism and growth and on accounting for the central role of energy in human economies. It’s not required, but read the highlighted portions and graphs of Smil, 2000, if you have time. Smil, presents an eye-opening history of modern fuel use that shows the central role of external energy in fueling modern human society and social transformations & transitions. How might Smil’s account relate to Tainter’s ideas about high and low gain systems, Hollings ideas on adaptive cycles, and a general “systems” perspective on human ecology?

In arguing for integrating nature’s constraints into mainstream economics, Hall et al., 2001, provides a springboard for embedding hierarchical socio-economic systems within broader biophysical systems. Fig 2 presents a good view of this idea. We chose Hall not to launch a polemic against standard economics but rather to stimulate discussion on widening our systems perspective to include nature’s economy, especially the role of energy. From a geographic perspective, how do energy sources “map on” to the distribution of humans on the globe? Is a Diamondesque view helpful, that the geography of energy sources influences patterns of wealth and development? How are these sources distributed, both originally and through redistribution networks, and what are the implications?

Hall et al., 2001, also raise the issue of integrating ecology and economics, which have natural parallels and paradigms. Both ecology and economics come from the Greek “oikos,” meaning “house.” They share similar ideas of “capital” as wealth, monetary wealth in economics and the “embodied capital” of the body and its abilities in human evolutionary ecology. Ecology’s food webs are clearly akin to human economies of buyers, sellers, firms, and so on. And optimization plays key roles in life history theory (i.e. fitness maximization) and economic theory (i.e. utility maximization). A well-known ecology textbook encapsulates the ideas that natural systems run on energy and use it efficiently in its title, The Economy of Nature. As Brown et al. discuss in “The fractal nature of nature,” a scaling perspective of human ecology makes the same argument.

Given how wide-ranging the idea of valuing natural resources generally*, I’d rather focus on energy and build explicitly on our conceptual foundations in systems theory, scaling, and life history. Economists Herman Daly, Partha Dasgupta, Robert Constanza, and Kenneth Arrow, among others, have written extensively on the importance of proper valuation of natural resources and the related concept of sustainability. From ecology, H.T. Odum pioneered an energetic perspective, and C.S. Holling, Carl Folke, Lance Gunderson, and Stephen Carpenter have further developed “systems ecology” with humans and energy in mind.

We’re considering the value of a systems perspective of human ecology. How does it differ from traditional views? This macroscopic view uses scaling and hierarchy theory to backlight the often invisible networks that move and connect genes, energy, and information. It uses complexity theory to understand how nodes in these networks, such as actors on an agricultural landscape, use simple rules to generate emergent, systemic behavior. And it effectively uses economic theory to see how costs, benefits, and trade-offs connect individual decisions to global outcomes.

Looking forward to our discussion,

Bill

* See Daily et al. 2000. The value of nature and the nature of value. Science 289: 395-396 for a good general discussion of valuing ecosystem services written by a “who’s who” of ecologists and economists.

** If you're curious, here's a link to the New Mexico state profile from the U.S. Energy Information Administration, which has a wealth of information: http://tonto.eia.doe.gov/state/state_energy_profiles.cfm?sid=NM

New web-related resources

2007-11-15T11:48:00.000-08:00

What's up everybody.
I've been meaning to add a few new blogs and links to the sidebar for some time and I'm just doing this now to point them out.
A couple of folks told me about this New York Times page on environmental issues. Its worth checking out.
Also from New York Times - next time you want to accidentally spend a few hours of your life in cyberspace, the Freakonomics blog is addictive, entertaining, and you can even learn stuff.
Another really good (and popular) link that I've been meaning to put up for a while, right here on blogspot, is the Dieneke's Anthropology Blog.
And last but not least, our very own British human macroecologist living in Mexico, has just updated his personal website with info about his research and whatehaveyou. Check out Marcus Hamilton's new site here.

I hope you take advantage of these and the other links on this site as they are fun and efficient ways to get good information, or at least some fairly intellectual entertainment.

Best wishes,
O

PS! And this just came to my attention. This is one of the coolest web resources I've ever seen. Maybe the coolest for anyone with an interest in big picture patterns of human demography. I highly recommend you all spend some time at gapminder.org.

2007-11-12T12:49:00.000-08:00

Hello human ecologists. I must say, I’ve been watching this blog from afar (well, from Mexico) with a fair amount of awe at the range of material you’ve been covering. I wish I’d had a class like this! For that matter I wish all anthropologists and ecologists had a class like this.

So, here’s a bit of background for the Hamilton et al. 2007 Proc Roy Soc Lond Ser, B paper you’re reading as one of the papers this week. This paper, and its companion, Hamilton et al. 2007 PNAS 104, arose from spending a lot of time with Oskar, going to the Biocomplexity Seminar a few years ago (now defunct) and hearing week after week about metabolic scaling theory and complex biological systems. After several months of trying to get my head around what it all meant, it suddenly occurred to me that if all these simple scaling laws lead to all this emergent complexity (and simplicity) in ecological systems, due to the fundamental constraints of physics, chemistry, thermodynamics etc, then the same must be true for human systems as we too are simply another biological species making a living within complex ecosystems. That is to say, as ecosystems are structured by the flows of energy, matter, and information between organisms and their environments, and these flows lead to scaling laws and complex structures, then human systems should display the same kinds of attributes. This should be true especially for those human systems that are arguably most subject to ecological heterogeneity, hunter-gatherers.

A couple of years prior, Louis Binford (2001) had published a large volume of research on hunter-gatherers, mainly from an archaeological perspective. But in that book he included tons of data on a worldwide sample of hunter-gatherer societies (n = 339) he had compiled, including simple metrics such as population size, territory size, and group size estimates at various levels of organization, as well as all kinds of ecological and environmental variables. So I asked the question, are hunter-gatherer societies complex adaptive systems? That is, is there something about their structure at one level, some emergent property, that arises from some underlying principle that feeds-back to impact individual fitness? So the first thing I noticed was what ended up in the Royal Society paper: There is a striking geometric scaling of group size (or strictly speaking, group size frequencies) across all levels of organization, and this is a classic pattern found in all kinds of complex systems (i.e., a hierarchical, modular, self-similar branching structure). This pattern denotes statistical self-similarity, and these fractal structures are found throughout nature from metabolic networks to the structure of river basins.

The second question was then, what kind of effect could this structure have on some measure of population efficiency? But more importantly, how might I measure this? This was answered by plotting population size as a function of territory size recognizing that the area a population uses is roughly equivalent to its energy catchment area. Because the scaling relation we found was sublinear, this means that population size increases faster than energy use (territory size), so larger populations are more energetically efficient than smaller ones. Moreover, the scaling relation we found, ~3/4, was suspiciously similar to the scaling of metabolic processes found throughout living systems. Therefore, hunter-gatherer social systems seem to show signs of a “social metabolism”, for what seemed to be the same reason as other biological systems, namely a fractal-like branching distribution network.

So this sublinear scaling (~0.75) demonstrates an economy of scale in hunter-gatherer socio-economies. Note that in the Bettencourt et al. paper (very cool paper), they find similar scalings for economies of scale in urban systems, ~0.8, yet they don’t suggest a mechanism. Might we have a universal scaling law for human economies of scale, from hunter-gatherers to urban economies? Watch this space...

Marcus

Week 13: Scaling part 2

2007-11-09T16:57:00.000-08:00

The following papers are required readings for next week. A few optional papers are in the ereserves folder as well.

*Hamilton M. et al. 2007. The complex structure of hunter-gatherer social networks. Proceedings of the Royal Society of London, Series B.

* Bettencourt, L. M. A., J. Lobo, D. Helbing, C. Kuhnert, and G. B. West. 2007. Growth, innovation, scaling, and the pace of life in cities. Proceedings of the National Academy of Sciences 104:7301.

*Moses, M. E., and J. H. Brown. 2003. Allometry of human fertility and energy use. Ecology Letters 6:295-300.

"Nets versus Nature": an interesting News and Views

2007-11-07T23:23:00.000-08:00

David Conover writes an interesting News and Views piece in the current Nature about a paper published this week in PNAS (here). Here's what he has to say about it:

"People like to catch big fish, sometimes so much so that fish sizes overall become greatly diminished. According to one view, the continual removal of large fish from a population sets the stage for rapid, undesirable evolutionary changes, including slower growth, earlier adult maturation and permanently smaller size^1,². This occurs because removing the largest fish directly opposes natural selection, which tends to favour large size.

What happens when these two forces simultaneously oppose one another? Can evolution respond quickly enough to track changes in fishing selection, or does natural selection counteract it? Writing in Proceedings of the National Academy of Sciences³, Eric Edeline and colleagues illustrate the outcome of this dynamic tug-of-war between the forces of natural selection and fishing selection."

He points out that the role of natural selection is often not considered in fishery's management because of the assumption that humans are just another predator in the system and we just need to regulate how much that one predator harvests. However, this paper shows that the size selective nature of human predation can have really different effects than other sources of mortality (including nonhuman predators), which tend to impact smaller, slower, weaker individuals. Thus, typical predators create selection for large size because not only is fitness generally higher at large mass but fewer things will eat you - whereas humans create pressure against it. The authors of the PNAS paper demonstrate these opposing forces empirically with a unique and high resolution data set on Pike in Lake Windermere, England. Humans did indeed selectively take large individuals whereas other sources of mortality weeded out the small. They also showed the predicted life history relationships between fishing intensity and growth rate, which are consistent with the models we discussed earlier in the semester.

This paper isn't written from the perspective of human ecology (although I'm sure lots of human ecologists are very interested in this) but it fits the aims of this class very well because it uses life history theory to demonstrate a relatively simple but previously somewhat overlooked feedback that underlies human predation and and a key ecological pattern. ...er something like that anyway...

Introduction to Week 12 and 13: Scaling in human ecology

2007-11-04T18:58:00.000-08:00

Metabolism, life-history, innovation, self-similarity, and social organization

The study of complex systems necessitates understanding the fundamental role of scale and hierarchical levels in governing dynamics and pattern formation. Scaling is a powerful tool used to relate the attributes of a system to changes in dimension. The next two weeks’ readings provide a brief introduction to issues of scale and a more in depth exposition of the recent uses of the scaling approach in human ecology.

Building on allometric and metabolic scaling, the recent metabolic theory of ecology is experiencing great success and controversy because it potentially provides a unifying framework for understanding the flows of energy and materials in ecological systems, as discussed by Brown et al. (2004). How might this theory and approach be extended and adapted to apply to human systems? Moses and Brown find that fertility rate in humans scales with metabolic rate just like in other organisms when total extra-metabolic energy consumption (e.g., electricity and gasoline use) is used as measure of metabolic rate, instead of physiological metabolic rate (Fig.1). But could this similarity be purely coincidental? A rigorous theory is necessary to demonstrate otherwise.

Bettencourt et al. (2007) discuss how cities are similar to and different from biological organisms. They suggest that their social organization, the cooperative interaction between individuals, leads to scaling relations uncommon in organisms, such as the scaling of wealth creation and innovation with city size. Yet how different are scaling relations for cities different from those in sedentary groups of other highly social organisms, such as ant colonies? In any case, an important step in the development of a metabolic theory of ecology will be to include the effects of interactions between agents, whether between individuals in a social group, species in a food web, or nations in a global environment.

Fractals and self-similarity pervade throughout the natural world. They emerge when a process is repeated across a range of a dimension. Due to the simplicity of the processes necessary for their origin and their commonness in nature, in many cases it may even be most appropriate to consider them as null models (e.g., in the spatial distribution of resources). Hamilton et al. (2007) discover an apparent self-similarity in the structure of social networks in hunter-gatherers. They suggest an intimate link between social organization and metabolism in hunter-gatherers (see also Hamilton et al. , 2007, PNAS).

As Brown et al. (2002) write, “Underlying the diversity of life and the complexity of ecology is order that reflects the operation of fundamental physical and biological processes”. Through the use of scaling, these readings investigate the potential existence of such order in human systems.

References

* Bettencourt, L. M. A., J. Lobo, D. Helbing, C. Kuhnert, and G. B. West. 2007. Growth,
innovation, scaling, and the pace of life in cities. Proceedings of the National Academy of Sciences 104:7301.

