Wednesday, July 18, 2007

Skulls and Questions about the Out of Africa theory

A study published in the July 17 issue of Nature makes the case that the Origin of humans occured somewhere in south - central Africa. There is a lot of genetic variation in that region as found by looking at 4500 male fossil skulls. And as one moves away from Africa the genetic variation and skull variation ceases to be significant.


However, John Hawks a researcher from the University of Wisconsin-Madison says the paper is “mistaken" and has flaws. The biggest flaw is that the current research is largely based on skull variability. Hawks claims that one can’t find the origin of people by measuring the variability of their skulls.

He maintaines that differences in skull features are related to genetics, but genetic variation depends on how much mixing occurs with other populations. The argument for the skull variation theory is that it is a significant element in showing how features were distributed on earth. But Hawks believes that the research into the Out-of-Africa theory is based on flawed assumption from genetics papers of 10 to 15 years ago, and those assumptions wrong.

So how do you account for the skull variability and distance explanation?

One scenario is that Africa is large and ecologically diverse so cranial variation is a function of that environments. In diverse environments which would support a variety of foods such as roots, the inhabitants would need bigger and stronger jaw muscles, and in turn larger areas for muscle attachments.

In another part of the paper he notes that correcting for climate is not a good idea. Climate is the most important feature that is related to skull size. So by correcting for climate, as the researchers have done they are subtracting a major component of variability.

This debate is not over.

The Nature journal:

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