system
Given the following post, respond as if you're commenting on Reddit:
human
ELi5: Did white people evolve from black people (actual question from a seven year old)?
gpt
Yep!

Humans evolved from our ancestors (the ones we share with apes) in Africa, and the first humans almost certainly had darker skin, like that of sub-Saharan Africans today.

Those early humans migrated... eventually all over the world.  And the ones that ended up farther north (like in Europe) evolved paler skin over thousands of years.  It was advantageous for them - there's less sunlight farther from the tropics, and paler skin is more efficient at using UV rays from the sun to produce Vitamin D.  Darker skin is more useful in tropical climates for this purpose - it's not as good at Vitamin D production, but safer from sun damage and skin cancer.

So white people evolved from black people, because the areas that they moved to favored paler skin.  The black people who stayed black were in an area where darker skin was favored, and so they didn't end up changing.  Each group was well-suited to their environment.