We Evolved Low Oxygen Adaptation in Under 3,000 Years
In encouraging news for species like ours faced with having to figure out how to survive the next centuries of unprecedentedly fast climate change, it appears that at least one evolutionary adaptation developed at breakneck speed.
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Tibetans seem to have evolved their unique ability to breathe at high altitudes in thin air in under three thousand years, UC Berkeley researchers have found.
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Their comparison of the genomes of 50 Tibetans and 40 Han Chinese in the July 2 issue of the journal Science shows that ethnic Tibetans split off from the Han less than 3,000 years ago and since then rapidly evolved a unique ability to thrive and produce children successfully at high altitudes and low oxygen levels. Without the adaptation, more infants are born dangerously underweight or die at birth at high altitudes.
“This is the fastest genetic change ever observed in humans,” said Rasmus Nielsen, UC Berkeley professor of integrative biology, who led the statistical analysis. “For such a very strong change, a lot of people would have had to die simply due to the fact that they had the wrong version of a gene.”
Usually when people move above 13,000 feet, with 40% lower oxygen levels, they are subject to headaches, exhaustion and altitude sickness. Despite lower oxygen saturation in the blood and lower hemoglobin levels, Tibetans have none of these problems.
After getting informed consent, researchers obtained DNA and took blood samples from 50 Tibetans and 40 Han Chinese from Beijing, who had at least three generations of ancestors at the same site. The Tibetans lived in two villages located at elevations of 14,100 feet and 15,100 feet.
The researchers measured oxygen saturation, red blood cell concentration and hemoglobin content in their blood and compared the genes of the two groups. The variation occurred near a gene called EPAS1, which earlier studies had suggested is involved in regulating hemoglobin in the blood as a response to oxygen levels.
They found that the common ancestors of Tibetans and Han Chinese split into two populations about 2,750 years ago and the larger group moved to the Tibetan plateau. Although the small group that stayed home thrived and expanded, the larger group of migrants to the higher altitudes died back dramatically.
But those few who survived evolved a survival mechanism, that showed up in 87% of the Tibetan migrants, but in only 9% of the Han who had stayed home: lower red blood cell count and lower hemoglobin levels.
Tibetans have been suggested for space missions to Mars because of this ability they have developed to tolerate very thin air. But such fast and resilient adaptation is good news for us even here on Eaarth, which will change beyond recognition due to our fossil-fueled climate change over the next few thousand years.
Image: Flikr user Reurinkjan
Source: eScienceNews
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