バジャウ族の人が長時間素潜りできる理由。アシカと韓国の潜水漁師との比較で息を止める潜水すると、脾臓が収縮して、赤血球を血管に押し出す、このために、あらかじめ脾臓を肥大化するという適応が見られる。他にも瞳孔の絞りにも違いがあったり。人間も環境に適応している。

Crémieux @cremieuxrecueil

The man holding this squid is Bajau, a member of an Austronesian ethnic group known to spend their lives living on the water. Bajau have an amazing adaptation: they can stay underwater for a very long time. Thanks to chubby seals and Korean pearl divers, we know why. twitter.com/i/web/status/1… pic.twitter.com/TWHqqnGHCw

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Crémieux @cremieuxrecueil

This is a Weddell Seal. He is also a wittle seal, but that's besides the point. When these things are fully-grown, they can dive for an entire hour and descend more than 500 meters. How do they manage it? It's all in the spleen. pic.twitter.com/bgnQDzE4ux

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Crémieux @cremieuxrecueil

In 1986, Qvist and colleagues speculated that the gigantic spleens of these seals contracted during diving to push out red blood and increase hematrocrit (the red blood cell part of blood), increasing arterial hemoglobin by 60%, giving them the oxygen they need to dive for longer pic.twitter.com/pPRUhCRUzK

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Crémieux @cremieuxrecueil

Hurford et al. thought about this and figured they'd give it a human test. There are a lot of human populations that are renowned for their diving, so why not see what happens to their spleens? They found that Korean pearl diving women's spleens also contracted during dives. pic.twitter.com/rYVae4pmZU

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Crémieux @cremieuxrecueil

But comparisons who didn't do breath-hold diving didn't have any marked splenic contraction! Fast forward: Ilardo et al., wanted to know if spleens explained the Bajau's diving skills. Step one? Figure out who to compare them to. Simple: their land-based neighbors, the Saluan! pic.twitter.com/H4gSXbvHKE

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Crémieux @cremieuxrecueil

The Bajau clearly have much larger spleens. But what if this is just because they spend their days diving? Well, among the Bajau, divers and non-divers have similar spleens. What's more, alleles that differentiate Bajau and Saluan spleens differentiate among the Bajau! pic.twitter.com/CMXShAdSXi

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Crémieux @cremieuxrecueil

The gene even appears to differentiate European spleens! The gene in question is PDE10A, and the large-spleened Bajau have reduced expression of it, which causes their bodies to produce more thyroid hormone. But how can we be sure this is the cause of the Bajau's large spleens? pic.twitter.com/OCjT9CNRpB

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Crémieux @cremieuxrecueil

Ilardo et al. got a bunch of mice and began injecting them with a PDE10A inhibitor called MP-10. The result? The mice that had PDE10A inhibited developed much larger and less dense spleens. pic.twitter.com/4JqowuHB2G

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Crémieux @cremieuxrecueil

The mystery seems solved: the Bajau are able to dive thanks to their incredibly adapted spleens But other sea-faring populations have their own cool adaptations! Here's three: the Bajau live in the green, the Orang Laut live in the orange, and the Moken live in the blue. pic.twitter.com/gEDOJQ2LRj

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Crémieux @cremieuxrecueil

The left eye belongs to a Moken child; the right, to a European one. The Moken have an incredible ability: they're able to constrict their pupils about 20% more than Europeans, letting them see twice as clearly underwater! pic.twitter.com/4nzwiXrM0h

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Crémieux @cremieuxrecueil

There are many other tribes like these globally, and they can reveal incredible things about human physiology through their adaptations to ocean living. We're very lucky to have such wonderful examples of the incredible breadth of human biodiversity. pic.twitter.com/EU0zG1TkOV

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Crémieux @cremieuxrecueil

Sources: journals.physiology.org/doi/abs/10.115… journals.physiology.org/doi/abs/10.115… cell.com/cell/fulltext/… frontiersin.org/articles/10.33… sciencedirect.com/science/articl…

PlumbLevelSquare @LevelSquare

@cremieuxrecueil I have a CRISPR wishlist: -100 plus IQ points -Raptor Vision - olfactory sense at least that of a K-9 - hold my breath for no less than 20 mins -echo location - infrared (heat) detection -my hair😂