If we’re to believe the digitally enhanced men of today’s silver screen, male body hair is in decline. Just compare male movie star chest hair from the 1960s to the what we see today. Doesn’t it seem like men—and specifically millennial men—are getting increasingly less hairy than their fathers, and their father’s fathers?
Obviously, some of this body baldness is the result of tireless hours at waxing parlours and being de-furred with lasers. But even a casual glimpse around the gym locker room these days reveals us to be a less hirsute group than the shaggy men you might remember from childhood trips to the pool.
So, evolutionarily speaking, are men getting less hairy?
“Basically, yes,” says Pavol Prokop, an associate professor of biology at the University of Trnava in Russia, whose research focuses on human evolutionary ecology. “The number (or, better, density) of follicles in humans is similar to other primates of similar size, but our body hairs don’t develop like they do in non-human primates.”
Put in simpler terms, the number of hair follicles we have has remained the same, but the actual hairs either don’t develop or are too tiny to be noticeable. “It’s a stark contrast with all other living primates,” Prokop adds.
As for why this is the case, well, that’s up for debate. “Molecular analyses suggest that this process started about 1.2 million years ago, but the exact reasons for it are still unclear,” says Prokop. He explains that a number of hypotheses have been proposed, but none of them have gained general acceptance. “Perhaps the most commonly held explanation for the evolution of the nakedness in humans is that it evolved as a cooling device,” explains Prokop. “It has commonly been thought that by abandoning the shady forest, the hunting ape exposed himself to much higher temperatures than those to which he had previously adapted. Thus, it’s been assumed that the hunting ape took off his hairy coat to avoid becoming overheated in the hot savannah.”
Even this theory doesn’t hold up under closer scrutiny, though. “Exposure of the naked skin to the air certainly increases the chances of heat loss, but at the same time it also increases heat gain and risks damage from the sun’s rays,” says Prokop.
Another theory revolves around human-to-human touch. “It’s been suggested that increased sensitivity to touch in humans has been particularly useful to us in a social sense, permitting more intense, mutually pleasant contacts between man and woman, and between woman and child,” explains Prokop. “But again, this theory doesn’t explain why hair was also shed from areas not associated with intimate contact.”
Either way, men and women have definitely gotten less hairy. But according to Prokop, this isn’t happening at a speed you’d notice from one generation to the next — it’s a very slow process. Instead, he proposes a much simpler explanation for the recent shift: “It’s just that more men are shaving or trimming their body hair.”
The data seems to back him up. Based on a 2014 Study of Men’s Grooming Appliances and Tools, a sizeable portion of men—39 percent—reported removing body hair below the neck—aka “manscaping”—at some point, up from only 6 percent in 2005.
As for why humans feel the urge to remove their body hair in the first place, Prokop thinks it has something to do with parasites: “According to the ectoparasite avoidance perspective, to be hairless is better because it reduces parasite loads,” he explains.