Three papers in this week's Science reveal genetic changes in humans that may have influenced brain evolution. Two genes involved in brain development have gone through positive selection in modern humans, according to two papers from the laboratory of Bruce Lahn at the University of Chicago. And Ajit Varki of the University of California, San Diego, and colleagues report the discovery of a recombinant protein that's expressed in human brains but not in the brains of other primates.

Recessive loss-of-function mutations in the genes Microcephalin and ASPM (abnormal spindle-like microcephaly associated) cause the disorder primary microcephaly. Brain architecture in those affected appears to be otherwise normal, however, which has led to the idea these genes specifically control brain size. Microcephalin and ASPM both seem to regulate neural stem cell proliferation, "but at the molecular level, their functions may be very different, and that's not well understood yet,"...

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