Friday, August 31, 2007

LHT wrap-up

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.

Wednesday, August 29, 2007

Thinking about life history theory

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,

Sunday, August 26, 2007

Readings for week 2

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,

The "Eco-Footprint" and the productivity and efficiency of land use

This posting in response to a small portion of Oskar's Orientation. The new blog entry is necessary to post images, and this is going to be quite long anyway, so please forgive its displacement from the comments section.

In response to the chart of relative Eco-footprints, George questioned the role of productivity differences between countries. Oskar's response in the Orientation post was somewhat speculative, so I thought I'd take a look at some data. While I don't think George was referring to agricultural productivity alone, agriculture is the most land-intensive human activity, and the Eco-footprint is cast in terms of hectares of land, so I'll follow Oskar in looking at arable land use, specifically the production of food crops, for which there's reasonable cross-country data available from the UN's Food and Agriculture Organization. I'll be using their year 2000 numbers, which are more complete than some of the more recent data.

The FAO breaks production of food crops into three groups, cereals, pulses (peas, beans, and lentils), and roots/tubers. The distribution of these three crop types is heterogeneous across the globe, with North America specializing the production of cereals, which account for over 90% of the mass of food crops produced. Roots and tubers become more prevalent moving from NA to Asia, then Europe, Latin America, and finally Africa, where they make up the bulk of food crop production. Pulses constitute only a small portion of production on a continent-level basis, but they do contribute a significant amount in many individual countries. In general, I'll handle this heterogeneity by considering the total mass of food produced, assuming geography determines which crops are produced but that, all else equal, the inherent productivity of land in terms of mass of food per hectare is equal.

This first figure results (click to enlarge). The total mass of food crops divided by the land area used to produced them is displayed for selected countries (those in the Eco-footprint chart and a few others of interest), ranked high to low from left to right as in the Eco-footprint chart, with the world average on the far right. While agricultural land in the US is much more productive than the average plot of land in the world, it is not the most productive, significantly no different than the average plot of land in China.

One potential explanation for the higher average productivity of land in the UK, Germany, Japan, and South Korea is the higher population density of these heavily industrialized countries. Economic theory would predict that as the total area of farmland is reduced, the least productive farmland will be recruited to other uses first, thereby raising the average productivity of remaining farmland. When a dwarf leaves a room, the average height of the remaining people goes up without anyone actually growing taller. This effect should be testable with the FAO's data over time, but that's outside the scope of this simplistic cross-country comparison.

Instead, I'll follow Oskar's lead and take a look at the inputs that are put into this productivity. Farmland in the US and China might be equally productive in a gross sense, but we need to consider net productivity. The next set of figures do just that. The most important input to agriculture, as mentioned, is land, so we can get an idea of the efficiency (or lack thereof) of land use by simply taking the inverse of the preceding graph: the amount of land (hectares) it took to produce a given amount (100 tonnes) of food in each country. Countries are ranked by how inefficiently they use the input, making the UK the most efficient at the bottom of the chart while Australia, with its wide, dry spaces is the most land-intensive producer among the selected countries. As you can see, the US uses land more efficiently to produce food crops than the world at large.

While the FAO doesn't have usable data on pesticide use, it does for fertilizer. As indicated in the chart below, the US used slightly more fertilizer to produce a given amount of food than the world average, but is much more efficient with this input than many industrialized and industrializing countries, including China. The intense use of fertilizers in South Korea and Japan may help explain their productivity advantage over the US, but at greater environmental cost. Nigeria stands out as the most 'efficient' user of fertilizers, barely using any to produce mostly tubers.

Next up is water used for irrigation. The scale of the chart is distorted by the extremely inefficient irrigation that occurred in Bangladesh, over 250 thousand cubic meters of water to grow 100 tonnes of food, while the average plot of farmland in that country was about at the world average. Japan also used exorbitant amounts of irrigation, which unlike Bangladesh helps contribute to relatively high productivity. Contrast Japan to the UK, which achieved the highest agricultural productivity per unit land with negligible irrigation--the most water-efficient of the selected countries. While China sat at about the world average for agricultural water use, the US used significantly less water to achieve the same land productivity.

