Why can this Tibetan family live at an altitude of 4200m?

At some point in the past, there was a family sitting on the roof of the world together, quietly looking up at the stars in the deep sky. They lived on the Tibetan Plateau at an altitude of 4200m above sea level, in what is today called Chusang. Modern people still wonder how they have survived in such a place with such harsh conditions and scarcity of oxygen?

The Thanh Tibetan Plateau is the largest and highest land in Central Asia and the world. Although not as comfortable as other lowlands, this area has its own advantages. The specific geological structure creates a source of energy to nourish the highlands and a hot spring of natural water flows throughout the day and melt the cold air.

Thanh Tibet plateau is at an altitude of over 4000m above sea level.

At some stage in the history flow, a family came to this pristine land and called it home. Every day, they work together in the vast sky, making friends with the cold winds and the taste of nature. At night, the whole family caught fire in the cave on the slope, the fire flickering warmly against the loneliness of the dense night.

Although the fire of the group's family has long since vanished, the imprints they leave are still surprising and shocking the world. 19 footprints, fingerprints of the family during the walks, the work still on the loose patches of spring, remind us of some mysterious and sacred ancient time .

From their footprints and fingerprints, we can see that this family has six members, including two young children. But who are they? What brought them to live on this altitude? The traces they saved do not respond to any questions. All that is known until now, according to a study published in January 2017, is that the footprints in Chusang appeared around 12,700 to 7,400 years ago. Accordingly, Chusang became the oldest archaeological relic on the Thanh Tibetan plateau.

According to anthropologist Aldenderfer of the University of California at Merced, the co-author of the study, the reason for the Chusang family to become special is because of their isolated, isolated lifestyle . Living in the middle of the Qing Tibetan Plateau, they could not simply move up and down the mountains in each season as the Tibetans used to do during this period. They had stayed here year-round, during the snowy season, cold winds, and across the glacier in winter.

The flames they had turned off for a long time but their imprints did not fade away.

Their survival is miraculous. Although they use fire to keep warm, the Chusang family also faces many other risks when living on the plateau, such as the higher the air becomes more dilute. At altitudes above 4000m, each breath contains an oxygen content of only 1/3 compared to when breathing in lower areas. It seems that deep inside their bodies, in their blood and DNA, there has been a strange ancient instinct about surviving at such an altitude.

Any climber can describe the shortness of the breath as it rises. It is not because the air is then low in oxygen - because the oxygen content in the air is always 21% anywhere in the world. The reason is that because the pressure drops when you go up, or soar up to the sea surface, the gas molecules disperse in all directions, and a lung can only stretch to that level.

There are many ways to deal with pressure changes . However, over hundreds of generations, people living on the Altiplano plateau of Andex range from Peru to Bolivia deep, have evolved the chest cavity in a circle to increase the amount of air inhaled. Since the late 1800s, scientists have discovered in their blood pumped with red blood cells and heamoglobin, cells that carry a lot of oxygen.

Because most studies of residents living in high altitudes focus on people living in the Andex range, the process of hematopoiesis is generally considered to be a reaction to low oxygen levels for nearly two centuries. It was only in the late 70s and early 80s, after climbing to seven villages in Nepal, Case Western Reserve University anthropologist Cynthia Beall began to discover that Tibetans did not follow. This regime.

Scientists were amazed to find that Tibetans had no physical adaptation to life in the highlands.

First of all, they don't have a large round chest, but seem to breathe faster than the Andex. The second is that at the end of the fall of 1982, Beall and his colleagues discovered that the Tibetans had very low hemoglobin content , only the same limit as normal people living in low and sea level. Although they live on the roof of the world, their physical condition is surprisingly similar to those who live on the "floor".

Mrs. Beall said, "At first, there was a worry in me, did I measure the wrong person? Did I use the wrong method? Did I miss anything?" But after returning to the two regions of Tibet and Nepal, collecting more data from many other villages, she found only more evidence to reinforce the initial results: in high coordinates, low oxygen environments, Tibetans reduce the amount of oxygen in the blood.

