Living at altitude really puts a strain on the human body. From slowing digestion to the extreme cold, there is a lot to contend with the higher up you go. Yet people living on the Tibetan Plateau have managed to survive at an altitude of around 4,500 meters (15,000 feet) for thousands of years.
A team of geneticists have now uncovered exactly how they manage this, including the genes they may have gained from an extinct species of human. After sequencing the entire genomes of 27 Tibetans, they managed to find five different genes that help them live at such lofty heights. The results highlight the influence the extreme environment faced by these people, who have been living there for at least 3,000 years, has had on their evolution.
The five gene variants discovered are all related to helping the body cope with the low levels of oxygen, high altitude, and poor diet. They also show how the ancestors to Tibetans at some point had shenanigans with an extinct human species. Some of these have already been identified before, as the researchers found the genes EPAS1 and EGLN1 both present in the population. These induce the body to produce more hemoglobin, which transports oxygen around the body when at altitude.
But they also uncovered a few genes we didn’t know about. Related to low oxygen levels, PTGIS and KCTD12 were also found in the genome of the Tibetans, as well as a variant of VDR, which has been linked to vitamin D metabolism. The researchers suspect that this may help the people deal with vitamin D deficiency, which is a common problem on the plateau due to the poor growing conditions, and thus diet.
“The comprehensive analysis of whole-genome sequence data from Tibetans provides valuable insights into the genetic factors underlying this population's unique history and adaptive physiology at high altitude,” explains Tatum Simonson, who co-authored the study published in PLOS Genetics, in a statement.
Simonson continues: “This study provides further context for analyses of other permanent high-altitude populations, who exhibit characteristics distinct from Tibetans despite similar chronic stresses, as well as lowland populations, in whom hypoxia-related challenges, such those inherent to cardiopulmonary disease or sleep apnea, elicit a wide-range of unique physiological responses.”
But what is really interesting is how the genetics of the Tibetan people can provide insight into how an extinct species of human, the Denisovans, lived. Known only from a few hand bones found in a cave in Siberia, it is thought that the EPAS1 gene is derived from these mysterious people, suggesting that as a species, they too may have been adapted to high altitudes.