Seriously, lovelies: if you want to make a brown or dark skinned elf, gnome, hobbit, dwarf, human, whatever character in a fantasy setting, you do NOT have to justify them not being white with scientific theories or anthropological reasoning.
Diversity does not have to be justified. It can just BE.
As a GM who likes good worldbuilding, I would appreciate it if your dark-skinned character at least had ancestors from the tropics. Black-skinned underground-dwelling elves still stick in my craw–though at least the Realms Timeline conceded that Illythiri (drow ancestors) were from the sub-tropical forests.
I am pretty sure you can accept fire breathing dragons that can shapeshift, walking skeleton warriors with the strength to cleave a man in half, and items of ethereal power that allow time travel without much justification beyond “it’s magic.”
So you should be able to just accept dark skinned characters without some “From the tropics or they have to be drow” bullshit.
You can worldbuild the anthropological and cultural facets of your world and its people, if you want to but you do not HAVE to.
I’ll say it again:
Non-white fantasy characters do not HAVE to be justified.
Notice how everyone who wants black or dark-skinned characters to be justified never asks the same of white characters. White is not a goddamn default, and black people don’t need a reason to be black like goddamn. If elves, dwarves, gnomes, etc etc can be white without question then why the hell do they need a special reason to be black?
building worlds, even if it is high fantasy, needs consistency to be acceptable, skin color is one of these consistencies, it is the location that the master decides DMing is cold in the far north, or south, in places with similar climate england, then yes is the default light skin, if in temperate climates so the default is dark-skinned, I demand justification in any of the situations.
Do not try to transform this into racism, if you do not care does not mean that others should not care for an explanation. growv up
And just who the fuck are you, you no-talent ass clown?