*Brown, J. H. 2002. The fractal nature of nature: power laws, ecological complexity and biodiversity. Philosophical Transactions: Biological Sciences 357:619-626.

*Brown, J. H., J. F. Gillooly, A. P. Allen, V. M. Savage, and G. B. West. 2004. Toward a Metabolic Theory of Ecology. Ecology 85:1771-1789.

*Gibson, C. C., E. Ostrom, and T. K. Ahn. 2000. The concept of scale and the human dimensions of global change: a survey. Ecological Economics 32:217-239.

*Hamilton M. et al. 2007. The complex structure of hunter-gatherer social networks. Proceedings of the Royal Society of London, Series B.
*Hamilton, M. J., B. T. Milne, R. S. Walker, and J. H. Brown. 2007. Nonlinear scaling of space use in human hunter-gatherers. Proceedings of the National Academy of Sciences 104:4765.

*Moses, M. E., and J. H. Brown. 2003. Allometry of human fertility and energy use. Ecology Letters 6:295-300.

Expanding the Wheel?: Lotka's Max Power Principle and Human Ecology

2007-11-02T10:59:00.000-07:00

A lot of blogs are about the most current and hottest new research published in a given field. For the blog to be interesting they have to get to it before most other people, often posting on papers that aren't yet released to the public. Or that's one approach anyway.

Going to another extreme, this is about a paper published in 1922 in PNAS by the influential physicist Alfred Lotka. The paper is titled "Contribution to the energetics of evolution." It's been cited thousands of times (unfortunately none of the citation indexes I have access to go back far enough to see how many) but I wonder what proportion of the people citing it have read it. A pdf of the paper is posted under week 12 (see sidebar to right). Yes it would have fit last week's theme better, but work with me here... It may alter the way you think about the world or you may just find it an interesting bit of science history - to read such an important paper that was published 85 years ago, count 'em, that's a lotta years.

The paper argues that a physical property underlies evolution by natural selection - the maximum power principle. A fairly concise view of the principle is given by the following quote:
"In every instance considered, natural selection will so operate as to increase the total mass of the organic system, to increase the rate of circulation of matter through the system, and to increase the total energy flux through the system, so long as there is presented an unutilized residue of matter and available energy.
This may be expressed by saying that natural selection tends to make the energy flux through the system a maximum…”

The point usually emphasized in the literature is this maximizing of flux through the system.

At the end of the paper, Lotka briefly ponders the relevance of his principle for an understanding of human evolution:
"We have thus derived, upon a deductive basis, at least a preliminary answer to a question proposed by the writer in a previous publication. It was there pointed out that the influence of man, as the most successful species in the competitive struggle, seems to have been to accelerate the circulation of matter through the life cycle, both by ‘enlarging the wheel,’ and by causing it to ‘spin faster.’ The question was raised whether, in this, man has been unconsciously fulfilling a law of nature, according to which some physical quantity in the system tends toward a maximum. This is now made to appear probable; and it is found that the physical quantity in question is of the dimensions of power, or energy per unit time…”

Lotka's views were echoed by a lot of later researchers who attempted to take a more thermodynamic view of human evolution - like Leslie White, Richard Adams, and Joseph Tainter. And were also applied to general biological phenomenal such as the evolution of body size (see Brown, Marquet, and Taper, The American Naturalist, 1993).

Its a classic and thought-provoking paper that should be read by everyone.

best,
Oskar

A breakthrough view of modern hunter gatherer societies

2007-11-01T13:54:00.001-07:00

With Regards: Myra & David

Week 12: Scaling (part 1)

2007-11-01T13:53:00.000-07:00

Required Readings
*Brown, J. H. 2002. The fractal nature of nature: power laws, ecological complexity and biodiversity. Philosophical Transactions: Biological Sciences 357:619-626.
*Gibson, C. C., E. Ostrom, and T. K. Ahn. 2000. The concept of scale and the human dimensions of global change: a survey. Ecological Economics 32:217-239.
*pages 1771-1777 of Brown, J. H., J. F. Gillooly, A. P. Allen, V. M. Savage, and G. B. West. 2004. Toward a Metabolic Theory of Ecology. Ecology 85:1771-1789.

Optional
Schneider, D. C. 2001. The Rise of the Concept of Scale in Ecology. BioScience 51:545 – 553.

Energy and "Cultural Development" in the US

2007-10-29T18:37:00.001-07:00

I'm posting this as a new entry rather than as a comment to the Week 11 post in order to include graphs.

White (1943) presents a very simple model of energy use and cultural development, E X F = P, where E is per-capita energy, F is efficiency of energy use, and P is productivity or the "degree of cultural development". The US Government, through the Energy Information Administration, provides just the data we need to get a picture of how this has worked in the US economy for the past nearly 60 years.

This first graph is P, "the total amount of goods or services produced" as measured by Gross Domestic Product, corrected for inflation by being expressed in year 2000 dollars. There has been some skepticism expressed in class that real wealth has been increasing in the US over the past several decades, so this figure should lay that myth to rest. Average real wealth has increased nearly 3 and a half times over the time span represented.

The next graph features E, per-capita energy use. Notice the increasing trend until the oil shocks of the early 1970's, after which per-capita energy consumption has remained statistically constant.

If we're not buying increased production through increased energy use, White's model predicts we're doing so through an increase in efficiency. This can be seen in the next figure, which graphs F, the productivity gained per unit use of energy.

While efficiency was increasing slowly before the oil shocks, the pace picked up in the 1970's, efficiency doubling in the years since 1973. This increase in efficiency shows up through more "efficient" use of pollution, as the next figure shows. The amount of greenhouse gases produced to generate each dollar of wealth has fallen significantly over the past quarter century for which we have data.

Week 11: Energetics, culture, and society

2007-10-26T14:19:00.000-07:00

These papers discuss the importance of energy in governing the dynamics and self-organization of complex systems. Howard .P. Odum, Leslie A. White, Boltzmann , Schrodinger (Schrödinger 1992), and Lottka (Lotka 1922) were some of the pioneers in researching the importance of energy in biological and human systems. Such scientists have sought to develop general principles of complex systems and evolution, often framed within the context of thermodynamics. Odum has had a profound influence in several scientific fields, including ecological economics, ecosystem ecology, general systems theory, ecological modeling, environmental engineering, and education. Tim F.H. Allen has been an important thinker in the development of ecological theory (e.g., Allen 1992). However, many of the ideas in these papers have yet to be rigorously developed and tested. In your writings for this week try to:

(1) carefully evaluate their reasoning and mechanistic explanations

(2) describe connections between these authors' ideas and other papers in the course

(3) and think of ways that these ideas could be built into more testable hypotheses.

Jordan

Please read the following for the coming week:

* White, L.A. 1943. Energy and the evolution of culture. American Anthropologist 45: 335-356.

* Odum, H.T. 1988. Self organization, transformity, and information. Science 242: 1132-1139.

* Tainter, J.A. et al. 2003. Resource transitions and energy gain: Contexts of organization. Conservation Ecology 7:  4 - 17.

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Additional references

Allen, T. F. H. 1992. Toward a Unified Ecology. Columbia Univ Pr.

Lotka, A. J. 1922. Contribution to the Energetics of Evolution. Proceedings of the National Academy of Sciences 8:147-151.

Schrödinger, E. 1992. What is life? Cambridge Univ. Press.

Follow-up on discussion, week 10

2007-10-26T08:52:00.000-07:00

Hey!
Great discussion on Thursday. There was definitely a lot more fodder for discussion than we could get into in just that class period.

A few notes:
Fred mentioned, in regard to the example about schooling behavior in fish, that just because you show that the emergent phenomena could result from localized and 'blind' interactions doesn't mean that you actually have shown it. While I think the school thing is still a good example of an emergent phenomenon, her comment points directly to one of the biggest issues in the use and interpretation of agent based models. You can give agents rules and tweak parameters until you get all kinds of different patterns. Once you've demonstrated that your model can generate a pattern like the one you're interested in, can you conclude that you've therefore explained it? (there is a tendency for modelers in this area to act as if generating the 'right' pattern with a set of rules is the same as explaining it). Not only could lots of different types of localized interactions, based on different rules and parameter values, potentially generate the same pattern but other external or top down controls might still be relevant even though the model generates a pattern without them. This creates a difficult situation for the use of such models but a lot of applications have shown that you can make more refined empirical predictions, which can in turn be tested with additional observation or fieldwork. Lansing's work may be the very best example of this in the social sciences. Keep in mind that the paper we read was from 1993 and he has done a lot of stuff since then. Check out his website if you're interested.

Als0 relevant to the Lansing and Kremer paper is the issue of agency. We all seemed to take some kind of issue with the contrast between 'blind' and 'deliberate' selection and what roll human agency played in Bali temple networks. I'm not sure we resolved this in class but we came up with at least two types of possible interpretation: 1) we disagree with Lansing and Kremer and think that they have shown the opposite of what they say they've shown - that blind localized interactions generate the temple network and that you don't need to invoke some special human agency at all - but that depends on what you think agency is. 2) that if you 'read between the lines' of their paper they are actually disagreeing with how a lot of anthropologists use the concept of agency and they are just doing so in a careful and stealthy way. It is most likely the case that they are making the point that the agricultural system falls apart without conscious human action, not at the level of the whole system but in terms of intentionally maintaining and managing plots of land, whereas other 'natural' systems presumably don't require this explicit planning. This would assume that human planning is qualitatively different from the planning done by say, a beaver. Agency can be a bit of a slippery concept. Regardless of these issues of interpretation, that this complex social structure could be generated as a 'self-organized' process of neighbor-to-neighbor communication is hugely important, provocative, and definitely not a typical variety of anthropological explanation.

I also liked how we kept finding more linkages between the papers the more we talked about them. Perhaps in the early days before the establishment of the temple networks and the social structures they help maintain, there would have been more problems of synchronization as the system was in more of an 'r' rather than a 'K' phase, as Paul pointed out. Maybe shrimp aquaculture is not so well-organized or structured and top-down controls are necessary to keep it from going chaotically out of control? We could attempt to categorize these issues and others with respect to Holling's phases to see if we are able to gain insight via application.
Have a great weekend. We'll be posting more shortly...
Oskar

Fitness landscapes: a way to visualize adaptation of complex systems

2007-10-24T14:53:00.000-07:00

"Evolution is sometimes characterized by biologists as a metaphorical uphill struggle across a “fitness landscape” in which mountain peaks represent high “fitness,” or ability to survive, and valleys represent low fitness. As evolution proceeds, a population of organisms in effect takes an “adaptive walk” across such a landscape." (http://gemini.tntech.edu/~mwmcrae/esre95.html)
"In biology, fitness landscapes are used to visualize the relationship between genotypes (or phenotypes) and reproductive success. It is assumed that every genotype has a well defined replication rate (i.e. fitness). This fitness is the "height" of the landscape. Genotypes which are very similar are said to be "close" to each other, while those that are very different are "far" from each other. The two concepts of height and distance are sufficient to form the concept of a "landscape". The set of all possible genotypes, their degree of similarity, and their related fitness values is then called a fitness landscape." (Wikipedia)
Fig: "Fitness is shown as a function of sequence: the dotted lines are mutational paths to higher fitness. a, Single smooth peak. All direct paths to the top are increasing in fitness. b, Rugged landscape with multiple peaks. The yellow path has a fitness that drastically lowers its evolutionary probability." (Poelwijk et al. 2007. Nature)
"Fitness landscapes are often conceived of as ranges of mountains. There exist local peaks (points from which all paths are downhill, i.e. to lower fitness) and valleys (regions from which most paths lead uphill). A fitness landscape with many local peaks surrounded by deep valleys is called rugged." (Wikipedia)
Effectively, rugged fitness landscapes have many local fitness optima (peaks), and the higher you are on one, the less likely “mutations,” whether real or metaphorical, will enable you to climb to a taller one. The reason is that the organism or system must decrease in fitness as it walks down one hill in order to start the adaptive climb up another. In general, the more connections (edges) between nodes in a complex system, the more rugged its fitness landscape.

Hopefully this biology-focused primer will help us apply the fitness landscape concept to human-environment complex adaptive systems, such as that modeled by Lansing & Kremer.

