If we look at multiple genes, the ethnic variations--such as the ones we found--are likely to be counterbalanced by other differences. It just happens that we looked at two genes for which the variants favored by selection have a higher frequency in some populations, such as Europeans. It might be that for the next two brain size genes we find, the variants favored by selection will have a higher frequency in Asians or Africans.

Bruce Lahn
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