Tibetans have evolved and maintained genetic adaptations that suit them to life above 15,000 feet:
Huff and co-authors published a study in April in PLOS Genetics analyzing for the first time whole-genome sequences for 27 Tibetan individuals. The research identified three new genes that help with mountain living, in addition to confirming two that were previously known. These gene variants give Tibetans the ability to metabolize oxygen more efficiently and protect against Vitamin D deficiency.
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One of the genes that helps Tibetans adapt to high altitude is known as EPAS1. The Tibetan variant of this gene does a surprising thing — it actually lowers the hemoglobin count in your blood at high altitudes. Hemoglobins are a protein in red blood cells that transport oxygen to your body. It’s surprising that Tibetans would have a lower hemoglobin count at high altitudes; normally our bodies respond to lower oxygen pressures by increasing hemoglobins in our blood, allowing for more O2 to reach the muscles. It’s even more surprising because other population groups that have adapted to high altitude environments, including the South American Andes and Africa’s Ethiopian Highlands, have done so in part by raising hemoglobin count.
The Tibetans, however, do things differently. Rather than upping hemoglobin count, their bodies have several adaptations that allow them to use oxygen more efficiently, so they need less of it. This allows them to keep hemoglobin counts relatively low at high altitude, which helps to avoid some of the potential downsides of a high hemoglobin count. Hemoglobins thicken the blood, and the thicker your blood the more likely it is to clot, which increases the risk of heart disease and stroke.