Comment by reissbaker

I don't know where you read that fair skin is a diet adaptation and not a sunlight one, but that's wrong: fair skin is an adaptation to northern latitudes due to reduced sunlight. The majority of people of African descent in America are vitamin D deficient, but in Ghana — where there is much poorer nutrition, but more sunlight — they're not. Meanwhile, the majority of white Americans are not vitamin D deficient. [1]

Getting sufficient vitamin D takes 6x longer sun exposure for black people than for white people. [2] In northern latitudes that's pretty difficult.

1: https://pmc.ncbi.nlm.nih.gov/articles/PMC7913332/

2: https://news.feinberg.northwestern.edu/2011/09/20/vitamin-d/