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Monday, November 27, 2023

Facial Hair Is Biologically Useless. So Why Do Humans Have It?

This story is adapted from Stuff You Should Know: An Incomplete Compendium of Mostly Interesting Things, by Josh Clark and Chuck Bryant.

There are really only two types of facial hair: beards and mustaches. Every style of facial hair you’ve ever seen is one of these two, or a combination of both.

Think about it like part of a Linnaean taxonomy of human traits that we just made up but totally makes sense, where facial hair is a family, beards and mustaches are each a genus, and their many varieties are individual species that could interbreed, as it were, to create hybrid subspecies like the duck-billed platypus of the facial hair family, the soul patch.


This might seem self-evident when you take a second to think about it, but then why would you be thinking about this at all unless you work in the relatively booming beard care industry or you’re a pogonophile—a lover of beards and the bearded. The Economist wrote about that very philia in a 2015 article about the growing trend of beardedness while reporting from the National Beard and Mustache Championship that was taking place in Brooklyn that year … obviously. (A year earlier, in February 2014, the New York Post ran a story about men in Brooklyn paying as much as $8,500 for facial hair transplants in order to grow better beards.)

If you are breathing right now, then you must be aware that the beards The Economist reported on were part of more than just a passing trend. Facial hair grew more popular over the rest of the decade until it became a full-blown phenomenon of 21st-century maleness. It even had a cameo in the beginning of the novel coronavirus pandemic. Media outlets stumbled on a 2017 info­graphic from the Centers for Disease Control showing which facial hair styles were OK with a standard respirator or N95 mask and which styles were less ideal because they “crossed the seal,” allowing all manner of nasty little things access to your wide-open mouth.

It shows thirty-six distinct styles:

Fourteen mustaches, twelve beards, nine beard-mustache hybrids, and a clean-shaven option. This chart also revealed something we hadn’t thought of before: Facial hair doesn’t seem particularly functional. And if that’s true, then the question is, why do we have facial hair at all?

Well, scientists aren’t exactly sure. But they have come up with a best evolutionary guess that makes a lot of sense, if you take a step back to see the forest for the trees—or the beard for the whiskers, as it were.

As it turns out, facial hair is not a functional physical human trait in the way we thought it was for many years. It’s an ornamental one. In fact, of all the physical features on the human body—including other kinds of hair—facial hair is the only one that is purely or primarily ornamental. That is, it doesn’t actually do anything or perform any kind of specific physiological function. Just take a look at what the rest of our hair does for us:

  • Body hair helps with thermoregulation.
  • Head hair protects your scalp from the beating sun, but also traps heat in if you’re in a cold weather climate.
  • Eyelashes are like screen doors for the eyes, keeping bugs and dust and little debris particles out whenever they’re open.
  • Eyebrows impede sweat from getting in your eyes.
  • Armpit hair, technically called “axillary” hair, collects and disseminates pheromones while acting like the WD-40 of body hair, reducing friction between skin on the underside of the arm and skin on the side of the chest as we walk and swing our arms.
  • Pubic hair also helps reduce friction, as well as provides a layer of pro­tection from bacteria and other pathogens.

But facial hair? You will notice it doesn’t appear on that handy list of adaptive hairy traits.

In the early days of studying this kind of stuff, evolutionary biologists thought it might serve thermoregulatory or prophylactic purposes similar to body hair and pubic hair. Beards and mustaches are around the mouth, after all, and the mouth takes in food and other particles that might carry disease. Beards and mustaches are also on the face, which is connected to the head, which loses a lot of heat out of its top if it isn’t covered by hair. It all makes sense when you look at it that way.

Except there’s a problem with this theory: It leaves out 50 percent of the population, i.e., females. Natural selection is ruthless, and it has sent A LOT of species the way of the dodo—for instance, the dodo—but rarely, if ever, does it select for a trait in a species like that and leave half the popu­lation hanging, especially the half that makes all the babies (i.e., the most important half). If facial hair were meant to perform important functions, it would be present across both sexes. Instead, thick, mature facial hair is pres­ent almost exclusively on the male half of the species, and its only job is to sit there on the face of its wearer as a signal to everyone who crosses his path.

What signal does facial hair send? Well, here’s where it gets a little compli­cated, as ornamental traits go. University of New Mexico professor Geoffrey Miller, one of the preeminent evolutionary psychologists in the field, put it this way: “The two main explanations for male facial hair are intersexual attraction (attracting females) and intrasexual competition (intimidating rival males).” Basically, facial hair signals one thing to potential partners (namely virility and sexual maturity, hubba-hubba-type stuff) and some­thing else to potential rivals (formidability and wisdom or godliness). Taken together, these signals confer their own brand of elevated status to the men with the most majestic mustaches or the biggest, burliest beards.