Bill

References:

McKinsery Quarterly_Escaping the red queen effect: http://gemini.tntech.edu/~mwmcrae/esre95.html

Poelwijk et al. 2007. Empirical fitness landscapes reveal accessible evolutionary paths. Nature 445, 383-386.

Wikipedia, fitness landscape: http://en.wikipedia.org/wiki/Fitness_landscape

Week 10: Complex human ecological systems & their dynamics

2007-10-19T13:02:00.000-07:00

Read the following, ideally in this order:

* (Recommended) Costanza et al. 1995. Modeling complex ecological economic systems. Bioscience 43: 545-549 (stop at “Fractals and chaos”)

*Holling, C.S. 2001. Understanding the Complexity of Economic, Ecological, and Social Systems. Ecosystems 4: 390-405.

*Lansing & Kremer. 1993. Emergent properties of Balinese water temple networks.

* Arquitt et al. 2005. A systems dynamics analysis of boom & bust in the shrimp aquaculture industry

Kruse, J. et al 2004, Liu et al. 2007, and Chapin. 2006. are optional but have some good points, definitions, and figures.

NOTE: You DO NOT need to summarize or comment on Costanza. ALSO, since Kruse was up as "required" for a day and Arquitt was not, you can summarize either for credit. Arquitt will be more useful to you, though.

FINALLY, you can take till Friday at 10am to e-mail us your proposals, and feel free to write compact annotations/comments this week. Just show us your understanding of the ideas and how they interact and any questions or ideas they raise.

************************************************************************

Unit II_ A Systems Perspective in Human Ecology: Complexity, Dynamics, Scaling, and Social Metabolism

This week we start our unit on a systems perspective on human ecology, pioneered by ecologists H.T. Odum and C.S. Holling, among others. A concept diagram for how the unit topics relate to those from this week is:

Systems thinking --> systems theory/science --> complex systems --> complex human ecological systems --> understanding how complex human eco-systems change over time (dynamics)

… modelers of systems usually look for boundaries that minimize the interaction between the system under
study and the rest of the universe in order to make their job easier. The interactions between ecological and economic systems are many and strong. So, splitting the world into separate economic and ecological systems is a poor choice of boundary. Costanza et al. 1993

Holling, 2001, advocates a particular view of human eco-systems and their dynamics. How does the idea of adaptive cycles differentiate a hierarchy from Holling’s notion of a panarchy? What are examples in human ecological systems? What do you think of this framework for understanding and modeling complex human eco-systems?

…a spontaneous process of self-organization occurred when we allowed water temples to react to changing environmental conditions over time in a simulation model. Lansing & Kremer, 1993

Steve Lansing, an anthropologist at U. Arizona, has worked extensively in Bali on the intricate ecological relationships between people and landscape, focusing on traditional agricultural and water-management systems. Lansing & Kremer, 1993, is a classic case study of a human-environment complex adaptive system. What are some “emergent properties” of the Balinese water temple networks? What’s an appropriate null hypotheses for their question? What role do feedbacks play in their understanding of the water-temple network?

Arquitt et al, 2005, showcases the “systems dynamics” approach. They are interested in modeling the boom and bust pattern of the Thai shrimp fishing industry as a system. In so doing, they aim to identify appropriate points and mechanisms for intervention to promote greater sustainability. Think about pros and cons of this approach. Think also about the similarities and differences between Arqitt’s approach and that of Lansing & Kremer.

Note the central role of adaptation in all three papers and approaches. Adaptation plays a central role in behavioral ecology, the study of behavioral interactions between organisms and their environment. In systems ecology, the system is the equivalent of an organism, and its “behavior” includes how it and its “outputs” change over time.

As we go move through this unit, think about how the idea of a system, as defined in the glossary, relates to a broad definition of metabolism—the acquisition, transformation, and allocation of energy, matter, or information. How can a metabolic perspective inform and enhance a systems perspective? Can we fruitfully extend this idea from organismal biology to human ecology?

Happy musings,

Bill

Glossary:

chaotic – behavior of a system over time whose trajectory is very dependent on initial conditions and that exhibits nonlinearity. Lansing & Kremer, p. 110, give a nice if abstract verbal description of the difference between chaotic and complex behavior of a system.

complex system – a energetically “open” system of parts, often organized hierarchically, that interact via complex feedback loops to produce nonlinear behavior and often emergent patterns. Examples include ecosystems, economies, and the human immune system.

complex adaptive system – a complex system containing adaptive agents, networked so that the environment of each adaptive agent includes others in the system. (Holland & Miller, 1991)

emergent properties / emergence – properties of a system that are unpredictable from just understanding properties and isolated behaviors of its components. For example, simply studying the behavior of individual ants would not enable you to predict the behavior of a large colony; the complex colonial behavior emerges from the collective, relatively simple behaviors of the individual ants that comprise it.

feedback – in a system, the effect of an output on an input. Positive feedback amplifies the output, while negative feedback dampens it. A classic example is the effect of temperature on a thermostat.

model – (n) a representation of a system; models can be verbal, graphical, or mathematical

nonlinear – behavior, as of a system, that is not a simple sum of the behavior of its elements

resilience – in ecology, the ability of a system to remain unchanged or well-functioning when under some type of pressure

robustness – ability to maintain function or effectiveness under different conditions or limitations. For example, a model is considered robust if you can change assumptions and the model still captures what you intended. Robustness usually refers to a system's function, while resilience refers to the system's structure.

stock and flow diagram – in systems dynamics, a flowchart diagram that highlights relationships between entities that accumulate or deplete over time, called stocks, and their rates of change, called flows

system – a group of “interacting, interdependent parts linked together by exchanges of energy, matter, and information.” Costanza et al. 1993

system dynamics – a) changes over time in a system, b) a field that explores how complex systems change over time

systems thinking – a nonreductionist approach to understanding and studying systems that considers the parts, their connections, and their interactions wholistically. Lansing & Kremer and Arquitt et al. are both examples of a systems approach to human ecology.

threshold – the “tipping point” between one state of a system and another. Landmasses on the sides of a geologic fault, for example, change relative positions when the pressure on them exceeds some threshold.

Additional readings

2007-10-16T14:50:00.000-07:00

Hey everyone,
Since there is so much interest in big picture takes on sustainability and related issues, we thought we'd add a few more papers written on the topic by prominent ecologists and published in major journals. These are optional but very short and worth checking out. (for those not in the class, you can access the pdfs by following the directions on the sidebar to the right).
Here's the references we added:

*Palmer, M., E. Bernhardt, E. Chornesky, S. Collins, A. Dobson, C. Duke, B. Gold, R. Jacobson, S. Kingsland, R. Kranz, M. Mappin, M. L. Martinez, F. Micheli, J. Morse, M. Pace, M. Pascual, S. Palumbi, O. J. Reichman, A. Simons, A. Townsend and M. Turner
2005 Ecology for a crowded planet. Science 304:1251 - 1252.

*Cohen, J. E.
2003 Human Population: The Next Half Century. Science 302:1172 - 1175.

*Cohen, J. E.
1995 Population Growth and Earth's Human Carrying Capacity. Science 269:341 - 346.

Great discussion today.

Campus event about Darfur

2007-10-16T12:12:00.000-07:00

Here's an event this weekend that might be of interest to some of you:

I thought you would like to know about Voices from Darfur, a national speaking tour featuring Darfuri refugees that will be visiting Albuquerque on Saturday. Voices from Darfur offers a unique opportunity to hear first-hand accounts of the genocide from the people who have lived through it.

On Saturday, October 20, you will have two opportunities to see Voices from Darfur:

2:30 p.m.
University of New Mexico
Anthropology Lecture Hall - Room 163
1 University of New Mexico
Albuquerque, NM 87131

7:00 p.m.
First Unitarian Church
3701 Carlisle Boulevard NE
Albuquerque, NM 87110

To learn more about these events, visit www.voicesfromdarfur.org and click on 'find an event'. You can also email Laura at laura@savedarfur.org for specific event information.

We hope to see you there!

Best,

Coby Rudolph

(this information was contributed by Helen Davis).

Week 9: Ecology and Geography of Wealth and Resource Use

2007-10-12T20:20:00.000-07:00

Exploring the global ecology, geography, and ecological economics of contemporary humans

“The human economy depends on the planet’s natural capital, which provides all ecological services and natural resources” (Wackernagel et al. 2002). Spatial flows of energy and materials, such as fossil fuel, wood, and food, between humans across the globe provide resilience to the global economy and sustain local economies in depauperate environments. Geographic differences in the natural, social, and economic environments govern this supply and demand network of flows. Some of the exchanges are necessary to sustain comfortable standards of living and the resilience of local economies, whereas other exchanges may maintain ecologically damaging differences in wealth or be unnecessarily wasteful. This week’s readings provide insight into these processes, examining the degree of matching between human demand and environmental resource supply, and some of the ultimate and proximate factors underlying geographic patterns in wealth and resource use.

As suggested by Liu et al. (2003), changes in the number and size of households result from complex interactions between local resource availability, per capita income, population dynamics, demographic changes, and cultural values. Individuals living in smaller households generally use resources and space less efficiently than larger households, thereby increasing their impact on the environment. Some of these impacts and patterns of consumption are investigated by Wackernagel et al. (2002) and Imhoff et al. (2004). Imhoff et al. describe remarkable spatial variation in the consumption by humans of ecosystem productivity. Wackergael et al.’s results suggest that Homo sapiens’ demand on the biosphere may exceed its current capacity.

Drawing from ideas developed by Jared Diamond in Guns, Germs, and Steel, Hibbs and Olsson’s (2004) use models to argue that the distribution of agriculturally supportive environments (namely related to climate and availability of plants and animals suitable for domestication) and the geographic orientation of continents account for a large part of differences in the wealth of nations. Many patterns in human consumption and environmental degradation reflect these differences in wealth. For example, individuals with higher per capita incomes may choose to live in large houses, commute further to work, and consume more energy and resources. Thus furthering our understanding of economic development and the geography of wealth is essential towards developing a theory of modern human macroecology. The Hibbs and Olsson’s paper is only one perspective and introduction to this vast subject.

Together these readings underscore the importance of developing an understanding of human ecology and biogeography that integrates the natural and social sciences from local to global scales. Such a synthetic understanding is essential towards effectively building a sustainable and relatively poverty-free future.

Cheers,
Jordan

Note to class: please post this week's proposal peer review assignment on last weeks proposal blog entry.

Readings

Hibbs, D. Jr., and O. Olsson. 2004. Geography, biogeography, and why some countries are rich and others are poor. PNAS 101: 3715-3720.
Liu, J., G. C. Daily, P. R. Ehrlich, and G. W. Luck. 2003. Effects of household dynamics on resource consumption and biodiversity. Nature 421:530-533.
Bounoua, L., T. Ricketts, C. Loucks, R. Harriss, and W. T. Lawrence. 2004. Global patterns in human consumption of net primary production. Nature 429:870-873.
Wackernagel, M., N. B. Schulz, D. Deumling, A. C. Linares, M. Jenkins, V. Kapos, C. Monfreda, J. Loh, N. Myers, and R. Norgaard. 2002. Tracking the ecological overshoot of the human economy. Proceedings of the National Academy of Sciences 99:9266-9271.

New explanation for megafauna extinction: extraterrestrial impact

2007-10-10T07:25:00.001-07:00

In a compelling and very interesting study, Firestone et al. propose a new explanation for why Clovis technology changed drastically (and disappeared) at about the same time the megafauna of the Americas went extinct.
Published yesterday in PNAS (their paper is open access and can be found here.), the authors present multiple lines of evidence suggesting that a comet either struck the earth at an unknown location or exploded in an airburst at about 12.9 kya. They propose that the ensuing fires and climatic changes caused the end-Pleistocene extinctions and the the cultural changes observed archaeologically at this time. The event is also proposed to explain the Younger Dryas climatic event. Much of their evidence relates to a well-known stratigraphic layer, called the blackmat, which has been observed directly above a number of buried Clovis cultural deposits. The blackmat layer has been found above but never below Clovis containing deposits (i.e., it must be just a bit younger than the time when Clovis people were active on the landscape and we don't see any evidence for Clovis after it was deposited). They demonstrate that the blackmat contains grains associated with the content of extraterrestrial bodies, comets, that are not found above or below it and are also found in other sediments of the same time period. No large now-extinct mammals have been found above this layer.

