A mixture of genes from two ancestral populations gave modern Tibetans their ability to withstand high altitude.
One of the ancestral groups developed a genome similar to the modern Sherpa by migrating to high altitudes about 30,000 years ago. Those people then interbred with another group, which had moved into lower altitudes and had genomes similar to lowlander East Asians.
The genes adapted for high altitude were then passed down over generations to form the population now referred to today as Tibetans, researchers report February 10 in Nature. The results suggest that sharing beneficial genetic mutations and having those genes favored over time is one way for organisms to adapt to new environments.