The large-scale use of industrial machinery and its intendant fossil fuel consumption and resulting emissions is the largest component of the high Eco-footprint of Americans. How does this shape up for agricultural production? The next figure displays the number of tractors on average used to produce 100 tonnes of food crops. Japan far exceeds the other selected countries and the world average here, heavily distorting the scale of the chart. Surprisingly, the US was below the world average in 2000, and used significantly fewer tractors on average to produce the same amount of food than most other industrialized countries in our comparison. For the first time, China is more 'efficient' than the US, relying on fewer tractors to farm the same amount of food.

The final input under consideration is labor. As seen the the chart below, the Southeast Asian countries relied on huge amounts of labor to produce food crops, India over 90 workers per 100 tonnes, while the UK and her former colonies used stunningly little labor, less than one worker in American fields to achieve the same production as 90 or so Indians, Bangladeshis, or Chinese. China and India alone contributed about 58% of the world's agricultural labor force in 2000, making them the prime drivers of the high world average.

Agricultural labor is even more interesting in the inverse. The mass of food on average produced by each farmworker is displayed in the final chart. Canadian farmworkers were the most productive, yielding an astonishing average of over 150 tonnes of food crops each, with the US slightly behind at about 122 tonnes/worker. The average Indian, in contrast, produced just 1 tonne of food in the year 2000, with many of the countries in our selection faring only slightly better. This indicates those huge masses of workers in Southeast Asia are primarily engaged in subsistence-level farming. Japanese workers produced just over 6 tonnes of food each on average.

It's interesting to compare the US to Mexico, where workers produced an average of only 3.6 tonnes of food each in 2000. Farm workers in the US were over 30 times more productive than those south of the border. Are Americans workers simply more productive than Mexicans, all else equal? This is clearly not the case, since the majority of the 3 million American workers in 2000 were Mexican nationals, legal and illegal. Mexicans are vastly more productive in America than they are in Mexico.

Why the difference? As we've seen, in addition to the relatively negligible amount of labor, American agriculture used less land, fewer tractors, and vastly smaller amounts of land and water to produce a given amount of food than most of the countries in our comparison and the world as a whole, with only slightly more fertilizer per unit of food. This is the result of technology, by which I mean the way the different factor inputs are used together to produce an output. American farms simply make better use of the resources put into farming, including, most spectacularly, people. Overall, the performance of agriculture in the US seems quite good under this comparison.

Japan's productivity, on the other hand, was based on extremely intensive use of fertilizer, tractors, and, for an industrialized country, labor, allowing it to get more food out of more limited land resources. But Japan's gross productivity wasn't that much higher than the US given its increased resource use, such that Japan may very well have much lower net agricultural productivity than the US. Unlike Japan, the UK made limited land more productive with much lower costs in terms of water, labor, and fertilizer, though they needed more tractors on average to do so.

So why do we Americans have such a huge Eco-footprint if we're doing relatively well in terms of agricultural land use? Part of the reason lies in the sheer scale of American activity. In 2000, the US produced over 30% more tonnage of food crops than India, using only 3 million farm workers compared to India's 263 million strong agricultural labor force. Only China, with its 511 million farm workers produced more food than the US. Only China and India farmed more hectares of land than the US. Only China used more total fertilizers, with the US using 12.5% more than the third largest consumer of fertilizers, India. But while both China and India have large-scale agriculture in the same league as the US, over 17% of the world's tractors were employed in America--nearly 4.7 million of them. India made use of just under 2 million tractors, while China used just under 1 million.

The Eco-footprint simply weighs several million tractors as far more harmful to the ecosphere than three quarters of a billion subsistence farmers. Whether this is a fair weighting is open to debate.

Finally, instead of asking "how many Earths"-style questions inspired by the Eco-footprint, we can ask what global agriculture would look like if every country employed American agricultural technology, all else being equal. This will require the assumption that corn fields in Africa are just as inherently productive as those in Kansas, potato fields in Canada just as inherently productive as those in Idaho; it's the use of input factors that matter.

