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1 .This is Scientific American 60-Second Science. I'm Karen Hopkin. This'll just take a minute.
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2 .When you hear the word "mutation," you may think of something destructive, or of Marvel's X-Men.
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3 .But some mutations which are just differences in DNA can be historic.
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4 .Take, for example, a genetic sequence found in the vast majority of people from Tibet.
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5 .Millions of Tibetans spend their days at average elevations of nearly 15,000 feet,
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6 .that's more than half the height of Mount Everest.
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7 .Up there, the air is thin with 40 percent less oxygen than at sea level.
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8 .That lack of O2 would leave most Westerners struggling for breath, but Tibetans seem to breathe easy.
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9 .To find out how these highlanders cope, researchers compared the DNA of 90 Tibetans to that of people who are not altitude adapted.
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10 .And they discovered a single change that prevents Tibetans' blood from becoming dangerously clogged with red blood cells, a response that can be deadly for non-native mountaineers.
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11 .The finding is described in the journal Nature Genetics.
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12 .This mutation appears to have originated just 8,000 years ago.
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13 .But it's so advantageous that today nearly 90 percent of Tibetans have it.
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14 .While it's virtually absent in even closely related lowland neighbors.
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15 .The finding demonstrates that a really useful mutation will always rise to the top.
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16 .Thanks for the minute, for Scientific American 60-Second Science. I'm Karen Hopkin.
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