16th March 2010
The ability to digest the milk sugar lactose - also known as lactase
persistence - is a selectively advantageous and recent evolutionary
genetic trait, which emerged about 7,500 years ago in Europe and
probably later in other parts of the world. This means that, once
weaned, people in most parts of the world (large parts of Africa, most
of Asia, and Oceania) cannot digest milk for the rest of their life.