The extraordinary ability of Tibetans to thrive at high altitudes with low oxygen levels could be explained by a genetic mutation, according to scientists.
Researchers from the University of Utah in America and University of Oulu in Finland have discovered a genetic mutation in Tibetans, indicating they evolved to survive in their high altitude surroundings.
At high altitudes beyond 3000 metres, when levels of oxygen in the air drop significantly, Westerners and lowlanders develop hypoxia – excessive production of red blood cells, a thickening of the blood – and show symptoms like sickness, severe headaches, and hypertension. At higher altitudes where oxygen is even thinner it can lead to heart failure.
Tibetans however rarely show any such symptoms. An estimated 4.5 million people live on the Tibetan Plateau, the “roof of the world” with more than half of them at altitudes of around 11,500 feet and 600,000 living at close to 15,000 feet – more than half the height of Mount Everest – where there is 40 per cent less oxygen in the air than at sea level.
They are believed to breathe more deeply and faster than lowlanders while their lung capacity and fitness remains unaffected and they are able to function normally in conditions where outsiders often struggle to walk.
Their physical resilience is also seen in the Andes, among Gurkhas and Sherpas in Nepal and hill people in Ethiopia. But while a genetic advantage has long been suspected, the Utah and Oulu researchers have finally confirmed differences in DNA that account for it.
They studied blood samples from more than 90 Tibetans in the United States and in Dharamsala, India, home of the Dalai Lama and the Tibetan government in exile, and discovered a significant change in the EGLN1 gene from those of nearby lowlanders and non-Tibetans.
According to the Utah-Oulu universities report, published in Nature Genetics, the mutation occurred around 8,000 years ago and prevented Tibetans from suffering the excessive production of red blood cells that thickens the blood and can cause death.
The genetic variation was found in 85 per cent of Tibetans compared to less than one per cent of non-Tibetans.
Mikko Myllymaki, one of the researchers on the study, said the mutation meant that “hypoxia cells don’t grow that well in Tibetans”.
“It’s a great example of human evolution, it shows how people can adapt over a long period of time to different conditions. This adaption stopped Tibetans suffering from hypoxia”, he said.