[andrewflnr]

I'd be very interested in hearing about that. My guess would have been that it was more a matter of the previously suppressed genes for dark skin coming back to the fore.

[nivertech]

I agree. Humans reached South (and even North) America only relatively recently in the evolutionary terms - 14-16 thousand years before present. It's not enough time for evolutionary processes to start kicking-in.

Another possible explanation (speculation) is that they met and mixed with yet undiscovered hominid species.

https://en.wikipedia.org/wiki/Settlement_of_the_Americas

[Retric]

The current view is skin color is simple evolutionary response which can easily occur on those timescales. https://www.psu.edu/impact/story/the-evolution-of-skin-color...

Several things have changed as recently as 11,000 years. “Examples for adaptations related to agriculture and animal domestication include East Asian types of ADH1B associated with rice domestication,[71] and lactase persistence.” https://en.wikipedia.org/wiki/Recent_human_evolution

[andrewflnr]

Very neat. I didn't know about the folate angle selecting for dark skin in the first place.