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How did humans learn to digest milk?

| | June 8, 2015

Got milk? Ancient European farmers who made cheese thousands of years ago certainly had it. But at that time, they lacked a genetic mutation that would have allowed them to digest raw milk’s dominant sugar, lactose, after childhood.

Today, however, 35 percent of the global population — mostly people with European ancestry — can digest lactose in adulthood without a hitch.

So, how did we transition from milk-a-phobics to milkaholics? “The first and most correct answer is, we don’t know,” says Mark Thomas, an evolutionary geneticist at University College London in the U.K.

Most babies can digest milk without getting an upset stomach thanks to an enzyme called lactase. Up until several thousand years ago, that enzyme turned off once a person grew into adulthood — meaning most adults were lactose intolerant (or “lactase nonpersistent,” as scientists call it).

But around 8,000 years ago in what’s now Turkey — just when humans were starting to milk newly domesticated cows, goats and sheep — mutations near the gene that produces the lactase enzyme started becoming more frequent. And around the same time, adult lactose tolerance developed. The mutation responsible for that may be between 2,000 and 20,000 years old; estimates vary.

Thomas thinks a combination of two reasons may explain the persistence of the lactase mutation in Northern Europe.

First, the farmers that settled there came from the Fertile Crescent, and they brought crops native to that region, like wheat and barley. But with Northern Europe’s shorter growing season, these crops were more likely to fail, causing famine.

The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion and analysis. Read full, original post: An Evolutionary Whodunit: How Did Humans Develop Lactose Tolerance?

The GLP aggregated and excerpted this article to reflect the diversity of news, opinion, and analysis. Click the link above to read the full, original article.
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