The hair removal business is enormous: millions upon millions are plucking, threading, waxing, melting, and burning any and all hairs on their bodies that aren’t either on top of their heads or within their noses. But why? Does it help them stay cool in the summer? Does it make them more attractive? Is it a good thing to do? But there is another question that needs to be answered before any of these can be, and that’s: why do humans have body hair?
Why Do We Have Body Hair?
There are two main theories as to why humans are not still covered in hair like their monkey cousins. One is focused on what one could call ‘cranny hair’—the hair humans have in their armpits and pubic regions. The other theory is focused on limb hair. As it turns out, the functions of the two types of hair, cranny and limb, are related to their locations on the body. If different locations, a biologist might say, then different functions; if different functions, different theories.
Pubic Hair and Armpit Hair
The first theory, a consideration of the function of armpit hair and public hair, has to do with the mechanisms of sexual attraction. The crucial piece of evidence for this theory, the observation that first led scientists to believe that the purpose of armpit hair and pubic hair might be related to sexual attraction, is the fact that hair follicles are almost always adjacent to glands that produce pheromones, bundles of molecules produced by the body as chemical signals to potential sexual mates.
The theory, famously put forward by zoologist Desmond Morris in The Naked Ape, is that the tangles of hair in the armpit and pubic regions serve as a natural net to catch and hold the body’s pheromones. These chemical signals are in essence nature’s silent flirting, and the hair in the pubic and armpit regions is like a megaphone shouting their message.
Leg Hair and Arm Hair
The second theory is also surmised from a current understanding of the evolution of humans. Key to this theory is the observation that leg and arm hair—also known as androgenic hair after the hormone (androgen) responsible for spurring hair growth—is nearly exclusive to males. Obviously females have body hair as well, but not nearly as much. The question, then, is: what do males do that females don’t, and how could androgenic hair help them to do it?
The trick to that question is the verb tense; it’s not what human males do now that’s important, but what they were doing when they adapted to keep some of the hair that evolution has, for the most part, removed from the species. During the bulk of the millions of years between the current day and the time the human species branched from the evolutionary tree, humans lived in primitive societies in which the men ventured out to hunt together while the women either gathered food from the land or remained at home to nurture the young. This meant that the males’ days were active, full of tracking, pursuing, and killing--in other words, full of high body temperatures - while the females’ were comparatively passive.
So what does this body hair have to do with this difference in daily activity? Thermoregulation. The human body cannot tolerate great heat or great cold, and hair is a very effective thermal conductor; in hot conditions it lays flat on the skin, increasing airflow at the skin and helping heat escape the body, and if the body is cold, it stands on end - think goosebumps - to trap bodyheated air close by. Ancient human males, hunting most of the day, could benefit greatly from that sort of regulation but females, with relatively steady body temperatures, would not benefit near so much. And so, sensibly, the females got rid of all that nasty arm and leg hair.
Eyebrow Hair and Eyelashes
A quick note on eyebrows and eyelashes. For humans, eyes are of the utmost significance, for social purposes as well as basic survival. Eyebrows draw attention to the eyes, can be quite expressive in and of themselves, and help maintain vision by channeling sweat and rain away from the eye. Eyelashes, similarly, help to highlight the eye (hence eyeliner) and also filter out particles in the air that might irritate the eye.
Hair Removal
So back to the original question: is hair removal smart? Plucking or otherwise thinning eyebrows is probably harmless so long as the brows can still help keep water out of the eyes. With regard to the thermoregulatory functions of arm and leg hair, most people can probably trim all the androgenic hair they care to without fear of negative consequences, because most people don’t live in environments that really tax the body’s heat regulation system. However, with regard to sexual attractiveness, removing armpit hair and pubic hair might be counterproductive; it means losing a powerful tool for attracting a mate, and no fancy perfume or cologne is going to match the body’s natural scents, perfected over millions of years.
Sources
The Naked Ape. 1967. Desmond Morris.
“Why do we have body hair?” Science World, September 2000. Dr. Bruce Perry.
“Sweatology: An Efficient Cooling System.” The New York Times: August 15, 2007 Abigail Zuger.
“The Hair Down There” PlannedParenthood.com (accessed March 24, 2010)
Thomas Acold - Thomas Acold is a teacher and writer living in Brooklyn, New York. A graduate of Yale University with a degree in English, he has written ...
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