1. Plica Semilunaris

Have you ever looked closely at the inner corner of your eye? We’re sure you have. The area is unfortunately prone to the aggregation of eye gunk and other undesirable crusties. But the location is also a hint at evolutionary past. Hundreds of millions of years ago, this little pink slit in our eye used to be a tertiary eyelid.

an eye from close up
Wikipedia

This eyelid would blink horizontally across the eye. This eyelid, which still exists in reptiles, birds, and even some mammals, is called the nictitating membrane. While it used to help protect these animals’ visibility, we didn’t really need it as time moved forward. And so, it evolved into something a little less invasive.

2. Palmer Grasp Reflex

The Palmer Grasp Reflex is a trait we show as infants. What happens is that babies under six-months-old, when prompted by a finger, will grasp on for dear life. The reason behind this trait is thought to be our arboreal past. When climbing around in the trees, it would be advantageous for a young infant to grab onto nearby appendages or branches.

New born baby Catch my little finger
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The converse should also be clear: if you don’t grab on, you might fall to your death. And so, the Palmer Grasp Reflex evolved. As a result, you can test any baby under six-months-old with a finger in their palm and see what happens. Once you do, you can thank evolution for the interesting peccadillo.

3. The appendix

Sometimes our body is burdened with evolutionary vestiges that it’d be better off without. The appendix appears to be one such vestige. The appendix, which hangs off an area of the large intestine called the cecum, apparently serves no function. While it may have served a purpose in our evolutionary prehistory, the thing serves no purpose now.

Appendicitis and appendix inflammation disease concept as a close up of human intestine anatomy as a 3D illustration.
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The one thing that the appendage now does is burst in 300,000 Americans per year. The result is a painful and dangerous spread of infectious material into your internal system. Ultimately, the appendix reveals another vestige: something that used to help us out that no longer really serves any purpose at all.

4. Palmaris Longus

The palmaris longus is a muscle that used to serve a purpose. When we lived in the trees, it would help us hold onto and swing from branches. But now that we no longer do these things (at least not to the extent that we used to), the muscle has begun to disappear in the population.

muscles in the arm
Flickr

14 percent of people no longer have this muscle. To see whether you are one of them, you can try to press your pinky to your thumb. If this small muscle that appears as a tendon shows up, you have it. If not, you are one of the small few that has lost the vestige to time. As we progress through human history, the muscle is likely to fade even more.

5. Wisdom teeth

Wisdom teeth, the bane of many of our existence. To get them removed often entails substantial effort. We need to be aesthetically subdued, given subsequent pain medication, and have the things yanked from our mouths. Back in our prehistory, however, the teeth actually served a purpose.

Dental equipment holding an extracted tooth
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Before our we developed agriculture and other easy-to-eat foods, our jaws had to work much harder. When they had to work harder, they grew larger to deal with taxing foods. But once these foods became easier to eat, our jaws shrunk in proportion. The result is that our wisdom teeth got pressed into a place no one wanted them to be. And because of this, many of us now need them removed.

6. Tailbones

Your tailbone is likely something you haven’t paid much attention to. The thing sits tucked up inside of you, only becoming salient if you land on your butt. And, as their name suggests, these tailbones used to serve as the start of our tails. Since we no longer have these tails, the bones that started them began to retract into their current placement.

human skeleton of articulated hip joint anatomy showing sacrum, hip bone, femur and lower lumbar vertebra
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In the embryo, you can actually see the purpose of this tailbone. In utero, we actually grow minor tails. As we progress through gestational development, however, the tail neglects to grow. While it might be cool to actually have one of these tails, the extra appendage is no longer needed. The result is that we now only have a tailbone.

7. Goosebumps

Goosebumps, also known as piloerection, are another vestige of our evolutionary past. When our hairs stand on end, the reason is often that we’re cold. When we had more hair, the response would help insulate our body. Another reason for the response was to help us appear large when in the midst of assault. If we look bigger, we might appear more formidable to potential predators or assailants.

