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Far from being the outcome of a perfect design, our bodies are in reality more like a collection of quirks, flaws, and sometimes malfunctioning parts. All were added through time on top of each other, as a result from random mutations that were differentially screened by environmental pressures. Why do we have an appendix that can threaten our life when it gets inflamed? Why do we have a blind spot in our eyes and why does our retina gets detached? Why are we using the same pipe for eating and breathing, hence risking to choke to death whenever we eat mochi? The reason for all these imperfection is that of course, our bodies were not designed, but that they evolved as a result of random mutations through time. Let's have a look at some examples of "unintelligent design".

This is the follow up of a previous post dealing with emotional quirks and why we get sick.

The eye

The eye forms images when light hits the retina by sending information to the brain through the optic nerve. In a well designed camera, that electrical wiring would have been added by the engineer at the back of the retina. Yet, in humans, it is connected to the retina on the side that receives light, creating a zone where no photo-sensitive cells can intercept light: the blind spot. This also create a structural weakness that can lead to retina detachment. Octopuses however have no bling spot since their nerves are connected to the back of the retina.

Test your blind spot!

blndspt1

Instructions: Close your left eye and fix your right eye on the cross (stay aware of the dot in your peripheral view but don't look at it). Place eyes about 1m away from the monitor and slowly move forward (distance may vary depending on the screen resolution). Stop when you notice the dot disappear.

The throat

The esophagus allows food to travel to the digestive tract, but is also connected to the pharynx and the larynx, which serves for breathing. Because these two pipes are connected, food and other objects can get stuck in the throat blocking the air flow and lead to choking. If the parts were not connected, just like in dolphins, there would be no risk of choking while eating.

dolphin human

Anatomy of the dolphin's breathing system compared to that of humans

The teeth

When human beings have evolved large skulls to fit larger brain. Unfortunately, this was accompanied by a reduction of the jaw to accommodate the need for space. As a result, humans often no longer have enough room to fit their 32 teeth. Wisdom teeth therefore tend to damage neighboring teeth when they start growing, and sometimes require having them pulled out. Other animals don't have this problem.

Impacted wisdom teeth

X-ray of a human jaw

The spinal cord

The cost of evolving such large and specialized bodies is that neurons have become so specialized that they lost their ability to regenerate. If the spinal cord is injured, the neurons cannot repair themselves like other body cells can, resulting in permanent paralysis. Other species have spinal cord neuron cells that are not so specialized and therefore, they are able to repair themselves after an injury.

human brain and spinal cord 3

Human spinal cord

The ear muscles

Through our evolution, we have been able to re-purpose a certain number of muscles past their initial function but some seem to still serve no function, such as the tiny muscles that surround our ears. While these muscles are useful to mammals with large ears so that they can direct their ears in the same direction of their eyesight, ours remain slightly functional, yet useless. Can you move your ears?

Gray378 ear muscles

Human ear muscles

The appendix

The appendix is a vestigial organ that served to our ancestors for the digestion of grasses. We can no longer digest cellulose and this organ has shrunk considerably through generations. Nowadays, the presence of this small appendix is a substantial risk for health. In 2000, almost 300,000 appendectomies were performed in the United States, and 371 deaths were reported from appendicitis. In spite of this, it is unlikely that the appendix will disappear completely because smaller appendixes get less blood supply, and therefore are actually more likely to get inflamed. Some secondary functions for the appendix have been suggested but they are usually not missed by those who had it removed before it might have ruptured.

appendicitis

Inflammation of the human appendix

To finish, here is a video of some of the less understood human features:

Any other example of weird features of the body? Share yours in the comments below!

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