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Getting to the Root of Enamel Evolution

Scientists have identified how natural selection may have acted to give modern human teeth their thick enamel, one gene at a time.

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Along with our big brains and upright posture, thick tooth enamel is one of the features that distinguishes our genus, Homo, from our primate relatives and forebears. A new study, published in the Journal of Human Evolution, offers insight into how evolution shaped our teeth, one gene at a time.

By comparing the human genome with those of five other primate species, a team of geneticists and evolutionary anthropologists at Duke University has identified two segments of DNA where natural selection may have acted to give modern humans their thick enamel.

Teeth have been an invaluable resource for scientists who study evolution, the authors said.

"The fossil record is always the most complete for teeth," said coauthor Christine Wall, associate research professor of evolutionary anthropology at Duke. "And enamel thickness has long been a key trait used to diagnose fossil hominins and reconstruct their diets and life histories."

Clear differences in enamel thickness among primates have been linked to diet. Of the six species included in this study, fruit- and leaf-loving gorillas and chimpanzees have the thinnest enamel; omnivorous orangutans, gibbons and rhesus macaques have an intermediate thickness; and humans possess the thickest enamel, well suited to crushing tough foods.

"Teeth also preserve their growth bands," Wall said, referring to...

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