Study Detects Recent Instance of Human Evolution

The New York Times is running a Sunday article regarding new evidence about 'recent' human evolution. A research team at the University of Maryland has done some work looking at the rise of lactose tolerance in the human populations of Africa. From the article: "The principal mutation, found among Nilo-Saharan-speaking ethnic groups of Kenya and Tanzania, arose 2,700 to 6,800 years ago, according to genetic estimates, Dr. Tishkoff's group is to report in the journal Nature Genetics on Monday. This fits well with archaeological evidence suggesting that pastoral peoples from the north reached northern Kenya about 4,500 years ago and southern Kenya and Tanzania 3,300 years ago ... Genetic evidence shows that the mutations conferred an enormous selective advantage on their owners, enabling them to leave almost 10 times as many descendants as people without them. The mutations have created 'one of the strongest genetic signatures of natural selection yet reported in humans,' the researchers write. "

Comments

Don't think so.

[Ihlosi]

The leading cause of death for infants less than 100 years ago in developed nations (and STILL the leading killer today in underdeveloped countries) was diarrhea. How do you get diarrhea? Hmm, lactose intolerance causes - guess? Diarrhea. Baby can't drink breast milk, so you give it something else - something more likely to be contaminated with diarrhea causing viruses. Net result? More diarrhea.

Erm. You're confusing general lactose intolerance with adult lactose intolerance.

General lactose intolerance is a bad thing. Any mammal that doesn't tolerate lactose while still nursing is in very deep doodoo. It's a mutation that'll basically kick you out of the gene pool immediately.

Adult lactose intolerance is, for most mammals, a normal thing (which is why you shouldn't give milk to cats/hedgehogs/etc). Adult mammals aren't supposed to seek out sources of milk, for obvious reasons, which is why the production of lactase usually stops once the mammal is old enough to eat real food. Of course, this mechanism evolved loooong before humans got the idea of domesticating goats/sheep/cattle and use the milk of a completely different species to supplement their diet. This made a mechanism that would have been faulty (adult mammal that tolerates lactose) suddenly become a genetic advantage.