Looking to shed some pounds? You can start by losing that spare rib!
1. THIRD EYELID
That tiny fold on the inside corner of your eye is a leftover of what’s called a nictitating membrane—a translucent covering still present in some birds, reptiles, and fish. The lid is meant to slide from side to side to protect the eye while maintaining visibility.
These tissues at the back of the throat filter out bacteria and viruses—but they’re prone to infection, which is why kids often have them removed. Luckily for adults, tonsils shrink with age and generally stop causing trouble.
3. MALE NIPPLES
These odd ornaments exist because all fetuses start out as females until the Y chromosome kicks in, turning some male. The nipples remain as a byproduct.
While you can certainly live without it, recent studies suggest that the appendix might not be as useless as once thought; it could function as storage for beneficial bacteria meant to repopulate the gut after an illness washes out our old bugs.
At the base of our spine lie three to five vertebrae, fused together—remnants of our long-lost tails!
6. WISDOM TEETH
Only about 5 percent of us have room for wisdom teeth, which leads to a lot of painful surgery. But back in the pre-toothpaste days when molars fell out, wisdom teeth were handy backup chompers.
7. SPARE RIBS
While most humans have 12 sets of ribs, .5 percent of humans and all chimps and gorillas have an extra set near the neck.
8. FEMALE VAS DEFERENS
Women have their own answer to male nipples: sperm ducts nestled near their ovaries. As a female fetus develops, these potential pipes shrivel into dead-end tubes.
9. ARRECTORES PILORUM
These mini muscles once made our ancestors’ body hair stand on end to conserve heat and to appear bigger and more threatening to enemies. Today, all they do is create goose bumps.
10. PINKY TOES
Our ape ancestors used all their toes to grab and swing from branches. But modern man can remain upright using his big toe with a little help from its three neighboring piggies. The fifth is just along for the ride.
This article originally appeared in mental_floss magazine. You can get a free issue here.