system
Given the following post, respond as if you're commenting on Reddit:
human
Where did skin color variation begin, and how does it fit into the theory of evolution and survival of the fittest?

Watching Malcolm X's movie today, and I realized I'd never thought about which came first. So, what is the widely accepted position on: the original skin color of 'man', the first few color variations, and how these happened or benefitted mankind?
gpt
We can't know what early human skin color looked like, as soft tissue doesn't preserve so well. The primary hypothesis for the reason of different skin colors is UV radiation. UV radiation is both bad and good, too little of it and you can't make vitamin D properly, and too much and it begins to degrade folic acid (also skin cancer, but it probably wasn't common enough to exert a selective pressure). So areas where you have to most UV radiation (i.e. the equator) people tend to be darker as their melanin helps absorb excess UVR and areas with little UVR tend to have light skinned people, to facilitate UV penetration of their skin. 

What color was the first man? We aren't sure, but many bioanthropologists think that the loss of hair had to coevolve with darker skin (as if your skin is covered by hair you can be as light as you want). In as man left Africa, he was probably a medium brown color, and as he moved out, the UVR selection pressure in novel geographic areas would have selected for different skin types based on the conditions.