(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
Wednesday, November 28, 2007
Toward a human macroecology
“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
Tuesday, November 27, 2007
UNM Statistics Clinic
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.
Friday, November 23, 2007
Week 15: Human Macroecology and Historical Dynamics/Course Wrap-up
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
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
Tuesday, November 20, 2007
Gapminder video
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
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
Thursday, November 15, 2007
Week 14: Economics of energy in human systems
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
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.
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.
Monday, November 12, 2007
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...
Friday, November 9, 2007
Week 13: Scaling part 2
The following papers are required readings for next week. A few optional papers are in the ereserves folder as well.
*
* 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
*Moses, M. E., and J. H. Brown. 2003. Allometry of human fertility and energy use. Ecology Letters 6:295-300.
Wednesday, November 7, 2007
"Nets versus Nature": an interesting News and Views
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:
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...
"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 size1, 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...
Sunday, November 4, 2007
Introduction to Week 12 and 13: Scaling in human ecology
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
*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
*Hamilton London
*Hamilton, M. J., B. T. Milne, R. S. Walker, and J. H. Brown. 2007. Nonlinear scaling of spaceNational Academy
*Moses, M. E., and J. H. Brown. 2003. Allometry of human fertility and energy use. Ecology
*
*Hamilton, M. J., B. T. Milne, R. S. Walker, and J. H. Brown. 2007. Nonlinear scaling of space
*Moses, M. E., and J. H. Brown. 2003. Allometry of human fertility and energy use. Ecology
Friday, November 2, 2007
Expanding the Wheel?: Lotka's Max Power Principle and Human Ecology
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
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
Thursday, November 1, 2007
Week 12: Scaling (part 1)
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
*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.
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