Here's the info and abstract for their paper:
Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

R. B. Firestone^a^,b, A. West^c, J. P. Kennett^d, L. Becker^e, T. E. Bunch^f, Z. S. Revay^g, P. H. Schultz^h, T. Belgya^g, D. J. Kennettⁱ, J. M. Erlandsonⁱ, O. J. Dickenson^j, A. C. Goodyear^k, R. S. Harris^h, G. A. Howard^l, J. B. Kloosterman^m, P. Lechlerⁿ, P. A. Mayewski^o, J. Montgomery^j, R. Poreda^p, T. Darrah^p, S. S. Que Hee^q, A. R. Smith^a, A. Stich^r, W. Topping^s, J. H. Wittke^f, and W. S. Wolbach^r

A carbon-rich black layer, dating to 12.9 ka, has been previouslyidentified at 50 Clovis-age sites across North America and appearscontemporaneous with the abrupt onset of Younger Dryas (YD)cooling. The in situ bones of extinct Pleistocene megafauna,along with Clovis tool assemblages, occur below this black layerbut not within or above it. Causes for the extinctions, YD cooling,and termination of Clovis culture have long been controversial.In this paper, we provide evidence for an extraterrestrial (ET)impact event at 12.9 ka, which we hypothesize caused abruptenvironmental changes that contributed to YD cooling, majorecological reorganization, broad-scale extinctions, and rapidhuman behavioral shifts at the end of the Clovis Period. Clovis-agesites in North American are overlain by a thin, discrete layerwith varying peak abundances of (i) magnetic grains with iridium,(ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v)carbon spherules, (vi) glass-like carbon containing nanodiamonds,and (vii) fullerenes with ET helium, all of which are evidencefor an ET impact and associated biomass burning at 12.9 ka.This layer also extends throughout at least 15 Carolina Bays,which are unique, elliptical depressions, oriented to the northwestacross the Atlantic Coastal Plain. We propose that one or morelarge, low-density ET objects exploded over northern North America,partially destabilizing the Laurentide Ice Sheet and triggeringYD cooling. The shock wave, thermal pulse, and event-relatedenvironmental effects (e.g., extensive biomass burning and foodlimitations) contributed to end-Pleistocene megafaunal extinctionsand adaptive shifts among PaleoAmericans in North America.

This paper cannot be ignored but I'm sure many will try. There's clearly something going on here and they do a great job putting their lines of evidence together.
Major weakness: Absolutely no link is made between the proposed effects of this impact and the strongly sized-biased pattern of the extinction event they propose to explain.
We know reasons why large animals might have been more prone to extinction - low population densities, low fertility rates, 'expensive' offspring, etc. - but it is not yet clear why the impact would operate on environmental parameters such that primarily large animals would be affected.
This needs to be addressed. In future studies it would also be nice to see a more detailed comparison of this event with other extraterrestrial impacts that caused extinctions. Obviously, this 'YD event' as they call it (YD for Younger Dryas) was of a lower magnitude, but how do the traces of the elements and the links to environmental productivity compare to previous events where the link to an impact event are robust and much more clear?

There has been a lot of buzz about this idea for some time as they've presented the argument at meetings and the like. This is only the first paper and I'm sure we'll see a good deal of debate and further papers in short order.

Just to give a few more details of their argument. Here's one of the their figures showing the microspherules that are found in the blackmat, don't seem to be found above or below it, and are found in lots of different layers that correspond closely to the date of the impact:

Fig. 2. High-titanomagnetite microspherules from Blackwater Draw, NM (120 µm) (a); Chobot, AB, Canada (150 µm) (b), Gainey, MI (90 µm) (c), and Howard Bay, NC (100 µm) (d).

Also, they show how specific the attributes of the impact are in terms of 'spikes' in the profiles of several stratified localities. Here's their figure depicting these spikes:

Fig. 1. Sediment profiles for seven sites. Concentrations are shown for magnetic grains, microspherules, charcoal, soot, glass-like carbon, carbon spherules, Ir, Cr, and Ni, which peak mostly in a narrow stratigraphic section spanning only a few hundred years. Ir open circles indicate values below detection, typically <0.5–1 href="http://www.pnas.org/cgi/content/full/0706977104/DC1">SI Fig. 8. The locations of all sites that were sampled are shown in SI Fig. 9.

I hope you all enjoy thinking about this new provocative argument and I look forward to the commentary that will follow. Its already gotten attention by the popular press and will certainly get lots of scrutiny by scholars in multiple disciplines.

Cheers,

Oskar

Project Proposal: Three stages, Three weeks, Infinite fun

2007-10-07T17:20:00.000-07:00

1) Short Preliminary Project Proposals

Assignment:

Write 6-8 sentences describing your project idea, approach to studying it, and its relation to the themes or general perspective of the class. You are not tied to doing what you propose, but this exercise will help you think through possible projects to find ones that really interest you and to think through how doable and appropriate they are.

Value: 2% of class project grade

Due: Posted to class blog by Tuesday, Oct 9, 9am. Please post your preliminary proposals as comments to this blog entry.

2) Peer review of another’s proposal
Assignment:

Write a short, one paragraph (3-6 sentences) constructive critique on another student’s proposed project.

Value: 2% of class project grade

Due: Posted to class blog by Tuesday, Oct 16, 9am. Please post your preliminary proposals as comments to this blog entry.

3) Project proposal
Assignment:

Write a description of your proposed project, including a summary of what you plan to research, how you plan to tackle it, and its general and personal relevance (i.e. why is it interesting or important for you?). Make these no more than 1 page, single spaced, one inch margins. But they can certainly be shorter. We don’t need an extensive list of references, so only include a few if they’ll help us better evaluate your proposal.

Value: 5% of class project grade

Due: E-mailed by Tuesday, Oct 23, 9am

Week 8 Background: how humans alter biogeographic patterns

2007-10-07T13:26:00.000-07:00

Humans and extinction:
As mentioned by Lyons et al. and thoroughly reviewed by Surovell, their are two basic camps in the contentious argument over the role of humans in the disappearance of very large fauna at the end of the Pleistocene. The overkill hypothesis argues that humans caused the extinction by overhunting the large slow reproducing game that probably occupied niches where risks of predation had been extremely low before human arrival. The climate change hypothesis argues that changes in temperature and precipitation that coincide with the start of the Holocene were more than the large bodied animals could cope with and this lead to their demise.

You would think these scenarios would be easy to test and evaluate but for our major case studies the timing of human arrival is about the same as the timing of the major climate change in question, as was the case (more or less) for Eurasia and North and South America. This makes isolating the effects of either climate or humans somewhat challenging. Australia is an ideal test case, which is why it is stressed by the Lyons et al paper. One lingering problem with Australia is that the paleontological finds are not well dated. This makes for a somewhat tenuous link between the timing of the appearance of humans and the disappearance of large animals there. This will undoubtedly be resolved in time.

In one sense the real difference between scholars in this debate is whether or not humans played a role in the extinction. The camps should really be named anthropogenic and non-anthropogenic and then subdivided into groups based on the specifics of their proposed scenario under each heading. The readings mention the hyper-disease idea and Diamonds' Sitzkrieg hypothesis which states that the extinction was anthropogenic. However, for Diamond, the extinction had little to do with predation but with human land disturbance, fire, and their cascading effects on the ecosystem. I like this view and think it may be correct but how do we really test it? Consider the possibility that it was simply a huge increase in the frequency of fires, started by humans, that led to habitat fragmentation. This could have been a special disadvantage for large-bodied herbivores because they need large home ranges for feeding and can't afford added costs to finding mates and rearing young. While some have found significant increases in charcoal flecks in pond sediments at about the time of human arrival, this is difficult to link definitely to humans, the fires they may have started started, and to the mortality of large herbivores.

It is interesting to note that, from my perspective at least, the more comfortable one is with overkill the more divorced they are from any actual analysis of the empirical record for human predation. This is in part because testing of any of the proposed models is difficult (discusses by Surovell) but also because evidence for direct predation of the extinct species is extremely rare. Note that the paper by Lyons et al. essentially ignores both data for the occurrence of megafauna in archaeological sites from the period as well as data on hunting patterns of living hunter gatherers (which would strengthen their argument).

The most outspoken skeptics for the overkill hypothesis are Donald Grayson (U of Washington) and Dave Meltzer (SMU) who think human predation has in no way been linked to the extinction of an animal in any prehistoric context.

One of the few approaches to the debate that has attempted to consider combined roles of both climate and predation comes from a thorough review published by Barnosky and colleagues. They review models, empirical evidence, climatological data, and ecological arguments.
Here's a figure from their paper published by Science (2004).

Fig. 1. Summary of the numbers of megafaunal genera that went extinct on each continent (Table 1), the strength of the extinction chronology, and a comparison of the timing of extinction with the timing of human arrival and late Pleistocene climatic change. Extinction timing for individual genera was judged as robust or provisional based on previous publications that evaluated quality of dates. Sources are as follows: Europe (3, 14, 47), Siberia (48), North America (11, 29, 46, 57), and Australia (4, 7). For humans, the date is the earliest generally accepted arrival of Homo sapiens sapiens; pre-sapiens hominins were present in Eurasia and Africa much earlier.

The other two papers:
Sutherland establishes that by many standards human languages are at greater risk and disappearing at a faster rate than species of birds and mammals. I'd add that there is very little 'conservation effort' to control or manage or slow this loss, mitigate the impact, or even to reverse the pattern. This would certainly be the case if we looked at funding.

Evans and Gaston show a positive but decelerating relationship between human population density and bird species richness in Britain. A positive decelerating correlation means that the two variables are correlated at lower values and the strength of the correlation weakens as one, population density, becomes larger. This generates a curve that flattens out at high values.
They present some more speculative evidence that human density lowers the rate at which new species are found in highly productive environments. They do this by isolating the effect of human density on the slope of the relationship between energy and species richness. They present this result because in many cases human population density is negatively associated with richness of other taxa and therefore their finding of a positive (but decelerating) correlation is somewhat surprising. Their analysis is interesting because it points suggests the possibility that humans and animals may yet both map onto highly productive environments. Alternatively, could it be that humans in cities may provide energy/food/shelter to birds in ways that facilitate their richness? Humans don't prey on birds, presumably, in British cities, they may reduce the number of predators, and may provide easy food sources. This is pure speculation and lots of the implications of this paper need more investigation, but the relationships in this paper are interesting.

See you on Tuesday,
Oskar

Week 8: Human influences on biogeographic patterns

2007-10-05T09:19:00.000-07:00

Hey all,
This is a complex topic and we could spend a long time on it. BUT - the goal here is to round-out our discussion of humans and biogeography by giving examples of not just how patterns in human variation follow biogeographic trends but also how some of the things humans do alter biogeographic patterns in other species. The easiest example here is with the human role in extinction but we certainly have impacts on the distribution, abundance, and rate of spread of a number of species. For example, where would cows be without us? Also, our investments in domesticates create a number of interesting dynamics from the discharge of fertilizers into the ocean to land disturbance causing the spread of some species over others. etc. etc.

The papers for this week are as follows:
*Evans, K. L., and K. J. Gaston. 2005. RESEARCH PAPER: People, energy and avian species richness. Global Ecology and Biogeography 14:187-196.
*Sutherland, W.J. 2003. Parallel extinction risk and global distribution of languages and species. Nature 423: 276-279.
*Lyons, K. S., F. A. Smith, and J. H. Brown. 2004. Of mice, mastodons, and men: human-mediated extinctions on four continents. Evolutionary Ecology Research 6:339-358.
*Surovell - a first proof of his entry entitled "Inter-regional studies/Big game extinctions" for the upcoming Encyclopedia of Archaeology.

We are going to do the reading assignment a bit differently this week because of Fall Break.
For your annotations you should read the Lyons et al (2004) paper and any one of the other three. Basically, your annotation just needs to make it clear that you read at least two papers (the Lyons paper and one other). If you are really interested in overkill (the debated role of human hunting pressure in the disappearance of large game at the end of the Pleistocene) then your second paper should be the Surovell chapter. If you are interested in language read the Sutherland paper. The Evans and Gaston paper speaks to some incredibly cool relationships but is fairly technical with respect to statistics. As always - please spend some time with all the papers - but you only need to focus on two.

