Home / news / Sherpas are the kings of the Himalayas .. Do humans still evolve biologically?

Sherpas are the kings of the Himalayas .. Do humans still evolve biologically?

Several decades ago, “Tohame” was a very quiet town, located in eastern Nepal near the highest peak in the world (Everest). Its few inhabitants work in agriculture, especially potatoes, and raising yaks, an animal that resembles a cow but a little larger. They respect it very much there. Although their religious rituals do not forbid the slaughter of animals for the purpose of food, they do not do so anyway, but they buy their meat from somewhere outside of town.

If you pass by any of the village houses, by pure coincidence, they will urge you to stay a little, and if you decide to enter the house you can eat the best possible meal of potatoes from the hands of Mrs. “Nima Sherpa” Perhaps, add to that that you will drink a cup of tea, perhaps you will not Never forget it, especially in this cold weather.

“Nima” means Monday, and in this village, which includes some members of an ethnic group living in Nepal and whose total number is about 150,000 people, many people are called the day they were born, so Mr. Dawa was born on Tuesday, and Bemba was born on Saturday. As for the second part of the name, it is the title of that ethnic group “Sherpa”, and some may prefer to add an adjective for his son or daughter, for the purpose of diversification, so it becomes “Anj Nima Sherpa” meaning “the beloved Nima”.

From the moment humans first decided to ascend the summit of Everest, the name Sherpa (1) appeared and spread around the world. If you ever wanted to go up there, you would undoubtedly deal with a group of them, as they do almost everything on this journey, preparing food, carrying gear, providing accommodation, and directing the teams of adventurers on the mountains all the way to the summit.

For you, it will be the adventure of a lifetime, but for them almost every home in this town, and other neighboring countries, has a person who has climbed to Everest, or at least worked in one of the support teams, in fact the current life of the Sherpa has completely changed with the emergence of the obsession of climbing into Everest, instead of farming and raising yaks, most families have turned to work in tourism, especially when you know that in order to go there, you will pay an average figure of 30-45 thousand dollars and may reach three times this number if you want specific hotel services.

But to understand how special the Sherpas, and all the peoples of neighboring Tibet are, let’s start from this high cost of the trip, because it is simply the price you would pay for the physiology of your body adapting over time! As it rises to the top, the percentage of oxygen compared to other particles remains constant in the atmosphere, which is approximately 21%, but the density of the atmosphere itself decreases, meaning that one breath that you take into your lungs will contain less than normal gases of all, this is called “hypoxia” (2) (Hypoxia) is an elegant term for defining asphyxia.

At an altitude of about 1500 meters above sea level (twice the height of Burj Khalifa), our bodies begin to feel a lack of oxygen, at that point your lungs will draw air at a higher rate than usual to compensate for the oxygen difference, and you will also feel heavier in movement and thinner, as you reach height About 3000 meters, the percentage of oxygen available to your lungs will be 30% less, here you will suffer from fatigue, general weakness, dizziness, nausea and headache.

As you climb higher than this limit, your body is exposed at any moment to hydrocephalus or pulmonary, as fluid accumulates around the lungs and brain, and by reaching the edge of 5000 meters, there is a very high chance of losing consciousness, then death.

But all of the above will only happen if someone was suddenly transferred from his home in Cairo to the summit of Everest, at an altitude of about 9000 meters, here this person will be at risk of death within only two minutes, but those who ascend Everest take a period of two months to move from a height For another, besides physical training on climbing hazards. In this case, their bodies achieve a vital acclimatization (3) with altitude, as respiratory rates rise and the levels of hemoglobin – the protein that carries oxygen – in the blood increases, which enables them to better deal with the lack of oxygen, when you return to your country, the levels of hemoglobin increase Back again to normal.

But despite that, over 7000 meters, you will often need an external oxygen tube to breathe because the percentage of oxygen in your surroundings will be 50% less than usual, and it will drop to about 30% by your arrival at Everest, and in that case even acclimatization will not help you much And there is always a chance of the worst medical event occurring.

Here appears Cynthia Bell, an anthropologist at Case Western Reserve University in the United States, Bell specializes in the study of human adaptation in the high regions of the world, and of course there is nothing higher than the “roof of the world”, the Tibetan plateau that arose 55 million years ago during a coalescence. We know it now as “India” with the Tibet region. This led to the emergence of an area roughly the size of the Kingdom of Saudi Arabia, but with a height of 3500-4500 meters.

About half of Tibetans live in this region, who are estimated to number six and a half million people. Hemoglobin in the blood, although it is a good adaptive mechanism, it may be harmful, because the more hemoglobin the blood becomes more sticky, and therefore the heart needs more effort to pump it to the whole body, which may cause severe heart problems.

