Nepalese sherpa and pack.

Sherpas are a Nepalese mountain people renowned for their climbing ability at extreme, potentially deadly altitudes.

Their biological ability to conserve energy and oxygen is what sets them apart, according to a recent study in the Proceedings of the National Academy of Sciences.

The Sherpas have fewer red blood cells at high altitudes, combined with an increase of nitric oxide, two factors that keep circulation going where it may slow or cease among “lowlanders” used to non-mountain living, concludes the team from the University of Cambridge.

“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,” said Andrew Murray, the senior author of the study. “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.”

The scientists followed two separate teams as they ascended the highest point on earth, Mount Everest. The expedition was part of Xtreme Everest, a project designed to improve survival for mountaineers.

Ten investigators took blood and muscle biopsies of the Sherpas at a laboratory at the Everest Base Camp. Those were compared with baseline samples taken from the same people in low-lying London, as well as 15 more Sherpas who were living in relatively low altitude areas.

The comparative takeaways:

  • The Sherpas’ mitochondria use oxygen more efficiently to produce ATP, chemical energy.
  • The Sherpas are better at metabolizing sugars, and produce less energy from fat.
  • Sherpas’ levels of phosphocreatine increase as time goes on at high altitudes – the opposite of “lowlanders.”
  • Sherpas’ free radicals – molecules created by lack of oxygen – are produced at much reduced rates compared to their peers.

The role of a gene controlling the peroxisome proliferator-activated receptor a (PPARa) was hypothesized as the selector for Sherpas’ ability to avoid hypoxia, despite their extreme barometric environment. Although the British team found a linkage between the two, the exact mechanism and its advantages remain unclear, they conclude.

The Sherpas’ ancestors first arrived on the Tibetan Plateau around 30,000 years ago, although the first human habitation only set root between 6,000 and 9,000 years ago. Selection may have occurred over the last several millennia, with poorer survival to reproductive age – and especially fetal and neonatal mortality – driving the selection of the gene, they add.