Ever wonder how Tibetans can thrive on the roof of the world while the rest of us suffer from altitude sickness just looking at Pike's Peak?
Scientists think they have the answer.
A team of researchers from China, England, Ireland and the United States identified a particular spot within the human genome that is linked to low hemoglobin levels, a variant specific to Tibetans.
The variant is called EPAS1, and it explains why Tibetans can live two miles above sea level without getting sick.
"Altitude affects your thinking, your breathing and your ability to sleep," co-author Cynthia Beall of Case Western Reserve University said in a press release.
"But high-altitude natives don't have these problems. They're able to live a healthy life, and they do it completely comfortably," she said.
Hemoglobin is the oxygen-carrying component of the blood. Humans not used to high altitude automatically make more hemoglobin when they climb so their bodies can carry more oxygen in a low-O2 world. That's one reason why athletes train at altitude: Higher blood oxygen levels boost performance when they return to lower elevations.
But people who get chronic altitude sickness suffer from too much hemoglobin. Tibetans, on the other hand, have lower-than-normal hemoglobin levels, ensuring that they're less susceptible to the disease than other populations.
The team studied 200 blood samples from Tibetans and compared them with lowland samples from China. The difference that emerged was one gene on chromosome 2, the same gene responsible for red blood cell production and hemoglobin concentration in the blood.
Although all humans have the EPAS1 gene, Tibetans are the only group of people known to have the special variation.
The findings, published in the journal Proceedings of the National Academy of Sciences, could explain why some people cope better with less oxygen than others, leading to more targeted treatments for people with lung cancer or chronic altitude sickness.
"Many patients, young and old, are affected by low oxygen levels in their blood - perhaps from lung disease, or heart problems," said co-author Hugh Montgomery of University College London.
"Some cope much better than others. Studies like this are the start in helping us to understand why, and to develop new treatments," he said.
Image courtesy of Wikimedia Commons.