There is a new paper out that finds that Tibetans are the product of admixture between a Han-like population and a Sherpa-like population – and that the altitude-adaptive alleles come from the Sherpa side, which split from the Han a long time ago (20-40k years) and have likely been living at high altitude for a long time. The admixture was a few thousand years ago. Last year, I talked about an article in MBE in that came to similar conclusions – but this new paper has gone farther, identifying the population source for these adaptive alleles. At least, they were the immediate source…
This is contrast to Rasmus Nielsen’s earlier paper, in which he argued that Tibetans and Han split about 3,000 years ago, and that the Tibetan altitude adaptations arose in that relatively short time frame. I thought that was obviously wrong, since the Tibetan adaptations work so much better than those in Andean Indians – and since there is archaeological evidence that people settled Tibet much earlier than that.
Maybe the silliest line in any of these papers was in the abstract of the new one, where they say (about adaptive introgression) “Therefore we identify a novel mechanism, beyond selection on new mutations or standing variation, through which populations can adapt to local environments. “
People have been deliberately using admixture in domesticated animals to add favored local traits for thousands of years. That ought to be long enough to get into the genetics curriculum, no matter what Ernst Mayr may have said.