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Odessa Chan
Apr 84 min read

“Useless” Body Parts

One modern pillar of Charles Darwin’s Theory of Evolution is the idea of universal common ancestry (UCA). As first suggested by Darwin, the theory of UCA states that all organisms share a common genetic heritage, and therefore one common ancestor at the beginning of the world. This can be seen through DNA similarities between different organisms. 


For example, chimpanzees are humans’ closest relative as a species, and we share at least 98% of genetics. Humans also share approximately 67% of DNA with mice and have been developing as a species for millions of years. According to Darwin’s theory, this would mean that throughout all of humanity’s existence, it is certain that some sort of evolution would have occurred due to random genetic outliers and natural selection.


Humans have largely differentiated from other species over time, meaning some of the physical traits displayed by us before would have disappeared. Including body parts, some traits have lost their function over the past few million years due to changes in our behaviour, lifestyle and natural genetic deviation. This article will explore these “useless” body parts in humans.


4 Commonly Known “Useless” Body Parts


1. The Appendix


According to a study in 2016, the appendix would have been a body part used to digest cellulose, the basic structural component of plant cell walls. While other plant-eating, or herbivorous, organisms still rely on their appendix to help digest plants, this organ is no longer an essential part of the human digestive system. Cellulose has also been deemed indigestible by humans, but it is unknown when or for how long this change took place.



Appendicitis, the inflammation of the appendix, happens when the inside of your appendix is blocked and can be caused by infections throughout your digestive tract. According to the National Institute of Diabetes and Digestive and Kidney Diseases, around 5-9% of people get appendicitis at some point in life. It causes severe pain in that area of the body, but because the appendix is not particularly functional in the human body, the common cure is a surgical removal of the appendix from the body. 


2. Wisdom Teeth


Wisdom teeth are known for being used to help our ancestors better digest tough food in the wild. Our ancestors also had bigger jaws in order to accommodate these teeth. However, due to the development of humans and our ability to gather food more suitable to us, we no longer need wisdom teeth. 


Over time, humans’ jaws have also adapted to be smaller due to the decreased need to chew hard foods. This means that there is less space for the wisdom teeth in humans’ mouths. However, they do still grow and appear in human bodies. Oftentimes, if wisdom teeth do come into the mouth, they grow in odd angles. This creates difficulty because there isn’t enough space for them, resulting in them hitting the jaw bone or sticking in the gums. When this happens, people commonly get their wisdom teeth removed through surgery, as they are not necessary either way.



3. The Coccyx, or “Tailbone”


Our ancestors needed tails for mobility and balance, but around 20 million years ago the tail began disappearing due to a decrease in need. Now, humans have no use for tails, or the tailbone. This is explained simply through natural selection, which theorises that our ancestors who didn’t have tails due to genetic mutations fared better and were able to reproduce and create more similar organisms. 


Now, human embryos develop a tail between five and eight weeks after conception, but the tail has vanished by the time the human is born, leaving just the coccyx, or tailbone.



4. Male Nipples


Male and female foetuses initially develop the same way, before testosterone and other hormones trigger the formation of male sex organs later. Before this occurs, nipples have already begun to develop in both male and female embryos. Therefore, even though both male and female embryos grow nipples, the body of a woman uses the nipples as a vehicle for milk when they feed their offspring, and men have no use for nipples. 


Conclusion


Throughout the course of human evolution, our bodies have gone through numerous changes and adaptations that have shaped us into what we are today. However, not all features have managed to hold onto their original purpose in our modern lives. These “vestigial” body parts serve as tokens of our evolutionary history. While they may not serve much function now, they provide us with insights into our ancestral past.


Works Cited


Cellulose | Definition, Uses, & Facts | Britannica. (2024). In: Encyclopædia Britannica. 

[online] Available at: https://www.britannica.com/science/cellulose [Accessed 20 Feb. 2024].


Healthdirect.gov.au. (2023). Removing wisdom teeth. [online] Available at: 


‌‌Indus Health Plus. (2023). Appendicitis: Causes, Symptoms, Treatment & Prevention 

Tips. [online] Available at: https://www.indushealthplus.com/appendicitis-causes-symptoms-prevention.html [Accessed 20 Feb. 2024].


‌Kotecki, P., Olito, F. and Focht, M. (2023). Useless body parts that humans no longer 


National Institute of Diabetes and Digestive and Kidney Diseases. (2024). Definition 

& Facts for Appendicitis. [online] Available at: https://www.niddk.nih.gov/health-information/digestive-diseases/appendicitis/definition-facts. [Accessed 20 Feb. 2024].


NHS Choices (2024). Treatment - Appendicitis. [online] Available at: 


‌Theobald, D.L. (2010). A formal test of the theory of universal common ancestry. 

Nature, [online] 465(7295), pp.219–222. doi:https://doi.org/10.1038/nature09014.

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