Running the numbers, in the year 2000, each of the 161 countries in my data set could have produced the same amount of cereals, pulses, and roots/tubers at US levels of efficiency (or inefficiency) with a small, about 6.4%, increase in global fertilizer use along with more 33% more intensive use of tractors (that's an additional 8.8 million of these machines). What would be gained from such increases? First, such American-style production would have reduced global water use for irrigation in 2000 by more than 63%, a savings of nearly 870 billion cubic meters of fresh water. It would have required 50% less land under the till, freeing up nearly 400 million hectares of land that could have been put to other uses (including returned to nature) or saved from slash-and-burn in the first place. Most dramatically, such a change would have implied a 98% reduction in agriculture workers, freeing some 1.316 billion people from toil in the fields.

This suggests that each tractor introduced in the year 2000 would have freed, on average, 150 people from a life of subsistence farming. I'd argue that much of the progress of western civilization is due to such emancipations. Just 3 million farmworkers in the US allow two orders of magnitude more Americans the freedom to specialize and increase non-farm productivity even more. Imagine how many potential Mozarts, Einsteins, and Bill Gates who have been born into a life of illiteracy and back-breaking labor among the teeming billions of subsistence farmers in the underdeveloped world. The Eco-footprint can in no way capture this cost to living 'sustainably', i.e. in poverty. 150 people per tractor sounds like a fair trade to me.

I did most of the data work in Access, but I've dumped the raw data, my (in)efficiency calculations, and American-technology projections into an Excel spreadsheet if anyone wants to have a closer look or play around with the numbers. The above analysis is almost stupidly simplistic, but at the worst it should yield some sense of the large differences between agricultural practices in different countries and the magnitude of those differences across the scales involved.

Malthusian trap

This somewhat dated but still very interesting book review in the NY Times just came to my attention:
It relates to demography, fertility, and and somewhat builds on our suggestion that we might view malthusian growth as a 'law' in light of our understanding of limit myths...

Also check out recent posts on the John Hawks weblog (link on sidebar to right), especially "Natural selection 101."

Saturday, August 25, 2007

How would you like your science today: hard or soft?

[This post was contributed by Verity Robert via email]

One of the remaining questions presented in class was what distinguishes hard science from soft science. A tour of these concepts on the internet leads one to believe that hard science is more accurate and objective than the soft science, and, as The Onion puts it, fields like quantum physics are
also “undeniably a really stupid, pointless thing to study, something you could never actually use in the real world” (Issue 38-21, 05 June 2002). Personally, I consider fields like physics to be hard science because, in addition to the description above, they have been able to represent the world and understand its processes through mathematics. Whether it be newtonian or quantum mechanics, cosmology or celestial bodies, we can understand how the universe works and what we may be missing from the model. And whilst the principles and laws may be defined only for ideal/perfect/vacuum conditions, they have put humans on the moon.

However, the comical point made by The Onion is one worth considering: is it worthwhile to develop a field so abstractly that it becomes pointless in every day life? Having studied astrophysics, I think it is reasonable to say that whilst quantum physics may not be practical on a day-to-day basis, the concepts and understandings that have come from it have provided insights into how the universe begun, the life and death of stars, and what may be missing from our model of the universe, such as dark matter/energy, to name a few. The point being that perhaps laws can only really help in our understanding of the world on a small scale, but nevertheless necessary to our understanding of how the world works on the large scale. And that maybe being able to understand the big picture requires our ability to make intuitive leaps between certain concepts. I think macroecology has the potential to do this and achieve all or most of the goals it has set out for itself, but the temporal aspect will be the most difficult to accomplish. Perhaps that is why ecology has had a difficult time in establishing laws and itself as a hard science; that though it may practice the scientific method, the ideas and theories it presents about how the world works may not always be verifiable for past processes. That even if it were to define the world to a point that everyone was happy with, taking into account all the “friction,” certain aspects of that “friction” may not be knowable about the past, and thereby not testable. Then there is also the question of how much of the “friction” is actually negligible and is there a way to test that necessary “friction” (perhaps through computer modeling, maybe multivariate statistics)?

