“Himalayan mutants”: genes of mysterious ancient people discovered in the DNA of Tibetans

Tibetans living at 4,500 meters above sea level are exposed to harsh environmental conditions that would knock most people off their feet.

In recent studies, several genetic mutations have been identified in people living in Tibet, which appear to be responsible for the incredible resilience that allows them to feel quite comfortable at high altitudes.

A team of researchers led by geneticist Chad Huff of the University of Texas in 2017 discovered genes in Tibetans that allow them to live and work in the dizzying heights of the Himalayas.

The Tibetan plateau, known as the “roof of the world”, is located at an altitude of over 4500 meters. There is a vast and arid steppe, mountain ranges and huge lakes. It rarely rains here, but when it does, it rains in the form of hail.

People have lived here for thousands of years, and according to genetic research, the population of this region acquired a special genetic profile through natural selection. Huff’s team uncovered gene variants that allow Tibetans to survive when oxygen levels are low and food is limited.

Incredibly, one of these genes, named EPAS1, was inherited from the Denisovans, a mysterious human subspecies that disappeared about 40,000 years ago. The name of this species comes from Denisova Cave, which is located in the valley of the Anuy River, on the border of the Altai Territory and the Altai Republic. The remains of representatives of this species were found there.

Thus, this study gives us information about the history and physiology of the Tibetans, and also tells us something about the human species that we know very little about.

Most people are not adapted for mountain life. Already at an altitude of over 2,100 meters, many of us will suffer from altitude sickness. Low air pressure will cause headaches and nausea, and breathing will be difficult.

The worst thing is that at high altitude some people can develop pulmonary edema with pulmonary bleeding and even heart attack. It is hard to believe that people voluntarily began to live in such harsh conditions. However, over time, populations of people living in such an environment begin to change genetically. During the study, the researchers analyzed the DNA of a group of 27 Tibetans.

As a result, Huff’s team identified two genes that, as it turned out, provide physiological adaptation to living at high altitudes. Both of these genes are activated when oxygen levels are low, causing increased production of hemoglobin, a protein in red blood cells that carries oxygen throughout the body. These genes prevent  hypoxemia  (decreased blood pressure and oxygen levels).

Unfortunately, very little is known about the Denisovites. The source of all available information is genetic information obtained from an ancient human finger phalanx, discovered in Denisova cave in 2010.

These hominids were more like modern humans than Neanderthals, and may have represented a distinct subspecies of Homo sapiens.

Moreover, the presence of the EPAS1 gene in Denisovans seems to suggest that they, like the Tibetans, lived in mountainous areas . According to the conclusions made after conducting genetic analysis, between 952,000 and 238,000 years ago, a separate population of people originated from the Denisovans. They mixed with the archaic Tibetan population, and now, according to researchers, 0.4% of the Tibetan genome belongs to Denisovans.

Incredibly, it took the Tibetans only a few thousand years (perhaps as little as 3,000 years) to develop mutations that allowed them to live at high altitudes.

In the future, the researchers plan to study the newly identified genes in more detail to better understand how they help Tibetans live at high altitudes. Another goal of the researchers is to study the Andean population, which, like the Tibetans, developed the ability to live high in the mountains.

A scientific article about the research was published in PLOS GENETICS