With a trip to the Galpagos two weeks away I’ve been reading the exhaustive Janet Browne biography of Darwin and have listened to The Origin of Species in its Audible version. So it was particularly interesting to run across this article in the NY Times this morning:

A surprisingly recent instance of human evolution has been detected among the peoples of East Africa. It is the ability to digest milk in adulthood, conferred by genetic changes that occurred as recently as 3,000 years ago, a team of geneticists has found.

Lactose Tolerance

It’s a short, accessible article about separate instances of genetic mutation in tribes with large milk-producing cattle herds. The mutation works to leave lactose tolerance opperative after weaning. The way the mutation spreads is that couples with permanent lactose tolerance leave some 10 times as many off spring as those whose tolerance is switched off — a perfect example of “survival of the fitest,” which is not usually survival in warfare or predation, but in better adaptaptability to the surroundings and eventual out-breeding of competing sub-species.