[Coda]

Actually, you've totally misread me. I'm not arguing that point. The only thing I'm saying is that the kinky-hair gene originated in Africa. It's definitely NOT atavism.

Yes. It's possible that the kinky-hair gene arose from two separate de novo mutations. It doesn't seem likely, though -- kinky hair is evolutionarily advantageous in equatorial climates and disadvantageous in northern European climates, mostly to do with UV light absorption (kinky hair blocks more).

What seems more likely according to the research I've read is that it's actually STRAIGHT hair that happened twice. Homo erectus had straight hair, and developed the kinky hair mutation in sub-Saharan Africa. When part of that population migrated into Asia, that gene mutated into the thicker straight hair seen in east Asians compared to the thinner straight hair seen in Europeans.

It should be noted that the kinky-hair gene is dominant. That means a population of straight-haired individuals will not have kinky-haired offspring, but a population of kinky-haired individuals can carry either of the straight-hair genes. Given the relative advantages of the two hair types, kinky hair would have been bred out in favor of thin straight hair as humans spread northward, until the gene was reintroduced by hybridization with the other branch of hominids that spread previously into Europe via Asia.