'Sea nomads' evolved big spleens for deep diving
April 20, 2018
Researchers have found that Bajau people of South-east Asia appear to have evolved enlarged spleens that may explain their extreme diving skills.
The spleen is a reservoir for oxygen-rich red blood cells that it can release into the bloodstream, when needed. A larger spleen means more oxygen supply in the blood, enabling Bajau people to hold their breath for longer periods of time under water.
The study — published in the journal Cell — offers fresh evidence that humans can adapt genetically to a lack of oxygen and support a lifestyle centered on diving for food as is the case with Bajau who scour sea floors for food.
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"We have examples of how humans have adapted genetically to new diets and to extreme environments, such as high-altitude living in Tibet or life near the Arctic Circle in Greenland," said senior study author Rasmus Nielsen, a professor of integrative biology at the University of California, Berkeley.
"Now we also have a new fascinating example of how humans have adapted genetically to a nomadic lifestyle on the ocean," Nielsen told Reuters news agency by email.
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The spear-fishing Bajau people, often referred to as Sea Nomads, regularly free-dive to depths of over 230 feet (70 meters), with only weights and a pair wooden goggles.
They spend 60 percent of their daily working time underwater and can stay underwater for up to 13 minutes at a time, the study said.
The Bajau, who are spread among the islands of Indonesia, Malaysia and the Philippines, have been living on houseboats for thousands of years and depend on the sea for most of their needs.
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The researchers used ultrasound scans to measure spleen sizes for Bajau people and members of the nearby Saluan community, who do not dive.
They found that Bajau had spleens about 50 percent larger than the Saluan.
That may translate into about a 10 percent increase in oxygen supply, Nielsen said.
Among the Bajau, there wasn't much difference in spleen size between divers and non-divers.
The findings could boost research in medicine by helping scientists understand how the body reacts to a loss of oxygen in different situations.
ap/rc (Reuters, AFP)