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Got Big Brains

Researchers have homed in on three genes that seem to give people their big brains, Reuters reports.

The human neocortex is some three times the size of that of chimpanzees, and previous work had implicated NOTCH2NL, a relative of the brain development gene NOTCH2, in governing brain size, HHMI notes in a press release. Though when the University of California, Santa Cruz, Genomics Institute's David Haussler and his colleagues traced it using the human reference genome, it at first seemed to be in a genomic region known to be involved in brain size, but upon closer inspection, it wasn't located there at all. However, as they now report in Cell, with the latest version of the human reference genome, they actually found three versions of NOTCH2NL in that region.

Haussler and his colleagues further report that this duplication of NOTCH2NL appears to have taken place about 3.5 million years ago, and only in humans, Neanderthals and Denisovans, and not in chimpanzees, gorillas, or orangutans

In a separate paper, also in Cell, the Université Libre de Bruxelles' Pierre Vanderhaeghen and his colleagues report on using RNA sequencing to uncover key genes for the development of the human fetal cortex. They, too, homed in on NOTCH2NL.

"The cerebral cortex defines to a large extent what we are as a species and who we are as individuals. Understanding how it emerged in evolution is a fascinating question, touching at the basic origins of mankind," Vanderhaeghen tells Reuters.