No Stupid Questions
No such thing. Ask away!
!nostupidquestions is a community dedicated to being helpful and answering each others' questions on various topics.
The rules for posting and commenting, besides the rules defined here for lemmy.world, are as follows:
Rules (interactive)
Rule 1- All posts must be legitimate questions. All post titles must include a question.
All posts must be legitimate questions, and all post titles must include a question. Questions that are joke or trolling questions, memes, song lyrics as title, etc. are not allowed here. See Rule 6 for all exceptions.
Rule 2- Your question subject cannot be illegal or NSFW material.
Your question subject cannot be illegal or NSFW material. You will be warned first, banned second.
Rule 3- Do not seek mental, medical and professional help here.
Do not seek mental, medical and professional help here. Breaking this rule will not get you or your post removed, but it will put you at risk, and possibly in danger.
Rule 4- No self promotion or upvote-farming of any kind.
That's it.
Rule 5- No baiting or sealioning or promoting an agenda.
Questions which, instead of being of an innocuous nature, are specifically intended (based on reports and in the opinion of our crack moderation team) to bait users into ideological wars on charged political topics will be removed and the authors warned - or banned - depending on severity.
Rule 6- Regarding META posts and joke questions.
Provided it is about the community itself, you may post non-question posts using the [META] tag on your post title.
On fridays, you are allowed to post meme and troll questions, on the condition that it's in text format only, and conforms with our other rules. These posts MUST include the [NSQ Friday] tag in their title.
If you post a serious question on friday and are looking only for legitimate answers, then please include the [Serious] tag on your post. Irrelevant replies will then be removed by moderators.
Rule 7- You can't intentionally annoy, mock, or harass other members.
If you intentionally annoy, mock, harass, or discriminate against any individual member, you will be removed.
Likewise, if you are a member, sympathiser or a resemblant of a movement that is known to largely hate, mock, discriminate against, and/or want to take lives of a group of people, and you were provably vocal about your hate, then you will be banned on sight.
Rule 8- All comments should try to stay relevant to their parent content.
Rule 9- Reposts from other platforms are not allowed.
Let everyone have their own content.
Rule 10- Majority of bots aren't allowed to participate here.
Credits
Our breathtaking icon was bestowed upon us by @Cevilia!
The greatest banner of all time: by @TheOneWithTheHair!
view the rest of the comments
But what's the evolutionary pressure keeping melanin levels among ethnicities that stayed black? And why does it affect people in Central and South Africa but not in North Africa and the Middle East, when both regions are about equally hot?
It's important to think about the time scale that evolution works on. These changes happened very slowly 50,000+ years ago.
The regions near the equator where people still tend to be lighter skinned have been in contact with and interbreeding with lighter skinned people for thousands of years, plus many migrations and invasions.over the past 10,000 years.
I seem to remember that the majority traits south of Sahara (black/very dark skin, and curly hair) can be traced back to something called the "great Bantu expansion", which was essentially the result of a group of people with these traits developing agriculture and wiping out most other peoples south of Sahara, much like the Europeans did to the Americas.
Some cultures south of Sahara did survive, which can be seen both genetically, and in some languages that are completely from other languages in the area (I believe the family of languages with "clicking" sounds is an example).
I'm on my phone now, but I'll have a double check and come back.
Ok, I've done some double checking: The Bantu expansion is approximately what I thought it was. I believe the language group I was thinking about that survived the Bantu expansion was the Khoisan.
My (very coarse) knowledge of this comes from a mixture of reading Jared Diamond (Guns, Germs and Steel) and from following it up with some Wikipedia. In short: The genetic makeup in a lot of the world is relatively dominated by the groups that were the first to adopt agriculture in their respective regions. Before the Bantu expansion, phenotypes south of Sahara were more varied, just like the phenotypes in the Americas were more varied before the corresponding "European expansion", or the equivalent expansion that happened in South-East Asia (I don't remember which society stood behind that one).
According to Diamond, we can trace a lot of (most?) surviving human phenotypes and languages back to relatively few societies, which after adopting agriculture, more or less wiped out / displaced neighbouring cultures due to increased resistance to a lot of infectious diseases and massively increased food production / need for land. This mostly happened less than 10 000 years ago, i.e. far too recently for natural selection to have a major impact on things like skin colour, hair type, height, facial features, etc. afterwards.
So: While major trends in phenotypes are of course a result of natural selection / evolutionary pressure in specific regions (resistance to skin cancer / sunburn vs. vitamin D production, or cooling down more efficiently with a wider nose vs. retaining heat with a slimmer one, or having an eye-shape that lets in more light vs. provides more shade), a lot of what we see today is simply a result of what phenotype the first group a given region that adopted agriculture had. This means that looking at the dominant phenotype in a region today will not necessarily give a good impression of what phenotype that is "optimally designed" to survive in the conditions of that region.
Most likely a conbination of the amount of sun exposure and other poaitive genetic mutations that happened alongside melanin levels.
An example of the complexity of genetic changes being intertwined is resistance to malaria and sickle cell anemia. The benefits of resistance to sickle cell anemia outweigh the negstives of the increased chance of sickle cell anemia so the mutation has persisted.
It is likely that North African populations had something that was beneficial as a tradeoff for their comparably lighter skin. Wearing clothing that covers a lot more of their body and having shelters from the sun could also help to mitigate some of the sun damage.
So it is complicated and most differences are due to a combination of genetic traits, they don't get passed down one trait at a time.