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I dimly remember reading childish texts (a long time ago) that explained that black skin colour evolved to protect humans in hot climates.
However, if humans all came from Africa, presumably, we were originally all black and some [of what became] races eventually evolved lighter coloured skin. Except, I can't think of a survival mechanism that would make that work.
I'm well aware of the potential here for racist nonsense and trolling so references only please to where I might be able to read about this in reliable sources.
Thanks -- Dweller ( talk) Become old fashioned! 17:52, 13 January 2019 (UTC)
Reading a bit more I realise I may have misunderstood something Count Iblis was trying to say, but most of my comments still stand. You can't assume genetic changes in another area could have happened which would have had the same effect and that there are simpler and so should have happened because that's simply not how evolution works. Especially when you haven't even demonstrated that the changes are more likely.
Notably, changes could easily have negative effects especially when there is also selective pressure in the same direction anyway. (E.g. changing the regulation system so that it's less depend on calcitriol could be a negative when there's also selective pressure towards increasing vitamin D production by lightening skin ton anyway.) To be fair, since it's likely you need a lot of changes you would probably expect some co-evolution of both until a reasonable balance is achieved provided either are reasonable changes. But no evidence has been presented this didn't happen anyway. (Note it's even possible that there were changes in regulation but because of the other advantages there were also changes in skin tone and eventually the changes in regulation went the other way.)
The fact that calcitriol is involved in regulation doesn't mean it's an arbitrary regulator. (Again, I don't know if the evidence is out there but Count Iblis has not presented it.) The article calcitriol and calcitriol receptor make me think that it could easily be an important physical component, in other words, you can't have the transcription factor without calcitriol or some alternative. This doesn't mean some other pathway wouldn't have worked, but like with the biosynthesis issue if for whatever reason it did evolve in this way, it's not going to magically change. And there could be so many reasons (likely more than one) why it evolved in this way, it doesn't have to be better than any alternative since again, we're talking about evolution not a super-engineer. It's not impossible that seasonal differences could be a factor, but then again, there's a very good chance this evolved where seasonal differences in sun exposure were minimal to whatever, perhaps single cell organism it first evolved in.
Ultimately of course, it's often not possible to be certain why something complex, especially something that happened a long time ago, evolved precisely the way it did.
A 2007 genetic study suggested some Neanderthals may have had red hair and blond hair, along with a light skin tone.[52]" Nil Einne ( talk) 09:24, 15 January 2019 (UTC)
Science desk | ||
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< January 12 | << Dec | January | Feb >> | January 14 > |
Welcome to the Wikipedia Science Reference Desk Archives |
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The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
I dimly remember reading childish texts (a long time ago) that explained that black skin colour evolved to protect humans in hot climates.
However, if humans all came from Africa, presumably, we were originally all black and some [of what became] races eventually evolved lighter coloured skin. Except, I can't think of a survival mechanism that would make that work.
I'm well aware of the potential here for racist nonsense and trolling so references only please to where I might be able to read about this in reliable sources.
Thanks -- Dweller ( talk) Become old fashioned! 17:52, 13 January 2019 (UTC)
Reading a bit more I realise I may have misunderstood something Count Iblis was trying to say, but most of my comments still stand. You can't assume genetic changes in another area could have happened which would have had the same effect and that there are simpler and so should have happened because that's simply not how evolution works. Especially when you haven't even demonstrated that the changes are more likely.
Notably, changes could easily have negative effects especially when there is also selective pressure in the same direction anyway. (E.g. changing the regulation system so that it's less depend on calcitriol could be a negative when there's also selective pressure towards increasing vitamin D production by lightening skin ton anyway.) To be fair, since it's likely you need a lot of changes you would probably expect some co-evolution of both until a reasonable balance is achieved provided either are reasonable changes. But no evidence has been presented this didn't happen anyway. (Note it's even possible that there were changes in regulation but because of the other advantages there were also changes in skin tone and eventually the changes in regulation went the other way.)
The fact that calcitriol is involved in regulation doesn't mean it's an arbitrary regulator. (Again, I don't know if the evidence is out there but Count Iblis has not presented it.) The article calcitriol and calcitriol receptor make me think that it could easily be an important physical component, in other words, you can't have the transcription factor without calcitriol or some alternative. This doesn't mean some other pathway wouldn't have worked, but like with the biosynthesis issue if for whatever reason it did evolve in this way, it's not going to magically change. And there could be so many reasons (likely more than one) why it evolved in this way, it doesn't have to be better than any alternative since again, we're talking about evolution not a super-engineer. It's not impossible that seasonal differences could be a factor, but then again, there's a very good chance this evolved where seasonal differences in sun exposure were minimal to whatever, perhaps single cell organism it first evolved in.
Ultimately of course, it's often not possible to be certain why something complex, especially something that happened a long time ago, evolved precisely the way it did.
A 2007 genetic study suggested some Neanderthals may have had red hair and blond hair, along with a light skin tone.[52]" Nil Einne ( talk) 09:24, 15 January 2019 (UTC)