http://www.smh.com.au/world/science/tibetan-genes-fit-for-the-high-life-20100702-ztzm.html
Tibetan genes fit for the high life July 3, 2010 TIBETANS may have undergone one of the fastest bouts of human evolution on record: those having genes that allow them to thrive at high altitudes and low oxygen levels rose from 10 per cent of the population to 90 per cent in less than 3000 years, a paper in the journal Science reports. One genetic variant, the EPAS1 gene, allows Tibetans - many of whom live at 4000 metres, where there is 40 per cent less oxygen than at sea level - to thrive where others live with difficulty. The research was done by scientists from China, Denmark and the Berkeley and Davis campuses of the University of California. ''This is the fastest genetic change ever observed in humans,'' says Rasmus Nielsen, a UC Berkeley professor of integrative biology, who led the statistical analysis. ''If the selective pressure is strong enough, it certainly could happen in 150 generations,'' says Bruce Beutler, the chairman of the genetics department at the Scripps Research Institute in California. Eventually their bodies begin to produce more oxygen-carrying haemoglobin and they adapt to the environment. But Tibetans, because of their genetic variations, are able to function with lower levels of haemoglobin despite the lower oxygen. The researchers compared the genomes of 50 ethnic Tibetans and 40 Han Chinese and found evidence based on shared genetic traits that the Tibetan and Han populations diverged less than 3000 years ago. They found more than 30 genes with DNA mutations that have become more prevalent in Tibetans than Han Chinese, nearly half of which are related to how the body uses oxygen. The idea that Tibetans somehow descended from Han is problematic for Tibetan scholars. Archaeological evidence shows people who were culturally Tibetan have been living on the Tibetan plateau for at least 11,000 years. Chinese scientists have for years ''tried to use apparently scientific arguments to prove that Tibet is part of China or that Tibetans are part of the Chinese race, people, nation or all three'', says Robert Barnett, from the Weatherhead East Asian Institute at Columbia University. ''What identifies a people isn't genetics, it's cultural heritage,'' Professor Nielsen says. Tribune Media
