Clearly, the people of Tibet must have evolved quickly to tolerate a life spent living at the top of the world. How quickly? A study out in this week's Science, which compared Tibetans to Han Chinese to see the differences in their DNA, says that the two groups may have diverged no more than 3,000 years ago. If natural selection has changed Tibetans in such a short time, it would be the fastest known example of human evolution. But not everybody is buying this time line. As DISCOVER noted when a similar study by another team came out in May, natives of the Tibetan plateau seem to survive the altitude because their bodies make less hemoglobin. It's somewhat counter-intuitive:

In theory higher levels of haemoglobin would be beneficial, because this would improve oxygen transport. But high levels could make the blood thicker and less efficient at carrying oxygen, says Jay Storz of the University of Nebraska-Lincoln [New Scientist]. (Storz writes the accompanying commentary in Science.)

Looking at the differences in genes that regulate that, the team found vast differences between the Han and the Tibetans, with one version appearing in 87 percent of Tibetans studied but only 9 percent of Chinese. However, the assertion by the scientists at the Beijing Genome Institute—that their findings mean the two group broke apart just three millennia ago—has ruffled archaeologists who believe that the Tibetan plateau has been continuously occupied for much, much longer: more like 7,000 to 21,000 years. For more about all of this, check out Razib Khan's post

at Gene Expression. Related Content: Gene Expression: Very Recent Altitude Adaptation in Tibet

Gene Expression: Tibet & Tibetans, Not Coterminus

80beats: Found: The Genes That Help Tibetans Live at the Top of the World

DISCOVER: High-Altitude Determines Who Survives in Tibet

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