Tibetans’ Unique Genetic Adaptations to High Altitude
Mountain air is thin, and thin air is oxygen-low. Therefore, if you travel in high mountains, most people will experience breathing problems and perhaps even the unpleasant altitude sickness. But not the Tibetans, who live on the Tibetan plateau by the famous Himalayan mountain range.
For more than 10,000 years, they have lived in the height of 4,000 meters, which is the average height of the plateau.
Now, new research shows that a certain genetic variation among Tibetans is the cause of its superiority in the mountains. There are researchers from China, England, Ireland and the US who, in cooperation, have found this particular gene variant.
The thin, low-oxygen air in the mountains makes people who live there produce more hemoglobin, which is the substance that transports oxygen in our blood.
Cyclists are familiar with what the effect of thin air is, who gladly train in heights to increase their oxygen absorption. But too much hemoglobin can be a problem too, which can be seen, for example, in altitude sickness.
However, the Tibetans maintain the low hemoglobin level in heath, making them less susceptible to the disease.
“Tibetans can live up to 4,300 meters altitude without experiencing as high hemoglobin concentrations as we see in other people,” said Professor Cynthia Beall, one of the authors of the study.
She has, together with researchers from four other universities, collected 200 blood samples from Tibetan villagers in three regions in the Himalayas. They were used to identify the genetic variations causing the Tibetans to have a relatively low hemoglobin level.
When they compared DNA from Tibetans with Chinese people from more low-lying areas, the results pointed in the same direction: against a genome called EPAS1 on chromosome 2, which helps control the red blood cell production and concentration of hemoglobin in the blood.
“Some of us worked with Tibetan DNA in general, while others looked at small groups of genes. We looked at the results together, we could see that both studies pointed to the same genome, EPAS1,” said Professor Peter Robbins from Oxford University, England.
All people have the EPAS1 gene, but the Tibetans carry a special variant that is adapted to life in height. Over time, Tibetans who inherited this variant received better survival opportunities, thus spreading among the Tibetan population.
Although, the researchers still don’t understand how the Tibetans get enough oxygen throughout their bodies when both their blood and the air they breathe are so low in oxygen.