Curly hair protects against sunstroke


Hair is straight, wavy, curly and very curly – curly. We talked about why hair curls: because it grows unevenly from the hair bag, because the hair cells are unevenly stretched from different sides, because keratin in the cells is synthesized and packaged differently. Some people like straight hair, others curly. But is there any biological meaning to curly hair?

Pennsylvania State University staff write to PNASthat there is meaning in curly hair, or at least there once was. The researchers set up an experiment with a thermal dummy, which can be maintained at a constant temperature by cooling it or heating it. Typically, such mannequins are used when assessing the properties of clothing, the ability to protect it from the cold. But now the mannequins were put on wigs with hair of varying degrees of curlyness and put in a wind tunnel in which it was possible to control the wind speed and air humidity. Special lamps imitating the sun were sent to the head of the mannequin, and the mannequin itself was programmed so that the temperature of its “skin” remained at 35 ° C.

Depending on how hot the mannequin’s head was, it expended a different amount of energy to cool down. The least amount of cooling energy was spent with a curly wig. The conditions were changed by adding wind and wetting the mannequin’s head with water, as if he were sweating. Based on the results obtained, a model was built according to which it turned out that very curly hair protects the head especially well from overheating in the climate of equatorial Africa.

Africa did not arise here by chance: it first appeared there A wise man, and there it evolved for some time, until at some point it went to Eurasia. As we well know, in the course of evolution, our anthropoid ancestors got on their feet and enlarged their brains (more precisely, natural selection favored those with larger brains and who could walk on their hind limbs). According to the authors of the work, when walking upright, the head heats up more, the brain needs to be cooled more vigorously so that sunstroke does not happen, and if the brain also gets bigger, it becomes even more difficult to cool it. Of course, there are sweat glands, but they, apparently, were not enough; in addition, with sweat, some amount of water and salts are still lost. In general, individuals with curly hair gained an evolutionary advantage because their head and brain were better protected from overheating.

Then some people settled in cooler places, and curly hair became less obligatory for them. Some remained in Africa, and now many African peoples are characterized by exceptional and almost universal curly hair. But in general, people everywhere have learned to protect themselves from overheating, and probably even Africans could now do without very curly hair on their heads. Maybe in the long term naturally curly hair will disappear altogether. However, we should not forget about sexual selection: as long as someone likes curly men and women, curly hair has a chance to stay with people longer.


Source: Автономная некоммерческая организация "Редакция журнала «Наука и жизнь»" by www.nkj.ru.

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