The appendix may not be so useless after all — but what about our other puzzling body parts? Ellie McInerney reports on our evolutionary leftovers.
The appendix has always copped a bit of flack for its uselessness in the human body, and gets whipped out at the first sign of appendicitis. Due to the lack of apparent side effects on removal, it’s earned the title of a “vestigial structure”, a body part that’s lost most of its original function through evolution. Yet, this little intestinal organ may actually be there for a reason.
According to recent studies, mammal species with an appendix have higher concentrations of lymphoid (immune) tissue in the cecum, which stimulates the growth of beneficial gut bacteria. This could mean that the appendix is being used as a “safe house” for storing good gut bacteria. When illness or infection flushes the intestines of everything, good and bad, the reservoir in the appendix can repopulate the gut flora.
Similar to the appendix, certain strains of RNA in our genetic code have been labeled as useless in our hard-working bodies. For a long time it’s been thought that they were leftovers from evolution, but it’s recently been found that they might actually play a part in controlling cellular stress.
These discoveries pose a serious question: what other body parts are considered useless that might actually have a function? Or are they truly evolutionary leftovers? Here are nine more to consider.
1. Third Eyelid
Next time you catch your reflection in the mirror, check out the corners of your eyes closest to your nose and you’ll see the remains of a third eyelid, a “nictitating membrane”. Birds, reptiles and some mammals have the small, thin eyelid which sweeps horizontally, but it’s rarely fully developed in primates and humans. Once used for sweeping out dirt and keeping the eyes moist while still allowing vision, they’re no longer needed.
2. Armpit Hair
Armpit hair’s greatest function is to keep the sales of shaving cream going strong, but unless you own stock in Gillette, armpit hair is just annoying. Theories for armpit hair include protection from chafing and amplifying our ability to attract a mate through body odour, with our body’s scent lingering longer when attached to the hairs.
3. Wisdom Teeth
Unless your version of clean eating involves chomping on coarse leaves, fibrous roots and stringy, raw meat all day, every day, it’s unlikely you’ll need your wisdom teeth. Our ancestors had larger jaws, and their necessary chewing power caused teeth to break down over time, so a spare set at the back of their mouths came in handy. Now, thanks to cutlery and cooking, we can do without them.
Debates as to whether the foreskin is useless or useful are still being argued. According to the encyclopedia for all things circumcision, Circ Info, it’s believed human males are born with foreskin as a means to protect the penis from being desensitised from brushing against long grass and shrubs, when our ancestors didn’t bother with CK underwear and jeans.
Long, long ago we had tails, just like our favourite four-legged friends. Our ancestors used their tails to communicate and stay balanced. Since we now walk on two feet, our coccyx — the tail bone — is no longer needed, but Mother Nature decided to let us keep it anyway.
6. Male Nipples
Guess what guys, you were once a girl! Yep, turns out all fetuses begin with the female template, and when it develops into a male, these female reproductive organs remain anyway. In other mammals, nipple formation is stunted by hormones, but in humans, seeing as these little glands are harmless — albeit useless for guys — they stick around.
Sinuses cause a lot of grief, but they did serve a purpose once upon a time. The story goes that we used these mucous-lined cavities to heighten our sense of smell and warm the air we breathe. And if you’ve ever wondered why you can’t breathe lying down with a bad cold, the sinuses naturally run when we’re horizontal — lying down, or on four legs. Thanks evolution.
8. Thirteenth Rib
Thanks to our gorilla cousins, 8% of adults have a spare rib. While the common number of ribs in humans is twelve, some of us have thirteen like our primate ancestors, although the extra is totally and completely useless.
9. Darwin’s Point
If you look at the top of your ear, some of us have a small downward point on the edge of the curl. That’s Darwin’s Point. According to John H. McDonald from the University of Delaware, the name came about because Charles Darwin mentioned it in his book The Descent of Man. Darwin believed it was evidence of our ancestry with primates, who have pointy ears.