human beings are “freaks” among mammals. Except for hippos and naked mole rats, almost all other mammals have fur on their bodies. Except for head hair, humans are almost naked and hairless. Why? Are most parts of humans hairless except for the head?
First, it’s crucial to understand why mammals have fur, which keeps animals warm during cold nights and protects them from sun burn during the day, says Mark Pegle, an evolutionary biologist at the University of Reading, UK. They lose most of their hair because they have a unique ability to make fires, sleep warm and get dressed.
This would explain why our human ancestors survived without hair, but not why hair faded over time. In fact, being hairless gave humans some kind of evolutionary advantage. There are 3 main theories, according to Pegel. This human evolutionary advantage can be explained.
First, thick fur may have overheated hominins in the midday heat, says Pegle: “If you’re wearing a thick fur coat in the African savannah during the hot season, you’re sure It’s going to be hot, wouldn’t it be nice to take this coat off? Humans have gradually achieved this over a long evolutionary process.” In addition, modern humans have evolved to have more sweat glands than their primate relatives, if we Having long body hair all the time is likely to be soaked in sweat, which makes it difficult for the sweat to evaporate and the body to cool down.
However, the so-called “body cooling hypothesis” does not fully explain human hair growth distribution patterns, for example: why men have more body hair than women, it is worth noting that in addition to hands, feet, lips and nipples, the human body also covers With fine colorless hairs. Hormones produced during puberty turn these fine, colorless hairs into longer, colored terminal hairs. But sometimes the head is the most densely hairy area of the body, aside from unkempt body hair.
Secondly, the second explanation theory is called the “Aquatic Ape Hypothesis Theory”, which believes that ancient humans lived in water for a long time. Most of the body hair is gradually lost, leaving only the head as the densest hair area. However, so far there is no conclusive evidence that humans have lived in water for a long time in the evolutionary process, so Pegel believes that the hypothesis is not very credible and cannot explain why humans lose a lot of fur tissue after leaving the water environment.
In 2003, Pegel published a research report and proposed a third theory, the ectoparasite hypothesis. Ectoparasites refer to parasites that live outside the host’s body. These parasites include lice, fleas, etc., which are the cause of cross-species disease. leading cause of illness and death. Ectoparasites may be less attracted to hairless skin tissue and are more easily removed with less hair tissue coverage, conversely, the less body hair tissue, the lower the number of ectoparasites, which may be the case in humans Dominant selection for evolutionary survival.
If hair suffers, why do we still grow hair?
As bipeds, we walk upright and our heads are directly exposed to sunlight. The African region near the equator is the birthplace of human evolution. The sunlight is very strong here. Having thick hair can help humans avoid body heat, Peg “Hair is like a built-in cool hat in Africa,”
says Pegle. “Hair also helps the body retain heat at night, and our brains are relatively small compared to the rest of the body, but the brain’s The metabolism is very active, and this activity generates heat, and the hair isolates this part of the concentrated heat.”
Sexual selection can also play a role, as people can style their hair differently to show their unique charm. This may have been the case with ancient humans, too, where hair served as a unique way of showing off to the opposite sex, and hair is often not directly fossilized and therefore cannot be preserved intact. Archaeologists have no direct evidence of ancient human hair, except for mummies in places like Egypt and Peru that preserve corpse hair intact. Observational analysis of modern Aboriginal people isolated from the outside world revealed that they also had their own unique hairstyles, suggesting that their ancestors did too. Pegel points out that this particular hair treatment may help attract partners of the opposite sex, and we don’t just grow our hair, but also in some form of hairstyle to attract the opposite sex.
