Tibetans and Han Chinese split apart as recently as 3,000 years ago

Biologists have found about 30 genes in which a version rare among the Han Chinese has become common among the Tibetans. The most striking instance was a version of a gene possessed by only 9% of the Han Chinese but by 87% of the Tibetans. The fact that there are significant genetic differences between the two ethnic groups - in spite of only splitting recently - is evidence that natural selection has strongly favored these genes in the Tibetans.