The genetic secrets that allow Tibetans to thrive in thin air

The online edition of Proceedings of the National Academy of Sciences today reports on the work of an international team involving UCL's Professor Hugh Montgomery that has identified a gene that allows Tibetans to live and work more than two miles above sea level without getting altitude sickness. A previous study published 13 May 2010 in Science reported that Tibetans are genetically adapted to high altitude. Now, less than a month later, a second study by scientists from China, England, Ireland, and the United States pinpoints a particular site within the human genome ? a genetic variant linked to low hemoglobin in the blood ? that helps explain how Tibetans cope with low-oxygen conditions. The study sheds light on how Tibetans, who have lived at extreme elevation for more than 10,000 years, have evolved to differ from their low-altitude ancestors. People who live or travel at high altitude respond to the lack of oxygen by making more hemoglobin, the oxygen-carrying component of human blood. But too much hemoglobin can be a bad thing. Excessive hemoglobin is the hallmark of chronic mountain sickness, an overreaction to altitude characterised by thick and viscous blood.