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Evolution has changed the spleen of the Bajau, men who live diving

The human being is not the strongest animal, nor the one who better nothing or the one who runs the most. But culture allows you to develop a powerful technology and live in a society that makes you very powerful in nature . Apart from that, his body, humble as it is compared to others, is a prodigy. First of all, it can be acclimated to difficult conditions, such as the shortage of oxygen in high mountains, through biological plasticity. Secondly, evolution sculpts the human genes with the passage of tens of thousands of years, just as it does with other living beings, through genetic adaptation .

Melissa Ilardo, a researcher at the University of Copenhagen (Denmark) has discovered a new test of how evolution shapes the genes of man. He has found out that, after millennia dedicated to free diving, the Bajau people in Southeast Asia have a different gene than the non-diver peoples of the region, as he concluded in an article recently published in ” Cell .” There he has found a mutation or allelic variant that could be related to the increase in the size of the spleen, a trait that is related to a greater ability to release oxygen in the blood during diving, at which time this organ contracts to release extra blood. According to the researcher, this feature could be one of the adaptations that allows these people to immerse themselves for many minutes and reach depths of up to 70 meters to look for food.

Melissa Ilardo heard about her incredible abilities and was interested in the human response to diving : a phenomenon that is activated when the breath is held and the face is immersed in water. At that moment, the heartbeat slows down, the blood vessels of the extremities constrict, the blood migrates to the viscera (brain, lungs and heart), and the spleen contracts, sending a blood supply of oxygenated blood to the bloodstream.

Ilardo wondered if the Bajau, a people that, apparently, has been at least a millennium living from diving in the sea, could have some type of genetically transmitted trait that would be beneficial to their extreme way of life.

Different genome and a larger spleen

With that goal in mind, they examined the genome of three populations close to the region, the Bajau (divers), the Saluan (non-diver neighbors, who live inland) and the Chinese. Thus, they identified 25 characteristic genetic regions among the Bajau.

Among all of them, there is a variant of the PDE10A gene that seems to be correlated with the possession of a larger spleen. Other studies have linked this gene with the regulation of thyroid hormone, and this hormone is related to the increase in the size of the spleen in mice. In addition, seals are considered to have very large spleens to provide extra blood during diving.

To confirm this, Ilardo spent several months in Jaya Batki, Indonesia, armed with an ultrasound equipment that allowed him to measure the sizes of the spleens and verify that, indeed, the Bajau have these organs of an unusually large size.

“Express” adaptation

Carlos Varea, Professor of Anthropology at the Autonomous University of Madrid, said that this is an interesting article whose most relevant contribution is that it “proposes a process of adaptation by natural selection very recent . ” In principle, as proposed by Ilardo, in just one thousand years, evolution chose those most capable of facing the hypoxia derived from diving to collect food.

However, added Varea, ” other adaptive processes that we know (derived from the consumption of milk in pastoral societies, pigmentation due to our expansion in Eurasia or the adaptation to hypoxia in high altitude areas) have been relatively rapid, but have behaved several tens of thousands of years (at least 10,000 years) »said the anthropologist.

In contrast, Ilardo’s study speaks of “at least a millennium of life associated with diving”, although when asked, the researcher points out that she is not sure how long the Bajau have been diving, and suggests that the antiquity of this way of life was greater.

Next, the researchers will track the other regions of the genome that appear to be characteristic in the Bajau. The authors have highlighted that this is another example of how culture and biology have evolved in parallel since ancient times, and have suggested that researching similar groups could allow new connections between human physiology and genetic adaptations for extreme life-styles.

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