Tolkien's Universe works under the laws of creation, not evolution.
Dwarves and Elves were created. They didn't evolve.
Conclusion: scientific logic doesn't apply to this particular fantasy.
Besides, Tolkien's lore allows for black Elves and Dwarves to exist, even though they are not directly named in the books.
Só yeah, it seems your argument has no substance. Too bad.
I ain't defending it, but dark elves in DnD aka. Drows, also live underground and their skin is fucking black.
In wow Dark iron dwarves are also black and they also live underground
You can make a finctional race the color you want, if you want 'em to be black they can be black, if green then green and so on.
But don't call it LOTR, when the original creator - Tolkien - never ever made any kind of hint to that.
Dark-skinned Dwarfs and Elves (even sub-terran ones) have roots in mythology and folklore of many countries and are present in modern fantasy (think Duergar/Drow in D&D). Unless the lore of Tolkien works categorically prevents these skincolors from existing, I am fine with it. I am more disappointed that they can't bring themselves to give dwarf women beards.
In Dungeons & Dragons there are dark elves and dark dwarfs who have completly black skin yet they all live miles underground with no sun in sight so what is your point exactly? Rings Of Power is a dogshit show but it's mostly because of crap writting. Casting dark skinned actors is the least of this shows problems. I actually found the black dwarf lady to be one of very few likable characters in the entire show so far that had some actual charisma and overall good vibe alongside with Durin. On the other hand the black elf guy is just dreadfully bad
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