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Body hair helps with thermoregulation.
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The scalp protects the scalp from the beating sun, but it also traps heat if it is in a cold climate.
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Eyelashes are like screen doors for the eyes, which keep insects and dust and small debris particles as long as they are open.
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Eyebrows prevent sweat from reaching your eyes.
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Armpit hair, technically called “axillary” hair, collects and disseminates pheromones while acting as the WD-40 of body hair, reducing friction between the skin on the lower arm and the skin on the side of the arm. chest as we walk and swing our arms.
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Pubic hair also helps reduce friction, as well as providing a protective layer against bacteria and other pathogens.
But facial hair? You will notice that it does not appear in this useful list of adaptive hair traits.
In the early days of studying this kind of thing, evolutionary biologists thought they could be used for thermoregulatory or prophylactic purposes similar to body hair and pubic hair. After all, beards and mustaches are found around the mouth and the mouth picks up food and other particles that can lead to disease. There are also beards and mustaches on the face, connected to the head, which loses a lot of heat from the top if it is not covered with hair. Everything makes sense when you look at it that way.
Unless there is a problem with this theory: it leaves out 50 percent of the population, that is, females. Natural selection is ruthless and has sent MANY species into the dodo’s path — for example, the dodo — but rarely, if ever, selects a trait in such a species and leaves half the population hanging, especially half. which makes all babies (i.e. the most important half). If facial hair were intended to perform important functions, it would be present in both sexes. In contrast, thick, mature hair is present almost exclusively in the male half of the species, and its only job is to sit there on the wearer’s face as a signal to everyone who crosses its path.
What a signal it makes send facial hair? Well, this is where it gets a little complicated as the ornamental features go. University of New Mexico professor Geoffrey Miller, one of the most important evolutionary psychologists in the field, put it this way: “The two main explanations for male facial hair are intersex attraction (attracting women) and intrasexual competition. (intimidating rival men) “. Basically, facial skins indicate one thing to potential partners (i.e., virility and sexual maturity, hubba-hubba-type things) and another thing to potential rivals (formidableness and wisdom or piety). Taken together, these signs confer their own mark of high status on men with the most majestic mustaches or with the largest beards and taunts.
The signal sent by facial hair also tends to be stronger and more reliable among males, who are more common rivals, than between males and females, who are usually mates. In fact, evolutionary biologists will tell you (if you ask them) that while some females like facial hair a lot, others don’t, and some don’t care less, the attraction is most often that they have so much to do with beard density like anything else. That is, if you are in a place where there are many beards (for example, a lumberjack convention), the clean shaved face is more attractive, but if you are surrounded by naked faces, it is better to shave.
In evolutionary genetics, this is called “negative frequency dependence” (NFD), which is referred to as science because the idea that when a trait is rare within a population, it tends to have an advantage. In guppies, for example, males with a unique combination of colored spots mate more often and are less preyed upon. This is a huge competitive advantage. It’s like going to Las Vegas hoping to lose $ 1,000, but hoping to balance it out, only to end up earning $ 1,000. This is a $ 2,000 swing. It is the same for a shot with NFD selection. The shot goes from fighting for his life to being the life of the party. The downside is that the competitive advantage can cause an overpopulation of others with the same trait very quickly, due to everything that makes the guppy look very interesting, which means it loses its rarity and becomes common. . Don’t worry, nature has a solution to this: as more guppies have this same trait, it leads to a decrease in the interest of mates and an increase in the attention of predators. What was once the new and interesting guppy becomes old news, in other words.