At this point I feel I am just rambling, so I will leave off here.

Thursday, August 23, 2007

Authoring a blog

Eventually all the enrolled students will receive an email inviting them to be an author on the blog. You do not have to write blog entries if you don't want to. This is completely voluntary. You can do all of the posting you need to just by using the comment link at the bottom of each blog but please feel encouraged to post blogs of your own!
Should you decide to post please be more concise than I am... :-) and we only ask that it be material with clear relevance to the class. If you are commenting on an existing post please use the comment function and only start a new blog if its a new subject or if you are reporting on a cool study you read or something to that effect.

Discussion of laws and macroecology

Hello everyone,
First I want to thank you all for contributing to a great discussion. Please continue to read the papers so carefully. We look forward to next Tuesday's look at human life history and the EEA.

I'll mention a few of the things that came up today and then add a few points that we didn't get to.

We spent a lot of time on Brown chapter 1. Figure 1.1 generated interest and confusion and we just want to point out that while each data point in the figure represents an individual mountain top it would be impossible to conduct a detailed study of the flora and fauna on each mountain because of time and money constraints. It is also probably not feasible to simply raise the temperature or cut down the forest at the tops of mountains to see how species respond to habitat loss. Those sorts of pragmatic features of the approach are what the example was meant to illustrate. By using the species-area relationship we can get a feel for what the average tradeoff, across mountain tops, might be between area and number of species. Note also that this prediction is very imprecise with a range between 9 and 62% of species lost. The loss of detail may often be accompanied by a loss of predictive power or precision. How should we feel about this? However, this prediction was also obtained after spending just a few days to weeks at the library, so as a rough low cost estimate it may be a reasonable place to start. It also is simply an example, good or bad depending on your reaction, of answering a question with an inductive, non-experimental, library-based analysis. (Inductive because it makes a general statement of a population based on the properties of a sample to the effect that we consider the statement potentially valid for the population of all mountain tops in the Great Basin. Also, the premises don't guarantee the truth of the conclusion, as in deductive logic where if the premises are true the conclusion must be true.)

One subject from the Brown chapters that could use further thought and discussion is the link between macroecology and complex systems and the topic of emergence. If you are not familiar with emergence, the wikipedia entry is quite good. In simple terms lets say that the first step in recognizing an emergent phenomenon is experiencing a level of surprise. You observe a pattern that seems to not follow from the characteristics of the entities that comprise the pattern. Given what you know about what you study, you didn't expect there interaction to lead to what you just found. This is often stated as the whole being more than the sum of (or different from) its parts. The important link between emergence and macroecology is seen in Brown's quote on page 11 - in that macroecology seeks to "develop more powerful macroscopes that will reveal emergent patterns and processes."

Brown lists 6 features of a complex adaptive system that would be good to think more about, especially in the context of human systems, that are relevant for thinking about macroecological patterns.

We should also keep in mind Brown's 5 characteristics of macroecology, page 18 - 20.

Brian Maurer, in his discussion of complexity and structure, points out that when the parts of a complex system interact the system may gain structure and inertia. In Brown's example of the gas diffusing through the room, the more the gas particles interact, by bumping into each other in the air, the more diffuse they become and hence the less structured. On the other hand, as with the plot of human territory size we showed in class, the more the humans in those systems interact the more structured they become. Lots of living systems have this property of structure being enhanced by interaction and this feature changes the behavior a lot and it should change our perspective as well. In Maurer's own words, when he talks about structure he means " the entities within the system interact or relate to one another in a consistent and stable manner so that the overall persistence of the system is enhanced.” (quote from his book, "Untangling ecological complexity, page 27).

