Milk Mutation "Strongest Signal of Selection"

More info is coming in on the report highlighted in Monday's post, Milk-Drinking Crucial to Human Evolution.

Scientific American has weighed in with its own article, African Adaptation to Digesting Milk Is "Strongest Signal of Selection Ever", by Nikhil Swaminathan.

According to University of Maryland biologist Sarah Tishkoff, the lead author of a study appearing in today's Nature Genetics, the mutation allowing them to "get milk" arose so quickly and was so advantageous that "it is basically the strongest signal of selection ever observed in any genome, in any study, in any population in the world."

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Tishkoff's team determined the date range when the mutation likely occurred: 3,000 to 7,000 years ago, which matches up well with the archaeological record that places pastoralization coming to East Africa about 5,000 years ago. The European trait dates back about 9,000 years.

Tishkoff believes that because she found so many markers associated with lactose tolerance in the sequencing of her 109 subjects, evolution clearly develops multiple solutions when there is a strong selective force. "There are some populations that can digest milk, and they don't have any of these mutations," she says. "There are more out there."

The abstract for the article can be found on the Nature Genetics website, but it won't mean anything except to specialists.

An even fuller version of the report is scheduled for the December 15, 2006 issue of Science, the premier science journal in the U.S.