XERTYX said:
I've never understood how a mammal can be lactose intolerant. It seems to me one would never survive infancy that way.
Time for some sciencey stuff ........
Yes, all mammals when born have an enzyme that breaks down and digests lactose, which is what allows them to live on mother's milk. But once the youngling mammal is weaned and begins eating solid food on its own, the gene which produces this enzyme becomes inactive, since it is no longer needed. So, all adult mammals are naturally lactose-intolerant and cannot properly digest milk. This is true of humans too.
BUT
Thousands of years ago, in specific geographic areas where agriculture had been established and humans had begun raising cows and goats, mutations appeared in which the gene for the lactose-digesting enzyme failed to switch off, and in these areas (particularly in Europe and parts of Africa) humans were able to digest milk lactose for their entire lives. So, most people who have European or east African ancestry have inherited this mutant gene and can digest milk as adults. But most other humans, from areas like Asia or the rest of Africa, do NOT have this mutant gene, and although they can digest milk as an infant, they become lactose-intolerant as adults once their lactose-enzyme gene switches off.
Is "science" cool, or what?
EDIT: Paragraphs, dammit.....
