Eskimo Evolution

There’s another report out on selection in the Greenland Inuit. They found clear signs of positive selection in FADS, the fatty acid desaturase gene cluster. More interesting was the discovery of strong selection on a region containing WARS2 and TBX15, located on chromosome 1. WARS2 encodes the mitochondrial tryptophanyl-tRNA synthetase, and TBX15 is a transcription factor from the T-box family that does all kinds of things – some of which (like skeletal development) can be inferred from the symptoms of people with Cousin syndrome, caused by beat-up versions of TBX15.
Probably the selected haplotype results in more brown fat, along with changes in waist-hip ratio and fat distribution. This haplotype is oddly differently from the standard human one, mostly because we picked it up from a population similar to Denisovans. It’s moderately common in Eurasia, very rare in Africa (prolly back-migration) and fixed in the inuit. It’s had hundreds of thousands of years to diverge from the standard AMH haplotype, possibly longer.

These adaptive changes picked up from archaic humans can be different (more complicated) from mutations like sickle-cell, because they can (sometimes)consist of several different linked adaptive substitutions that accumulated over a long, long time. Sickle-cell is recent, and just one nucleotide has changed. More than that, in at least some cases, such as EPAS1 (a Denisovan-origin altitude adaptation allele in Tibetans) the adaptation has progressed: it’s something a bit more sophisticated,not the first solution that came down the pike. The Tibetan adaptation is similar to that seen in mammals that have lived at high altitude for millions of years – while the altiplano adaptation is more like an exaggerated version of individual acclimatization.

Archaic humans had lived in and around the Tibetan plateau for a long time, perhaps as much as two million years. They were the go-to guys for classy altitude adaptations. In much the same way, archaic humans had lived in Eurasia during the Ice Age, freezing their nuts off, for up to two million years. They probably weren’t as good at making warm clothing as anatomically modern humans (Sharp Dressed Man), since they did not make needles. They should have had relatively sophisticated metabolic changes that adapted them to living in an icebox, adaptations worth stealing. There may be other cases like WARS2/TBX15 in the Inuit – and there may be other evolutionarily significant environmental factors (like changes in length of day) that existed in Eurasia and were largely absent from Africa.

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22 Responses to Eskimo Evolution

  1. ursiform says:

    I would think it would be “Warm Dressed Man” who had the survival advantage in the arctic. “Sharp Dressed Man” sounds more like a sexual selection thing. More peacock tail than blubber.

    • Johanus de Morgateroyde says:

      More than anything, Mother Nature selects for things that get you laid.

    • Patrick Boyle says:

      I don’t know about the blubber thingee. I had a close friend in college who was as Eskimo. We went swimming one day and it struck me that George had no subcutaneous fat whatsoever. He looked like an anatomy diagram or a body builder who had burned off all his under skin fat with a pre-competition crash diet. It struck me at the time as exactly the wrong physique for the north. George was a well known Eskimo – I met friends of his all across America – but maybe he was some sort of anomaly.

      • CA Spears says:

        Have you ever thought that George ate a Western diet and so not high enough in fat to make him look like a typical eskimo, but if he ate what his ancestors ate he would have more body fat?

      • TWS says:

        All my Eskimo cousins are layered. Even when they are in shape they are still ‘layered’ a bit. I imagine they’d have to eat nothing but meat to lose that and even then maybe not.

  2. Would be interesting to find something which accounts for Inuit low ability, which otherwise goes against a simple “cold winter prunes out the foolish” hypothesis.

  3. j says:

    There is no need “to steal” genes. The Inuit are genetically close to the Mongols, who generously donated all over Asia.

  4. AppSocRes says:

    I’m throwing out a wild idea here, and I’m fully aware of just how wild it is, but it’s not totally off-topic, and I’m just curious if anyone out there thinks it’s the least bit plausible. . So don’t be too vicious if you think it’s silly.

    Although Carleton Coon’s theory of divergence of the major human racial lineages from separate branches of Home erectus has landed in the dustbin of human evolutionary theory, he made an observation whose validity I’ve never been fully able to ascertain. A medical examiner once told me that a decent predictor of racial descent from facial bones is based on the following rule of thumb: prominent jaw = African; prominent cheek ridges = Asian; prominent nasal opening = European. Coon claimed that the same rule applied to Homo erectus skulls found in these different regions to the point that a trained physical anthropologist could predict general skull provenance from the configuration of the facial bones. Coon argued that this was either a truly extraordinary case of parallel evolution or evidence in support of his theory. Now I am wondering if facial configuration provides such a selective advantage in these different regions that the genes determining it might have passed from Homo erectus through archaic humans into modern populations.

  5. Bob says:

    I thought this was going to be a post on the Ashkenazim….

  6. Greying Wanderer says:

    fascinating stuff

  7. IC says:

    Follow the rule of survival the fittest, adaptive change to challenging enviroment can be both behavioral and genetic. Cerainly most primitive creatures from virus to plants adapt with genetic change (evolution). Animals start with behavioral adaptation. Obviously human is at peak of such ability to adapt with behavioral change through analysis, learning, tool making, clothes, ect. The very g factor change might be only significant genetic adaptation of human to enhance behavioral ability. This gets philosophical.

    Maybe only worthwhile genetic adaptation is mental ability which seems outperforming all other biological genetic adaptation. But most primitive creatures like bacteria only with genetic adaptation seems beating all others so far. Advantage of behavior adatptions is fast and diverse. Advantage of biological adaptation is long lasting. But virus and bacteria can have genetic evolution as fast as human ability to learn. Certainly ability to learn itself is genetic at end.

    Which pathway will be the final winner?

    • melendwyr says:

      Humans can’t survive space travel, while lithovoric bacteria could probably survive being blasted offplanet by asteroid impacts and freezing solid. I think it’s quite plausible that they’ve already ‘won’, and life didn’t originate here. We’d need to find a tectonically-active planet with liquid water to confirm, though.

  8. Rios Steven says:

    “Archaic humans had lived in and around the Tibetan plateau for a long time, perhaps as much as two million years.” Interesting things. I’d like to find more.

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