Friday, February 4

Dream Paper

A few months back, a paper which excited me to no end. It was the kind of work I fervently wished I could do, and in all honestly, there's not too much I would have given to be the first author of that paper.

However, I this was evidently not to be. Still, I had hoped to give me the original paper a respectful nod here for being totally amazing. Even this, I was unable to accomplish, as my workload exploded.

Now, I have a chance to save face, since the author, esteemed primatologist Kevin Langergraber of the Max Plank Institute EVA and Boston University, has released another paper which might be even finer than the first.

Perspective first: the original paper was a big collaboration featuring Boesch, Mitani, Wrangham, Vigilant, a bunch of the Japanese crew, and others. Not quite the 1999 paper by Andy Whiten and just about anyone who ever studied wild chimpanzees. The second paper is a bit smaller in depth, but for me, quite a bit more interesting.

I see now that in my excitement, I've not given more than the barest inkling of an explanation of just what type of research this is. Well, the first was titled Genetic and 'cultural' similarity in wild chimpanzees. Title says quite a bit, but it doesn't give the reader an instant understanding of how similar these two measures are where the similarity might lie.

Langergraber et al. basically take Whiten's premises that chimp populations have distinct behaviors, some of which are shared between groups, and some of which are unique, and attempts to correlate them with genetic data from these same chimp populations. Authors' report: correlation is strong.

More specifically, levels of overall behavioral dissimilarity was highly correlated with overall genetic dissimilarity. Meaning, few behavior varied between groups who were genetically similar, whereas groups between which much genetic distance exists shared fewer behaviors.

The authors stress that reader should not be drawn in by the correlation fallacy. These data reveal that genetics could very easily be playing a role, but that does not mean they are. Cultural effects may be in play, which are unfortunately notoriously difficult to measure in our species, much less chimpanzees.

So what's new? What do Kevin Langergraber and company have for us this time?

Genetic differentiation and the evolution of cooperation in chimpanzees and humans
Langergraber K, Schunert G, Rowney C, Wrangham R, Zommers Z, Vigilant L (2011) Genetic differentiation and the evolution of cooperation in chimpanzees and humans. Procedings of the Royal Society Series B doi: 10.1098/rspb.2010.2592

It has been proposed that human cooperation is unique among animals for its scale and complexity, its altruistic nature and its occurrence among large groups of individuals that are not closely related or are even strangers. One potential solution to this puzzle is that the unique aspects of human cooperation evolved as a result of high levels of lethal competition (i.e. warfare) between genetically differentiated groups. Although between-group migration would seem to make this scenario unlikely, the plausibility of the between-group competition model has recently been supported by analyses using estimates of genetic differentiation derived from contemporary human groups hypothesized to be representative of those that existed during the time period when human cooperation evolved. Here, we examine levels of between-group genetic differentiation in a large sample of contemporary human groups selected to overcome some of the problems with earlier estimates, and compare them with those of chimpanzees. We find that our estimates of between-group genetic differentiation in contemporary humans are lower than those used in previous tests, and not higher than those of chimpanzees. Because levels of between-group competition in contemporary humans and chimpanzees are also similar, these findings suggest that the identification of other factors that differ between chimpanzees and humans may be needed to provide a compelling explanation of why humans, but not chimpanzees, display the unique features of human cooperation.

The paper combines three of my favorite subject in science, perhaps even the world: behavioral genetics, altruism, and chimpanzees. This is a great premise: compare the genetics of our closest ancestors with comparative human populations. The authors chose to look at modern populations, and not just hunter-gatherers, but also pastoral/agricultural populations. They examined different types of Africans, Aborigines, Pacific Islanders, and American Indians, to see if any connections exists between group genetics, competitive behavior, and altruism.

The work smacks of Mitani's research, in many ways, since it relies on his detailed research into the brutal, territorial male chimp. However, the authors take a more serious look at the other side of aggressive behavior as well, plus, spend much of the paper comparing to humans to test the hypotheses of Samuel Bowles. 

Ultimately, between-group genetic differences in humans were not found to be greater than the between-group differences in chimps. Hooray, negative data! Since these genetic differences are approximately the same between species, the authors suggest that these particular genetics are not responsible for human altruism.

I do take some issues with this paper, compromising their main message for me.
I don't agree with the author's selection of groups representative of humankind at the time when modern levels of cooperation first developed. I commend them for looking at populations outside of contemporary hunter-gatherer, and going out of their way to find minimally admixed population that have displayed significant cultural development. But its still too tenuous an assertion, though the crux of my reasoning is way too elaborate to stick into this already monster post, so I'll need to return to it later.

Nevertheless, this is a great starting point, and the paper was a spectacular read. It definitely elucidated a numbering lingering question about Bowles' theories.  I sincerely hope that this is not the last of such papers we see from Langergraber, and that others will pursue similar lines of research in order to enrich the field.

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