The human body has a few unneeded parts. We no longer rely on these organs or structures for any serious function, or they have atrophied or degenerated to the point that they don’t serve the function they used to.
Charles Darwin pointed to these vestiges of anatomy in humans and other animals as evidence for evolution. Eventually, by noting how the vestigial organs in one species were similar to functioning organs in other species, biologists concluded two otherwise dissimilar creatures must have shared a common ancestor. Here are five of the most notable vestigial organs in humans:
The Appendix: This small pouch attached to your large intestine, at the junction of the small intestine, no longer aids in digestion, and none of the 1 in 20 people who have one removed seems to miss it. In plant-eating vertebrates, it remains part of the digestive system. And a study in 2009 found that the human appendix might be useful, serving as an important storehouse for beneficial bacteria, which can’t wait for a chance a case of diarrhea so they can rush to the gut and save you.
The Tailbone: Grandpa didn’t have a tail, but if you go back far enough in the family tree, your ancestors did. Other mammals find their tails useful for balance, but when humans learned to walk, the tail because useless and evolution converted it to just some fused vertebrae we call a coccyx.
Male Nipples: This one might surprise you. Men have nipples because early on in the womb, the gender of a fetus could go either way. Essentially, every fetus starts out female. Eventually, testosterone causes a fetus to veer toward male or female. It’s worth noting that some men have been known to lactate, and men can get breast cancer.
Erector Pili and Body Hair: Goose bumps aren’t just to alert you of cold. And in many creatures, fear and confrontation cause muscle fibers called erector pili to activate, forcing hairs to stand up and make the animal appear larger and more threatening. That would’ve been useful to your distant ancestors, those hairy beasts!
Wisdom Teeth: Little more than a pain for many people, wisdom teeth probably once served a function, scientists figure. But the human jaw has become smaller over time and the wisdom teeth just have nowhere to grow. It’s also possible that dental hygiene is partly to blame. Before tooth brushing, a young adult would have lost many or most of his teeth, and the incoming wisdom teeth would have been timely.
Read More: 10 Useless Limbs & Organs.