The main point from Ginzburg is that ecology has laws and we've only been wrong about the way we think about laws and in our conceptions of what they should do. Physical laws are often defined in a vacuum using the concept of a limit myth. With a precise physical law you can exactly explain behavior on a frictionless plain or in a vacuum but the real world is full of frictions and external forces so these 'laws' often have to be adjusted to account for such forces. Sometimes this can be done perfectly but other times there will be exceptions or noisy aberrant behavior to the system. This does not mean that the law is false, only that we haven't accounted for the friction. Is it possible that ecologists and anthropologists study systems that experience a lot of 'friction' in that they are acted upon by an exceptional number of external forces and thus accounting for them all can be quite difficult?

Also recall their example of the Titius-Bode law that ended up not being a law at all. We may have to chase after a pattern for a while before we find out that its just a curious fact and not the law we thought it was. Is there some way to avoid this potential? Plugging the pattern into existing explanatory theories that can make deductive predictions might help.

(ps - its very very unlikely that most of our blogs will be this long...)

See you Tuesday,

Tuesday, August 21, 2007


On the first day of class we had a brief lecture that attempted to define the perspective toward human ecology that we will be developing in this class and gave a few examples of the relationships we'll be looking at later on. I'll give a brief breakdown of some of the main points of the lecture here.

The first goal was to define our approach to human ecology as a macroscopic transdisciplinary enterprise aimed at identifying mechanisms, simple governing principles, and explanations for complex large scale patterns. The specifics of the macroscopic perspective is defined in the chapters by Brown. Our perspective differs quite a bit from the sorts of topics generally associated with human ecology (see journal by this name for examples). We often refer to our perspective as human macroecology to make a distinction. We are interested in very large scale patterns and we draw from several disciplines.

The forager lifestyle and the EEA:
Anthropologists traditionally had a great deal of interest in the study of human foragers - populations that subsist by some combination of hunting, gathering, and horticulture. Unfortunately, detailed field studies of the few remaining indigenous populations who still subsist with a forager economy are very few in number, embarrassingly low I would argue, given that anthropology should be the field responsible for the description, documentation, and explanation for the depth and breadth of diversity of human cultures and lifeways of the past and present. But that's the subject of another blog.
We are interested in foragers because the overwhelming majority of our evolutionary past was spent as foragers. A concept often used in evolutionary psychology is the EEA, which stands for environment of evolutionary adaptedness. The EEA is an important concepts because in many ways our psychological and behavioral predispositions were molded in an environment much different from the modern industrial context. We evolved under conditions of much smaller group sizes where cooperation and food sharing were essential and prevalent and where we hunted and/or gathered our food. The industrial economy and lifestyle is very different from the EEA and we might want to know what sorts of patterns in human behavior, organization, or demography of humans has changed as a function of this change in lifestyle. This change might also have affected the way humans impact other ecological systems and species.

Human Uniqueness:
It is striking how different the lifestyles of modern humans can be. We hear a lot about human uniqueness in both anthropology and ecology. Anthropology is practically built on the idea that humans are outside of nature and therefore biological concepts are not relevant to the social sciences - there are plenty of exceptions to this notion but it is still very common.
If we wonder why humans have so much behavioral and organizational diversity we might wonder if its because we are especially diverse genetically. This is not the case. Individual populations of chimpanzees have more diversity than all living humans combined (see figure).

So, while humans may be unique in their diversity at the phenotypic level (at least with respect to behaviors and lifestyles) they are unique in the homogeneity at the genetic level. This is a very interesting combination of observations. Now, it may be that time is responsible for the lack of genetic diversity, as humans are a relatively recent mammal, but that still begs the question as to what happened to allow so much diversification in such a short time?

Humans have grown very rapidly (some say exponentially) and spread over most of the globe in a fairly short period of time. Is it possible that some of the adaptations that allowed for this rapid spread and growth are related to our modern day impacts on the environment and sustainability issues?
From the observations presented up to this point (there were more in the original lecture) some fundamental questions might be asked: Why do humans have so much variability? What are the patterns of this variability? How do these patterns compare with other ecological patterns? What laws and patterns determine which patterns we follow and which ones we don't?

We then gave a few examples of human patterning. We want to be skeptical of assuming that humans are unique with respect to some pattern or attribute. Uniqueness needs to be demonstrated. (Also, we wouldn't suggest that humans are NOT unique either - all biological species are unique by definition).

