What are they?
According to Biological Dictionary, vestigial structures are “various cells, tissues, and organs in a body which no longer serve a purpose.” They can originate from mutations in the genome, which cause changes in the proteins that are required for the formation of the structure. The appendix is a prominent example of a vestigial structure in humans. Although they may be perceived as useless, these structures can give researchers insight into the evolutionary history of humans.
Significance In Evolution
Evolution takes a long time to occur for even the smallest of traits. Traits that are beneficial for an organism are passed down to the next generation, while deleterious ones are selected against. However, traits or structures with no impact on the quality of life of organisms or neutral traits are passed down because they aren’t harmful, as explained by ThoughtCo. Sometimes they go away as people age. There are many forms of vestigial structures in humans.
Image is courtesy of Wikipedia.
Examples of Vestigial Structures
Appendix
When the appendix, which is positioned off the cecum, becomes inflamed, it necessitates surgery to remove it. Humans can still operate normally without the organ. In a 2012 study at Midwestern University, researchers discovered that the appendix may have served a purpose in prior human generations. Several additional species have an appendix, which has evolved over 30 times in certain mammalian lineages and does not disappear all at once. According to their results, the organs’ job was to create a reservoir for gut bacteria and accelerate their growth.
Wisdom Teeth
Britannica explains wisdom teeth as a vestigial structure. As humans evolved, there was a shift in nutrition as a result. Humans no longer require strong teeth to eat meals because cooking and processing have made the meals we consume softer. As a result, human jaw sizes decreased, making humans’ third molars more likely to be used for eating. Wisdom teeth are becoming increasingly rare.
Pyramidalis Muscle
Pyramidalis muscles can be in a variety of numbers, with some persons having two, one, or none at all. They are found in the lower abdomen between the rectus abdominis muscles and the muscle sheath. It is used to contract the linea alba, an activity that is unrelated to the abdominal muscles’ function.
Auricular Muscles
This muscle regulates the visible section of the ear and is functional to mammals for localization and emotional expression. However, they are seen as non-functional for humans, although with effort, some people have been able to successfully wiggle their ears. According to Charles Darwin, humans were able to hear through the positioning of the head.
Embryo Tails
During pregnancy, embryos are seen to have tails during the sixth week. After weeks of growth, the tail vanishes and the vertebrae unite to form the coccyx, or tailbone, in the adult. Humans and apes differ from other primates in part because they lack tails, although the reason is still unknown. A human newborn with a vestigial tail is a rare occurrence. The tails lack vertebrae and are usually harmless, albeit some are linked to spina bifida, which is the failure of the vertebrae to completely enclose the spinal cord.
Overall, vestigial structures are an important piece of our evolution as they communicate our history as a species.
Article Author: Idil Gure
Article Editors: Stephanie Sahadeo, Victoria Huang