Blonde Girl With Long Hair Posing On The Tree

Alternatively, some intuit that tightly coiled hair that grows into a typical Afro-like formation would have greatly reduced the ability of the head and brain to cool. They reason that although hair density in African peoples is much less than their European counterparts, in the intense sun the effective 'woolly hat' produced would have been a disadvantage. However, anthropologists such as Nina Jablonski make the opposite argument with regards to this hair texture. Specifically, Jablonski's assertions suggest that the adjective "woolly" in reference to Afro-hair is a misnomer to the extent that it connotes the high heat insulation derivable from the true wool of sheep. Instead, the relatively sparse density of Afro-hair, combined with its springy coils actually results in an airy, almost sponge-like effect. This, in turn, Jablonski argues, more likely facilitates an increase in the circulation of cool air onto the scalp. Further, Afro-hair does not respond so easily to moisture and sweat as straight hair. Thus it does not stick to the neck and scalp when wet. Rather, unless totally drenched, it tends to retain its basic springy puffiness. In this sense, the trait may enhance comfort levels in intense equatorial climates compared to straight hair (which, on the other hand, tends to naturally fall over the ears and neck to a degree that provides slightly enhanced comfort levels in cold climates relative to tightly coiled hair).
Further, some interpret the ideas of Charles Darwin as suggesting that some traits, such as hair texture, were so arbitrary to human survival that the role natural selection played was trivial. They argue that Darwin's explanation which was that sexual selection may be responsible for such traits. However, the concept of "triviality" is a human value judgment, and hair texture still may have played a role. In fact, while the sexual selection hypothesis cannot be ruled out, the asymmetrical distribution of this trait vouches for environmental influence. Specifically, if hair texture were simply the result of adaptively arbitrary human aesthetic preferences, one would expect that the global distribution of the various hair textures would be fairly random. Instead, the distribution of Afro-hair is strongly skewed toward the equator. Further, it is notable that the most pervasive expression of this hair texture can be found in sub-Saharan Africa; a region of the world that abundant genetic and paleo-anthropological evidence suggests, was the relatively recent (~200,000 year old) point of origin for modern humanity. In fact, although genetic findings (Tishkoff, 2009) suggest that sub-Saharan Africans are the most genetically diverse continental group on Earth, Afro-textured hair (along with a small cluster of other physical features) approaches ubiquity is this region. This points to a strong, long-term selective pressure that, in stark contrast to most other regions of the genomes of sub-Saharan groups, left little room for genetic variation at the determining loci. Such a pattern is, again, not indicative of human sexual aesthetics.