The first example is latitudinal gradients. Diversity in languages seems to map onto diversity patterns in plants. Is it possible that the underlying processes are also similar?

Ex. 2: Modern human fertility often is taken as a case where humans must be very unique. Many countries in Europe have below replacement fertility and the wealthiest classes in most or all countries have the lowest fertility rates. How can this be? Does it mean that humans are not following biological patterns with respect to an important Darwinian parameter, fertility?
That depends on your perspective. To the extent that energy budget is related to fertility rate it can be shown that across species those with higher metabolic rates have lower fertility rates (as those with larger body sizes have lower fertility rates). But if we consider the possibility that all of the energy available to an organism, not just what it can eat and drink, determines its fertility we might see a different picture. The next two figures illustrate this. The first shows the pattern with metabolic rate and the second plots industrial nations with an energy budget determined as the average power consumption of an individual in that country (see Moses and Brown 2003 for explanation).

One should always be skeptical of scaling plots, at first. What is this measure on the x-axis anyway? Can we trust it? The next figure suggests that the relationship is at least something more than a statistical artifact. It shows the relationship for two measure of fertility for every year in the United States from 1850 - 2000.

So, maybe there is something to this relationship and maybe modern human fertility is not a complete mystery after all. In one sense our fertility patterns seem really unique in terms of number of offspring. But what is more unique, relatively, about humans - the number of kids they have or the amount of energy they consume per individual and the lack of constraints on the delivery of this energy? These plots suggest that on average humans are making the same basic tradeoffs between energy and fertility as other species. This may not be correct but it certainly deserves our attention.

I think most people see themselves as really autonomous agents and we don't like the idea that we are points following some huge pattern - well some of us don't. And it might seem odd, given how personal fertility decisions are, that such a simple pattern with energy availability should emerge. There's a huge black box of complexity that influences what might affect ferlity. the fact that we can put energy in on one side and get the theoretically predicted exponent out on the other, is quite astounding. We haven't talked about how theory predicts this exponent, but we will. We will read this paper later in the semester too.

We might also think about what the implications are of this plot, if the relationship survives future scrutiny. What are the most important variables to consider with respect to the sustainability of human populations? Certainly the number of people and the amount of energy the consume are among the most important of these. Here, these two variables are connected, but the relationship is the opposite of what we might ideally desire. What do we do if the only way to lower birth rates is to increase per capita energy consumption? that would be a bind. I'm not suggesting that this is the case, but its an issue that we should confront and think about.

Just for fun, note in the following that an additional and important demographic variable also varies with per capita power consumption:

So, we've seen two cases where humans more or less follow ecological and biological patterns.
Now lets look at urban ecology - clearly the human imprint on the ecosystems they interact with tends to be especially robust, particularly in industrial contexts.
Eco-footprint analysis calculates the amount of area it takes to support the average consumer of a country (or other defined region/area) based on typical consumption patterns.
Here's a figure made by William Rees that I got from a handout he used (and emailed to me when I asked him for it) for a presentation at the AAAS meetings in Seattle a few years ago:
The world average is 4 ha per individual. We can ask questions like, 'if everyone in the world lived like the average US citizen, how many earths would it take to support the world?'
One student asked if increasing agricultural outputs would affect this picture. In one sense the answer is yes - the calculation of the productivity of arable land has an impact on the size of the footprint. But I might also caution against accepting those claims that agricultural lands have become more productive in some regions because often those estimates don't factor in the costs of the inputs. That is, we put more and more energy into equipment, fertilizers, and pesticides, etc and the actual productivity of the land is the difference between what goes in and what comes out - not just a measure of the harvest...

We also talked about a paper we'll read later in the semester that looks at cities at metabolizing structures. Its a great perspective that also focuses on energetic features of human societies that helps us understand how the human city, as a system, compares to and influences ecological systems.

