They can cause jaw pain, skin issues, unexpected injuries, and even emergency surgeries. They’re
your organs and they can be a pain, but at least they’re working hard to keep you alive - right?
Not exactly. The human body has a surprising number of vestigial organs - body parts leftover
from an earlier point in evolution that no longer serve a purpose.
Here are some of those organs and body parts that really aren’t pulling their weight anymore.
Let’s start with one that’s most obvious in babies. Have you ever touched a little
baby’s palm - only to be surprised when the baby immediately tightens its grip on
your finger? It’s weird that this is one of the first controlled motions the baby
exhibits - or so it seems. It’s actually a reflex, stimulated by tendons in the palm,
and it can even be seen in utero as early as sixteen weeks into gestation.
It continues until the baby starts developing fine motor skills several months after being born.
So why is this such a key reflex for infants?
Biologists have been studying it for a while and believe it originated in primate species with
more fur, like chimpanzees. The reflex allows the infant to grip onto their mother’s fur
without being directly carried, so mom can forage. The hunter-gatherer lifestyle is
mostly gone for humans, and mom is more likely to carry the baby in a stroller these days,
so all this reflex does is make it easier for the baby to grab her hair.
This next vestigial trait is the bane of teenagers everywhere.
Normally, teeth are a good thing. You keep them clean, and in exchange they let you
tear into some corn on the cob. But some teeth are more trouble than they’re worth.
The wisdom teeth are the last teeth to emerge, usually coming in during the teen years and
early adulthood. Most people have four of them, but some have fewer or none. When they come out,
there can be trouble - they can become impacted, causing pain and infections. If they do emerge,
they can crowd other teeth and be hard to clean. More often than not, wisdom teeth get pulled.
So why does our jaw even bother?
Wisdom teeth are large, powerful molars - and in the old days, having more molars was
helpful. After all, the average primordial human diet consisted of raw meat and tough,
fibrous plants. You needed some power to rip through those. Now, you don’t really need that
jaw force to get through your Big Mac and Fries. Not only are the wisdom teeth less necessary,
but the average size of the human jaw has shrunk - meaning no room for them to come in comfortably.
For this next vestigial organ, it’s all in the wrist.
Try touching the pads of your fourth finger and thumb. Does a line appear when you flex
your wrist? If so, you’re one of the roughly 85% of humans who still have the Palmaris Longus
muscle. This body part is so useless that a lot of people have evolved out of having it all together,
and those who do have it won’t get much use out of it. While it can be found in many of our
common relatives like gorillas and chimpanzees, they also don’t seem to have much use for it.
So is it actually good for anything?
Biologists suspect that it was used more before opposable thumbs evolved in the primate world,
and it just stuck around since then. The only difference between those who have it and those
who don’t is that those without it have slightly lower pinch strength, but the effect is so minor
that it’s frequently removed and used in those who need tendon grafts in another part of their body.
This next one might just give you goosebumps.
The body has a lot of different muscles - but these are among the smallest in the
human body. They’re the Arrector pili muscles, and they control the movement
of the hair follicles. That means that they can make your hair stand on end,
and are most commonly reflected in goosebumps - those weird little skin bumps you get when
you’re too cold or you’re nervous about something. So these muscles are definitely
still working - but they’re not all that helpful and can be more annoying than anything.
But in other animals, it’s a very different story.
Humans don’t have too much body hair, so there isn’t much for the Arrector pili muscles to do.
But in animals with a much thicker fur coating, having their hair stand on end can be helpful.
If they’re moving into a tight space, their hair extending can help to warn them of danger before
it hits their skin. And if they’re trying to scare an enemy or impress a potential mate,
they can puff out their hair to look more impressive. Now that might be useful when
that one guy cuts in line at the coffee shop, but alas, humans aren’t built that way.
And it’s not the only area of the body where the animals have the edge on us.
Have you ever watched your cat or dog when they notice something? One of the first things
that happen is their ears start twitching towards the source of the noise! It’s cute
and should immediately be posted on YouTube - but it’s also useful to them, as they can point their
ears towards the source of their surprise and hear better. They use some tiny muscles
called the auricular muscles to manipulate their ears, and humans have three of these muscles too.
Our versions are much less useful.
Two of the three auricular muscles in humans are pretty useless, but one - the anterior auricular
muscle - has a subtle effect. It can draw part of the upper ear up and forwards. The human ear
is evolved to provide a pretty good listening experience regardless of where we’re standing,
so we don’t need to shift our ears with these muscles. However,
being able to wiggle your ears is a pretty good party trick.
This next organ is either the stuff of life - or just some extra skin.
It’s one thing virtually all mammals have in common - nipples. In female mammals,
they’re attached to breast tissue that provides vital milk to their young.
Some animals have long rows of nipples, but humans only have two. And all humans
have two - even though men don’t really seem to need them. Male nipples are usually flat,
not attached to milk-producing organs, and seem to provide no evolutionary purpose.
So why haven’t they been eliminated by evolution yet?
Some schoolyard bullies would probably say it’s because to do so would eliminate the
purple nurple. But scientists sent them to detention and provided an alternative
theory - males and females start from the same genetic base, and the foundation of the nipples
in the fetus actually comes before the point in development when it’s determined whether
the future baby will be a boy or a girl. These remnants of fetal development don’t provide
a vital function, but they do hold a bundle of sensitive nerves that can cause arousal.
