If you have traveled somewhere located at high altitudeslike Peru, many of you will have experienced significant difficulties adapting to low oxygen levels. In contrast, local communities seem accustomed to these hypoxic circumstances– low levels of oxygen in the air and blood. However, the inhabitants of the Tibetan plateau go beyond this. It is not in vain that Tibet is known as ‘the roof of the world’. a new studypublished in the journal Proceedings of the National Academy of Sciences (PNAS), reveals an unusual adaptation in the tibetan women.
The researchers noted that those who have more children, even up to 14, have a unique set of blood and heart traits which helps your body supply oxygen. Showing evolutionary advantages that the rest of the population does not have. A process that began thousands of years ago and that, according to Cynthia Beall, an anthropologist at Case Western Reserve University in the United States, told ‘Science Alert’ that “it is a beautiful example of how and why our species has so much biological variation.” .
Beall explains to ABC that this ability probably originated with the Denisovansextinct relatives of modern humans “who lived in Siberia about 50,000 years ago. And the first emigrants to Tibet brought at least one of the genetic variants involved – the gene (EPAS1) that controls oxygen regulation. Permanent residence on the plateau dates back to about 10,000 years ago. Although he clarifies that “this is controversial because there is evidence of a sporadic adaptation 30 or 40,000 years ago,” he says.
Previously, in 2006, Beall’s team determined that Tibetans they exhale more nitric oxide (NO) when compared to people who live at sea level or in areas of the Andean mountain range. NO widens the blood vessels of the lung, favoring increasing blood flow and oxygen transport.
A successful combination
In the present work, they studied 417 Tibetan women between 46 and 86 years old living in Upper Mustang (Nepal)at the southern end of the Tibetan plateau at an altitude of between 3,000 and 4,000 meters above sea level. They analyzed their reproductive history, their DNA samples, as well as social and physiological factors.
His team specifically measured elements of oxygen extraction from the air (hemoglobin concentration) and oxygen transport to tissues (hemoglobin oxygen saturation percentage, heart and lung function).
While “lowlanders respond to high altitude with substantial increases in hemoglobin concentration and reduction in percent oxygen saturation, with the result that our heart has to work harder to pump blood to our lungs and to our systemic circulation,” details Beall. They detected a successful combination of characteristics in women who had given birth more times because they had average hemoglobin levels which is the molecule that transports oxygen, but ua higher oxygen saturation allowing a more effective supply to the cells. The advantage of this combination is to avoid the problem of thick blood. The more viscous the blood is, the more effort the heart has to make.
“This is a case of continuous natural selection. “Tibetan women have evolved in a way that balances the body’s oxygen needs without overloading the heart,” said the researcher. «Another successful combination of traits was high blood flow to the lungswhere it is oxygenated. AND a high flow of oxygenated blood to the heart and from the heart, with wider cardiac ventricles. This was possible because the responses described above avoided thick blood,” he says.
In addition, the Bajau, which are individuals capable of submerging up to 70 meters deep and lasting 13 minutes without breathing. Other examples of extreme situations at high altitude are those of the Quechua and Aymara ethnic groups of the Andean plateau and ethnic groups Amhara and Oromo of the eastern African plateau. «These people adapt differently to the Tibetans. For example, populations on the Andean plateau have very high concentrations of hemoglobin that lead to thick blood and stress on the heart and lungs that can increase the risk of certain diseases,” says Beall.
The usefulness of these discoveries, as Beall points out, is that the population, in general, suffers from many diseases associated with hypoxia. Asthma, chronic obstructive pulmonary disease (COPD) or covid-19 are examples of this. «Knowing the successful responses of healthy people with inevitable and permanent hypoxia, such as the Tibetans, can serve as guide to understanding the pathobiology of patients here and at sea level. And they are still unique capabilities and an example of the functioning of ongoing evolution.
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