Most humans are lactose intolerant, meaning our bodies stop producing lactase (an enzyme needed to digest the lactose in milk) after childhood. But some of us, particularly those with Northern European or Middle Eastern ancestry, are able to produce lactase and consume dairy without a problem into adulthood. Scientists are looking for the reason that lactose tolerance evolved among those populations. It begs the question: how might dairy consumption have helped our ancestors survive?

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.

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Photo by Benson Kua