Facts need to be substantiated by objective reasoning: numbers and hard evidence. No one yet has any clue as to what genes work to produce hair form and yet we here such facts, probably from the view point of some American or Western person who's most familiar dark skinned group are people with mostly recent West AFrican ancestry. And admixture with whom, themselves? As i've said we barely have an itch on the genes in the field (we may be getting closer) and i have friends who have no recent relatives with less curly or coily hair, all black skinned black people and the oldest son has almost curly hair, while the daughters don't. Also, the straight hair i see in the tropics is like that of most mammals that live in the heat, sort of rough looking, and not smooth and oily like that of Northern Eurasians, or like Penguin feathers or whatever it is on walrusses. The fact is that there are Mountains up and down East Africa (where we originate), in Northern Africa, and in West Africa, whose populations are usually less heavily pigmented than other groups (Ethiopia is familiar) possibly because of the angle of the UV rays (like elsewhere). It's unscientific to speak definitively on an issue all based on subjective posterings, ie, admixture. Further, the article isn't about admixture but what selective factors may be at play here. Unless you're aim is to tell people whose ancestors may have had nappy hair that they formerly had such, which would not be very possible at the moment let alone smooth. Again, who says the whole range has to originate from admixture instead of slow evolution of diversity (which decreases on its way to Eurasia, so you'd have to hypothesize on they instantly loose diversity in comparison with others, including Native American groups who weren't even there long enough to become depigmented.