"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."