system
Given the following post, respond as if you're commenting on Reddit:
human
Why is it that Europeans have many colours of hair, when everywhere else, (Africa, Australia, Americas, Asia) have only black?

Clearly I am talking the genetic ancestry of these places. I realize there can be a blonde in any of these places and that genetic mixing is far more common now. However, in evolution terms, these non-European places span huge ranges of latitude, climates, and environmental conditions.
gpt
Here's a simplified version.

There was one mutation thousands of years ago, among the ancestors of present-day Europeans, that caused lighter colored hair. As the years went by, sub-mutations of this one ancient mutation diversified that into several different shades. All these sub mutations are dependent on the first one having occurred.

Ultimately, it all goes back to having lighter pigmentation. All these mutations are dependent on the one that codes for less pigment.

I hope that was understandable and accurate. Feel free to correct me.