The signal that facial hair sends also tends to be stronger and more reliable between males, who are more commonly rivals, than it is between males and females, who are more commonly partners. In fact, evolutionary biologists will tell you (if you ask them) that while some females really like facial hair, and some don’t, and some couldn’t care less, more often than not attraction has as much to do with beard density as anything else. That is, if you’re in a place where there are a lot of beards—say, a lumberjack convention—then a clean-shaven face is more appealing, but if you’re surrounded by bare faces, then a beard is best.


In evolutionary genetics, this is called “negative frequency depen­dence” (NFD), which is science-speak for 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 preyed upon less. This is a huge competitive advantage. It’s like going to Vegas expecting to lose $1,000 but hoping to break even, only to end up winning $1,000 instead. That’s a $2,000 swing! It’s the same thing for a trait with NFD selection. The trait goes from fighting for its life to being the life of the party. The downside is that the competitive advantage can result in overpopulation of others with the same trait very quickly, because of all the getting-it-on the very interesting-looking guppy does—which means it loses its rarity and becomes common. Not to worry, nature has a solution for that: As more guppies bear that same trait, it leads to a decrease in interest from mates and an increase in attention from predators. What was once the hot new guppy thing becomes old news, in other words.

This yo-yoing back and forth between common and uncommon doesn’t just explain the variability in the attractiveness of facial hair from population to population; it also explains why the dominant theory for the evolution of facial hair has begun to resolve around intersexual competition. Because it’s not enough simply to be attractive: You also have to be more attractive than the people around you, and in enough of the right ways to stand out. This goes a long way toward understanding the ebb and flow in the popularity of facial hair across time. Sporting a killer ’stache or a bushy beard is only effective, evolutionarily, as long as it still makes you part of the hot new guppy thing around the pond. When it makes you old news, shaving becomes the more effective choice.

Throughout history, people have donned facial hair or shaved it as a response to the choices of their enemies and rivals. The ancient Romans went clean shaven for 400 years because the ancient Greeks, their rivals during the Hellenistic Period, celebrated beards as symbols of elevated status and high-mindedness. For the 270 years the English lived under threat of Viking invasion (and, in some parts, actually lived under Viking rule), a period from 793 to 1066 AD tellingly called “the Viking Age of Invasion,” Englishmen went clean shaven as a cultural reaction to their bearded Viking invaders. During the Protestant Reformation, many Protestants grew out their beards in protest against Catholicism, whose priests were typically clean shaven.

What’s even more fascinating is how great an impact rulers and other high-status individuals have had on facial hair trends. The emperor Hadrian brought beards back to Rome in the second century AD, and the entire leadership class of the Roman Empire followed suit, including a num­ber of Hadrian’s successors. In the Middle Ages, Henry V was the first king of England to go clean shaven, and because he was such a great monarch, English society and the subsequent seven kings followed in his beardless footsteps. It wasn’t until Henry VIII came along, in all his egotistical, prof­ligate, murderous glory, that the beard made a comeback, undoubtedly as a way for him to distinguish himself from his predecessors.

It’s not just facial hair, yea or nay, where the choices of rulers and other high-status people have impacted the choices of those around them and for generations to come. You can see it in the evolution of specific facial hairstyles as well. Remember that chart of facial hairstyles issued by the CDC in 2017? Each style has a name. Nine of them—a full 25 percent—are named after influential figures, mostly in the arts. A few of the styles have normal names but are so obviously connected to one or two people who made them famous that you’re more likely to identify the popu­larizer than you are the “official” name.

Changing tastes and the influence of high-status men in competitive environments are all well and good, but nothing moves the needle one way or another on the popularity of facial hair like a good crisis. Indeed, it was the coronavirus pandemic that brought the amazing CDC chart to our attention, and not in the most positive way. London’s Daily Mail published a piece about it under the headline “Could Your Facial Hair Put You at Risk for Coronavirus?” (The CDC chart was, in fact, from years earlier and not related to the coronavirus outbreak.) This is not the first time facial hair has fallen under scrutiny in the midst of a disease outbreak. In a 1916 piece in McClure’s magazine, one doctor managed to blame facial hair for the spread of nearly every communicable disease known to humanity. “There is no way of computing the number of bacteria and noxious germs that may lurk in the Amazonian jungles of a well-whiskered face,” he said, “but their number must be legion.” With more column inches, who knows what other ailments the good doctor would have tied to beards.

Then sometimes, a crisis goes the other way and leads to a period of increasing beardedness. A period like the one that produced the 2015 Economist article about pogonophilia, the CDC facial hair chart in 2017, and the expansion of the National Beard and Mustache Championship in 2019 from 18 categories to 47.

So what will happen to facial hair when a health crisis meets a political and an economic crisis? Your guess is as good as ours, but if and when it happens, you can be pretty sure it’s going to look funny.

Excerpted from Stuff You Should Know. Copyright © 2020 by Josh Clark and Chuck Bryant. Excerpted by permission of Flatiron Books, a division of Macmillan Publishers. No part of the excerpt may be reproduced or reprinted without permission in writing from the publisher.

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