John Hawks responds to the new paper in PNAS, Close correspondence between quantitative and molecular-genetic divergence times for Neandertals and modern humans.
- Log in to post comments
Advertisment
John Hawks responds to the new paper in PNAS, Close correspondence between quantitative and molecular-genetic divergence times for Neandertals and modern humans.
I don't have the paper in front of me and I only very briefly skimmed it, so I could be talking complete and utter crap here. However, I don't usually let that stop me, so......
John writes:
But their analysis assumes that genetic drift accounts for all changes. I don't deny the role of genetic drift, but I do deny that it explains much about recent skeletal evolution in humans. Random chance cannot do much in a very large population in a few hundred generations.
Yet in the conclusion to the paper, Weaver et al say:
Brain size relative to body size appears to have increased in both the Neandertal and the modern human lineages (56, 57). These parallel trajectories may indicate that directional natural selection was acting on both lineages independently, resulting in differently shaped but similarly sized brain cases (58). To the extent that the measurements considered here reflect these changes, our results would imply that although natural selection may have produced the similarities in size, genetic drift lead to the differences in shape. We are not arguing that natural selection had no effect, just that it appears not to have played a dominant role in producing differences.