Lactase Persistence

As a mammal being able to digest milk as an adult is a uniquely human trait. Most mammals only digest milk as babies, which makes sense, mothers only give their babies milk. Lactase tolerance (while common in America) is actually still not as common as Lactose Intolerance worldwide. The SciShow gives us a simple explanation of the Mutants who Love Milk.

Science News for Students briefly sums up the history of Milk in their story

Got Milk? How?

HHMI Bio Interactive digs in deeper