>>13943954As Africans lost melanin in their scalp to produce denser hair follicles, it became even more important to protect them, leading to denser, thicker, more coily hair to scatter light in a feedback mechanism.
>>13943894Eventually hair thickness stopped being about protection and more about sexual selection. People with denser, longer hair were healthier, more nourished, over time the association between hair and health turned into a genetic thing, where people intentionally chose mates with longer, denser hair. Non-Africans weren't exposed to such ultraviolet intensive environments so they lost the coils but still kept the sexually selected hair length/thickness because it's a good way to judge how healthy you are.
