Ah, hair.
Who doesn’t love it?
We style our hair, use it to express ourselves, and do our best to keep it healthy so we can
show it off.
That is, unless it’s there.
Or there.
Or especially there.
Yes, there’s one type of hair that most people could do without - body hair.
Whether it’s back and chest hair, underarm hair, or the hair that lurks beneath your
underpants, this hair can be an unwelcome sight for many people - and it’s hard to
get rid of, especially permanently.
People subject themselves to different treatments to try to get rid of body hair, including
shaving - with all the nicks that come with it - to using foul-smelling hair removal cream.
Then there’s those painful waxing sessions to get rid of large strips of hair, and we
can’t forget plucking those stray hairs out with tweezers and trying not to pinch
your skin.
Alternatively, you could just go au naturel - even though some particularly hairy people
would probably rather not hear “Mommy, there’s a Bigfoot on the beach”!
The question is, why?
Why do we still have body hair and what purpose does it serve?
And why are people so determined to get rid of it?
We’re obviously not the only mammals to have hair all over our body, as anyone who’s
whiled away hours petting a cat can tell you.
And when we get closer to our relatives - primates - we see the same thing.
Most have fur covering their entire body, although the length, color, and thickness
of the hair varies.
But their hair is more uniform and covers them mostly evenly, which is not the case
for human hair.
So what sets human hair apart?
Human hair is divided into two distinct types, and we’re the only species to have this
unique hair pattern.
The hair you know and love is called Terminal hair, and it grows on the scalp, eyebrows,
and eyelashes - along with on the feet and chest and other areas.
This hair is thick, unusually long for hair, and grows on the scalp continuously.
Other large apes have terminal hair as well, but small apes and monkeys do not - hence
their thinner, sleeker fur coat.
The other type of hair, you might not even be aware of.
Vellus hair is the earliest form of body hair.
It’s extremely thin, light-colored, and wispy - growing all over the body except a
few areas of skin like the lips, palms, soles, and some areas of the genitals.
It has a purpose - helping to insulate the body during the winter and keep it cool in
the summer by wicking away sweat.
It’s almost invisible unless you’re looking for it, so it’s very rare for people to
shave it - especially as it’s most common during childhood.
So what changes in this light, invisible hair?
In a word, puberty.
This hormone change causes the immature vellus hair to be replaced with terminal hair, making
the previously invisible body hair suddenly very visible.
While women will develop some additional body hair, usually in the legs and armpit areas,
it’s men who get the brunt of this transformation.
Most women’s body hair will maintain the quality of vellus hair, but men can expect
to develop thicker facial hair as well as hair all over their body.
This is called androgenic hair, and while it rarely grows to the same length as the
terminal hair on the scalp due to a shorter active period and a longer dormant period,
it can still grow to several inches long.
Hence, why getting rid of body hair became a major industry.
The question is why we have this hair at all.
The answer, as with most things, is a story of evolution.
Our current status as the dominant species of Earth wasn’t always the case, and in
past times we had a lot more to fear from the world around us.
Our body hair served as a protective barrier, allowing our body to perceive movement and
vibration in our hair before something reached our skin.
This is particularly useful when making our way through close quarters - say, near bushes
with thorns on them.
When our hairs get brushed, we know to give the area a wider berth so our skin doesn’t
get harmed.
This is similar to the function of whiskers on cats, as they use them to sense if they
can squeeze into a tight space.
If their whiskers clear the opening, they know they won’t get stuck.
But what’s the function of body hair on other areas of the body?
One of the areas that becomes hairy during puberty is the underarms, and it’s also
one of the areas that people work the hardest to keep hair-free.
The location of this hair, which is usually among the longest on the body aside from the
scalp, is a puzzle to scientists.
After all, the underarm is usually kept protected by being folded under the shoulder.
It’s a hidden area that won’t usually come into common with too many exterior dangers.
That is, at least any dangers that we can see.
One theory about why we have armpit hair is that it’s for protection from sweat.
The hair naturally wicks sweat away from the underarm and keeps it from becoming a breeding
ground for bacteria in the moist area.
This can prevent irritation and infection, especially among those who work out or do
manual labor and are producing more sweat than usual.
This is contrasted to the common fungal infections that happen around the feet like Athlete’s
Foot.
There’s usually no hair between the toes and they’re usually covered in socks and
shoes with no way for moisture to escape, so the moisture, bacteria, and fungal spores
get trapped.
But microscopic infections aren’t the only danger to the skin.
In the past, when most people were hunter-gatherers, they spent a lot of time in contact with nature.
That led to a lot of dangers - like being mauled by a stray tiger - but many of the
threats were smaller.
Parasitic insects like ticks and mosquitos could cause infections and carry diseases,
which could be fatal without modern medicine.
Even today, malaria is one of the deadliest contagious diseases in the world.
A thick coating of body hair could make it harder for insects to penetrate to the skin,
and make it easier for humans to detect them early and get rid of them before they cause
damage.
The trade-off is that some parasites flourish in hair, like lice - as any parent who has
gotten a note about a head lice outbreak knows.
With all the things out there, the question might be - why don’t we have more body hair?
