A new study has tried to understand why it was so advantageous to drink milk in different parts of the world over the last 10,000 years.
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.
The study debunks one leading theory: that milk provided a valuable source of vitamin D, which would’ve helped people absorb its calcium.
Read the full, original story: Revealed! Why people started drinking milk thousands of years ago