For the Himalayan Sherpas, and neighboring Tibetans, they inhale more air with every breath, they also breathe more quickly, and they maintain this unusual breathing pattern and elevated lung capacity throughout their lives, even if they go down to places at sea level, add to that their bodies It produces more (5) amount of nitric oxide (almost twice) compared to the rest of the people, which works to expand their blood vessels more, so the blood flows in them faster.

It is an amazing mechanism for adapting to hypoxia to levels up to half the situation for us on the surface of the Earth, and this has drawn the attention of several researchers in this range, and with them Bell, to look for any differences in the genes that may be the cause of this difference, because if you climbed to the summit Everest once, twice, or ten times, even if you decide to live on the Tibetan plateau for years and then marry there, you will have children whose bodies work in a way that is adapted to sea level, but only Tibetans are born with these abilities, so it seems like hereditary.

In 2010, an international team of researchers found that Tibetans have mutations (6) in several genes, which help them deal more effectively with low levels of oxygen. These mutations were found in 87% of Tibetans and only 9% of the Han people, which is one of the nationalities. That make up the Chinese people, although the two groups separated from each other only in less than 5,000 years.

Imagine our human DNA as a CD carrying encoded data for a movie that will be shown on your computer screen, and just as that data determines the arrangement of scenes and the nature of the colors in them for each small “pixel” over time, so the DNA also carries packets of data that define our characteristics, color Eyes, hair, the shape of the nose, the length of the arms, the color of the skin, etc., down to the most accurate molecular morphologies within the systems of our bodies, these bundles are what we call – a simplification that may disturb accuracy – genes.

These genetic changes were so remarkable that they prompted scientists to conduct a more in-depth examination, specifically for a gene called “EPAS1, in which the differences between the Tibetans and Han were great. The results appeared in 2014 in the Nature journal (7) to say that the Tibetans seem to have benefited from a genetic gift that came to them before Tens of thousands of years when Homo sapiens intermarried with another race of human beings, which is the Denisovans.Like Homo sapiens (contemporary), the Dinosovans were a member of the Homo genus, and we do not know much about it yet, so all that scientists have obtained from its remains are the teeth of a young girl who lived More than forty thousand years ago, a pinky bone was found in Denisova Cave near the Altai Mountains in Siberia.

This gene is known specifically that it helps regulate how the body responds to low oxygen levels, it is also called (8) the “super athlete gene”, because we know that some humans who have some special copies of this gene have better performance in games Powers.

And it is not just this gene, but subsequent studies (9) have found a larger group of genes that contain changes that help Tibetans to adapt naturally to environments that are very harsh for us below, for example another international team discovered the presence of changes in a group of genes Like ADH7, it is associated with higher weight and BMI scores, so that it helps Tibetans’ bodies store energy during times of scarcity.

On the other hand, a change appeared (10) in the “MTHFR” gene, which enhances the production of the vitamin folate necessary for pregnancy and fertility, especially since folic acid decomposes when exposed to high levels of ultraviolet rays (which are higher the higher we are above the surface of the earth). HLA-DQB1 “contributes to the regulation of proteins essential to the immune system, and changes in it are especially important for Tibetans in their harsh living conditions that make them more vulnerable to disease than others.”

So far, this remains one of the strongest examples of natural selection that has been documented in humans (11). Take, for example, the change in the EPAS1 gene, which humans inherited from their ancestors who mated with Denisovans. This gene spread at weak frequencies in multiple regions of various heights of The continent of Asia, but it was effective only in increasing the chances of survival for those who lived at great altitudes, thus helping them to pass their genes better than their comrades, and in the end we reach a stage where this particular change in this gene prevails in most of the population of this region.

Of course, there are still many questions that need to be answered, but it is really striking to reflect on other groups of people that live at high altitudes in separate regions of the world, Bell (12) for example found that the people of the Andean highlands adapt completely differently from their comrades in Tibet. , Who in turn differ from their comrades in the Ethiopian highlands, all three of them are able to live at heights of more than 3000 meters, in conditions that may be fatal for the average person in Egypt, Morocco or Qatar, for example, but for them it is considered a “natural thing”, but that pushes us to A more urgent question in turn: What is normal ?!

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Sources

  1. The Sherpa cheat sheet: 9 things you were embarrassed to ask
  2. What is hypoxia and hypoxemia (low blood oxygen)?
  3. Acclimatization: how the body prepares for an eight-thousander
  4. Two routes to functional adaptation: Tibetan and Andean high-altitude natives
  5. Nitric oxide in adaptation to altitude
  6. Genetic Evidence for High-Altitude Adaptation in Tibet
  7. Altitude adaptation in Tibetans caused by introgression of Denisovan-like DNA
  8. With Help From Extinct Humans, Tibetans Adapted To High Altitude
  9. Genetic signatures of high-altitude adaptation in Tibetans
  10. Mutations may reveal how Tibetans can live on world’s highest plateau
  11. strongest instance of natural selection documented in a human population
  12. Scientists Discover New Adaptation to Oxygen-Poor Air at High Altitudes

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