In 2000, famed evolutionary theorist Stephen Jay Gould said, “There’s been no biological change in humans in 40,000 or 50,000 years. Everything we call culture and civilization we’ve built with the same body and brain.” Now, 22 years later, most evolutionary biologists beg to differ. Natural selection is still operating on humans, they say — and they have evidence to back up the claim.
Take, for example, lactose tolerance. Most people lose the ability to digest lactose after they’re weaned. However, roughly 35 percent of adults worldwide have one specific genetic variant that allows them to digest lactose throughout life. Recent genetic research has found that this variant became common only after humans domesticated animals and started drinking their milk. Even today, the trait is more common in populations with a history of dairy farming than in populations whose ancestors did not raise animals for milk.
