Diet can drive changes in genetic copy number, according to a study published online this week in Nature Genetics. The authors found that human populations with high starch diets have more copies of a gene that helps break down starch.The study is one of the first examples of natural selection favoring increases in gene copy number in humans, Hildegard Kehrer-Sawatzki at the University of Ulm in Germany, not a coauthor, told The Scientist. "The extra calories from roots and tubers that early human ancestors dug up could have fed a larger brain size," said Nathaniel Dominy at the University of California, Santa Cruz, lead coauthor on the study. Starch is metabolized in part by salivary amylase, which is encoded by AMY1. The number of copies of AMY1 found in people varies greatly across populations. Dominy and his colleagues investigated whether such copy number variation of AMY1 was...

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