Throughout the human body there are certain muscles that have lost their presumable original function or have developed minor new ones. We call this human vestigiality. Many of these human features have appeared to become physiologically useless throughout evolution. Let’s take a look at a few known vestigial muscles and uncover the mystery of their existence.
- PALMARIS LONGUS: The palmaris longus originates on the medial epicondyle of the elbow and inserts on the palmar surface of your hand. It is absent in about 14% of the population. This varies greatly among different ethnicities. This muscle is believed to have been essential for primates to hang from trees and easily grasp branch to branch. Interestingly enough, there are studies that show the palmaris longus has little to no effect on human grip strength, despite it’s role with “arboreal locomotion” in the early days! Because of it’s little role in our lives as humans, this little guy is often used as a tendon graft with surgeries.
- AURICULAR MUSCLES: Also known as the extrinsic ear muscles, this group consists of the anterior auricular, superior auricular, and posterior auricular. Surrounding the top of your ear, these muscles pull your ear forward, upward, and backward. Excluding humans, the auricular muscles are important for localizing sound and expressing emotions. Very few people can actually isolate these muscles since we often position our heads to locate the noise stimulus. Not a lot of research here, but an estimated 10-20% of the population can actually activate their auricular muscles. Can you “wiggle” your ears? If so, you are part of that 10-20%!
- PLANTARIS: Starting from behind the knee and inserting onto the medial heel, the plantaris has some functionality as a weak knee and foot flexor. It is often overlooked due to the strong gastrocnemius, but it is still rather painful if injured! It is absent in 7-10% of the population and like the palmaris longus, it is commonly used as a tendon graft. Because of it’s long skinny tendon and minor role in plantarflexion, this muscle is often mistaken as a nerve by first year medical students and has earned the title “The Freshman Nerve.” Now, after reading this blog, if you ever go to medical school you’ll never mistake the plantaris!
It’s important to note there are many other vestigial structures in the human body ranging from the anatomy of the appendix to the behavioral reflex of goose bumps. The muscles above are just a few examples of how we evolved over time. If you want to learn more, feel free to watch this short video or read this friendly article.
Isn’t science fun? We hope you enjoyed learning about Mystery Muscles. Now go practice wiggling your auricular muscles!