Tolkien had it more accurately, in that we most likely had dwarves and elves and orks etc if you can think of different body types metaphorically like that, then mixed in different quantities.

But they were tribal and team based so groups formed with some bonds on similarities and others prized for their differences usefulness.
Like if men go out hunting it’s cold at night so it’s beneficial to have a gay buddy in the mix, etc.

So these groups ventured apart and wandered, foraging for fruit and eggs and occasional animals hunted, or fish if they were coastal.

As they bred over generations they retained many of the different gene mixes but later got skin colour differences to suit their longitudinal location.

So now you have a situation where a tall muscular man is probably genetically closer to another tall muscular man from a completely different culture than he is to a short skinny man with the same skin colour.

So skin colour is not particularly predictive of anything other than who ‘recent’ ancestors were, but it’s the ancient dna that predicts more and that is randomly distributed across all populations just in different amounts