how come a lot of people are lactose intolerant if everyone started off by drinking milk as a baby?

Question

how come a lot of people are lactose intolerant if everyone started off by drinking milk as a baby?

In: 327

Answer 1

Lactose intolerant people lack the enzyme lactase that breaks down the milk molecules and allow you to digest it adequately.
They lack it because the part of the DNA that tells the body to produce lactase gets “stored away” aka condensed over time.
The natural/normal thing is for animals (including humans) to become lactose intolerant when growing up, and to be able to easily digest lactose is the mutation.