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:

Illustration: Carly Monardo

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: