Sherpas Evolved to Live and Work at Altitude

The Nepali ethnic group handles oxygen more efficiently, allowing them to more easily live in the mountains

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This week, Kilian Jornet, one of the world’s most accomplished ultrarunners, attempted to set a world record for summiting Mount Everest without supplemental oxygen or fixed ropes. He zoomed from the world’s highest peak,​ traveling from basecamp to summit in an incredible 26 hours—a trek that takes most climbers four days and lots of bottled oxygen. Though he was awarded the title of "fastest known" time, Jornet fell short of the locals. In 1998, Kazi Sherpa unofficially performed the same feat in a mere 20 hours and 24 minutes.

But it turns out that Kazi may have had a secret weapon: Sherpas, a Nepali ethnic group that lives in the shadow of the world’s tallest mountains, are genetically adapted to living and working at high altitude, reports Roland Pease at the BBC.

Since outsiders began trekking and climbing the tall peaks in Nepal’s Himalayas, researchers and explorers have marveled at the Sherpa population's ability to operate in low-oxygen environments that exhaust or even kill those unaccustomed to the height. In the nineteenth and early twentieth centuries explorers hired Sherpas to carry gear up the mountain. Today, Sherpa mountaineers remain the first ones to climb Mount Everest each season, placing ladders and ropes for later climbers.

To study this super human strength, scientists followed a group of ten unacclimated researchers, dubbed "lowlanders," as they made their way to Everest. The team collected blood and muscle samples from the researchers in London before their trip to the mountain, when they arrived at 17,598-foot Everest Basecamp, and again after they had spent two months at basecamp. They compared those results to samples collected from non-mountaineering Sherpas living in relatively low-lying areas who also journeyed to basecamp.

The results suggest that the Sherpas' mitochondria, their cells' powerhouses, were more efficient than the lowlanders' mitochondria. The Sherpas also had lower levels of fat oxidation, another sign that they were more efficient at producing energy. Burning fat for fuel is oxygen intensive, while burning sugar uses less O2. While the numbers for the research team changed the longer they spent at altitude, the numbers for the Sherpas did not move much from their baseline measurement, meaning it's likely their advantages are genetic.

“This shows that it's not how much oxygen you've got, it's what you do with it that counts,” Cambridge Professor Andrew Murray, senior author on the study in The Proceedings of the National Academy of Sciences tells Pease. “Sherpas are extraordinary performers, especially on the high Himalayan peaks. So, there's something really unusual about their physiology.”

There were other differences as well, according to a press release. First was the levels of phosphocreatine, which allows muscles to continue contracting even when adenosine triphosphate, or ATP (a key molecule in transporting chemical energy within the cell), runs out. Phosphocreatine crashed in the lowlanders after two months at altitude. In the Sherpas, the levels of phosphocreatinine actually increased. Second are free radicals, molecules created by lack of oxygen that can damage cells and tissue. These also increased in the lowlanders while the Sherpas' levels remained low.

As John Dyer at Seeker reports, it is believed that Sherpas began developing their high-altitude tolerance when they moved into the mountains about 9,000 years ago. “It’s an example of natural selection in humans, which is absolutely incredible,” says Tatum Simonson, a geneticist at the University of California San Diego who has studied Sherpas but did not participate in the study.

“Sherpas have spent thousands of years living at high altitudes, so it should be unsurprising that they have adapted to become more efficient at using oxygen and generating energy,” Murray says in the press release. “When those of us from lower-lying countries spend time at high altitude, our bodies adapt to some extent to become more 'Sherpa-like', but we are no match for their efficiency.”

Dyer reports that the team also put the Sherpas and researchers on exercise bikes at Everest basecamp to study their metabolism, which will appear in another study. The hope is that understanding the ways Sherpas use oxygen more efficiently might help researchers develop new ways to help medical patients who struggle to breathe efficiently.

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