Larger Spleens Help Bajau “Sea Nomads” Dive

October 11, 2018 9:40 AM

'Sea Nomads' Are First Known Humans Genetically Adapted to Diving. "For hundreds of years, the Bajau (previously) have lived at sea, and natural selection may have made them genetically stronger divers."
posted by homunculus (9 comments total)

Seems like every cool story about an animal evolving or adapting to a specific environment ends with capitalism either cutting them down or soon to be doing so in some fashion. Would be interesting to see what homo sapiens might look like if populations had more time and space to develop independently without global capitalism swooping in to unite everything and everyone under the same horrible umbrella. It's also fucked up these folks don't have their rights.
posted by GoblinHoney at 9:45 AM on October 11, 2018 [3 favorites]

I love this not just because it is clearly very awesome but also because I feel like Hippocrates would be very excited about this.
posted by poffin boffin at 10:01 AM on October 11, 2018 [1 favorite]

I wish there were more detail about why larger spleens would be an advantage when diving - is there a plausible hypothesis for that, or is it just something that was different between this group and another, and therefore might be explanatory?
posted by Salvor Hardin at 10:25 AM on October 11, 2018

Seems like it based on previous studies showing aquatic mammals having enlarged spleens to help deal with blood oxygen stuff. Some whales even have up to 14 (!) spleens. So I think they're going off other animal studies, not just what's different between the Bajau and other populations.
posted by GoblinHoney at 10:46 AM on October 11, 2018 [1 favorite]

From the last article "When people plunge into water, they respond with the so-called diving reflex: the heart rate slows and blood vessels constrict as a way to shunt blood to vital organs. The spleen also contracts, squirting a supply of oxygen-rich red blood cells into the circulation. An enlarged spleen seems to function like a bigger scuba tank."
posted by zeoslap at 11:00 AM on October 11, 2018 [3 favorites]

"The spleen also contracts, squirting a supply of oxygen-rich red blood cells into the circulation. An enlarged spleen seems to function like a bigger scuba tank."

Excuse me, scuba tanks squirt blood? I have been woefully misinformed by The Undersea World of Jacques Cousteau.
posted by Quindar Beep at 1:04 PM on October 11, 2018 [3 favorites]

More from Ed Yong: How Asia's Super Divers Evolved for a Life At Sea

One gene, known as PDE10A, stood out. It does many things, but it’s especially active in the thyroid gland, and controls the release of hormones. The version of PDE10A that’s common in the Bajau is associated with higher levels of thyroid hormones, and those hormones, in turn, make spleens grow bigger—at least, in rodents. This might explain why the Bajau have such large spleens, and thus, such extraordinary breath-holding skills. “This shows, for the first time, that there may be a genetic background to the spleen response in humans,” says Schagatay, who was not involved in the study.

PDE10A is only part of the story. Ilardo’s team also found signs of adaptation in other genes, which they now plan to study further. One of these, BDKRB2, is the only gene that’s been previously linked to diving in humans. It affects the constriction of blood vessels in the extremities, and so controls how much oxygen reaches the core organs like the brain, heart, and lungs.

Another candidate, FAM178B, influences the levels of carbon dioxide in the blood—which is also an important factor to control when holding one’s breath. The version of FAM178B that’s common in the Bajau seems to have come from the Denisovans, a group of ancient hominids who lived in Asia. It’s clear that when modern humans entered Asia, they had sex with Denisovans and inherited some of their DNA. One Denisovan gene provides modern Tibetans with a crucial adaptation that allows them to survive at high altitudes. It’s possible that another gives the Bajau an advantage underwater. “But we haven’t confirmed that yet,” says Ilardo. “We need to do more analyses.”

Previous posts on the Tibetans and Denisovans.
posted by homunculus at 1:14 PM on October 11, 2018 [2 favorites]

(Optional Musical Accompaniment To This Post.)
posted by homunculus at 1:17 PM on October 11, 2018

Is there a gene for making or falling for tautological arguments?
posted by srboisvert at 2:27 PM on October 11, 2018 [1 favorite]