If you look for racism, you'll find it, even when it's not there. Skin color is a function of two things:

1. Amount of environmental sunlight (latitude).

2. Amount of circumstantial exposure to sunlight (lifestyle).

If the assumption is that early humans have lived more outdoors than sitting in caves all day like the modern human does in practice, then yes they'll have darker skin overall.

Is it racist to just state basic facts, or should we brainwash everything to be uniform and average across time and space?