A lot of vestigial organs are about protection - even when it’s not needed anymore.
It’s a weird little quirk of the eyes - what’s that little lump of tissue at
the corner near where it meets your nose? Not only doesn’t it seem to fulfill any purpose,
but it’s one of the first places in the eye to get irritated by allergies or smoke.
The only use it seems to have is making your eyes water more and to make it more
obvious when your eyes are getting red. In animals, though, it’s a very different story.
Are you ready to meet the third eyelid?
Humans have two eyelids - the more flexible top one, and the protective bottom layer. But
many animals including birds and reptiles have a third layer called the nictitating
membrane that can be drawn over the eye for extra protection. Few mammals still have it,
but they do have the base it evolved from - that little corner of eye tissue. Only one primate,
a small Loris from the rainforests of West Africa, still kept this unique eye feature functional.
Some organs come from a much older, primal time.
The human body has a number of sense organs that control our senses of sight,
hearing, touch, smell, and taste. But one smell organ isn’t what it used to be. Jacobson’s Organ,
or the vomeronasal organ, is a tiny organ located in the nasal cavity and can be found
in all snakes and lizards. Some mammals like dogs, cats, and pigs have it too, and humans
often have a vestigial organ based on it. But don’t get too excited - it’s not good for much.
Wait, why do the animals get all the secret smells?
Jacobson’s organ is designed to detect specific chemical compounds, particularly those coming
from predators and prey. It’s also useful for detecting sex pheromones from potential mates.
In other words, it’s useful for wild animals who live their lives by primal functions of hunting,
being hunted, and looking to reproduce. Humans haven’t been living that way for a
very long time, and so this organ is out of work.
Just because an organ isn’t useful doesn’t mean it can’t be painful.
It takes up much of the lower legs and can be the bane of runners everywhere - the Plantaris
muscle. This long superficial muscle is the longest tendon in the human body and
runs all the way from the knee joint to the heel. And for all that length,
its function is...weak flexion of the ankle joint and knee. It might also help the central nervous
system perceive where the foot is positioned. But its overall function to the body is minimal.
So it may cause more trouble than it’s worth.
The Plantaris muscle is susceptible to injury caused by too much pressure on one leg. Tennis,
basketball, and soccer players often suffer ruptures that can take some time to
heal - although injury to the muscle doesn’t cause the long-term damage to physical ability that
tearing other tendons or muscles can. The tendon can be removed and used for tendon transplants,
and scientists believe it’s more useful in other primates who commonly grip things with their feet.
This next organ might be funny to say - but it’s not essential for life.
Spleen! This organ resembles a large lymph node and mostly works as a blood filter. Its name comes
from ancient Greece and it removes old red blood cells, stores blood, and recycles iron into the
blood. It also provides a home for lymphocytes packed with antibodies, which boost the immune
system. It’s a helpful organ that can be found in all vertebrates - but it’s also delicate.
So what happens if something goes wrong?
The spleen is prone to rupture when injured, and it usually has to be removed.
Immune system disorders can also affect the spleen’s function. And if that happens...don’t
worry, the body has you covered. There can be some deficits in the immune system as a result, but the
liver takes over most of the spleen’s function. People without a spleen can live a long healthy
life - and probably have to deal with chuckles when they tell people which organ they’re missing.
But it’s more useful than this next organ - it’s all in the name!
The appendix. It’s a small tube attached near the colon,
and it’s one of the most common causes of early childhood surgeries. If the appendix
gets inflamed or infected, it can cause severe stomach pains. If left untreated,
it can burst - a life-threatening condition that sends dangerous bacteria through the body. Today,
the appendix can be removed safely and quickly, but in the past, it was a common cause of death.
And for all that trouble, what does the appendix actually do?
For a long time, people thought the answer was nothing - it was just a random body part
that didn’t help until it randomly tried to kill you. Today, scientists believe
nothing is without purpose. The appendix is essentially a storage tube, packed with
beneficial gut bacteria that help your digestive health. It’s useful, but not necessary - millions
of people have had their appendix removed and none of them seem to have any long-term health issues.
Finally, here’s something that’s a remnant of a MUCH older time.
The tailbone, or coccyx, is probably the most annoying bone in the body.
The last part of the vertebral column in apes and humans, it’s a pointy bone that
you don’t usually notice - until you fall on it the wrong way. Then it reminds you of its
existence with a painful jolt. If fractured, it can cause difficulty walking for a long
time and force you to wander around with a donut-shaped cushion to sit on. Awkward.
But ages ago, it served a very different purpose.
The coccyx is a short, stubby thing in humans today. But in our ancestors, it was longer - a
lot longer. The coccyx is our vestigial tail, the last trace of when we were swinging around
the trees and using our tails to hold on to branches. Today it’s mostly useless, although it
does provide attachments to various other muscles and tendons in the area. But it’s a far cry from
its former self - it would be kind of useful to have a tail you could hold a cup of coffee with.
For more on this strange body we inhabit,
check out “20 Things Your Body Does That We Don’t Know Why”, or watch this video instead.