In addition to these topics, during the semester we'll also discuss:
1) variation in human growth and development
2) the human role in the extinction of birds and mammals
3) patterns in the distribution of wealth and poverty
4) human cultures as complex systems

Finally, we feel that this class is really unique in format and content. It will be challenging but fun. We are trying to convey not only a different approach to thinking about human ecology but a different approach to science.
The ultimate goal is to discover, describe, and explain emergent phenomena that characterize human systems.

Readings for week 1

For week one we are reading the first two chapters of two books. The goal is to orient the class on the basic tenets and themes of macroecology and to start thinking about underlying law-like behaviors that often characterize complex ecological and social systems. These chapters are available on ereserves in the folder for week 1. Let one of us know or email if you have problems with ereserves.

Here's the citation info for the readings:

*Brown, J.H.1995. Chapters 1 – 2 in Macroecology. University of Chicago Press.

*Ginzburg, L., and M. Colyvan. 2004. Chapters 1 – 2 in Ecological Orbits: How Planets Move and Populations Grow. Oxford, Oxford University Press.

The Brown chapters do an excellent job of defining macroecology. Pay attention to the example in chapter 1 for how to 'think big' with regard to an important ecological question. Also think about how Brown approaches the issue of species responses to climate change from a different perspective than would a traditional ecologist. Pay close attention to Brown's discussion of complex systems and ecological complexity in chapter 2.

For the Ginzburg and Colyvan chapter the emphasis is on their discussion of laws and ecology, first and foremost, but also appreciate their use of the analogy between planetary motion and population growth. You may not be familiar with some of the terms and/or concepts in chapter 1. Don't worry. We won't be talking about population dynamics per se. Appreciate that they have their own goals regarding a fascinating topic in population biology (I highly recommend reading the entire book at some point) but their approach to defining the problem and their philosophy of science is what we are most concerned with. Most of this is in chapter 2. You don't really need to read the preface. I only included it because I like the quotes so much. I'll state the one by MacArthur here; "Difficulty in imagining how theory can adequately describe nature is not a proof that theory cannot." Does the Ginzburg and Colyvan approach to thinking about laws and what laws are differ from what you have been taught before?

If you are interested in complex systems approaches to ecology in general check out Brian A. Maurer's book "Untangling Ecological Complexity: The Macroscopic Perspective," published in 1999. This gets more into the specifics of chaos and nonlinearity and might be especially interesting for students with more of a mathematical background. Another good book on the subject is Sole and Goodwin's "Signs of Life: how complexity pervades biology".

Friday, August 17, 2007


This is the first entry for a new course,"Perspectives in Human Ecology," which is being offered by the University of New Mexico for Fall 2007. The class is team-taught and multi-disciplinary. The instructors are: Jordan Okie (ecology), Bill Burnside (ecology), and myself Oskar Burger (anthropology). This class seeks a macroecological perspective on human ecology - in the ways humans organize themselves, process energy, alter their environments, and follow basic biogeographic patterns in some cases while being exceptions in others. UNM is an ideal setting for such a course because numerous faculty members here have made pioneering contributions to the theoretical and empirical foundations that this course is based upon. In the social and natural sciences UNM has professors who have sought fundamental explanations for complex phenomena while using and encouraging crossdisciplinary collaborations (e.g., James H. Brown, Hilly Kaplan, Ric Charnov, FA Smith, Bruce Milne, Jim Boone, Kim Hill, Stephanie Forest, Melanie Moses). Check out the wiki for the Program in Interdisciplinary Biomedical Science. However, while on campus resources here are strong, the goal of this blogspot is to invite further contribution from experts around the globe in the hopes that this will broaden the perspective of the course and foster a collaborative and diverse atmosphere.

The course will begin on Tuesday, August 21. We hope this blog takes on a life of its own and that many contribute.


Reading list by week

This is of course subject to change, but here is the basic itinerary for assigned readings:
(To access the readings in pdf format go to Follow the student link and enter the course info Biology 402 and the password is lobo402.)

Week 1 (8/21, 8/23): A tutorial in thinking big: laws and macroecology

*Brown, J.H.1995. Chapters 1 – 2 in Macroecology. University of Chicago Press.

