Have you ever wondered why your body does some of the things it does? There’s a logical reason for most functions that we experience everyday. On the other hand, there are more than 100 vestigial anomalies in humans that are just a relic of evolution. They’re features that no longer serve a purpose such as the third eyelid, hair or wisdom teeth. But what you might not know, is that when you faint, have fever or sneeze, there’s a series of specifically programmed events that always have an important goal in order to keep you alive and functioning. Most of the things your body does are there to protect you. Let’s see which ones are useful and which ones are there just because.

Fever

When your body temperature rises above the average which is between 36,5–37,5, it does it because there’s something harmful in your body that needs to be eliminated. The threat causes release of immunological mediators, which trigger the thermoregulatory center of the hypothalamus, leading to fever. Whether it’s there for infectious causes or non-infectious causes, it’s not a disease, but your body’s way to react to danger. Why the normal temperature is around 37°C, must be a compromise made by evolution. Since 37°C is a good environment for many enzymes in the body, it also kills microbes that have a low heat tolerance. A higher temperature would require greater energy consumption. If it goes lower than 35°C, it’s usually caused by outside factors like being exposed to too much cold for the body to handle. It will lower the body temperature in order to cause a protective “shut down” to preserve heat and protect the brain. Low body temperature can slow brain activity, breathing, and heart rate.

Fainting

Another often useful act of your body is fainting. In fainting, the loss of consciousness is caused by a momentary, self-correcting stoppage of blood flow to the brain. Other causes can make you lose consciousness as well, but when it comes to fainting that occurs in response to a sudden drop in heart rate or blood pressure, it’s usually for protection. For example, when someone is in a lot of pain, they might lose consciousness. Fainting causes your body to end up in a gravitationally neutral position and therefore gives better chances for restoring blood supply and to preserve brain function. Losing consciousness also has another consequence: things happening during it are no longer experienced. So at least in the case of undesirable experiences, fainting could be a transitory trait to escape a situation that can’t be handled. Seeing blood or other unpleasant things triggers it for some people. The price paid for this is high though, as fainting can cause injuries and makes the fainter defenseless. 

Freeze, flight or fight

One reaction that occurs during danger is freezing. It can be considered as a “stop, look and listen” reaction, that sets all senses in alert mode in order to assess a possible danger properly. It’s similar to the “Flight or fight” response. Those two categories cause an obvious enchantment of sympathetic nervous system outflow resulting in increased heart rate, high blood pressure and dilatation of skeletal muscle vessels. The choice that has to be made between escape and struggle depends on the circumstances as well as the type and size of the opponent.

Wisdom teeth

Wisdom teeth. The ones that cause us to go to the dentist for the feared procedure of removing them. Most humans nowadays have too small of a mouth for them and the last time they were useful was when we only ate raw food. Still causing us dentist phobia for no reason. Teeth also had more space before dental hygiene was what it is now, since teeth tended to fall out at some point.

Grip reflex and hair

As we know, body hair has decreased a lot during evolution. The reason for this was that a thick layer of hair would have caused the body, especially the head and brain to overheat. People also lost the need to look big and scary for the predators. Because we started using clothes, shelter and protection from insects and such was not needed anymore. Getting goosebumps is also a relic from that time. It made the fur coat appear thicker, which probably helped repel predators. Goosebumps helped to stay warm as well. People who have been in contact with babies, must have noticed that when you put something in a newborn’s hand, the baby instinctively grabs it. This reflex is also a leftover from a time when our descendants could grab onto hair to stay aboard – just like monkeys do today. Both of the mother’s hands were free and she could then continue her tasks with the baby. A research found that human newborns, relying on their grasp reflex, could hold their own weight for at least 10 seconds when hanging by their hands. Monkeys can still do it for half an hour.

Third eyelid

In the inner corner of your eye, on the side of the nose, there is a small part of skin that is no longer useful to modern humans. The human eye is protected by the upper and lower eyelids, the part which is lined by eyelashes. We could still have the possibility to see underground or underwater with the third eyelid, called plica semilunaris. This third eyelid has atrophied on humans. Birds and reptiles still have it, allowing them to close it for protection and moisture while still being able to see, also under ground or water. Maybe you’ve seen a cat blink horizontally? Well, we used to do that too.

Ears

Of course, ears are very useful to modern humans. But most of the ear is not. The human ear is still lined with a set of muscles that used to help us move our ears. Unlike some animals like monkeys or cats, who move their ears to hear better, humans can hear quite well even with their ears in one place. Even though some people have the ability to still wiggle their ears, it’s not useful for anything but having a weird flex. 

Ovulation

A woman’s orgasm is a leftover from more than 150 million years ago. It used to be important in terms of reproduction. When ovulation was separated from sex by evolution, it became practically useless. Females had access to regular sex with males, and orgasm as an ovulatory mechanism was no longer useful. Instead of this, the female body evolved a new system that we get to enjoy in the form of monthly PMS and pain: releasing eggs in a regular, monthly cycle.

Nipples (men)

Their physiological purpose is to deliver milk, which is not, and has never been necessary for men to have. The only reason for men having nipples is that they could have been women. It’s just developing before the gender does, and stays there for no reason. Similar to a belly button, useless after birth. Belly button does work as a good way of entering the body during medical procedures though. 

Taika Soihtu

Sources:

nlm.nih.gov – Physiology, Fever

academic.oup.com – Vasovagal syncope in humans and protective reactions in animals

yle.fi – Naisen orgasmi ja 8 muuta hyödytöntä ominaisuutta, joita et enää tarvitse

britannica.com – 7 Vestigial Features of the Human Body