CLOSE UP, MACRO, DOF: Unknown Caucasian person gets goosebumps during a cold tropical rainstorm. Close up shot of arm hair fluttering in the breeze as unrecognizable girl can't escape the cold rain.
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Now that we don’t really have the hair, the phenomenon is merely vestigial; it shows that we used to use this hair for the above specified reasons. If we so desired, we could use the erect hair follicles to indicate our emotional state. Maybe we’re cold. Maybe we’re afraid. Maybe we’re priming our body to engage in battle.

8. Plantaris Muscle

The plantaris muscle, in contrast to the palmaris muscle of the arm, was something we used to use to enable our feet to grip objects like branches and bananas. Since we no longer really grip that many things with our feet, the muscle has withered into obscurity.

3d rendering medically accurate muscle illustration of the plantaris
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One sign of just how vestigial this muscle has become is that it is now used by reconstructive surgeons to rebuild certain muscle fibers elsewhere in the body. If the muscle served any function nowadays, this would not be the case. It would be cool, however, if we did have this muscle functioning as it did before. I, for one, could imagine a few uses of having a foot-like hand.

9. Vomeronasal organ

The vomeronasal organ, as the Latin suffix nasal suggests, is involved in smell. But, the function it once served in no longer relevant. In the past (and in other animals), the organ serves as a way in which to detect pheromones. These pheromones serve as a way to detect other members of your tribe, potential sexual partners, and sometimes even signals of fear.

The flehman grimace of a buffalo bull as he tests the urine of a cow to check her stage in her oestrus cycle.
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The detection of these pheromones used to be of vital importance. But ever since we primates became a species primarily of sight, our nasal capabilities began to fade—and along with them the ability to detect pheromones in any reliable way. We still, however, have the organ. It just doesn’t work very well. 

10. “Junk” DNA

Junk DNA, which is, admittedly, a misnomer, consists of unused DNA that used to be responsible for building structures that once served a purpose. The DNA, unlike that that gets read and turned into useful things like ear muscles and noses, does not get read or turned into something.

Genetic engineeering concept with 3d rendering dna helix and a part of dna
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In this junk DNA, however, we see the history of our past. Some of this DNA contains the script that, if read, would produce things like better smell or longer bones. Since the DNA builds structures that don’t serve as great a purpose as they once did, it has been turned off. Now it resides in our cells, a quiet and unread vestige of our past.

11. Philtrum

The philtrum is the area between your nose and upper lip. The interesting fact about this piece of flesh is that it isn’t present in some of our distant mammalian cousins. What this suggests is that it served a purpose for our ancestors yet not those that moved in another evolutionary direction.

profile of natural lips of a young woman (shallow dof)
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Evolutionary biologists now have evidence that the philtrum comes from our fishy past. During gestation, the area would become gill-like structures in fish. In humans, since we, for the most part, don’t really have gills, the thing just turns into a boring section of upper lip mayhem. Either way, the thing represents a nice little chunk of our evolutionary past.

12. Hiccups

Hiccups are another one of those things that hints to our evolutionary past. The reaction of having hiccups is called “singultus.” The trait is thought to have emerged primarily from our amphibian relatives. In both them and us mammals, there is a specific part of the brain that can trigger these hiccups.

Woman covering her moth after drinking cola
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What this suggests is that the phenomenon likely served some purpose in our ancient cousins. While we’re not sure what that purpose, the feature did appear to help the amphibians of the past. It might have been used as a way in which to expel unwanted fluids from the amphibian lungs.

13. Backaches

Backaches, as awful as they are, are another hint at our evolutionary past. In case you didn’t notice, we are the only primate species remaining that is completely bipedal. Prior to our take to two legs, our bodies were adapted to a life of a horizontal spinal cord. Our internal organs and all else was adaptive to this lifestyle. Everything changed once we stood on two feet.

