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submitted 1 week ago by linucs@lemmy.ml to c/askscience@lemmy.world

I'm referring to the human race evolving in the African continent and then migrating to the rest of the world.

Evolving in Europe made people light skinned to account for the reduction in sunlight exposure, are there any other traits which other ethnicities developed to adapt to their new environment? Or are the diifferent traits in different ethnicities just stuff that developed by chance and got somehow reinforced because of the isolation between populations?

This question came to my mind first thinking about "Asian eyes", do they serve any "purpose"?

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[-] TauZero@mander.xyz 2 points 3 days ago

It is important to remember that, unless accompanied by convincing evidence for selective advantage, any single inheritable trait is more likely to have arisen from genetic drift, not from natural selection! There is, in my opinion, too much focus on conversation about superficial phenotypic traits like "shape of the nose" this and "angle of the eye" that, all the arguments about how one is better than another. Could the asiatic epicanthic fold give advantage against icy winds? Maaaybe... But it doesn't even have to. What about the asiatic dry earwax gene? You'd struggle to even come up with a story of how dry earwax or wet earwax is actually better under certain conditions, or you could just say "it's a single nucleotide polymorphism that could have spread by genetic drift" and be done.

Very few human traits have definitely been naturally selected for: light skin in non-sunny climates for better vitamin D production, sickle cell gene for malaria resistance, lactase persistence for animal milk consumption. Even there, the estimated selective advantage is actually much smaller than you'd expect: lactose tolerance confers only something like 1% advantage! There are many more possible neutral mutations than advantageous ones, and each one has a chance to be fixed in the entire population by genetic drift, meaning that any widespread human trait that is less clearly advantageous than lactose tolerance is more likely to be neutral than advantageous at all.

Even mildly disadvantageous mutations can be fixed by genetic drift, especially in humans since we have had many bottlenecks and founder effects. There was an area in Appalachia populated by blue-skinned people due to founder effect. No one is going to try to argue how having blue skin was actually advantageous for them to blend into their environment! There is an area in Dominican Republic with a very high rate of children born intersex, again due to a founder effect mutation. They are not considered exceptional and live normal lives as their culture has adapted to treat them as routine, as a kind of third gender. But they are not some kind of new level of human evolution, an adaptation for an intersectional era!

The only mutations that definitely cannot spread by genetic drift are those that definitely kill you.

[-] linucs@lemmy.ml 2 points 2 days ago

Very nice explanation, thanks!

[-] arthur@lemmy.zip 35 points 1 week ago* (last edited 1 week ago)

Yeah, depending on what you consider "new".

  • Nose shapes to account for dryer air on Africa and middle east.
  • Nose shapes to account for colder weather.
  • There are a group of people that have larger spleens to make them able to ~~drive~~ dive for longer periods (Bajau People).
  • "Asian" eye-shape, afaik, is an adaptation to protect the eyes from sand.

The list is actually very long.

[-] _haha_oh_wow_@sh.itjust.works 25 points 1 week ago

There's also sickle cell anemia: IIRC it protects against something like the tse-tse fly or mosquito borne illnesses native to parts of the African continent

[-] HelixDab2@lemm.ee 17 points 1 week ago

I believe that it offers a degree of protection against malaria. Or, enough protection that you live long enough to reproduce before dying a terrible, agonizing death.

[-] _haha_oh_wow_@sh.itjust.works 8 points 1 week ago

Yeah, I think you're right (on both counts unfortunately, but that's evolution for you).

[-] linucs@lemmy.ml 3 points 1 week ago

Cool! Do you know any sources where I can read more about it?

[-] ShittyBeatlesFCPres@lemmy.world 27 points 1 week ago* (last edited 1 week ago)

One more is that some people in the Himalayas (Nepalese, Tibetans, etc.) have some pretty recent adaptations for living at extremely high altitudes where there’s less oxygen. This Wikipedia article has more examples of recent adaptations: https://en.m.wikipedia.org/wiki/Recent_human_evolution

Another interesting factoid is that Africa has more genetic diversity than the rest of the world. So, don’t sleep on the fact that that Homo sapiens spent more time radiating throughout Africa than radiating out of Africa.

[-] shalafi@lemmy.world 4 points 1 week ago

I've read that people in Colorado have far more blood carrying capacity from the high altitude. Seems something one can develop.

[-] linucs@lemmy.ml 2 points 1 week ago

Super cool, thanks!

[-] dizzy@lemmy.ml 18 points 1 week ago

Less than 5000 years ago, northern europeans developing a genetic mutation that allowed them to digest cow’s milk.

[-] NoneOfUrBusiness@fedia.io 3 points 1 week ago

But then how do other non-European groups like Middle Easterners and Asians drink it normally? Did they independently evolve the same mutation?

[-] MalReynolds@slrpnk.net 9 points 1 week ago

Fermentation (kefir, yoghurt, cheese). Recently lactase.

[-] dizzy@lemmy.ml 6 points 1 week ago

I’m no expert but I think it’s a mutation that still isn’t universal i.e. there is still a very large lactose-intolerant population in east-asia, which is also reflected in their cuisine.

[-] shalafi@lemmy.world 8 points 1 week ago

Read what turned out to be a fairly racist article back in the day, about the differences in blacks and whites.

One thing that rang true was hair types. When wet, kinky hair sheds heat more easily and flat hair is insulating. Anyone know if this is true?

[-] Guest_User@lemmy.world 6 points 1 week ago

I learned in a university course that kinky hair holds sweat better and allows for better cooling. Where straight, greasy hair drips it off faster.

Another interesting environmental trait is sickle cell because it can prevent or at least lessen malaria.

[-] Skyrmir@lemmy.world 6 points 1 week ago

I don't think epicanthic folds would be considered evolution. Most human changes are in our immune system and sense of smell.

[-] linucs@lemmy.ml 6 points 1 week ago

Interesting, can you recommend some reads about it?

this post was submitted on 24 Jun 2024
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