8000-year-old mutation helps Tibetans thrive at high altitudes
August 18, 2014 – 4:00AM
Nicky Phillips
Science Editor
In an environment where most people struggle to survive, Tibetans are thriving in the thin air of the Tibetan Plateau and now an international study has uncovered one mechanism their bodies use to cope with these high altitudes.
The Tibetans’ advantage comes from a tiny change in their genome, which occurred about 8000 years ago, that means their blood does not thicken while in low-oxygen environments.
On the Tibetan Plateau, which has an average height of 14,800 feet, locals live with 40 per cent less oxygen than communities at sea level.
The study finds 88 per cent of Tibetans have this genetic variation – a single base pair change in a gene known as EGLN1 – but it is extremely rare in populations of closely related lowland Asians.
That the mutation has spread through the population in such a short time suggests it is one of the strongest examples of natural selection in humans.
The leader of the study, Josef Prchal from the University of Utah, says: “These findings help us understand the unique aspects of Tibetan adaptation to high altitudes, and to better understand human evolution.”
In people without the adaptation, low-oxygen environments make the body produce excess red blood cells – an attempt to deliver more oxygen to tissues and organs – which causes the blood to thicken. This condition can cause long-term and life-threatening complications.
But the genetic variation, reported in the scientific journal Nature Genetics, reduces the body’s response to low oxygen.
Dr Prchal says the genetic variation probably has other important functions, and that other genetic changes are likely to be responsible for the Tibetans being able to live at high altitude that are yet to be discovered.