Tuesday, August 06, 2013
Evolution in Action - Milk Drinking Mutants Conquering the Earth
Amazingly the estimate, from the degree of variation in DNA, is that this happened 7,500 years ago (5,500 BC) in Hungary. This isn't long before the earliest recorded history yet it has been enough to repopulate Europe (not to mention America and Australasia) at least of this gene.
The other areas of lactose tolerance, the western Sahara, Saudi Arabia and coastal Pakistan are said to be caused by different mutations. I assume the numbers in Sahara and Saudi are very small (perhaps the Saudi and Pakistani variants are the same gene since they are close to each other). Why didn't they grow so much - perhaps because northern Europe is ideal dairy farming country. It is implied the others are older mutations so perhaps they had some side effect.
However the fact that such a favourable mutation happened, or survived, only 4 times since agriculture started 11,000 years ago shows how difficult the initial mutations are. And the fact that it has spread so far in such a short, in normal evolutionary terms, shows how easy it is when the conditions are right.