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”?
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
drivedive for longer periods (Bajau People). - “Asian” eye-shape, afaik, is an adaptation to protect the eyes from sand.
The list is actually very long.
Is there much sand in Asia?
The Middle East and the Gobi desert come to mind. Asia is pretty big.
Middle easterners don’t have Asian eyes though.
That trait didn’t appear in the region, so it could not be selected. It appeared in the east Asia, and were selected.
Someone also commented that we don’t have conclusive evidence that some of those characteristics are adaptations to the environment, and could be just genetic drifts. So the shape of the eyes may be just a coincidence and not a real advantage.
It looks good, that’s a pretty big advantage.
Cool! Do you know any sources where I can read more about it?
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
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.
Or, enough protection that you live long enough to reproduce before dying a terrible, agonizing death.
I think it’s protective when you have one copy of the gene, and detrimental when you have two copies. Unfortunately, malaria was a strong enough pressure that the sickle cell gene was selected for, up to a certain percentage of the gene pool.
I thought that there was supposedly something about the altered shape of the cells themselves that offered a degree of protection from malaria? IDK, I don’t live in an area where malaria is endemic, so it’s mostly not a concern, just something we covered in biology and genetics in high school.
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.
Super cool, thanks!
I’ve read that people in Colorado have far more blood carrying capacity from the high altitude. Seems something one can develop.
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.
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?
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.
Less than 5000 years ago, northern europeans developing a genetic mutation that allowed them to digest cow’s milk.
But then how do other non-European groups like Middle Easterners and Asians drink it normally? Did they independently evolve the same mutation?
Fermentation (kefir, yoghurt, cheese). Recently lactase.
