How do Tibetans thrive in high altitudes when most other humans struggle? In the findings of a recent study at the University of California, Berkeley, scientists pinpointed the difference to a gene called EPAS1. Study leader Rasmus Nielsen explains that for most humans, the gene’s response is maladaptive because it can increases the risk of certain diseases.

"When you go into a high altitude, the normal response is to produce a lot of red blood cells. We produce so many red blood cells that our blood becomes very thick and we have increased risk of various diseases such as stroke. Tibetans avoid that by producing fewer red blood cells at high altitude because of this genetic variant in EPAS1. Might sound counter-intuitive but they do that to avoid these negative fitness consequences of having blood that’s too thick."

Nielsen’s team has been studying how the Tibetans manage with fewer red blood cells.

"What we think is that somehow the Tibetans are better at producing energy anaerobically than they are doing it aerobically, their muscle cells can better deal with being deprived of oxygen."