You Hairy Beast: Why Do We Have So Many Types of Body Hair?

Every hair on your body—from your head to your toes—serves an evolutionary purpose. Here's how all that fur helped your distant ancestors weather the storm.


If evolution has taught us anything, it’s that everything on the human body, from cuticles to goosebumps, serves a purpose—or at least, it did for our distant ancestors. Hair is no exception—below, you’ll find a top-to-bottom examination of every different type of fur sprouting from your body and why it’s there in the first place.

Head Hair

While scientists can’t say for certain why our head hair grows longer, thicker and in higher numbers than the hair covering the rest of our body, they have a few theories. The first (and most likely) is that the hair helps to insulate our heads—without it, we would have a constantly frigid noggin due to the large surface area and the constant flow of blood to our brains, both of which allow for large amounts of heat to be released. That’s because blood that’s constantly flowing near the surface of the skin is easily cooled by the outside air, then proceeds to make its way throughout the body, lowering our body temperature as a whole as it does so.

This same theory claims that the development of warm clothing replaced the need for  excessive hair anywhere besides our head, thus phasing it out of the gene pool. The reason our head hair wasn’t replaced by warm headwear is because hats and caps obscured the vision of our hunter-gatherer ancestors, meaning headwear didn’t pick up until we no longer had to catch our own food.

The second theory for why our head hair outgrows our body hair revolves around an evolutionary theory called homo aquaticus, which states that our ancestors evolved on the coast, gathering food from the sea. Being covered in body hair would have made it more difficult to wade around in the water (and to catch fish), giving an evolutionary advantage to those with less body hair, resulting in the genetic extinction of voluminous body fur. Head hair remained simply because we need to keep our heads above water to breath anyway, so the hair on our heads didn’t get in the way of gathering food.


The main function of eyebrows is to protect our eyes from dust, dandruff, rain, sweat and other moisture. They’re particularly good at this because they’re ergonomically engineered—i.e., the hairs intercept moisture, and the downward angle of our brows causes it to run off the side of our face, avoiding our eyeballs altogether.

Eyebrows also play a huge part in facial recognition, according to a study conducted by an MIT behavioral neuroscientist. When test subjects were given altered images of recognizable celebrity faces and asked to identify the person in each photo, they could identify faces with missing eyes 60 percent of the time. But when the eyebrows were missing, the participant’s facial recognition abilities dropped to 46 percent.

Nose Hair

Think of nose hair like an air filter for our lungs: It lets fresh oxygen in while catching dirt, bacteria and toxins that try to tag along with it. The hairy strands that line our nostrils also help to humidify the air we breath by collecting moisture from the outside world, which keeps the entire respiratory system from drying out and causing constant cough-inducing irritation.

This theory is backed by a study by researchers at the Hacettepe University School of Medicine, which found that people with sparse nose hair are nearly three times more likely to suffer from asthma than those with shaggy nostrils. Don’t toss out the clippers just yet, though—as long as the hairs are still coating the inside of your nose, there’s no added benefit to letting them hang down to your lip.

Ear Hair

Aside from the fact that it filters dust particles and pathogens and, thus, helps prevent infections, not much else is known about ear hair’s purpose. What we do know is that The same androgen hormone that triggers male-pattern baldness, DHT, is responsible for causing a surge in ear and nose hair growth. Which means the moment hair starts falling from your head, it’s likely that it will start to sprout from your ear canal and nostrils. Thanks, nature.

Beard Hair

From an evolutionary perspective, why men grow facial hair is still widely unknown. One study, however, suggest that it may be for social reasons. In it, the researcher compares the human beard to the lion’s mane, noting that male lions without manes are treated very differently than those with manes—they’re attacked more often and have less success with females. If humans were as similar to animals as this author suggests we were, this implies that there are both survival and reproductive benefits to having facial hair.

That said, other studies suggest that women prefer the clean-shaven look, as those “with facial hair were perceived as more aggressive, less appeasing, less attractive, older, and lower on social maturity than clean shaven faces.” So, at the end of the day, facial hair remains something of a mystery.

Armpit Hair

Underarm hair has at least three purposes: 1) It wicks sweat away from the skin to keep our pits from incessantly dripping; 2) it reduces the friction between our underarms and torso to prevent chafing; and 3) it acts as a pheromone diffuser. Put in simpler terms, it helps spread our irresistible, musky scent to potential mates—a scent that, according to a 2007 study, not only increases a man’s perceived attractiveness, but also helps women feel more relaxed.

Chest Hair

For troglodytes, having a lot of chest hair made you an attractive proposition. Before the days of bug spray, a frontal forest was the first line of defense against parasites, since it made it difficult for blood-suckers to make their way to the skin. Chest hair also increases our skin sensitivity, which for our ancestors, meant a chance to notice and swat unwelcome critters before they had a chance to feast. Then, as now, a bug-free mate was a good mate.

The theory as to why men still have their chest hair while women don’t is based on sexual selection. Once bugs became less of an issue (perhaps with the introduction of more insulated shelter), either women found hairy men more attractive, or men preferred non-hairy women. Therefore, men with hairy genes and women with not-so-hairy genes reproduced more often, passing down said genes as they got it on.

Pubic Hair

In addition to keeping us warm, our pubes provide cushion against any kind of friction (wink, wink) that may cause skin abrasion and injury. They also protect us from bacteria and other unwanted pathogens sneaking into our nooks and crannies. In fact, cases of both gonorrhea and chlamydia have seemingly increased as a direct result of pubic hair trimming and shaving, according to Scientific American.

Leg (and Foot) Hair

In the days before pants, extra hairy legs kept us from freezing to death at night and (sun)burning to death during the day. While nobody’s totally sure why our legs have gradually become less and less hairy, chances are, shedding some fur helped our ancestors beat the heat when they ditched shady woodlands for warmer climates.

Now that we know why we’re covered in hair, you can respect it, enjoy it, or just shave it off, if that’s what you fancy—after all, it may have done our primate ancestors some good, but these days it’s just there for decoration.