If the first humans were black, how did we become white? I get how sun could make a white person black, but not the other way round
It has science in its name so you know it’s legit.
The sun could make a black person blacker.
White people came about because of evolution due to natural selection. In certain latitudes, there is a reproductive advantage to lighter skin. Natural selection causes a shift in the genes of a given population.
You also might ask yourself how early humans got to be black in the first place. At some point, their ancestors were not black.
We migrated north into snowy climates with far less sunlight. The skin color was probably to absorb Vitamin D (or, rather, the rays that help create it) from the more limited solar radiation, with the tradeoff being less protection from sunburn. The long narrow nose is more conducive to warming up frosty air. The hair texture, I believe, is also supposed to be better in cold weather for retaining heat around the head and heck, although I don’t remember how or why. Some diffs may have no pro-survival / better-adapted function, but were simply traits that ended up being expressed in the majority of the population that headed north and were less well-represented in the population that did not.
Chimps and humans are thought to share a common ancestor, if you look at a chimp, underneath all that fur, they are often pretty light-skinned. I’ve read that after the creature we evolved from lost all that hair at some point this created an evolutionary trigger for the development of dark skin pigmentation. UV radiation destroys folate which causes things like neural tube defects. So whatever animal we evolved from probably did not have the darker skin, but the process started before we evolved into modern Homo Sapiens, so the first humans were probably dark but not necessarily as dark African people today, for instance if you look at some, but definitely not all Ethiopians a lot of them have fairly light pigmentation compared to other African groups.
Then when people emerged from Africa and dispersed around the globe, the evolutionary pressures changed with things like much lower amounts of sunlight and lack of Vitamin D in the diet and this allowed further change and you got white skin. Not sure how accurate but other sources have said white people really in a sense may not have existed until as recent as 40,000 years ago, and then you also have the role of sexual selection and some probably found lighter skin or blue eyes more sexually attractive because of its novelty and this also allowed those genes to spread further.
it could also be due to random chance-if only a few people managed to survive some event whatever genes they passed on would become common in the population. As long as it doesn’t have an obvious survival disadvantage any trait can persist.
This scenario is not true in this case. The genes for white skin and some other traits have spread in Europe due to strong selection for them.
Actually Science, along with Nature, is the most prestigious general scientific journal in the world.
Then you probably don’t get how the Sun could make a white person black, either, because the process is exactly the same. It’s not like a Just So Story where the first people in Africa got really dark tans, and so their children were born with tans, and so on. In both cases, it’s because there’s some variation in skin color, and under various conditions, some colors are more advantageous than others, and those people with the more advantageous color tended to have more descendants than others.
Just to be clear, do you understand what evolution by natural selection is and how it works?
Because your question could be rephrased as: How does any population of organisms change over time into something different?
The scientific journal part of it is (and is also one of the most retracted), not that that’s relevant for evaluating the actual scientific content. But the linked article is from the magazine section; it’s just the author’s summary of a presentation she saw at a conference, a paper preprint from bioRxiv, etc. So doubly irrelevant.
The actual research article preprint is at DOI 10.1101/016477 if anyone is curious about it. It has not yet been peer-reviewed. Note that it addresses the likely origins of genes associated with light skin (and milk digestion and height). For information about how the skin genes are associated with vitamin D, see 10.1016/S0140-6736(10)60588-0 .
That could be purely mechanical, a matter of better coverage. Specially the neck part: try getting a proper mane with those tiny curls. It’s possible but it requires a lot more total hair than if it’s straight; for the same amount of protein, straighter hair means more effective length. I just have enough of a wave to be frustrating and it can mean 1 or 2" of difference between dry and wet hair; for someone with completely straight hair there would be no noticeable difference.
White people of European descent all have a particular genetic “defect” in a gene that regulates the production of melanin in the skin. In European light-skinned people the gene exists, but due to a defect, it doesn’'t copy the protein properly and the skin fails to produce melanin. The lack of melanin is what makes the skin lighter. Skin color isn’t controlled by just this one gene, but all light skinned people of European descent have this particular genetic defect.
Studies have shown that this particular genetic defect spread very quickly through Europe, much faster than you’d expect through random chance. Scientists aren’t completely sure why these gene was so strongly selected. The best theory that I’ve heard is the one that Chronos mentioned upthread - that the lighter skin allowed those people to more easily produce vitamin D in lower light levels, making those folks more healthy in those conditions. So in a way, you can blame it on the weather. That’s the theory, anyway.
What is interesting is that northern Asians also developed lighter skin. Lighter skinned Asians have lighter skin due to a combination of genes, but, importantly, they don’t have the same genetic defect that lighter skinned Europeans have. This means that lighter skin didn’t spread to northeast Asia from Europe, but instead developed independently. The fact that lighter skin developed at least twice, independently of each other, also tends to hint at a strong natural selection for the trait, again, likely due to lighter skin enabling vitamin D production in lower light levels.
So basically, we have white people because people moved to where the climate sucks.
Since humans left Africa relatively recently, is it probable that white skin comes from our Neanderthal ancestors?
Just a nit pick, but I believe it’s not just “a gene” but several. Also, they don’t work in the typical DOMINANT/recessive way we learned in Jr High. Hence, someone like Obama has medium-dark skin, instead of “white” or “black”.
One of the many problems with the Vitamin D hypothesis is that studies show skin tone doesn’t seem to matter when it comes to 25-hydroxycholecalciferol production:
yeah, I think it’s the other way around: there is strong selection for people with darker skin in hot, sunny places but there is no disadvantage to having light skin in less sunny places. I suspect it’s a founder effect possibly coupled with many people’s apparent preference for blue-eyed blond partners.
On the other hand, you could also make the case that you need darker skin in the northern climates for warmth.
I read it differently. The OP is postulating the hairlessness in sunny climes caused the skin to darken. What was the mechinism to lighten it back up.
It seems that Neanderthals had pale skin (and red hair) but it was due to a different mutation of the same gene. The pale skin of Europeans was acquired independently (which supports the argument that pale skin was advantageous in the European climate). Some other genes related to skin and hair however do seem to have come from Neanderthals.