Tibetans can live at high altitudes thanks to a unique gene that affects blood oxygen and allows people to survive in thin air, a DNA sequence that is also found in an ancient human relative, a new study says.

Publishing their findings in the journal Nature, scientists wrote that the Tibetan version of the gene to help people live at high altitudes has been discovered in DNA from Denisovans, which are believed to be human relatives similar to Neanderthals, the Associated Press reported.

Denisovans are based on fossils in a Siberian cave dated to around 50,000 years ago, and scientists have found their DNA in other modern populations.

"We have very clear evidence that this version of the gene came from Denisovans," said principal author co-author Rasmus Nielsen, from the University of California, Berkeley, as quoted by BBC News.

Officially known as the EPAS-1 gene, the DNA sequence helps Tibetans live at altitudes of 2.5 miles year-round. Tibetans are protected from the blood pressure other people would experience at high altitudes when their blood becomes too thick.

"If you and I go up to high altitude, we'll immediately have various negative physiological effects," Nielsen told BBC News. "We'll be out of breath, we might suffer from altitude sickness.

"After a little while, we'll try to compensate for this by producing more red blood cells. But because we're not adapted to the high altitude environment, our response would be maladaptive--we would produce too many red blood cells."

Nielsen and a team of researchers found the Tibetan variant of the EPAS-1 gene in 2010, but they were unable to pinpoint why it was different until they examined ancient genome sequences to compare.

"We compared it to Neanderthals, but we couldn't find a match. Then we compared it to Denisovans and to our surprise there was an almost exact match," Nielsen said.

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