A new study has shown for the first time that humans can genetically adapt to diving. Evidence suggests that the Bajau, an Indonesian-based ethnic group, has genetically enlarged spleens that allow them to dive at depths of up to 70 meters.
It has previously been hypothesized that the spleen plays an important role in allowing humans to dive freely for extended periods of time, but the relationship between spleen size and diving capacity has never been studied at the genetic level in humans.
published in the research journal Cell may also have medical implications regarding the disease known as acute hypoxia, which can cause complications in emergency medicine.
For more than 1000 years, the Bajau people, known as "sea nomads", have traveled in houseboats across the Southeast Asian seas, gathering food by free diving with spears. Today, they are native to the Indonesian islands and known throughout the region for their exceptional skills. Members of the Bajau can dive up to 70 meters with just a set of weights and wooden goggles. Since they never compete, it is uncertain how long the Bajau can stay underwater, but one of them told the researcher Melissa Ilardo that he had dived once for 13 consecutive minutes.
Ilardo, the first author of the newspaper, suspected the Bajau. Emagazine.credit-suisse.com/app/art … = 157 & lang = DE may have genetically adapted spleens, which is due to the results of other mammals is. "There is not much information about human spleen in terms of physiology and genetics," she said, "but we know that deep-diving seals, such as the Weddell seal, have disproportionately large spleens." I thought, when selection plays on the spleen a central role in extending free dive time as it is part of the so-called human dive response.
When the human body itself is submerged in cold water for a short time, this reaction is triggered as a method of helping the body in The heart rate slows, blood vessels in the extremities shrink to preserve the blood for vital organs, and the spleen contracts.
This contraction of the spleen creates an oxygen boost by discharging oxygenated red blood cells into the circulation and was found to deliver up to 9% oxygen gain and thus prolonged tauc
To obtain evidence for this study, Melissa Ilardo spent several months in Jaya Bakti, Indonesia, taking genetic samples and performing spleen ultrasounds on both the Bajau and her land-based neighbors, the Saluan. The results were sequenced at the University of Copenhagen and clearly showed that the Bajau had a median spleen size of 50% greater than the Saluan. Enlarged spleens were also visible in non-diving Bajau individuals as well as in those who regularly dive.
The international research team, led by academics from the Universities of Copenhagen, Cambridge and Berkeley, therefore eliminated the possibility that larger spleens were simply a plastic response to diving and began to study the genetic data of the Bajau. They discovered that members of the Bajau have a gene called PDE10A that the Saluan do not have. It is thought that the PDE10A gene controls the levels of the thyroid hormone T4.
"We believe that in the Bajau they have an adaptation that increases thyroid hormone levels and thereby increases their spleen size," said Melissa Ilardo. "It has been shown in mice that thyroid hormones and spleen size are linked together, and if you genetically modify mice to lack the thyroid hormone T4, their spleen size is drastically reduced, but this effect is actually reversible with a T4 injection."
This is the first time that a genetic adaptation to human diving has been traced. Ilardo added, "So far, it is not known if the sea-momentum populations genetically adapt to their extreme way of life.The only feature that has been studied before is the superior underwater vision of Thai Sea Nomad children, but this was a plastic reaction on training, and was reproducible in a European cohort. "
Ilardo was initially warned to do this study for her PhD thesis at the University of Copenhagen by her superiors – Professor Eske Willerslev, who holds a dual role at St John's College in Cambridge and at the University of Copenhagen, and Professor Rasmus Nielsen, who also holds twofold, to make positions at the University of Copenhagen and the University of California, Berkeley. "We told Melissa that this is a very risky PhD thesis and she needs to be aware that she probably will not find anything," said Professor Willerslev. "She said she wanted to do it anyway, and that paid off, Melissa was right and our misgivings were wrong."
The study also has implications for the world of medical research. The human dive reaction simulates the conditions of acute hypoxia in which body tissue undergoes rapid oxygen depletion. It is a major cause of complications in emergency care and has therefore already been the subject of several genetic studies, especially with regard to groups of people living at high altitudes.
The study of sea creatures such as the Bajau offers a great potential for researching acute hypoxia in a new way. "This is the first time that we really have such a system in humans for study," Dr. Rasmus Nielsen. "It will help us to establish the connection between genetics and the physiological response to acute hypoxia, a hypoxia experiment that nature has made for us and allows us to study people as we can not in a laboratory. "  These findings open up the possibility of further research on other marine nomad populations, such as the Thai Moken Population and the Haenyeo Dive Women of Jeju in South Korea. Examining similar groups of people could shed more light on the nature of the link between human physiology and genetic adaptations to extreme lifestyles and whether these genetic adaptations have evolved separately.
The next steps in this area of research are a somewhat urgent task as the traditional ways of life in many communities are threatened. "This study is a wonderful example of how valuable it is to study these small populations living in extreme conditions," said Professor Eske Willerslev. "Many of them are threatened and that is not just a cultural and linguistic loss, but also for genetics, medicine and the sciences in general, there is still a lot of information from these under-explored populations."
Free divers have long defied science – and we still do not really understand how they go so deep
"Physiological and genetic adaptations for diving in Sea Nomads" Cell (2018). DOI: 10.1016 / j.cell.2018.03.054