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Among all the physical characteristics, there is one in particular that distinguishes Tibetans from the rest of the humans on the surface of the planet.
The Tibetans have an extraordinary ability to live without problems in the highest mountains, where most of us could not. Extreme altitudes do not pose an issue for them.
The reason for this unique adaptation resides in a gene, transmitted to their ancestors when they crossed with another human species to whose extinction, paradoxically, the Tibetans also contributed.
That gene was identified by a group of researchers at the University of California at Berkeley, who publish their findings in Nature.
The Super Human Gene
A rare variant of a gene related to the production of hemoglobin (the molecule responsible for transporting oxygen in the bloodstream) spread among Tibetans after they moved, several thousand years ago, to the high plateaus they currently occupy.
And it is precisely this genetic variant that has allowed them, and allows them even today, to survive despite the low levels of oxygen that are present at altitudes of 5,000 meters above sea level, where most people would have serious health issues.
“We have very clear evidence that this version of the gene came from Denisovans,” said principal author Rasmus Nielsen, UC Berkeley professor of integrative biology.
“This shows that humans evolved and adapted to new environments by obtaining their genes from another species.”
We've known for a while that our ancestors live alongside and mated with other species of humans. But a recent study suggests genes inherited from this interspecies mating are why Tibetans do well at high altitudes. pic.twitter.com/UBEKzQPZff
— Ancient Code (@theAncientCode) March 13, 2018
The Gene, called EPAS1 boosts hemoglobin and red blood cell production only slightly, avoiding the negative cardiovascular effects seen by those with other variants of the gene that causes thicker blood.
“We found that part of the EPAS1 gene in Tibetans is nearly identical to the gene found in ancient Denisovans and very different from all other humans,” Nielsen said.
“We can do a statistical analysis to demonstrate that this gene must have originated from the Denisovans. There is no other way of explaining the data.”
This mystery gene was discovered in 87 percent of Tibetans who were tested in the study.
On the Tibetan plateau, oxygen levels are about 40 percent lower than at sea level.
“There may be many other species from which we also obtained today’s DNA, but we don’t know it because we don’t have the necessary genomes,” Nielsen said.
“The only reason we can say that this bit of DNA is Denisovan is because of this lucky accident of sequencing DNA from a little bone found in a cave in Siberia. We found the Denisovan species at the DNA level, but how many other species are out there that we haven’t sequenced?