Woman suffering from back ache on the bed, healthcare and problem concept
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When we became bipedal, our bodies didn’t necessarily adapt that quickly. The result is that our spine has a lot of weight to bear and not in a way that induces longevity. The result is that many of us will develop back pain. While the newly acquired bipedalism helped us hunt, use tools, and see longer distances, it also left us with back pain. We’ll say it’s a useful tradeoff. 

14. Poorly supported intestines

Another consequence of our bipedalism is the effect that trait had on our organs. As mentioned previously, the adaption wasn’t exactly helpful for our internal organs. Our intestines, for instance, were no longer supported as well once we began to stand on two feet.

partial view of woman holding paper made large intestine on grey background
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Now, our intestines sit above a few other organs. Sometimes they will dip down to places they shouldn’t be. When this happens, we can suffer an inguinal hernia. While this unfortunate dilemma is mostly only present in men, it is still something that shows our evolutionary history. Other animals (lucky for them) don’t ever have this problem.

15. Choking

Choking is another of those vestiges of our ancient past. Our trachea, that thing which channels air from the atmosphere into our lungs, is placed in horrible relation to our esophagus. The result, unfortunately, is that some subset of us will succumb to choking at some point.

A girl needs assistance
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This isn’t the case in cats or other mammals. Because we had to adapt our vocal cords and trachea to speak, the orientation of our esophagus in relation to our trachea ended up giving us an unfortunate disposition to occasionally choke on our cherries or Legos. Let’s just try to chew our food a bit better from now on.

16. Hairless apes

Another vestige of our past is our current lack of hair. Unlike our primate cousins, we don’t have fur. In part, this loss of hair is thought due to the ancient presence of lice and ticks. Those with hair were those more likely to acquire infections from the annoying pest. Therefore, those that began to lose the hair were better off.

A baby chimp and her handler. The rescued chimp is being rehabilitated for release into the wild.
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The unfortunate result of this hairless disposition is that we succumb to cold winters with a little bit more sting. We don’t like our primate or other mammal cousins, have a nice coat of fur to keep us warm. Perhaps the trade-off is worth it: we lose our hair and the affiliated problem of ticks and lice. Since we have clothes, the problem isn’t really that great.

17. Darwin’s Tubercle

Darwin’s Tubercle is a muscle on the ear that used to be used to help us move them. In our earlier human history, we would use these muscles to help orient our ears in the direction of important sounds. These may have come from mates, predators, or susurrus in the bush that might have insinuated lions.

Darwin's tubercle on a monkey and human
Wikipedia

After we evolved to have more mobility in our necks, however, the need for this muscle began to fade. It became more advantageous, then, to devote the physiological resources we once used for it elsewhere. The evidence of this is that the muscle has began to shrink and lose function. Now it just looks like a little bump on the ear.

18. Obesity

Obesity in the current era is often the result of incongruencies in our brain’s evolution and the food we’re given in the modern era. While in our evolutionary past we would forage for foods like berries and meats, in the modern day we have an abundance of bread, sugars, salts, and fats. The result is unbecoming.

Gourmand Girl Eating Tasty Hamburger at Fast Food Restaurant
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Our taste buds evolved to enjoy (and guide us to seek out) foods high in salt in fat. In fact, it built our brain to eat these beyond our normal capacity to eat food. Now that we live in a world with these foods in abundance, we are guided to them and guided to them often. Because of this, many of us have been unwittingly led into health problems like obesity. 

19. The phrenic nerve

The phrenic nerve is one of those nerves that helps to control muscle movement in the body. In humans, it controls the diaphragm. Ultimately, it helps us to breathe. What’s weird about this nerve is that it travels in circuitous and windy ways to get to its ultimate destination: the diaphragm.

organs in the body
Flickr

Like with some of the other traits we mentioned on this list, the phrenic nerve is thought to have been built from our fish-y ancestry. In them, the nerve doesn’t travel as weird and circuitously as it does in us. In us, the thing is a sign of our ancient past when things were just a tab bit more simple. Now, as we see with the phrenic nerve, they travel a bit more aimlessly.

