People are not yet produced. We continue to improve and adapt to the adaptation of our surrounding world, written in our bodies.
We know that there are certain environments that can make us bad. Mountain climbers often surrender to the height of the disease – the body’s reaction to a significant drop in atmospheric pressure, which means that each breath is taken so less oxygen.
And yet, at a high Tibetan plateau height, where oxygen breathing in the air is particularly lower than lower height, the human community flourishes.
Over 10,000 years, the region has been resolved, and the bodies of the people living there have changed so that the population could maximize the atmosphere that most people are not sufficient to supply oxygen through the blood cells to the body tissues – a condition called hypoxia.
“Adaptation to high height hypoxia is fascinating because the stress is difficult, with all the height and quantitatively evaluated,” Anthropologist Cynthia Beall from Case Western Reserve University said.
“This is a beautiful example of how and why our species has so many biological variations.”
Beall has been studying a person’s reaction to hypoxic living conditions for many years. In research published in 2024. In October, she and her team presented some specific adaptations in Tibetan communities: traits that help bring blood to oxygen.
To unlock this discovery, the researchers immersed themselves in one of what we call evolutionary fitness: reproductive success. Women who present living babies are those who convey their traits to the next generation.
Features that maximize a person’s success in a particular environment are probably women who are able to survive pregnancy and childbirth stress.
These women are more likely to give birth to more babies; And those babies who inherit survival features from their mothers also tend to survive until the age of majority and to convey traits to the next generation.
This is a natural selection at work, and it can be a bit strange and contradictory; For example, in areas where malaria is common, sickle anemia is high because it includes a gene that protects against malaria.
Beall and its team conducted a study of 417 women aged 46 to 86, who lived in Nepal over about 3,500 meters (11,480 feet) for a lifetime. Researchers recorded the number of live births, ranging from 0 to 14 per woman, on average 5.2, as well as health and physical information and measurements.
Among them, the measured things were the level of hemoglobin, the red blood cell protein responsible for the oxygen supply to the tissues. They also measured the amount of oxygen wearing hemoglobin. Interestingly, women who demonstrated the highest percentage of live births had the amount of hemoglobin, which was neither tall nor low, but on average for the test group.
But the oxygen saturation of hemoglobin was high. The results together show that adaptations can maximize oxygen supply to cells and tissues without ensuring blood – a result that increases heart stress as it tries to pump more viscosity fluid resistant to flow.
“We used to know that lower hemoglobin is useful, now we realize that the intermediate value has the greatest benefit. We knew that higher hemoglobin oxygen saturation is useful, now we realize that the higher saturation, the more useful the number.
“It was unexpected to notice that women could survive many live births with low value for some oxygen transportation features if they have favorable values of other oxygen transportation features.”
Women with the highest percentage of reproductive success also had high blood flow speeds in the lungs, and their hearts had wider left ventricles, cardiac chamber responsible for oxygen -saturated blood suction to the body.
All together, these traits increase the speed of oxygen transportation and childbirth, allowing the human body to make the most of the low oxygen in the air.
It is important to note that cultural factors can also play a role. Women who start to reproduce young and have long marriages seem to have longer pregnancy, which also increases the number of live births, found by researchers.
But even in view of this, the physical features played a role. Nepalese women with physiology most similar to women in a low -height environment usually had the highest level of reproductive success.
“This is a case of constant natural selection,” said Beall. “Understand how populations such as these adapts are better to understand the processes of human evolution.”
The investigation has been published Publications of the National Academy of Sciences;
The previous version of this article was published in 2024. October