How do black dwarves make sense? Their entire species lives deep underground and never sees the light of day, so they don't need to evolve to protect their skin from UV rays.

It's not like humans randomly became black or white, skin color is a result of thousands of years of evolution because of our surroundings. If you're going to apply the real world here, then you have to admit that black skinned dwarves make no sense from a biological point of view, since as we can see in the real world things tend to get paler and paler the less UV they're exposed to.

I don't know enough about Tolkien elves to comment on there being no black elves though

You really really didn't think this through. While they live deep underground and don't need to protect from UV light, they also don't need to have white skin to let in sunlight for vitamin synthesis.

In the real world, skin didn't get paler simply because there wasn't enough UV. It got paler because less sunlight meant that darker skin couldn't absorb enough light for synthesis. If this wasn't case, our skins would still be dark.

So there is absolutely 1000% no reason at all why their skin would be any specific color. Dark or white, all are justifiable.

> How do black dwarves make sense? Their entire species lives deep underground and never sees the light of day, so they don't need to evolve to protect their skin from UV rays.

This is EXACTLY my issue with the show. This kind of forced diversity fuccs up the lore and detaches me from the depicted universe. At least make them all of the same skin color so it is coherent.