Academic journal article Journal of College Science Teaching

Milk Tolerance

Academic journal article Journal of College Science Teaching

Milk Tolerance

Article excerpt

A discovery by an international team of scientists led by a University of Maryland researcher identifies, for the first time, genetic mutations in East Africans that are associated with the ability to digest milk as adults.

Sarah Tishkoff's study of DNA found that the mutations evolved at the time in history when some Africans were beginning to raise cattle, and they evolved independently from the mutation that regulates milk digestion in Europeans. The findings not only provide evidence of how genes and culture coevolve, explains Tishkoff, "they reveal one of the most striking genetic footprints of natural selection ever observed in humans."

The researchers explain that human adults were not designed to digest milk. It took a genetic mutation to enable humans to tolerate lactose, the main sugar found in milk. But not everyone has the mutation. Most northern Europeans, whose ancestors domesticated cattle, have the mutation. Descendants of cultures that did not raise cattle for milk (many southern Europeans, most Asians, and many Africans) do not have the mutation and cannot digest milk products. …

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