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The Evolution of Modern Humans

Chris Stringer’s new book, Lone Survivors: How We Came to Be the Only Humans on Earth, attempts to reconcile the age-old conflict between the “Multiregional” and “Out of Africa” hypotheses of Modern Human origins. Stringer has long been identified with the “Out of Africa” hypothesis, and his criticism of the Multiregional model pretty much still hold. In the Multiregional model, different groups of a human ancestor, i.e., Homo erectus (and friends) existed over a large region of the earth (Africa and Eurasia) and different populations of that ancestral populations evolved in parallel to become different groups of humans, sometimes regarded as different races. In the Out of Africa model, the same hominids would have been spread around the world (the evidence for that is incontrovertible) but only one population, an African one, became “fully modern” and they replaced all the other groups with varying levels of interaction.

It is important to mention at this point that a third hypothesis, often classified as a subset of the Mutiregional model, had been proposed by C. Loring Brace. In this model a large continuous ancestral population was transformed regionally. The use of fire, Brace claimed, was invented in East Asia, and this transformed hominds in a certain way, and the use of improved projectile spears was invented in Africa, transforming those individuals in different ways. Specifically, the East Asians got smaller teeth and the Africans got more gracile bodies. These two transformations spread from their centers and overlapped each other and eventually transformed the entire global population.

Stringer’s new model isn’t like Braces in detail, but does account for the evidence better than both the Multiregional and Out of Africa models, assuming that evidence is sufficient to even develop a story for the rise of Modern Humans. Stringer still has a basal Modern Human form coming out of Africa, but then there is considerable interaction with extant non-Modern Human populations during which technologies, other aspects of culture, and genes, are exchanges. The results R us.

As you know, I’ve got my own theories about the origin of Modern Humans. I see the evidence of modern looking technology in Souther Africa quiet a bit before any evidence of symbolic behavior (i.e., the Fauresmith culture as documented by Peter Beaumont and others). A group of us led by Richard Wrangham published the idea that fire was controlled by early Homo and this transformed an asutralopith (roughly) like creature into Homo Erectus. By the time we get to the last interglaical, there is pretty good evidence of a very nearly modern human in Southern Africa and elsewhere on that continent. This, however does not obviate the idea of later spread and interaction with other populations, in accord with recent evidence from the genetics.

I don’t think we are there yet. I think we have a very coarse resolution and we are looking at a fairly fine tuned problem. Having said that, I would recommend Stringer’s book as an excellent window on the current thinking that does not privilege genetics (as is so often done these days in the larger discussion, because of the spectacular genetic finds) and incorporates both old and new evidence from physical and archaeological remains.

It is possible that I could assign this in an upcoming human evolution class. It is a good, easy read yet full of data and stuff. As one would expect form Chris Stringer.