I will put a separate post up this weekend about background information for the papers.
Please let me know in an email if there is anything specific you'd like to have defined/explained.

Best,
Oskar

PS - everyone did a great job on Thursday. I think we had an excellent discussion of the McDade and Sherman and Billing papers. Was this because of the interest in the material or because of the coffee!?

Mashco-Piro Video on BBC

2007-09-30T12:07:00.000-07:00

The BBC has a video up on their website of footage capturing a remote forager population in Peru. The video isn't very clear but its worth checking out and they do a good synopsis.
See it here.

Week 7: Cultural, linguistic, genetic diversity patterns II

2007-09-28T23:49:00.000-07:00

For this week, please read the following, ideally in the order listed:

[suggested] Reread Pagel & Mace, 2004, starting at “Cultures and gene flow,” p. 276

Cavalli-Sforza et al., 1988. Reconstruction of human evolution: Bringing together genetic, archaeological, and linguistic data.

Sherman & Billing. 1999. Darwinian gastronomy: Why we use spices.

McDade et al., 2007. Ethnobotanical knowledge and child health in Bolivia.

[Optional] Ackland et al. 2007. Cultural hitchhiking on the wave of advance of beneficial technologies.

**********************************************************************

This week we will a) look explicitly at the relationships between genetic diversity and linguistic diversity and their relation to human evolution, b) continue exploring cultural diversity gradients, focusing on a gradient in the use of spices, derived from plants, and c) explore how maternal knowledge about plants effects child health. I think these connections are pretty amazing, and I hope you enjoy the papers. This last article, in a sense, brings us full circle back to some basic life-history considerations.

Keith Hunley, an assistant prof of Anthropology at UNM, will lecture on Tuesday and asked that we read Cavalli-Sforza as background for his talk. Cavalli-Sforza pioneered the use of gene frequency data and allied methods to study the movements and evolution of people and their biological and linguistic traits. This paper has some jargon and a genetics and evolution bent, but focus on the overall findings and implications. The last portion explicitly relates the overall findings to human ecology. Think about the forces that selected for general language ability and, at the same time, the partitioning of this human universal into about 6900 varieties.

There’s debate about the correspondence between patterns of linguistic and human genetic diversity patterns. Some authors have reached different conclusions from Cavalli-Sforza. Think about likely mechanisms underlying linguistic & genetic evolution. Why would or wouldn’t you expect agreement between them? What ecological factors likely affect them? And how might you test for relationships?

Sherman & Billing take a macroecological approach to analyzing patterns in spice use across the globe. It’s an innovative look at cultural diversity gradients and at a hypothesis for an underlying mechanism. What other mechanisms could underlie this pattern? Paul Sherman wrote a well-cited paper called “The Levels of Analysis,” which the authors cite in the article we read and which argues that researchers should consider both the “proximate” and “ultimate” explanations for traits. A proximate explanation focuses on physiological and genetic mechanisms, while an ultimate explanation focuses on underlying evolutionary reasons. For example, a proximate explanation for the spiciness of chiles is the concentration of the tongue-searing biochemical capsaicum and the prescence of genes coding for it. An ultimate explanation is the adaptive benefit to chiles of deterring mammals from eating their fruits, because mammals are more likely to chew the seeds and drop them too close to the parent plant or deep underground. Birds are much better dispersers of chile seeds and, not surprisingly, don’t taste capsaicum. What are possible proximate reasons people in warm climates use more spices, and are they compatible with the authors’ hypothesis for ultimate reasons?

“… the intergenerational transmission of knowledge regarding the use of available plant resources has historically been an essential function of culture.” McDade et al., 2007

McDade et al., 2007, looks at the relationship between parent’s ethnobotanical knowledge, or knowledge of local plant resources, and the health of their children among the Tsimane, a foraging society in Bolivia. It links together several themes we’ve discussed, including diversity gradients, health and local ecology, height differences, human learning period, intergenerational knowledge transfer, and longevity. Try drawing a diagram linking these ideas. How would you expect spices with anti-inflammatory properties, such as turmeric, to affect longevity, and why? How might gradients in plant and spice diversity affect linguistic patterns? How could you test for such relationships?

Lastly, I want to encourage the quieter voices in the class to let us hear your thoughts and insights a bit more. Likewise, I want to encourage bolder students to leave a bit more “air time” for others to enter the discussion, even if that means the occasionally silence. One of the strengths of a diverse class is the potential for a diversity of perspectives. And just as species diversity includes both “richness” and “evenness,” I want to maximize the diversity of our discussions, with all participating in a significant way. Thanks for your consideration and effort on these points.

See you Tuesday.

Bill

Glossary:

admixture – mixture of two or more genotypes; mixing of genetically different groups

allele – version of a (polymorphic) gene. For example, a population of wild rose that has both red and white flowers has different alleles for flower color.

bootstrap – (also called bootstrapping) a statistical technique for making educated guesses about a population by randomly sampling with replacement from the sample you have, creating distributions of those samples, and assuming the distribution of those samples mirrors the “sampling distribution” of your original population. So if you just have one sample from a population and you don’t think the pop has a normal distribution, you use the distribution of samples of your real sample to infer what the distribution of actual samples from the true population what look like. Regardless of the specifics, it’s a powerful method for inferring characteristics of a population based on a single, usually large sample. Cavalli-Sforza used bootstrapping to test hypothetical human evolutionary “trees” using a large sample of genetic distances for genes shared by human populations. If you want to know more, read “The Bootstrap Conjecture” in http://www.uvm.edu/~dhowell/StatPages/Resampling/Bootstrapping.html.

demographic bottleneck – a sharp reduction in population size, which tends to reduce genetic diversity the same way taking a small handful of M&Ms from a giant bowl is unlikely to capture the variety of colors in the original “population”

electrophoretic – involving electrophoresis, which is the identification of organic compounds via the distance they move through a gel when under an electric charge; small compounds move faster and so further in a given time

gene frequency – relative frequency of a given gene in a population

genetic distance – relative genetic dissimilarity between individuals, populations, or species. A common null hypothesis is that the genetic distance between two samples, such as between two populations of people, indicates the amount of time they’ve been separated. The underlying reason for this null hypothesis is that much of our DNA, including the “genetic marker” portions used for many studies, has no real effect on our genetic fitness or adaptedness yet still accumulates “adaptively neutral” mutations at a low, stable, background rate that can be used as a “molecular clock.” The number of unshared mutations between populations on such a genetic marker represents the “ticks” of this clock: the time the two groups have lived apart, not interbred, and undergone separate evolution. What’s an alternative hypothesis for the genetic distance between two populations?

genetic drift – change in the frequency of one or more genes in a population due to chance, as because some members happen to have more offspring for reasons unrelated to adaptatedness; along with natural selection, genetic drift is one mechanism behind evolution; the frequency of a given gene is more likely to “drift” one way or another in a small population, just as a small number of coin tosses is more likely to give a non-50/50 ratio of heads/tails than a large
number of coin tosses

linkage analysis – an analysis of the amount of linkage between genes. Linkage is the tendency for genes located near each other on a chromosome to be inherited together.

maximum likelihood – statistical method for evaluating phylogenetic trees that favors the “tree” with the highest probability of being correct given your constraints

maximum parsimony – statistical method for evaluating phylogenetic trees that literally favors the “tree” that requires the fewest evolutionary changes to explain the variation in a group of related organisms

phylogenetic tree – evolutionary family tree, as of genes or of languages.

polymorphism – alternate version of a trait or gene

population – the individuals of a species living in the same area at the same time and so having a good chance of interbreeding; Note that biological evolution occurs within populations as the frequency of genes changes among its members.

Week 6: Cultural, linguistic, & genetic diversity patterns 1

2007-09-20T16:51:00.000-07:00

For the coming week, please read the following, ideally in this order:

1. Moore et al. 2002. The distribution of biological & cultural diversity in Africa

2. Collard & Foley. 2002. Latitudinal patterns & environmental determinants of recent human cultural diversity

3. Pagel & Mace. 2004. The cultural wealth of nations.

4. (Optional) Nettle. 1998. Explaining global patterns of language diversity. [Nettle

5. (Optional) Cashdan. 2001. Ethnic diversity and its environmental determinants.

6. (Very Optional) Serre & Paabo. 2004. Evidence for gradients of human genetic diversity

Maps: (top) topography; (2nd) annual precipitation; (3rd) vascular plant species diversity, (bottom) world language diversity

Click on these maps to see them in greater detail.

********************************************************************************************

Humans are part of ecological systems and have various ecological relationships and associated life history patterns. Then again, unlike other large mammals, humans have permanent settlements on every continent and in almost every known terrestrial environment. Humans are relatively genetically homogenous, yet we display astonishing cultural and linguistic variability that follows clear geographic patterns. Is that variability a function of environmental variables, like climate or ecosystem type? Where human cultural patterns mirror biogeographic patterns of other species, are humans responding to the same forces? In the same ways? Why or why not, and how do you test such questions anyway? To start with, how do you fruitfully think about variation in cultural and social patterns—as discrete entities, as clines, or otherwise? Are these differences comparable to other biogeographic differences, and why? More broadly, what is the relationship between culture, language, and environment? Finally, how does human life history, such as lifespan and learning period, factor into such patterns and relationships?

These are some of the questions we’ll ponder and discuss over the coming two weeks. You will struggle with these ideas, occasionally you will triumph, you will laugh, you will cry. I’ll provide Kleenex.

On a more serious note, carefully read the required articles and, if time, the abstracts and figures in the optional articles. Moore et al., 2002, focuses on the relationship between language “richness” (see Glossary below) and species richness in Africa. Collard & Foley, 2002, takes a macroecological look at latitudinal patterns of cultural diversity and possible environmental determinants. Pagel & Mace, 2004, is a good, readily digestible review of current hypotheses on the relationship between culturo-linguistic diversity and environmental variation.

The optional articles provide good reference for the required ones and offer additional hypotheses. Nettle is very active in debates about linguistic diversity, and this paper gives his most widely-known view, which Pagel & Mace summarize and reference. Cashdan has done lots of work with hunter-gatherers and looks carefully at several ecological variables. If you are interested in reading more or following this topic for your project, Nettle and Cashdan are great starting points. Serre & Paabo provides some good recent context on the relationship between human genetic & linguistic patterns, but it’s useful here just for context on how human mating and migration patterns relate to linguistic patterns; we’ll focus explicitly on this topic next week.

If you come across terms in the papers you don't know, consult the Glossary below for reference and understanding. You don't need to memorize these terms, but understanding these concepts will help with the papers.

Ciao,

Bill

p.s. Also consider that languages and cultures, like species, are disappearing at a clip. A recent NYT article (http://www.nytimes.com/2007/09/19/science/19language.html?em&ex=1190433600&en=7e3479621ae1b054&ei=5087%0A)

estimated that one of humanity’s approximately 6900 languages is “lost” every two weeks. Indeed, language and cultural documentation and preservation is an active field, and a major thrust is the tight link between biological and culture-linguistic diversity.

