Sherpas Aren't Just Acclimatized to Everest — Their DNA Is Borrowed From an Extinct Human Species

Put a fit foreign trekker and a Sherpa mountain guide side by side at 5,364m, the altitude of Everest Base Camp, and measure their blood. The trekker's body is often panicking, pumping out extra red blood cells to compensate for the thin air, thickening the blood and raising the risk of the altitude sickness that turns back a meaningful share of first-time high-altitude visitors. The Sherpa's blood barely reacts at all, and that calm is not just a lifetime of living at altitude. It is written into their genes, and the gene did not evolve in modern humans. It came from the Denisovans, an extinct branch of the human family that vanished tens of thousands of years before anyone ever looked at Sagarmatha and called it the top of the world.

The discovery, mapped by geneticists studying Tibetan and Sherpa populations and confirmed in a wider Himalaya-spanning study, centres on a roughly 32,700-letter stretch of DNA within the EPAS1 gene — a gene that controls how the body senses and responds to low oxygen. Modern humans whose ancestors never left low altitude do not carry this version, and neither do most other humans on Earth. It shows up almost exclusively in populations who have lived on the Tibetan Plateau and in the high Himalaya for thousands of years, and geneticists traced its origin to the Denisovans, a cousin species to Neanderthals known mostly from a handful of bone and tooth fragments found in a Siberian cave.

Why this matters more than a fun fact

For a lowlander, the body's first response to thin air is to manufacture more red blood cells, thickening the blood to carry more oxygen per litre. It works, up to a point — but overdo it and the blood becomes sluggish, raising the risk of clots and the severe form of altitude sickness that hospitalises a small number of Everest Base Camp and high-pass trekkers every season. The Denisovan-derived EPAS1 variant does something smarter: it dampens that overreaction, letting Sherpa physiology stay efficient without the blood-thickening spiral. Combined with other adaptations, this is part of why Sherpa climbing crews can move loads at altitudes that leave clients gasping, and why NMA-certified Sherpa guides are the backbone of every serious Nepal expedition, not just a hiring convenience.

The pattern is not random. Across Himalayan populations, researchers found the frequency of the gene variant tracks almost exactly with how high up a group has lived for generations — a statistical correlation described as among the strongest ever measured for a human genetic trait. Simulations put the original selection pressure at somewhere between roughly 2,800 and 10,000 years ago, meaning this is a relatively fast, ongoing case of human evolution, not an ancient, settled one.

It also reframes something trekkers often say half-jokingly on the trail — that their Sherpa guide is barely breathing hard while they themselves are seeing stars near Dingboche. It is not exaggeration and it is not just fitness. It is tens of thousands of years of Denisovan and Tibetan ancestry doing exactly what it evolved to do, on the same trail a visitor is walking for the first time. Hearing a Sherpa guide explain how their body reads the mountain differently from yours is one of the quietly extraordinary parts of trekking in Nepal that has nothing to do with the scenery.

Source: “Wide distribution and altitude correlation of an archaic high-altitude-adaptive EPAS1 haplotype in the Himalayas,” PubMed Central, National Institutes of Health.

Cover photo: Ali Kazal via Pexels (Pexels License).