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Trends Genet. 2006 Nov;22(11):608-13. Epub 2006 Sep 15.

Did brain-specific genes evolve faster in humans than in chimpanzees?

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Department of Ecology and Evolutionary Biology, University of Michigan, 1075 Natural Science Building, 830 North University Avenue, Ann Arbor, MI 48109, USA.


One of the most distinctive characteristics of humans among primates is the size, organization and function of the brain. A recent study has proposed that there was widespread accelerated sequence evolution of genes functioning in the nervous system during human origins. Here we test this hypothesis by a genome-wide analysis of genes that are expressed predominantly or specifically in brain tissues and genes that have important roles in the brain, identified on the basis of five different definitions of brain specificity. Although there is little overlap among the five sets of brain-specific genes, none of them supports human acceleration. On the contrary, some datasets show significantly fewer nonsynonymous substitutions in humans than in chimpanzees for brain-specific genes relative to other genes in the genome. Our results suggest that the unique features of the human brain did not arise by a large number of adaptive amino acid changes in many proteins.

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