While some humans are naturally hairy, even the hairiest person isn’t going to have
the thick coat of fur that we’ll see on a gorilla.
That is, except those suffering from Hirsutism, a condition caused by an endocrine imbalance
that causes excessive hair growth.
This can cause a male pattern of hair growth on women, including significant facial hair.
In more extreme cases, it can create a full-body hair growth more akin to those seen in other
mammals.
Those with extreme cases of Hirsutism in the past often found themselves isolated or working
in circus freakshows with such insulting names as “Bearded Lady” or “Wolf Boy”.
But the average person is far less hairy than our mammalian cousins.
So when in evolution did this change?
Scientists believe the shift from a traditional full-body fur coat came at least two million
years ago, but possibly over three million.
One of the clues they look at is when two species of lice diverged.
Pubic lice, which were more common preying on animals with full fur coats, and head lice,
which are more specifically geared towards targeting the thick coat of hair we have on
our heads.
They also believe that this shift happened when humans became more evolved at protecting
ourselves from the elements.
One of the biggest advantages of a fur coat is the warming effect in the winter.
But at a certain point, we evolved so that protection from the cold was less important
than a more manageable amount of body hair and fewer hair parasites.
So are all humans equally hairy?
That would be a clear no.
Studies across populations indicate that some populations have much more body hair than
others.
Indo-Europeans, Spaniards, and Semites are the most hairy, while Native Americans, East
Asians, and Australian Aborigines have almost no body hair.
While the reason for this isn’t clear, most scientists believe that it’s a quirk related
to the evolution of hair follicles to be sensitive to enzymes generated during puberty.
So is body hair just a quirk of evolution, or does it still serve a purpose today?
Before modern man, wearing clothing was rare.
Early man was either naked, or wearing only a thin piece of protective cloth like a loincloth
to guard sensitive areas.
Now, we’re usually clothed over the majority of our body for the entire day - except for
nudists.
So the need for body hair as protection isn’t there anymore, since we add our own.
But body hair still serves its other purpose - moisture reduction.
Wearing clothes can trap the moisture on the skin, especially if you’re wearing tight
clothes during an intense workday or at the gym.
That could result in irritation or infection - but body hair can reduce that risk by wicking
the moisture away and keeping it from concentrating on the skin.
That’s why most doctors will recommend boxers over briefs, to let the skin breathe and the
hair do its work.
So if hair has an evolutionary purpose, why do many people eventually lose it?
You may remember it from watching your dad comb his hair and pull away a few more hairs
every day, but many men eventually lose the hair on their heads.
This is called balding, and is usually a sign of aging caused by a combination of genetics
and natural male hormones.
It can happen to women as well, although it’s usually less severe, and can be triggered
by physical or mental stress.
Some level of hair loss is common in women following pregnancy.
While it can sometimes taper off, male-pattern baldness is usually progressive - and permanent,
leaving millions of men to go hat-shopping.
Another kind of hair loss, though, is more severe.
Alopecia areata is an autoimmune disorder that can cause sudden hair loss.
This can happen in one spot when the hair follicles go dormant, but it can also spread
over the entire scalp resulting in complete baldness - or even over the entire body, resulting
in the loss of every single hair down to the smallest vellus hair.
What causes this sudden effect isn’t clear, but it’s speculated that the body’s immune
system perceives hair as a foreign object and ejects it from the hair follicle.
This condition is usually permanent but some efforts to slow its process or reverse the
effects with immunotherapy and steroids have shown some success.
Awareness of alopecia has become more widespread thanks to public statements by famous people
including Congresswoman Ayanna Pressley and athlete Kevin Bull.
So it seems like we’re all just stuck with whatever amount of hair our genetics want
us to have, right?
This is mostly true, but hair removal and prevention has become a massive industry.
Temporary removal methods like waxing, shaving, and plucking are common, but the hair will
usually grow back quickly.
That’s why people who want to remove unwanted hair permanently, especially stray ones on
the face or other visible areas, are turning to high-tech methods.
While depilation, or removing the hair above the skin, is only a temporary measure, epilation
can have more permanent results.
This is the removal of the entire hair including the part below the skin, and the most popular
measure is electrology.
This uses a thin probe in the hair follicle to destroy the germ cells needed for hair
growth.
But are there ways to reduce hair growth permanently beyond targeting specific hairs?
Laser hair removal uses an intense beam of light to target hair and destroy the hair
follicle.
While at first it’ll grow back, several sessions can permanently destroy the follicle.
The length it’ll take to do this will vary based on how thick and dark the hair is, and
there’s enough interest in the method that many hair care manufacturers have created
at-home kits for laser hair removal.
The problem is, the type of lasers that are safe to use at home are weaker than the ones
used by professionals, so results using at-home kits will vary.
While nothing will happen from removing a few pesky hairs, it seems like evolution knows
what it’s doing.
We haven’t lost our body hair because it still has a purpose - helping us regulate
moisture and temperature and protecting our skin, even if it’s not always ideal for
beach season.
For more on the genetic quirks of hair, check out “Why Do We Have Different Skin, Hair,
and Eye Color?”, or check out “Things That Happen to your Body When You’re Asleep”
for more on the complex way your body operates.