*Ginzburg, L., and M. Colyvan. 2004. Chapters 1 – 2 in Ecological Orbits: How Planets Move and Populations Grow. Oxford, Oxford University Press.

Week 2 (8/28, 8/30): Basic ecology & life history of Homo sapiens

*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

Week 3 (9/4, 9/6): Core concepts for human biogeography

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

* Lomolino et al. Intro chapter to biogeography text book.

Week 4 (9/11, 9/13): The ecogeography of body form, life-history, and population density, Part 1

*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.

Week 5 (9/18, 9/20): The ecogeography of body form, life-history, and population density, Part 2

*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 18:295-311.

*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.

*Crimmins, E. M., and C. E. Finch. 2006. Infection, inflammation, height, and longevity. Proceedings of the National Academy of Sciences 103:498-503.

Week 6 (9/25, 9/27): Cultural, linguistic, and genetic diversity patterns, Part 1

*Pagel, M., and R. Mace. 2004. The cultural wealth of nations. Nature 428: 275-278.

*Moore, J.L, Manne, T.M., Brooks, N., Burgess, R., and Davis, L.A. 2002. The distribution of biological and cultural diversity in Africa - Proc. R. Soc. Biol. Sci., Ser. B 269: 1645-1653.

*Collard, I.F., and I.A. Foley. 2002. Latitudinal patterns and environmental determinants of recent human cultural diversity: do humans follow biogeographic rules? Evolutionary Ecology Research.

Week 7 (10/2, 10/4): Cultural, linguistic, and genetic diversity patterns, Part 2

*Rosser, ZH et al. 2000. Y-Chromosomal Diversity in Europe Is Clinal and Influenced Primarily by Geography, Rather than by Language . Am. J. Hum. Genet., 67:1526-1543, 2000

*Barbujani, G. and R.R. Sokal. 1990. Zones of sharp genetic change in Europe are also linguistic boundaries. Proc of the Nat Acad of Sciences 87: 1816-1819.

*Serre, D., and S. Paabo. 2004. Evidence for gradients of human genetic diversity within and among continents. Genome Research 14(9): 1679 - 1685.

Week 8 (10/9, Fall Break): How humans alter biogeographic patterns of abundance distribution and extinction among other species

*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.

Week 9 (10/16, 10/18): Geography of wealth and resource use

*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.

Week 10 (10/23, 10/25): Complex systems and feedbacks

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

*Lansing, J.S. 2003. Complex adaptive systems. Annual Rev of Anthropology 32: 183-204.

*Kruse, J. et al 2004. Modeling sustainability of Arctic Communities: an Interdisciplinary Collaboration of Researchers and Local Knowledge Holders. Ecosystems 7: 815-828.

Week 11 (10/30, 11/1): Energetics, culture, and society

*White, L., A. 1943. Energy and the Evolution of Culture. American Anthropologist 45:335 - 355.

*Tainter, J. A., T. F. H. Allen, A. Little, and T. W. Hoekstra. 2003. Resource Transitions and Energy Gain: Contexts of Organization. Conservation Ecology 7:4.

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

Week 12 (11/6, 11/8): Scaling, part 1

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

*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.

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

Week 13 (11/13, 11/15): Scaling, part 2

*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.

Week 14 (11/20, Thanksgiving): Urban Ecology: Footprints and Community Metabolism

*Smil, V. 2000. Energy in the twentieth century: Resources, conversions, costs, uses, and consequences. ANNUAL REVIEW OF ENERGY AND THE ENVIRONMENT 25:21-51.

*Rees, W. E. 1996. Revisiting Carrying Capacity: Area-Based Indicators of Sustainability. Population and Environment 17:195 - 215.

* Decker, E. H., S. Elliot, F. A. Smith, D. R. Blake, and F. S. Rowland. 2000. Energy and Material Flow Through the Urban Ecosystem. Annual Review of Energy and the Environment 25:685 - 740.

Weeks 15, 16: Term Paper Presentations, Concluding remarks.

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