Glossary:

allopatry – separation of a population into two or more groups via a physical barrier, such as a mountain chain or a river; allopatric speciation is the formation of two or more species as such physically divided populations genetically and behaviorally diverge

biome – one of the Earth’s main, usually terrestrial, ecosystem types, such as desert, tropical rain forest, and tall-grass prairie

carrying capacity – the maximum population size of a given species that a given environment can support relatively stably over time

correlation – in statistics, the strength and direction of the linear relationship between two variables

diversity, species—in ecology, a measure of the diversity of species in a given area that considers both “richness,” or number of species, and “evenness,” or evenness of the population sizes of those species

endemic—native and often unique to a given area

evapotranspiration—the transfer of water vapor from Earth's surface to the air from evaporation and transpiration (transpiration is the release of water vapor from plant leaves & stems as a byproduct of photosynthesis) ; potential evapotranspiration is the maximum water vapor an ecosystem could release if it got enough rain.; actual evapotranspiration is the amount of water vapor an ecosystem does release given the average precipitation it usually gets.

genetic marker— a known DNA sequence whose presence and variation can be used to infer the degree of relatedness among groups of organisms

horizontal transmission— transmission, as of a word’s meaning or a custom, within a society other than between parent and child (i.e. other than “down the generations”)

PCA (principal components analysis)— a statistical technique for reducing the number of dimensions of interest among a group of variables; generally, it helps you see which attributes of a dataset contribute most to the patterns of interest; it’s a complex idea that you don’t really need to know…I’m just defining it generally because a paper refers to it

phylogenetic tree—a tree-like diagram showing the evolutionary relationships among species or other entities sharing a common ancestor

population —in ecology, the individuals of a given species living together and interbreeding in a given area

productivity—in ecology, the amount of new living (plant) tissue produced, usually over a year’s time[so warm areas with high precipitation produce lots of new plant material per unit time and so have high productivity]; Gross primary productivity is the total CO2 transformed into living tissue, while net primary productivity is this "gross" amount minus the amount used for the plant's metabolism

reproductive isolation—the separation of two or more groups from possible interbreeding; over time, reproductive isolation often promotes the formation of distinct species, or speciation

richness – number or variety, as of species, languages, or cultures. (e.g. The endemic plant species richness of New Mexico is simply the number of plant species native to the state.)

Rapoport’s rule – the tendency for species range size to increase with increasing latitude (i.e. species at high latitudes tend to occupy large ranges and vice versa)

spatial autocorrelation— the degree of spatial, usually geographic, clustering among features of interest; for example, closely related species tend to have ranges that are spatially autocorrelated simply because they descend from a parent species that presumably lived in the general area (i.e. their ranges aren’t clustered simply because the species have similar niches); very generally, it says two points close together are more likely to be similar than two points further apart

species-area relationship – the positive relationship between the size of a habitat and the number of species it can support and that you'll find there [how might this logic be extended to human ecology?]

sympatry – (literally, “same father”) deriving from a single parent species and living in the same area; so sympatric speciation is the formation of two or more species from the same “parent species” without the help of some obvious barrier to interbreeding

vertical transmission—transmission, as of a word’s meaning or a custom, between parent and child (i.e. “down the generations”)

Contributed blog: density dependence and human body size

2007-09-15T15:26:00.000-07:00

Greetings human macroecologists,

I asked Rob Walker, the lead author on one of our papers for next week ("Growth rates and life histories in 22 small-scale societies"), to blog about some of his research and his thoughts on what determines adult body size in humans. Some of the exciting and relevant features of Rob’s research include his argument that there are two pathways to small body size. One driven by resource limitation that causes smaller growth, and the other by high mortality. I am biased to favor this view because Rob is an old friend and collaborator and more importantly, his view agrees with the Charnovian perspective we covered in class (remember the equation with growth over mortality? – Rob’s model shows the same predictions as that model we went over). Think about how these processes of body size change might relate to the patterns demonstrated in Ruff and the potential implications for H. floresienses (to the degree that insular dwarfism may be a possible explanation for this dwarfed hominid).

Rob has written a slew of papers on human life history and behavioral ecology. To check out his other papers go to his homepage.

Here’s Rob’s blog:

I have some general interests in the evolution of the human life course and especially factors that influence patterns of growth and development. To prepare the paper on ’22 small-scale societies’ that you are reading, I started putting together data from as many societies as I could that had life-history information (e.g., growth rates, age at menarche, first reproduction, and age-specific mortality). I wanted to get a better feel for the overall variation in these traits across human populations. We were able to show that in general larger, better-nourished societies have faster/earlier growth and development (we call this the conventional model). However, while the sample is rather small, there is also some indication that societies that suffer from high mortality also grow relatively fast (relatively given their adult body size, a proxy for energetic intake). This may support the general life-history model where higher mortality prompts faster growth and development in order to get past the high mortality juvenile stage (or high mortality at small body size).

The results from this paper led to some more thinking about how mortality, resource limitation, and growth related to patterns in size and density dependence seen among contemporary hunter gatherer populations. This led to the development of a life history model for human body sizes – a manuscript presenting the model can be found here.

Here's a non-technical summary of that paper:

Average body size ranges immensely across human populations. Many of the world’s smallest populations, like the Agta hunter-gatherers in the Philippines, live on islands at relatively high population densities. We show that population density has a negative effect on adult body mass across hunter-gatherers. Humans slow down growth and development and demonstrate smaller adult body sizes in high population density contexts presumably because of less food and more disease. In addition, there is evidence of selection for relatively faster/earlier development in societies that suffer from high mortality. We interpret this finding as natural selection for earlier reproductive maturity (menarche and first birth), and consequent smaller adult body size, in high mortality regimes in order to more quickly pass into the safer adult stage. In sum, comparative results support density-dependent effects on body size that act through two pathways (energetic constraints and juvenile mortality) at varying intensities in different societies contributing to a nearly two-fold range in body size across human populations.

These ‘two pathways’ to smaller adult size are summarized in the following figure:

Cheers,

Readings for week 5: variation in human body form part 2, the role of density dependence

2007-09-15T09:22:00.000-07:00

This week we are reading a few papers that establish links between life history theory and body size evolution in general and also serve to better acquaint us with the empirical patterns of body size and growth in living humans. (note: these papers are slightly different from what's on the syllabus! We substituted Crimmins and Finch with Palkovacs)

The assigned papers are as follows:

Walker, R., M. Gurven, K. Hill, A. Migliano, N. Chagnon, R. D. Souza, G. Djurovic, R. Hames, A. M. Hurtado, H. Kaplan, K. Kramer, W. J. Oliver, C. Valeggia and T. Yamauchi
2006 Growth rates and life histories in twenty-two small-scale societies. American Journal of Human Biology 18(3):295-311.

Palkovacs, E. P.
2003 Explaining adaptive shifts in body size on islands: a life history approach. Oikos 103:37 - 44.

Stiner, M. C., N. D. Munro, T. A. Surovell and E. Tchernov, Bar-Yosef, Ofer
1999 Paleolithic Population Growth Pulses Evidenced by Small Animal Exploitation. Science 283:190 - 194.

The Walker et al paper shows empirical patterns in growth and body size among contemporary hunter-gatherer populations. Pay close attention to the general relationships that this paper demonstrates. In parts of the paper there are a lot of statistics that you may or may not be familiar with. As always, do not get bogged down in the technical language. Do your best and maybe google some or all of the terms you aren't familiar with (if there are any). The discussion section of the paper is quite lucid and does a good job of clarifying the implications of the statistics in the paper.

The Palkovacs paper takes a life history approach to explaining the patterned changes in body size that are described by the Island Rule. To the best of my knowledge this is the only life history approach to the problem that has been published. What do you think of the approach taken in this paper? Is it more complicated than it needs to be? Is there anything missing or is there any extraneous detail? Remember the definition of a reaction norm that we mentioned briefly in class on Thursday. A given gene doesn't necessary code for a single static phenotype. Phenotypes can change depending on the conditions of the external environment. This capacity for change is a reaction norm. Some examples include changes in skin color in response to sun exposure or changes in growth rate in response to energy availability.

The paper by Stiner and colleagues is an archaeological analysis of data that might seem removed from what we've been talking about. But when do we see changes in human diet and what types of changes occur? What might cause these changes? What was going on with human body size at this time? Do any of the patterns we see in Stiner et al. relate to what we are learning about body size change in Walker et al. and from Palkovacs?

We have also posted a few optional papers showing that some of the same tradeoffs we've been discussing in the contexts of the Island Rule and among hunter-gatherer growth patterns are present in industrial economies. These papers are really exciting and I hope you can check some of them out, especially now that you're armed with some theoretical tools to put these patterns into a larger context. (For readers outside the class - note that you can access these papers by following the directions and hotlink on the sidebar to the right where it says 'ereserves').

Please let me know or post a comment as soon as you can if there are questions about terms and/or concepts in these papers.

I hope you all have great weekends.
Oskar

Island Rule Blog

2007-09-13T08:09:00.000-07:00

The Island Rule:
A generalized trend of changes that occur when species from large land masses colonize islands. Larger colonizing species often form dwarfed populations and small species generally become larger. On the island, space is more limiting and the number of species present is relatively lower. These very general differences lead to changes in evolutionary pressures on the organism, although individual islands and circumstances may have idiosyncratic differences as well. Plants also have insular trends, however, that may related to similar pressures as those which cause the changes seen in mammals. Plants that are herbaceous annuals on the mainland often become tree-like perennials on islands. Additionally, birds and insects have been known to loose their ability to fly after colonizing islands.

We are reading two papers about the island rule.
Lomolino, M. V.
2005 Body size evolution in insular vertebrates: generality of the island rule. Journal of Biogeography 32:1683 - 1699.

Palkovacs, E. P.
2003 Explaining adaptive shifts in body size on islands: a life history approach. Oikos 103:37 - 44.

The Lomolino paper was optional for week 4 but the Palkovacs paper is required for week 5.

Lomolino's abstract:
"Aim My goals here are to (1) assess the generality of the island rule – the graded
trend from gigantism in small species to dwarfism in larger species – for
mammals and other terrestrial vertebrates on islands and island-like ecosystems;
(2) explore some related patterns of body size variation in insular vertebrates, in
particular variation in body size as a function of island area and isolation; (3)
offer causal explanations for these patterns; and (4) identify promising areas for
future studies on body size evolution in insular vertebrates.
Location Oceanic and near-shore archipelagos, and island-like ecosystems
world-wide.
Methods Body size measurements of insular vertebrates (non-volant mammals,
bats, birds, snakes and turtles) were obtained from the literature, and then
regression analyses were conducted to test whether body size of insular
populations varies as a function of body size of the species on the mainland
(the island rule) and with characteristics of the islands (i.e. island isolation and
area).
Results The island rule appears to be a general phenomenon both with
mammalian orders (and to some degree within families and particular
subfamilies) as well as across the species groups studied, including non-volant
mammals, bats, passerine birds, snakes and turtles. In addition, body size of
numerous species in these classes of vertebrates varies significantly with island
isolation and island area.
Main conclusions The patterns observed here – the island rule and the
tendency for body size among populations of particular species to vary with
characteristics of the islands – are actually distinct and scale-dependent
phenomena. Patterns within archipelagos reflect the influence of island
isolation and area on selective pressures (immigration filters, resource
limitation, and intra- and interspecific interactions) within particular species.
These patterns contribute to variation about the general trend referred to as the
island rule, not the signal for that more general, large-scale pattern. The island
rule itself is an emergent pattern resulting from a combination of selective forces
whose importance and influence on insular populations vary in a predictable
manner along a gradient from relatively small to large species. As a result, body
size of insular species tends to converge on a size that is optimal, or fundamental,
for a particular bau plan and ecological strategy."

Why study the Island Rule in human macroecology?
there are many reasons, but a few include the following:
- Understanding the nature and causes of the Island Rule provides insight into really general features of mammalian evolution. With this comes the potential to generalize the insights to other cases where body size changes. This helps us understand selection in general in addition to life history evolution because of the strong interaction between life history attributes and body size.
- The variables that seem most important for understand the Island Rule include resource availability, predation pressure and/or mortality, population density, and competition. On islands we might be able to isolate, more or less, the sustained effects of changes in these key ecological variables. We want to understand how these variables have affected human evolution via changes in range expansion and body size, among others.
- Something we did not talk about in class is that we also need to understand how humans affect the other species. It is often difficult to link human activities like predation and land disturbance to the disappearance of other species. Yet when humans prey on an animal, they are influencing its mortality rate and when humans disturb habitats they may be altering resource availability via effective territory size. Therefore, there is an important link between two of the important variables in the island rule, resource availability and predation pressure, that might help us understand how humans alter the demographic features of their prey or other species they interact with. If humans hunt animals or take their eggs (and the like) then they are altering their mortality rates. If they disturb habitats they may be limiting resource availability for certain species.

(I had intended to do a lot more with this blog. I hope this helps clarify and keep us all on the same page.)

