Here are ten vestigial traits and behaviors you knew you have but have no idea why.

Evolution has really done quite a lot to us all. All species seem to have a few traits and behaviors that their ancestors needed very much but don’t make any sense clinging to them now. As we evolve, these traits and behaviors become “vestigial” — they now exist as a result of an evolutionary vestige and are no longer needed, but we can’t get rid of them.

At their best, these vestigial features are just needless, nonetheless. At their worst, however, they are pretty much a detriment to us — what scientists term as an example of “evolutionary baggage.” Dear friends, here are ten vestigial traits and behaviors you still have.

#1. Plica Semilunaris

Also known as your “third freaking eyelid,” your plica semilunaris is a small fold of tissue on the inner corner of your eye (it’s not the little bump in the very innermost corner, but the small flap right next to it. Image above. It is the vestigial remnant of what is referred to as the nictitating membranes — commonly found in birds, reptiles, and some amphibians. (Here’s the membrane of a masked lapwing as it closes over its eye).

It’s typically translucent, serving as an eye moistener, clearing debris, and helping stare down weeping angels. Unfortunately, we aren’t able to use our third eyelids, but come on, take a glance at them in the mirror and you’d notice how amazing they are.

#2. The Palmar Grasp Reflex

This is common among babies, but it isn’t a vestigial feature as it is a behavior. From a 1932 study, as many as 37 percent of infants who grasped an object when placed in their palm were able to support their own body weight if they were suspended; (and the reverse motion happened when the backs or sides of the baby’s hands were stimulated).

The grasping reflex is probably an evolutionary behavior that we still have in common with well-known primates such as monkeys, chimps, and the like. This gives the young ones the ability to hold on tight to the mothers when moving around.

#3. Male Nipples

Seriously? Nipples on a man are like the blind having a television, what’s the use? Blame it on evolution, what else? There have been rare occasions of males who lactate, but biologically speaking, nipples on a man is of no use, and their vestige on this list is one that still remains a mystery. However, they aren’t as a result of an evolutionary event that left them there, but rather an embryological development. Truth is, all fetuses effectively begin life in the womb as females. 

During embryogenesis — the development of an embryo — if the embryo starts developing without the presence of a Y-chromosome, it develops as a female. When a Y-chromosome appears, then the fetus starts producing hormones like testosterone and develops into a male. But the nipples are there already and will have no use in the future. So, guys, you were once upon a time a girl. Remember that!

#4. Tonsils

Your tonsils are purported to be your body’s first line of defense against inhaled or ingested pathogens, but they, inasmuch as your appendix (see #10 below), also invoke infections and pain in your body. They tend to become infected, inflamed, and dangerous for you that makes most people wonder why is it there in the first place; and even if they serve a more or less definitive function, it’s just there for surgeons to get a job of removing it for some extra cold hard cash.

#5. Arrector Pili

Ever had “goose bumps”? Your arrector pili are the smooth muscle fibers that contract involuntarily to give you that sensation. For most furry woodland creatures, for instance, this could even provide some insulation — thick, standing fur that traps air between their erected hair follicles, which helps keep them warm.

Or better yet still, make them look bigger, indicating the difference between being prey or predator. For example, a porcupine seems more like a predator rather than prey. But unfortunately for us, we aren’t furry and don’t have these features.

#6. The Ear

This isn’t the entire ear, but definitely, the human ear has lost some touch with certain peculiar features. There are some muscles attached to your ear that make it seem like a satellite dish trying to pick up a signal (that’s known as the pinna in a mammal), and it seems others (like dogs) still have the ability to move ‘em around. Unfortunately for us, we can’t. Sorry!

However, a few individuals can, nonetheless (not to say we’re jealous anyway), but has no function to us any longer. What’s even more, there’s a chance that one in every ten of the population shows signs of vestigial features in the outer rim of the ear, also known as the helix. These features, called “Darwin’s tubercle,” occur at the juncture of the upper and middle thirds of the ear, and it’s a common feature in many mammals. Nonetheless, some of us use it for hanging ornaments.

#7. Coccyx

Better known as your tailbone, it’s the last part of you that says you’re vertebrae and the remnant of a tail. In fact, every mammal once upon a time had a tail at some point in their evolution — even if it was a short while developing as an embryo. For instance, humans at the first stage of embryogenesis have a tail-like structure that later gets lost. 

This embryological development was the main basis of the theory of recapitulation, commonly known as “ontogeny recapitulates phylogeny,” which basically states that the process of developing from an embryo into an adult parallels various stages of the organism’s evolution from an ancestral state to its current one. So what’s the function? You were once growing a tail but unfortunately lost it.

#8. Wisdom Teeth

They aren’t what they sound like; and what has the wisdom to do with your teeth? We have no idea. They are just like unwanted house guests at a party that’s already full. There isn’t any room for them to push their way into your mouth, but they’ll do so anyway (even if you don’t want); and when they do, it’s very uncomfortable. So what’s their function? You’d end up seeking dental assistance to do rid of them.

#9. Sinuses

These are basically pockets of air that are hidden inside your face, but their biological role is a huge topic of debate which has little-to-no conclusion on their actual purpose. Here’s one thing we can all agree on: the sinuses are at their worse when it’s infected. If you’ve ever had a sinus headache, then you know their purpose isn’t that bright. Ever had a sinus headache before?

#10. The Appendix

This is by far the most widely known vestigial human organ which is often seen as the “vermiform process” in this image above. The appendix might have been an aid for our evolutionary ancestors in the digestion of cellulose-rich plants, according to biologists.

However, modern scientists believe that the appendix still plays a role in storing good, digestion-aiding bacteria; but you ask anyone who has paid for an appendectomy and they will tell you that its true purpose was just there for the surgeon to get a job in its removal when it’s infected. That’s all.

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Written by: Nana Kwadwo, Sun, Mar 21, 2021.

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