This is scientific Americans 60 second science. I'm Karen Hopkins. This will just take a minute.

When you hear the word mutation, you may think of something destructive or of Marvel's X-Men, but some mutations, which are just differences in DNA, can be historic.

Take for example a genetic sequence found in the vast majority of people from Tibet.

Millions of Tibetans spend their days at

average elevations of nearly 15,000 feet. That's more than half the height of

Mount Everest. Up there the air is thin with 40% less oxygen than at sea level.

That lack of O2 would leave most Westerners struggling for breath, but Tibetans seemed to

breathe easy.

To find out how these highlanders cope, researchers compared the DNA of 90 Tibetans to that of people who are not

altitude adapted, 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.

The finding is described in the journal Nature Genetics.

This mutation appears to have originated just 8,000 years ago, but it's so advantageous that today nearly 90% of Tibetans have it,

while it's virtually absent in even closely related low land neighbors.

The finding demonstrates that a really useful mutation will always rise to the top.

Thanks for the minute.

For Scientific Americans 60 Second Science, I'm Karen Hopkins.