The mutation for milk-drinking evolved independently in different parts of the world over the last 10,000 years as a result of strong natural selection, but why was it so advantageous?
Among the more momentous developments in human evolution was the ability to digest milk beyond early childhood.
Mutations that enabled lifelong milk drinking appeared independently in several parts of the world over the last 7,500 years, according to growing evidence. And those genes spread rapidly. Today, about a third of adults around the world can drink milk without stomach problems, a trait known as lactase persistence. Read more.