When we look at primates, one of the first characteristics we identify is the amount of hair, which is very thick and even tangled, and covers the entire body of the animal. However, only humans among extant primates, an order that includes gorillas, lemurs, and monkeys in general, have little hair. The explanation lies in the process of human evolution.
However, a correction must be made. In fact, humans have just as much fur as some species of ape. To be precise, there are at least five million hair follicles scattered throughout the skin, but most of these follicles are shallow and produce very short and soft hairs, unlike other primates.
“Technically, we have hair all over our bodies, but they are miniature follicles,” Tina Lasizzi, a biological anthropologist at the University of Southern California in the US, explains about BBC. “They’ve been so miniaturized that, functionally, they no longer protect us,” he adds.
Now, looking at the human body, it’s easy to see the deepest and thickest of the follicles: in the head. In some ways, this covering is similar to the hair that is so common in most primates. Another facial similarity identified after puberty in men is the beard. In addition, there is thicker underarm hair and pubic hair.
Why does it seem that humans have less hair than monkeys?
Science still doesn’t know why hair is so different in humans, but there are some really interesting hypotheses. Among them, the most accepted is that hair loss is related to the body’s cooling needs, known as the “Savannah hypothesis”.
Here, it should be clarified that during the Pleistocene period, it was Homo erectus And other human species practiced continuous hunting in the savanna. This means that, to capture prey, the animal was chased for hours until it reached the point of extreme exhaustion. Because of the intense activity and the heat, they were at risk of overheating.
As humans lost their hair, the sweat glands took on the job of cooling the body better, through perspiration. “We can imagine, with a bit of confidence, that this happened 1.5 to 2 million years ago,” Lasisi says.
More hypotheses explain fewer hairs in humans
Another hypothesis about the characteristic primate hair loss involves the issue of parasites, known as the ectoparasite hypothesis. Among the proponents of this idea is Mark Bagal, professor of evolutionary biology at the University of Reading, UK.
Before we continue, it is worth considering briefly. Ectoparasites are arthropods that depend on the host’s skin at least at some point in life. This classification includes insects (fleas, flies and even lice) and mites (ticks).
Bagal advocates that “parasites may have been and still are one of the greatest selective forces in our evolutionary history”. “If you look around the world, the ectoparasites [até hoje] Big problem, like flies that bite and transmit diseases. These flies have specialized in landing, living on hair, and laying their eggs.
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