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December 13, 2004

The Dusk of Human Culture?

I purchased The Dawn of Human Culture about 6 months ago because of late my study of human evolution has been a bit genocentric, and I wanted to reacquaint myself with skulls & bones. Stanford palaeoanthropologist Richard G. Klein knows his morphology, serving up a breezy 300 page tour of the latest research in paleontology from the fossil's-eye-view.1 But, the book is also an argument for the genetic basis of the "Great Leap Forward" (GLF), that is, that about 50,000 years ago modern humans underwent a major qualitative change in character which underwrote both their range expansion out of Africa and their cultural creativity. Of late I have expressed skepticism of this viewpoint, primarily because the data points are starting to get a bit sloppy. Nevertheless, I still tend favor some form of this argument over the gradualist position espoused by Stephen Oppenheimer in The Real Eve.

Klein's thesis is simple: about 50,000 years ago a genetic event, saltational in character, triggered the rise of man-as-we-know-him. Language, driven by FOXP2, is implicated as a major culprit, with complex symbolic thinking being the seminal byproduct of the new neural operating system. Klein appeals to neurological rewiring because he can't tie the change to cranial capacity increase, a gradual process that had ceased by about 200,000 years before the present in the homonid line that led to Homo sapiens. Those who stand at the antipode to Klein's hypothesis would assert that gradual evolution of human culture occurred after the cranial plateau and offer that if aliens observed the change in human society after 1500 and the scientific revolution they might also wonder if a genetic change might be the cause.

This got me wondering. If a group of 10 individuals from a modern Western society were dropped on a desert island what would happen? If they were going to survive they would probably abandon their specialized niches and attempt the hunter-gatherer lifestyle. Though they might teach their children literacy it seems plausible that the complex information rich suite of modern society would be severely attenuated, and barring recontact the descendents of the moderns might resemble another hunter-gatherer group with legends of great days past. But, I still suspect that they would express some religious sentiments and engage in artistic activities. These to me seem human universals, not products of cultural evolution or learning, that is, they are motifs that emerge out of our cognitive predispositions. Just like language they need only minimal triggers, and the presence of other human beings in a social context might allow them to manifest themselves.

As it happens, we have a primitive form of "desert island" abandonment that we can use to test my hunch: Tasmanian aboriginals. Their material culture was extremely poor, the most deprived of any human group known. Being cut off from extended information networks they tended to "forget" many skills which they had brought to Tasmania. If the culture of the GLF was purely learned and markers for symbolic thought were cultural innovations rather than rooted in a genetic change, doesn't it seem likely that the Tasmanians would be the prime candidates to manifest a regression to a pre-modern (that is, pre-50,000 before present) way of life? What I know suggests that they still remained modern. Their toolkit was narrow and constrained, but still not as primitive as that of anatomically modern but pre-GLF folk. And, they made necklaces. The capacity for symbolic thought is hardwired, it's not an innovation. Of course, I'm still sketchy about the details of the GLF....

1 - Genetics is secondary to the narration, but followers of the field will have some issues. Klein leans heavily on the Puncuated Equilibria theory proposed by Niles Eldridge and SJ Gould, but what he really seems to want to express is something more similar to Sewall Wright's adaptive landscape. As for many palaeoanthropologists genetic drift often turns into a deux ex machina for Klein, and his implication that small isolated populations "mutate more" seems to be confusing the point he was trying to get across that random genetic drift is more salient in smaller breeding groups. Overall, Klein has a tendency not to decompose the impact of natural selection and genetic drift in various contexts because the drivers of the evolutionary process serve as background props rather than the main storyline.

Posted by razib at 04:18 AM