The peculiarities of the climate and the need to find food in hard-to-reach places largely determine which mutations will take hold in the human population and how society will develop. RIA Novosti tells about peoples who, thanks to natural selection, have adapted to difficult environmental conditions.
Mountain tribes of Tibet and the Andes
The human body is not adapted to life in the mountains. At an altitude of 2500 meters above sea level, due to the rarefied atmosphere, it is difficult to breathe, hypoxia develops with nausea, vomiting, dizziness, and muscle weakness. At an altitude of 7600 meters, it is generally impossible to be without breathing apparatus.
However, the tribes of the Tibetan Highlands and the Andes have adapted to the highlands, and on the basis of two opposite principles. The blood of the inhabitants of the Andes, living at an altitude of 4500 meters, contains more oxygen-carrying hemoglobin than that of the plain population. In Tibetans, on the other hand, there is little hemoglobin in the blood, and the speed and volume of blood flow are almost doubled due to the increased concentration of nitrogen decomposition products - nitrates and nitrites.
According to recent studies, these features of Tibetans are determined by the genes EGLN1 and EPAS1, and the latter could have been inherited from another species of Homo - Denisovan man.
Tibetan nomadic shepherd in Yushu county in the mountains of Qinghai province / AFP / Nicolas Asfouri.
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Fulani of Africa
In most mammalian species, lactose, or milk sugar, can only be absorbed by babies that feed on breast milk. Our distant ancestors, too, at the age of three to five years, no longer digested lactose. But about nine thousand years ago, a mutation occurred in the DNA of people inhabiting the territory of modern Europe, which allowed them to drink raw milk. In the body of Europeans, the LCT gene, responsible for the absorption of lactose, has ceased to be disabled. There is no such mutation in the genome of other people, therefore, among the adult population of Asia and Africa, lactose intolerance reaches 90%.
The exception is the Fulani nomadic tribes in northern Nigeria, which have been breeding cattle from time immemorial. In arid and harsh climates, milk was an excellent source of additional energy. Therefore, today Fulani are among the few Africans who can drink raw milk. Interestingly, the Fulani mutation is different from the European one, although both are in the MCM6 gene, which makes the LCT gene work in an adult organism.
Baggio - the fish man
The Bajo people from Southeast Asia, also known as "sea gypsies", dive to a depth of 70 meters and stay under water for a long time without any special devices. They only have wooden goggles and fishing tackle. Scientists have found that these amazing baggio abilities are associated with several mutations in genes, which, among other things, led to an enlarged spleen. In the baggio, this organ is, on average, half as large as in other people.
The spleen plays an important role in filtering blood, and its size determines the so-called response to submersion under water - a mechanism that helps to survive in an oxygen-free environment at low temperatures. When diving, this organ contracts and releases red blood cells, which increases the oxygen level in the blood. This allows the person to hold their breath longer.
For the Baggios, who traditionally live in houseboats and roam the entire southeast coast of Asia, the survival of the entire tribe depended on the ability to dive deeply and for a long time. This is what determined natural selection.
Baggio fishermen on the island of Sulawesi, Indonesia. 2009 / AP Photo / Irwin Fedriansyah.
Navajo Indians
Some mutations that occur in humans as they adapt to their environment have side effects. Thus, the Navajo Indians living in the territory of modern Mexico and Latin America inherited from their distant ancestors a rare mutation that leads to the development of type 2 diabetes.
The culprit is the mutant variant of the SLC16A11 gene, which is found in about half of the descendants of the indigenous population of America, in ten percent of East Asians and is very rare among Europeans and Africans. Even one copy of this version of the gene increases the risk of type 2 diabetes by a quarter. Having two copies inherited from their parents increases the likelihood of developing diabetes by half.
Interestingly, according to some reports, this same mutation prevents the development of coronary heart disease. Perhaps that is why she was not culled by natural selection.
Navajo Indian. Photo: ANOXLOU.
Pygmies
This tribe living in the equatorial forests of Africa is distinguished by its short stature and short life span. For a long time, it was believed that the short stature of pygmies is the result of natural selection. They stop growing immediately after puberty, and this gives them time to acquire offspring, and most importantly, the opportunity to direct all the body's resources to reproduction.
Scientists from the University of Pennsylvania have shown that the growth of pygmies is a consequence of hormonal regulation of the immune system, fixed in the genes. Researchers have discovered a specific nucleotide sequence in the CISH gene that is associated with both growth and immune system activity. It is assumed that short people are better at resisting infections.
The average life span of pygmies does not exceed twenty years. Most often, they die from infectious diseases, which are favored by a hot and humid climate.
Ba aka pygmy family, Congo / Photo: L. Petheram / USAID.
Alfiya Enikeeva