A gene mutated in people but not in chimpanzees around 2.8 million years ago, shortly before brain size swelled in the Homo lineage, according to a report in the Sept. 3 Proceedings of the National Academy of Sciences.
This DNA alteration prevented the gene from doing its normal job: producing a particular sugar molecule that attaches to the surfaces of cells, say molecular biologist Ajit Varki of the University of California, San Diego and his coworkers.
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