How and why black people turn white?

[Riva]

First of all hi everybody, I'm new here.

As the title says, in my project a group of people migrated from a southern continent to a northern, colder one by intervention of a group of gods, so I was wondering how many years it would approximately take for a black population to turn white and why it would happen. From my understanding of genetics it could be caused by a genetic mutation but I don't see what advantages a paler skin would bring for it to be favoured by natural selection and then becoming the dominant skin tone as it seems happened in Europe.

Thanks for the eventual answers.

Sorry for eventual grammatical errors or bad English I'm not a mothertongue.

 

[Ban]

Skin colour is determined by melanin, the primary purpose of which is protection against UV rays. In northern climates, vitamin d is harder to obtain and protection against UV rays less necessary, therefore low levels of melanin are more advantageous in Ice age Europe.

 

[Devor]

As Ban said, lower levels of melanin help your skin to produce higher amounts of vitamin D from the sun, and higher levels block some UV rays to protect against the sun. It's a very weak sun shield.

As an evolutionary question, it's not that simple, nor is it nice. Most likely the human race first separated on skin color through a process of self-segregation and ostracism. In the friendliest version, someone said "Let's go North!" and those with lighter skin said, "Yes! It's too hot here!" and those with darker skin said, "No! It's too cold up there!" I will leave the crueler versions to your imagination.

But that also means answering your question from the perspective of pure scientific evolution... the answer is no, the skin color probably wouldn't change, not in 10,000 years - evolution is just that slow, and you've already separated the gene pool. That is, not unless they mixed with light-skinned natives. Either they would find other ways to adapt or they would migrate out on their own accord.

But there's this storytelling question, of why would you want a black population to change their skin tone? A lot of people, I can guarantee it, will be offended by that, and not without cause. Assuming this is just a worldbuilding quirk you've stumbled into, I would suggest that the story and the setting will be much more interesting if you let them keep their skin tone, and other aspects of their pre- migration culture.

 

[Riva]

Thanks for the responses.

As to why would I want to change their skin tone, it is simply because it seems it would happen sooner or later as it happened in Europe and some part of Asia. Yes, surely for the first thousands or tens of thousands of years it seems, they will keep a dark skin tone, but eventually natural selection would favor a lighter skin tone (because of vitamin D). So I just wanted to know when and why.

 

[FifthView]

the answer is no, the skin color probably wouldn't change, not in 10,000 years

I read a few articles today on the topic. Apparently, most central and southern Europeans had darker skin color until around 8000-8500 years ago. Around that time, a flood of Near East migration into Europe brought genes for lighter skin color; then, about 4500 years ago, another migration, this time from herders on the steppes north of the Black Sea, brought yet another gene for lighter skin color.

The northernmost populations of Europe already had lighter skin color. The natural selection re: vitamin D and protection against the sun played a role in that.

I don't know when those genes developed for these immigrants from the Near East and the steppes, before they migrated into Europe. After arriving, perhaps some of that unpleasant social selection, or even outright war and violent confrontation, led to those genes becoming dominant for central and southern Europeans—over a relatively short time. It does seem possible from this evidence for a shift in skin color to occur more quickly than natural evolution would suggest, if such mutations occurred in areas where the physical consequences weren't as extreme as, e.g., in the far north of Europe.

A recent story about "Cheddar Man," a man who lived in England about 10K years ago, claimed that computer models suggest he was most likely "black" or "dark black." There's been a bit of controversy over that, for all sorts of reasons, some of which aren't based on science. The prediction of skin color from DNA isn't an exact science yet, and I think that result had something like a 75% chance of being the case. However, this result would probably fit in with the results of other studies suggesting that lighter skin for central and southern Europeans is relatively new.

 

[Insolent Lad]

The actual mutation for lighter skin could happen spontaneously anytime. No need to wait millennia for that. How soon it spreads is another question — in a small population, the process would go more quickly. Note too that Asian peoples of cold climates have not gotten lighter as thoroughly (or as quickly) as Europeans. Possibly the relatively cloudy wet climate of Europe played a role in that.

 

[Agam Ridelle]

If it's a fantasy story, you can invent a magical reason for the color to change. Like a pantheon of Gods favoring white people and turning everyone white, or a magical power that drains their color. If it's sc-fi, you can invent a scientific reason, like a virus or a bio-tech intervention, and then you can make them not just white but in all colors and even with splatters of color.

 

[WooHooMan]

Isn't there evidence to suggest people initially developed in east Europe/west Asia and then migrated south?
I'd say go with Agam's response. If the gods are involved, the change could happen overnight.

 

[Queshire]

Isn't there evidence to suggest people initially developed in east Europe/west Asia and then migrated south?
I'd say go with Agam's response. If the gods are involved, the change could happen overnight.

Not that I'm aware of...?

 

[WooHooMan]

Not that I'm aware of...?

It's a recent discovery. I remember hearing about it last year.

 

[TheKillerBs]

It's a recent discovery. I remember hearing about it last year.

Isn't there evidence to suggest people initially developed in east Europe/west Asia and then migrated south?

As far as I'm aware of, let alone good ole Homo sapiens, ALL of Homininae originated in Africa. There have been waves of Hominins migrating out of Africa since about 2 million years ago, with fossils belonging to other members of the genus Homo having been found outside of Africa dating from that period, and it's mostly accepted nowadays that modern humans are the descendants of a mix of early Homo sapiens (a species native to Africa) and other archaic humans which are the descendants of the first wave of Hominins that emigrated from Africa.

 

[DragonOfTheAerie]

It wouldn't necessarily happen at all. Native Americans from northern Canada still haven't become super pale. Then again there is some debate about how long people have lived in the Americas.

 

[WooHooMan]

As far as I'm aware of, let alone good ole Homo sapiens, ALL of Homininae originated in Africa. There have been waves of Hominins migrating out of Africa since about 2 million years ago, with fossils belonging to other members of the genus Homo having been found outside of Africa dating from that period, and it's mostly accepted nowadays that modern humans are the descendants of a mix of early Homo sapiens (a species native to Africa) and other archaic humans which are the descendants of the first wave of Hominins that emigrated from Africa.

I'm not saying it's a sure fire thing, I'm just saying there's evidence.

 

[Agam Ridelle]

Maybe this book will help clear things up:
https://www.amazon.com/Sapiens-Humankind-Yuval-Noah-Harari/dp/0062316095

 

[Queshire]

I'm not saying it's a sure fire thing, I'm just saying there's evidence.

Link to it?

 

[valiant12]

It wouldn't necessarily happen at all. Native Americans from northern Canada still haven't become super pale. Then again there is some debate about how long people have lived in the Americas.

If I remember correctly the reason for that is that their diet is rich in vitamin D and If you eat a lot of food rich in vitamin D having a darker skin is more beneficial.