Shai Oster “Tibetans Had ‘Fastest Genetic Change Ever’ in Humans” http://blogs.wsj.com/chinarealtime/2010/07/02/tibetans-had-fastest-genetic-change-ever-in-humans/
The study compared the genomes of 50 Tibetans and 40 Han, the majority ethnic group in China, and found the Tibetans had mutations in their DNA that let them better use oxygen. One mutation that occurs in only 10% of the Han was present in 90% of all Tibetans.
The mutation that give Tibetans a high-altitude edge is near what’s sometimes called the “super-athlete gene,” or more prosaically, EPAS1, because the gene is associated with better athletic performance, according to the statement.
According to the research, the group that eventually became what are now known as Tibetans split off from a common ancestor 2,750 years ago. Those immigrants may have intermarried with or replaced the people already living on the plateau.