Monday, October 29, 2007

Energy and "Cultural Development" in the US

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.

US Real GDP per Person 1949-2006
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.

US Energy Consumption per Person 1949-2006
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.

Dollars of GDP per Unit Energy 1949-2006
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.

US Greenhouse Gas Emissions per Dollar of GDP 1980-2005

Friday, October 26, 2007

Week 11: Energetics, culture, and society

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.


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.
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

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...

Wednesday, October 24, 2007

Fitness landscapes: a way to visualize adaptation of complex systems

"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." (
"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.



McKinsery Quarterly_Escaping the red queen effect:

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

Wikipedia, fitness landscape:

Friday, October 19, 2007

Week 10: Complex human ecological systems & their dynamics

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,



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.

Tuesday, October 16, 2007

Additional readings

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

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 and click on 'find an event'. You can also email Laura at for specific event information.

We hope to see you there!


Coby Rudolph

(this information was contributed by Helen Davis).

Friday, October 12, 2007

Week 9: Ecology and Geography of Wealth and Resource Use

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.


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


  • 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.

Wednesday, October 10, 2007

New explanation for megafauna extinction: extraterrestrial impact

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. Firestonea,b, A. Westc, J. P. Kennettd, L. Beckere, T. E. Bunchf, Z. S. Revayg, P. H. Schultzh, T. Belgyag, D. J. Kennetti, J. M. Erlandsoni, O. J. Dickensonj, A. C. Goodyeark, R. S. Harrish, G. A. Howardl, J. B. Kloostermanm, P. Lechlern, P. A. Mayewskio, J. Montgomeryj, R. Poredap, T. Darrahp, S. S. Que Heeq, A. R. Smitha, A. Stichr, W. Toppings, J. H. Wittkef, and W. S. Wolbachr

A carbon-rich black layer, dating to {approx}12.9 ka, has been previously identified at {approx}50 Clovis-age sites across North America and appears contemporaneous 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 layer but 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 {cong}12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with 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 evidence for an ET impact and associated biomass burning at {approx}12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and 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:

Figure 2

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:

Figure 1

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="">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.



Sunday, October 7, 2007

Project Proposal: Three stages, Three weeks, Infinite fun

1) Short Preliminary Project Proposals


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

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

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

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,

Friday, October 5, 2007

Week 8: Human influences on biogeographic patterns

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.


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!?
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