How can this happen? What initially seems very contradictory - not to mention the potential danger - is actually very reasonable, because it helps Tibetans not suffer from some side effects of life on the plateau.

For example, one benefit can be seen to reduce the chance of blood vessels breaking or breaking . If you have a high level of hemoglobin in your blood, your blood will be more viscous, and this may cause many harmful effects, researcher Tatum Simonson from the University of California in San Diego said. Concentrated blood will need to use strong pumping force to be able to push through the body. So the heart will be over-exercised.

The impact caused by this increased stress on the entire respiratory system is the cause of chronic altitude sickness, also known as CMS , first introduced by a Peruvian doctor named Carlos Monge Medrano. . This disease can make people who are used to living in misery for many years suffer. "The initial symptoms are unknown" Ms. Beall said: "However, people with this disease will feel short of breath, become pale (their lips and nose are blue), they cannot work or sleep - they always feel tired".

For temporary altitude sickness, the treatment is to lower the elevation, bringing the person into a concentrated oxygen environment. But it cannot be completely cured. Fluids can build up in the lungs (pulmonary edema due to elevation or Hape) or in the brain (elevation of the brain edema, or Hace), and may be congested in some organs. important. The worst case is death.

In the Peruvian Andes, 18% of people here to a certain age will suffer from CMS altitude sickness. But the number of people suffering from this disease in the plateau Very rare organ bar is just over 1%.

It is the diluted blood that helps reduce the risk of getting CMS , but it is certainly not the only cause for Tibetans to live comfortably at such a height. In 2005, Beall and her colleagues discovered that Tibetans breathed more nitrogen than those in Andex or those living in lowland areas. Essentially this gas is described as a relaxation agent, which helps the blood vessel walls in the lungs and around the body expand, also called vasodilation .

And as researcher Simonson mentioned what would happen if Tibetans didn't need as much oxygen as normal people? If their muscles are better able to endure?"Maybe their body's mechanisms are so good that they don't need to add red blood cells and hemoglobin to get more oxygen," said Beall. And she is focusing her research in this direction.

Rapid changes in genes can allow ancient people to survive and thrive in this environment.

Although he went to the Tibetan Plateau several times to do research, Simonson continued to survey the area's history in the laboratory. As a geneticist, she can review the genome (the entire DNA sequence of a person) of Tibetans to find out what lies behind their unique adaptability to life above.

In 2010, by comparing the genes of 30 Tibetan people with Han Chinese living in Beijing, Simonson could detect these genes only in people living in high areas. This is easier than expected, since the two peoples have an intimate relationship but only one people live on high for thousands of years, the fundamental difference between the two genomes must be mainly due to adaptation to change. change of environment, eg low oxygen air.

The field of human gene research has become easier thanks to the unity of human strains: at the level of DNA or genes, they have very high similarities. In general, there is not much difference between ethnic groups, according to researcher Rasmus Nielsen of the University of California at Berkeley. Genetic variation shows the most difference between groups of people is the difference in hair color, eye color and skin color.

Our differences are few and present on the surface. When we are under the skin, deep in DNA, we are almost the same. From these great similarities, important genetic changes between ethnic groups can be considered very small but the unique difference has broken the surface of the genome. But when deeply studying the EPAS 1 gene in the Tibetan genome, Nielsen not only found it to be a big change, but also a unique change. After thoroughly studying a 1000 gene project, he could not find the same thing anywhere. Nielsen said simply the DNA sequence we found in Tibetans was so different.

It is like a Tibetan who has inherited this gene from another species. And in fact, it is exactly what happened.

The genetic transformation has helped the Tibetans survive and survive at high altitudes, possibly from an extinct ancient strain.

Through more than 50 thousand years of development, this story has not yet ended. Although the origins of this group of people have been known, the areas that make Tibetan EPAS1 unique are largely unregulated. Specific changes leading to lower levels of hemoglobin are still unknown."All geneticists have it in a very difficult area to organize , " said Beall. New adventurers, data mountains and genomes, are still a long journey ahead.