One limitation to our understanding of body size changes on islands is that it is not usually approached as a life history problem. We'll talk more about that next week as we read the Palkovacs paper.
Have a good weekend
Oskar

small edits to Blog in response to recent questions

2007-09-10T21:23:00.000-07:00

Hi folks,

In response to blogged questions, I added definitions for clinal variation and directional selection to the main posting for this week. And in response to another question, I pasted reference info and a condensed abstract for Pilbeam & Gould, 1974 (mentioned in one of our readings) just below the last definition for the week.

Feel free to ask me if either definition is unclear or for a graphical explanation. See you in class.

Bill

Readings for week 4: variation in human body form

2007-09-08T13:14:00.000-07:00

This week we read two papers that show interesting patterns, across space and through time, in the size and shape humans. Here they are:

Morwood M.J., Soejono R.P., Roberts R.G., Sutikna T., Turney C.S.M., Westaway K.E., Rink W.J., Zhao J.x., van den Bergh G.D., Due R.A., Hobbs D.R., Moore M.W., Bird M.I. & Fifield L.K. (2004) Archaeology and age of a new hominin from Flores in eastern Indonesia. Nature, 431, 1087-1091

Ruff, C. 2002. Variation in Human Body Size and Shape. Annual Review of Anthropology 31:211 - 232.

There is some technical language in each paper. For instance, the Ruff paper discusses some of the methodological issues in estimating stature from skeletal measurements. Don't worry about the specifics here but it is interesting to think about how the lifestyle behind the fossil in question and its geographic location affect its size and how we estimate it. Its also good to think about the details of data gathering for these big picture trends, which are not addressed by a lot of the papers we'll read. The Morwood et al paper has some details about specific dating techniques. I don't plan to discuss these at all - just know that they used a variety of techniques to determine the range of dates that bound the geological context of the finds. If you want to understand the specifics of the techniques let me know or try a google search.

Pay special attention to the trends in body size change and the brief mentions of their proposed explanations. Note that even though there is not any life history theory here, we know that major shifts in size must be related to shifts in life history characteristics. What sets body size? Why should an organism get bigger or smaller? But the focus of both papers is the range in variation in body size and the 'clinal' patterning we see in time and space.

Some Flores background:
Most of you have probably heard about the Flores finds - the potentially new species of hominid found on the Island of Flores in the Lesser Sunda Islands a few years ago. Its been hotly debated ever since. A lot of researchers do not like the idea that H. floresiensis is a dwarfed form of H. erectus, but this was the first proposed explanation and still represents an important and current study with implications for human biogeographic patterns of size, colonization, evolution, and so on. It is often referred to as the 'hobbit' because of its very small size.

This is a figure from a news and views piece in Nature by Lahr and Foley that helps place the Flores finds in the context of our evolutionary tree (assuming you accept the finds as that of a new species).

Nature
Published online: 27 October 2004; doi:10.1038/4311043a

Human evolution writ small

Marta Mirazon Lahr & Robert Foley

Figure 1. Homo floresiensis in the context of the evolution and dispersal of the genus Homo.
a, The new species as part of the Asian dispersals of the descendants of H. ergaster and H. erectus, with an outline of the descent of other Homo species provided for context.

b, The evolutionary history of Homo is becoming increasingly complex as new species are discovered. Homo floresiensis (left) is believed1 to be a long-term, isolated descendant of Javanese H. erectus, but it could be a recent divergence. 1, H. ergaster/African erectus; 2, georgicus; 3, Javanese and Chinese erectus; 4, antecessor; 5, cepranensis; 6, heidelbergensis; 7, helmei; 8, neanderthalensis; 9, sapiens; 10, floresiensis. Solid lines show probable evolutionary relationships; dashed lines, possible alternatives.

Here you see how floresiensis compares to other hominin species with respect to brain and body size (from the same article by Lahr and Foley - yes the same Foley that wrote the paper we read in week 2).

Human evolution writ small

Marta Mirazon Lahr & Robert Foley

Figure 2. The relative brain and body size of H. floresiensis.
The dimensions of the skull and skeleton (LB1) described by Brown et al. fall well outside the extremes seen in H. sapiens and the 'erectines' (a range of hominin species, of which H. erectus is the most familiar). LB1 is closer in size to, but even smaller than, the australopithecines, of which the best known example is Lucy. On various anatomical grounds, however, Brown et al. believe that LB1 represents a dwarfed H. erectus.

There is a vast amount of discussion of the Flores finds on the John Hawks blog as well.

Terms and concepts:

clinal variation – [in response to Steven’s question] within a given species or related group of species (also called a taxon), gradual variation in a trait along some geographic axis. For example, the gradual decrease in the size of rabbit ears with increasing latitude is a clinal variation. Another example is a gradual change in some plant’s flower color from red to reddish pink to pink to light pink to white over the plant’s range. If instead the plant just had red flowers in one area and white in another, with no “mixtures” in between, you’d say the plant exhibits “discrete variation” in flower color.

directional selection – [in response to Dennis’s comment] selection toward an extreme version of a trait. For example, a population of rabbits in which small-eared individuals are most likely to survive and reproduce is undergoing directional selection for ear size. Think of direction selection shifting the bell curve for some trait toward one end or the other.

Sexual dimorphism: difference between the sexes. For height this is often expressed as average male size divided by average female size (or vice versa). It is often thought that higher levels of dimorphism reflect important behavioral and mating characteristics. If males compete for access to groups of females, they may have to be very large to fight off rival males. When females and males are closer to the same size it is sometimes considered to indicate a prevalence of monogamy. If so, observing an increasing trend toward lower levels of dimorphism in the hominin fossil record has important implications for social structure and life history. Potentially, when male investment becomes more important, pair-bonds become more stable, and male-male competition over females decreases. This might link to some arguments about slow growing and highly dependent offspring that are key characteristics of the human life history. The grandmother hypothesis that we talked about a few weeks ago is at odds with the view that increased similarity in size between males and females indicates that our species was pair-bonding (stable marriage-like pattern of male-female bonding). The grandmother hypothesis argues that males produce meat from hunting in order to gain access to mates apart from their wives. Essentially, males are actually parasites on the productivity of their wives and their wives' mothers and meat is not really a nutritionally important resource. Please think carefully about interpretations of sexual dimorphism.

stature - height

bi-iliac breadth - this is one of a few measures of human body form mentioned by Ruff. It is the widest distance between the pelvic bones. (the bones that you can feel as your 'hips'). it is measured with a special kind of caliper.

Bergmann's Rule - Mammals and birds tend to be larger at colder temperatures and higher latitudes.

Allen's Rule - Warm-blooded animals tend to have shorter limbs in colder climates.

secular trend - a trend that continues over large periods of time. Often meant to mean directional change.

clinal variation - Gradual continuous change in an observable physical (morphological) trait across space and within the range of some group of related organisms. The observed change is usually related to some environmental feature.

stegodon - an extinct species of elephant. Dwarf stegodons were found near the Flores hominids; in the same levels and close by. A common trend is that large mammals that colonize become much smaller. It has been hypothesized that this process, insular dwarfism, may explain the small hominids on Flores.

what do we call ourselves? There is a lot of nomenclature in the readings this week. Keep in mind that the evolutionary tree for primates is getting reorganized all the time and often this requires using new terms or changing the definition of existing terms. For the most part - hominid refers to all great apes. This includes fossil relatives like australopithicines and living species like chimps, orangutans, and gorillas. Note that for the sake of confusion some authors used hominid to refer to only bipedal ancestors. Hominin is used by Ruff to mean humans and their ancestors (homo sapiens and the extinct varieties of homo that preceded us) but slightly different definitions exist as well.

Condensed abstract of Pilbeam & Gould, 1974, in response to blog query:

Pilbeam, D. and Gould, S.J. 1974. Size and scaling in human evolution. Science 186: 892-901.

“Our general conclusion is simply stated: many lineages display phyletic size increase; allometric changes almost always accompany increase in body size. We cannot judge adaptation until we separate such changes into those required by increasing size and those serving as special adaptations to changing environments.
In our view, the three australopithecines are, in a number of features, scaled variants of the "same" animal. In these characters, A. africanus is no more "advanced" than the larger, more robust forms.
The fossil hominids of Africa fall into two major groupings. One probable lineage, the australopithecines, apparently became extinct without issue; the other evolved to modern humans. Both groups displayed steady increase in body size. We consider quantitatively two key characters of the hominid skull: cranial capacity and cheek tooth size. The variables are allometrically related to body size in both lineages.”

Helen Davis, the ghost student, writes about her human health project in South Africa

2007-09-06T12:42:00.001-07:00

Dear class,
Did you know we have another student that you have not yet met? Why, you ask? Because she is currently working with the People's Health Movement of South Africa on an important project aimed at lowering the rate of fetal alcohol syndrome in two South African rural communities. Here's someone out there trying to make a difference in the world of human ecology by doing some applied work and Helen's been nice enough to write us a little blog post about her efforts there that I think you will all find very interesting. A couple of articles about fetal alcohol syndrome that are related to the project can be found here and here. Helen will join the class in person later this month.

That's enough from me - here's a brief synopsis of Helen's work down there that she submitted via email:

My research thus far has focused on the substantive role of health and ecology on juvenile development. Specifically, I am interested in the extent to which health, structural, and cultural constraints impact variation in juvenile development and cognitive performance. Over the last couple of years my interests have broadened to include the social and practical applications of this research. Specifically, I am interested in assessing and documenting the obstacles transitioning populations face as they acculturate into a market economy—the ultimate goal being to develop culturally appropriate public health and education programs.

The University of Cape Town in South Africa is a unique research institution which uses Anthropology, Public Health, Human Rights and Medicine to combat many issues that have come to light since the end of apartheid (such as battling the world’s highest rates of HIV/AIDS and Fetal Alcohol Syndrome, as well as growing health issues in children due to maternal exposure to toxins and pesticides while pregnant). I am currently working on two projects here at UCT in order to learn how this program approaches the health concerns and issues facing many transitioning and/or disenfranchised populations.

One of the projects is looking at Fetal Alcohol Syndrome (FAS) and possible methods of intervention. FAS is an entirely preventable congenital anomaly manifesting as abnormal development, such as cognitive and personality impairments, as well as physical deformities in children, is an issue of great concern and debate within South Africa. Recognizing and recording how these situations have arisen, their repercussions and to develop preventative methods for future generations is overarching goal of this project, which is funded by the Center for Disease Control (CDC).

Alcoholism among traditional populations and within developing countries has been attributed to poverty, exploitation and a lack of education. Within South Africa, historical exploitative labor practices under apartheid—known as the DOP system—paid laborers and farm workers in the form of alcohol rations. As a result alcohol dependency and problem drinking is widespread in farming communities in the Western Cape Province of South Africa, and the region is host to the highest rate of FAS in the world (studies estimate that 4 to 6% of school-going age children in rural areas of the Western Cape have the full-blown FAS syndrome). The consequence of FAS for families, communities and society at large are enormous.

As a student working with this research program I have been granted the opportunity to work with the development, implementation and evaluation of interventions that may reduce the risk of alcohol-exposed pregnancies, and are specific to the individual at risk, service providers and the general community. Three levels of interventions are currently being evaluated. Since there is little evidence of the effectiveness of different prevention approaches, they must be determined through carefully controlled evaluation studies.

This study is taking place within 2 distinct sites: City of Tshwane, in Gauteng, and the West Coast of the Western Cape. I work solely with the project in the Western Cape. If anyone wants more information about the project itself or the target population I would be glad to provide it; however, I feel I have probably already bored everyone to tears.

Niche Construction

2007-09-06T06:27:00.000-07:00

We've had a lot of questions and comments about niche construction so I thought some additional information might be worth while. The authors of the book that Terrell cites in his paper have a pretty nice website that I recommend checking out. Here's an excerpt that explains how they think of niche construction:

"Niche construction is the process whereby organisms, through their activities and choices, modify their own and each other's niches. By transforming natural selection pressures, niche construction generates feedback in evolution, on a scale hitherto underestimated, and in a manner that alters the evolutionary dynamic. Niche construction also plays a critical role in ecology, where it supports ecosystem engineering and part regulates the flow of energy and nutrients through ecosystems. We are developing a new approach to evolution - one that treats niche construction as a fundamental evolutionary process in its own right. We call it extended evolutionary theory. "

If you are interested in this topic I highly recommend spending some time on the website. Also note that they have posted a pdf of the first chapter of their book, which you can get by clicking here. Its really an interesting read. They make the point that we are missing a fundamental process of evolution if we don't specifically pay attention to how the feedbacks between organism and environment alter selective pressures. In short, they argue that niche selection changes the way we view the processes of evolution. It of course has rather large implications for humans as we are seemingly big-time niche constructors.

