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Did you know you have body parts that came in handy back in our evolutionary timeline, but they no longer serve much of a function in modern humans? These are called vestigial body parts, and while many appear useless, some do retain some function.
Probably the most “popular” vestigial organ, the appendix, is well known because it can become infected. You probably know at least one person who has had hers removed. This is a medical emergency, but the appendix can be removed, generally with no resulting issues to its owner. The appendix, at one time, likely had some digestive function, but now it hangs out harmlessly unless and until it gets buggy on you, then out it goes.
Corner of the eye
In the inner corner of both of your eyes, you’ll find a structure that is called plica semilunaris — a big word that refers to the remnants of a nictitating membrane that our ancestors had at one time. An example of the nictitating membrane is the sort of gross second eyelid that you’ll see slide across the surface of your dog’s eye when he gets tired. Some animals still have fully functioning nictitating membranes that help protect the eye and maintain moisture. We humans, however, do not.
The tailbone is more properly known as the coccyx (see it, down there at the bottom?), and it is the remnants of — you guessed it — a tail. During embryonic development, all mammals have some form of tail. Yes, even you. It does continue to serve some function as an attachment point for some muscles. But we definitely don’t sport tails any more.
At around your 18th birthday, you may become aware that you’re “teething” yet again. Humans have long evolved out of a need for a third set of molars, but most people are lucky enough to pop out a third set of hardcore chompers. Since our jaws are smaller than those of our ancient ancestors, they can cause pain, infection and major jaw problems, and many folks have to have them surgically removed.
In many animals, the ear is surrounded and supported by a strong set of muscles that allow the creature to move the ear in a variety of different directions. Most humans can’t move their ears much at all, but we all still sport a shiny array of vestigial ear musculature. These muscles are pretty cool, but they don’t do a whole lot, which renders them into the “useless” category.