Let’s Call It Lactase Non-Persistence in 2013!

Here at Chez Gique this topic comes up pretty often, because one of us can’t drink milk or eat soft cheese without experiencing Tummy Problems. The other one eats and drinks dairy products with impunity. It’s sometimes an issue when eating out or at family dinners, though.

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 milk-a-holics? "The first and most correct answer is, we don’t know," says Mark Thomas, an evolutionary geneticist at University College London in the UK.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 non-persistent" as scientists call it.But now that doesn’t happen for most people of Northern and Central European descent and in certain African and Middle Eastern populations. This development of lactose tolerance took only about 20,000 years – the evolutionary equivalent of a hot minute – but it would have required extremely strong selective pressure.

via An Evolutionary Whodunit: How Did Humans Develop Lactose Tolerance? : The Salt : NPR

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