Best,
Oskar

Genome sequence of individual human

2007-09-04T13:10:00.000-07:00

Here's a cool paper hot off the presses at PL0S Biology:

The Diploid Genome Sequence of an Individual Human

It shows how diverse a single genome can be by comparison with other samples and suggests that, in a nutshell, humans might be slightly less genetically homogeneous than previously thought.

One weekly blogged question can be a comment instead

2007-09-03T16:29:00.001-07:00

Odds are some of your ideas on and from the readings are more comments than questions, so feel free to make one of your weekly blog entries a comment or reaction to the readings or to questions in our posted blogs.

Bill

Society for Human Ecology, International Conference

2007-09-03T09:58:00.001-07:00

Our friends over at Human Ecology Forum have posted a reminder that the annual meetings for the Society for Human Ecology are approaching. This year they will be held in Rio de Janeiro from October 4 - 7. A few of you have asked about conference information - follow the links to see what the society for human ecology is up to and to get a better feel for the kinds of topics they address.
best,
O

More thoughts on human biogeography

2007-09-02T20:30:00.000-07:00

Here are some thoughts and questions to accompany your reading and thinking about human biogeography, the topic of our third week. I’ve defined some vocabulary words at the end.

Chapter 1 of Lomolino et al. contains an excellent discussion of the philosophy of science generally and biogeography specifically. It’s well worth reading. Terrell’s article is nicely historical and provides both good information and provocative ideas.

First familiarize yourself with biogeography as a topic and as a science. Like other scientific fields, biogeography starts with the relationship between pattern and process. What are some examples from human ecology not covered in the readings? How might you go about investigating them? For example, how does “isolation by distance” affect human ecology? How might you “test” for human uniqueness in this respect?

Lomolino et al. note that “H. sapiens possessed an unrivaled ability to adapt to, modify, and eventually dominate a variety of environments.” What are some implications of such “niche contruction” ability, as Terrell would say? Terrell also stressed the importance of environmental factors in structuring human biogeography. How might one begin to tease such distinctions apart?

How might the development of key technologies, as with seafaring vessels, parallel hypotheses about the drivers and pace of biological evolution? (Hint: look for info on John Maynard Smith’s ideas about evolutionary innovations and transitions) , This perspective might be useful for examining modern aspects of human ecology.

Terrell notes that “Although the basic ingredients of what might be called human biogeography have long been part of academic life, these elements have not become a prominent feature of modern advances in ecology and evolution.” From what you know, do you agree?

Vocabulary

admixture – mixture of genetically different groups

biogeography – “the science that attempts to document and understand spatial patterns of biodiversity”. Biogeographers explore how biodiversity varies over the Earth and underlying reasons for this variation. Biogeography is typically a comparative and observational science rather than an experimental one.

island biogeography, equilibrium theory of (Lomolino p. 734, 2nd to last paragraph)– idea that the number of species on an island “represents a dynamic equilibrium between opposing rates of immigration and extinction.” It’s an “equilibrium” because new arrivals are offset by extinctions, and it’s “dynamic” because the precise makeup of species changes over time. Ecologists Robert MacArthur & E.O. Wilson proposed it in 1967.

mesic (p. 730, paragraph 2, Lomolino) – relatively moist, with relatively stable temperatures

taxon cycle (Lomolino p. 738 bottom) – a “cycle” of colonization, evolved specialization, and eventual replacement by new generalized colonists. E.O. Wilson proposed the idea to explain patterns in the Melanesian ant fauna, and Jared Diamond extended it to humans

vicariance (p. 730, end of paragraph 1, Lomolino) – geographic separation due to physical events, such as tectonic shifts, rather than active dispersal of organisms

xeric (p. 730, paragraph 2, Lomolino) – relatively dry

Readings for Week 3: Humans and biogeography

2007-09-02T07:37:00.000-07:00

This week we are reading an article and a couple of sections from a prominent text book in biogeography.

Lomolino, Riddle, and Brown. 2005. Biogeography 3rd Edition, Sinauer Press. pages 3 - 12 and 728 - 743.

Terrell, J. E. 2006. Human biogeography: evidence of our place in nature. Journal of Biogeography 33:2088-2098.

The excerpts from the biogeography text book define the field of biogeography and give good examples of human biogeographic patterns. It also contains good background information on human colonization of the world.

The Terrel paper gives good background for the valuable contributions that biogeography can make to the social sciences. It also provides a philosophical discussion for how perspectives on the human place in nature have changed through time and by discipline. I contacted Dr. Terrell to see if he would be willing to chime in to our blog discussions of his paper. He responded with interest but is traveling next week. As an alternative I will email him a few of our questions and we can post his responses. So please think of very good discussion questions that you can ask to the author directly.

LHT wrap-up

2007-08-31T17:06:00.000-07:00

So far we’ve tried to weave together some themes that we will continue to develop during the semester as we look at topics in human ecology. We take a macroscopic viewpoint. We are interested in basic governing principles and law-like generalizations that capture basic large scale, emergent, features of the systems we encounter. We want to identify ways in which humans are unique, given background ecological patterns, and ways in which humans seem to conform to these patterns. Part of this is being critical of ad-hoc claims of human uniqueness or mere assumptions that humans are outside of nature, which are common in the literature.

Given this perspective, we want to address the role of life history theory (LHT) in (human) macroecology. We want it to be as clear as possible why we chose to cover LHT and how it ties into the other themes of the class. Please ask us questions about this…

Life history attributes scale with body size, as do other important ecological variables. Such scaling relationships can be used to make deductive predictions. For example, we know that size at weaning is about one third of adult size, so it’s a constant linear proportion, and by combining this with the Smith-Fretwell model we can deductively predict the -1/4 scaling observed for fertility rate (Charnov and Ernest 2006).

Human uniqueness. Life history points us to some key features of the human life history that are truly unique. Importantly, these differences are quantitative rather than qualitative in that humans differ by going to extremes of a continuum not by having features that in and of themselves are something ‘new under the sun.’ Some key life history features that makes us unique are: 1) a long lifespan; 2) long juvenile (growth) period; 3) slow growth; 4) low mortality rates; 5) high levels of support and/or provisioning from males; 6) support from post-reproductive females (also know as grandmothers). These traits are identified by cross-species comparisons where humans are shown to be consistent outliers. Importantly, LHT ties together and explains the observations on the human life course. By investigating the energetic tradeoffs behind these features we’ve learned a lot about the human evolutionary niche. And we’ve also learned, by studying the adaptive nature of these traits, some things that must have been true about past environments where humans evolved. Embodied capital theory has been proposed to unite these observations into one cohesive framework (see Kaplan et al 2000 in Evolutionary Anthropology or Kaplan and Robson 2002 in PNAS).

Lastly, with respect to the EEA (environment of evolutionary adaptedness) concept, I think Foley’s concerns are valid in that it is an easy concept to misuse. This is especially true if the features of this EEA are too narrowly defined. However, as we saw in the Hill and Kaplan paper, it is common to assume that some behavior we study today, among industrial or foraging populations, is an adaptive attribute from some past selective environment. My take is that the EEA can be a useful concept, in some cases is necessary, as long as we don’t assume that it refers to one narrowly defined place and time.

Thinking about life history theory

2007-08-29T13:50:00.001-07:00

Hey everyone,
Great discussion on Tuesday. Please don't be shy about posting here and a good number of you need to come up with one more question! Note that if you click directly on the title of a post on the blog archive on the sidebar to the right it displays the post and all the comments on the same page.

A couple of things to think about:
In the introduction of the Hill and Kaplan paper they state the following: “Our goal here is to show how life history theory and anthropology can be combined to organize social science research on the major demographic trends that will affect standards of living, crowding, urbanization, conflict and warfare, and the environment of the next century”
What do you think of this view? Can life history theory really be employed in such a way that it will help social scientists address such complicated issues?
At this point it is probably obvious (from class) that I favor the possibility that individual choices that affect the life history budget - or how we allocate energy from growth (this includes school and other forms of skill development) and reproduction have cascading effects to higher orders of social organization and are connected to major demographic trends. The connections here are difficult to make at times and I encourage you to be skeptical of this view.

On page 406 they say: "The diversity of life histories is presumably due to the fact that the shape of the relationships between investments and outcomes varies ecologically." If this is true, what can we say about the ecologies where humans evolved? (this is answered in the paper). or more simply, what do they mean by this?

On Thursday we will begin with just a bit more of a summary of life history theory in general and then we'll talk in depthly about the Hill and Kaplan paper. We'll probably discuss the quantity-quality tradeoff and embodied capital but please come prepared with your own discussion questions and we'll see where things go.
See you tomorrow,
Oskar

Readings for week 2

2007-08-26T20:15:00.000-07:00

This week we are reading a couple of papers that help us understand what humans are like from an evolutionary perspective while also introducing some important theoretical concepts (Life history theory and the EEA).
Your discussion questions can go as comments to this posting by using the link below. Recall that at least one question should be posted by Monday night at 8:00 pm. You should post two questions during the week. Its up to you if you want to wait until after class on Tuesday to post the second question or post them both at once. Feel free to respond to your classmates questions.

Here is the bibliographic information for this week's papers:

Foley, R.A. 1996. The adaptive legacy of human evolution: A search for the environment of evolutionary adaptedness. Evolutionary Anthropology 4: 194 – 203.

Kim Hill, Hillard Kaplan. 1999. Life History Traits in Humans: Theory and Empirical Studies. Annual Review of Anthropology 28: 397-430

I realize that the Hill and Kaplan paper might be somewhat... thick.... for those of you who have not encountered these concepts before. Please do your best to wade through the material and note sections of the paper where you seem especially confused so we can talk about them in class. Its worth spending time with this paper, however.

Some comments on why these papers were selected:
Its important to understand the basics of Life History Theory (LHT). Only a minority of anthropologists use LHT but its made major contributions to the field in the last couple decades or so. LHT applications to humans are inherently interdisciplinary because they are anthropologists using biological concepts that ultimately derive from economics, which fits the theme of the course quite well. Most life history traits (life span, age at first reproduction, mortality rate, age at independence, etc) tend to scale allometrically with body size when large samples of organisms are considered, like all mammals. Hence, such traits are candidates for law-like generalizations for ecology that are relevant for humans. These scaling relationships describe emergent evolutionary patterns spanning several orders of magnitude in biological organization. LHT is also tied to some important energetic principles that link to other energy-based theories of evolution.

More pragmatically: we want you to be able to define LHT. What is it and what does it tell us? What traits of the human life history seem different from other mammals? How has life history theory been used to explain these difference in humans and what have we learned about human evolution along the way?
Because humans are all over the globe we won't compare just their geographic distribution to other species as an interesting biogeographic pattern. We might focus on the biogeographic distribution of specific traits - life history traits among them.

Foley and the EEA:
The human life history evolved in a nonindustrial environment. This is the link to the environment of evolutionary adaptedness, or EEA. Note that Foley is critical of the EEA concept but along the way in his critique he presents some very relevant information about human ecology and our evolutionary history. We don't want to spend a lot of time going into why some people like the EEA concept and some people don't. A lot of the differences are semantic and have to do with other conflicts between human behavioral ecology and evolutionary psychology that are beyond the scope of this class (not that we can't discuss them some). Clearly, we have lived in different environments in the past but is it the case that past evolutionary environments may have tuned us for contexts very different from where a lot of humans are today? Think critically about how much we can and can't learn about our evolutionary past via the study of extant foraging populations. Do we have enough 'microscopic' studies of human foragers to see the macroscopic patterns relevant to investigating life history variation and the EEA?

We want to know to what degree patterns in modern behavior that seem somehow out of step with the environment are tied to behaviors that were more clearly adaptive at another time and place. Hence, the EEA concept is important in lots of discussions and is often implicit well outside of evolutionary psychology where it was widely adopted.

Also keep in mind the notion of 'human uniqueness' in the context of these papers.

See you Tuesday,
Oskar