Genetic adaptations to diving discovered in humans for the first time

[Swordsmyth]

Evidence that humans can genetically adapt to diving has been identified for the first time in a new study. The evidence suggests that the Bajau, a people group indigenous to parts of Indonesia, have genetically enlarged spleens which enable them to free dive to depths of up to 70m.

It has previously been hypothesised that the spleen plays an important role in enabling humans to free dive for prolonged periods but the relationship between spleen size and dive capacity has never before been examined in humans at the genetic level.
The findings, which are being published in the research journal Cell, could also have medical implications in relation to the condition known as Acute Hypoxia, which can cause complications in emergency medical care.
For over 1000 years the Bajau people, known as 'Sea Nomads', have travelled the Southeast Asian seas in houseboats and collected food by free diving with spears. Now settled around the islands of Indonesia, they are renowned throughout the region for their extraordinary breath-holding abilities. Members of the Bajau can dive up to 70m with nothing more than a set of weights and a pair of wooden goggles. As they never dive competitively it is uncertain exactly how long the Bajau can remain underwater, but one of them told researcher Melissa Ilardo that he had once dived for 13 minutes consecutively.
Ilardo, first author on the paper, suspected that the Bajau could have genetically adapted spleens as a result of their marine hunter-gatherer lifestyle, based on findings in other mammals. "There's not a lot of information out there about human spleens in terms of physiology and genetics," she said, "but we know that deep diving seals, like the Weddell seal, have disproportionately large spleens. I thought that if selection acted on the seals to give them larger spleens, it could potentially do the same in humans."
The spleen plays a central role in prolonging free diving time as it forms part of what is known as the human dive response. When the human body is submerged under cold water, even for brief amounts of time, this response is triggered as a method of assisting the body to survive in an oxygen-deprived environment. The heart rate slows down, blood vessels in the extremities shrink to preserve blood for vital organs, and the spleen contracts.
This contraction of the spleen creates an oxygen boost by ejecting oxygenated red blood cells into circulation and has been found to provide up to a 9% increase in oxygen, thereby prolonging dive time.

More at: https://phys.org/news/2018-04-genetic-humans.html

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Aquatic Ape Hypothesis

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