20. Male uterus

The aptly named “male uterus” is also called the more anatomical prostatic utricle. This little part of the male anatomy is an undeveloped female organ that males have as a useless sack. This sack hangs off of the male prostate. Interestingly, the Latin of prostatic utricle means “pouch of the prostate.”

Image of a doctor in a white coat and model of the reproductive system of women above his hands. Concept of a healthy female reproductive system.
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Unfortunately, the thing does not sit there entirely free of use. In some people, it will develop cysts. These then have to be removed to salvage the health of the affected person. Let’s just hope that’s not you. Either way, the thing shows that not all of our body gets used in the same way as we evolve to fit our niches. While the male uterus might have served a purpose in past species, it certainly serves little purpose now.

21. Male nipples

Male nipples are another of those things that are a vestige of our past. While it makes sense that females have nipples—they have mammary glands that supply milk to babies—it doesn’t necessarily make sense that men have them. Men, in case you were unaware, don’t often produce milk.

man with both hands on breast because of hard breathing and angina pectoris on grey background
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Male nipples, however, are not necessarily anything related to evolution. Instead, they are the result of sexual differentiation in the prenatal environment. Here, female nipples are given a suite of hormones than prepare them for functionality. In males, this is not the case. But the ability of early nipple development suggests that they can become one of the other.

22. Tonsils

Tonsils are a part of the lymphatic system and work to help with circulation and immunity. While they were previously thought to serve no function (and thus be considered and evolutionary vestige), this thought has been retracted in favor of another, better-supported hypothesis.

Doctor checking with depressor sore throat to teenage girl
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The tonsils are the first defense our body has against bacteria and viruses that enter the mouth. When something that enters that is considered unhealthy or dangerous, the tonsils will show spots, which represents that the immune system is attempting to act through them. So while the tonsils might at a superficial glance appear to serve no purpose, they actually do help us with some things.

23. Thirteenth rib

Thirteenth ribs, also known as lumbar ribs, are an extremely rare occurrence. They develop in around one percent of the population. The ribs are free-floating in that they don’t attach to the sternum. Our other ribs, in contrast, do. While many have speculated on the possible advantages of such floating ribs, the reasoning is difficult to support.

X-Ray image of the human chest
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Unfortunately, the ribs seem to offer more problems than any observable benefits. The ribs can get broken or displaced, for instance, which would induce considerable discomfort in the person experiencing the displacement. It’s possible, although not certain, that these ribs are a vestige of our ancestral humans.

24. Armpit hair

Armpit hair is another of those things that has been preserved by our evolutionary past. While most of the hair on our bodies was subject to loss, the onslaught of lice and ticks that made us lose it was not annoying enough to have us lose it everywhere. Our armpits and pubic hair were a few of the preserved places.

Pretty Woman with Hairy Armpits on White Background
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The armpit hair, however, actually helps to serve some purpose. This purpose, however, might be vestigial. Many hypothesize that the hair might have served a purpose in the production of pheromones, those communicatory molecules that signal whether we want to mate with or fight someone as an enemy.

25. Neck ribs

Neck ribs are another possible evolutionary vestige that appears in humans. Unlike a thirteenth rib, these neck ribs show up in the cervical regions of the spine (nearer to the neck). But unlike thirteenth ribs, these occur in a smaller subset of the population.

Human skeleton anatomy visible through a transparent magenta skin against a black background.
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It is estimated that the neck ribs occur in around .2 to .5 percent of the population. This is a lower number of people than that of those who suffer from psychopathy. But while the experience is rare, it might hint at a past where such growths were helpful. Maybe they protected us against assaults to our neck. While it’s difficult to know with any certainty, the possibility is there.