If you think of the human body as a kind of evolutionary roadmap, it's clear our ancestors had some pretty freaky bits and pieces. From swiveling ears to tails, there are some interesting parts that have been left (at least partially) behind.

Here's a look at nine vestigial structures — body parts that have lost some or all of their original function and are just evolutionary relics.

1. Appendix: You never really hear much about the appendix unless someone is having it removed. This tiny pouch is located where the large and small intestines meet, yet it doesn't seem to play a role in digestion — at least not anymore. Researchers think it is left over from when early humans had a plant-based diet. Thousands of people have their appendix taken out each year apparently without any problems. Although that seems to show that we don't need the little pouch, recent research says it may be a place to store good bacteria.

2. Tailbone: You have to go way back on the family tree to find an ancestor with a tail. But at one time our forefathers had them and now all that's left is the coccyx — a few fused vertebrae at the bottom of the spine.

3. Wisdom teeth: At one time, these third molars likely served a function. But as the human mouth has evolved and become smaller, there's often no room for these teeth to come in. That's why so often they are just pulled out.

4. Vomeronasal organ: Also called Jacobson's organ, this structure in the nose is used to sniff out pheromones emitted by a potential mate. It's found in amphibians, reptiles and mammals, but scientists are pretty sure that the structure is non-functioning in humans.

5. Darwin's point: Check out the inside of your upper ear. Do you have a small bump? About 10 percent of people have this tiny protuberance, known as Darwin's point or Darwin's tubercle, because Charles Darwin first described it when discussing genetics. The extra flesh is most likely left over from a far-removed ancestor who had a folded-over ear. That point may have been the vestiges of the joint that let the ear flop down or swivel.

6. Erector pili: These tiny muscles at the base of the hair follicles contract with the pilomotor reflex, causing goose bumps. Goose bumps (aka "chicken skin") used to be key to help raise body hair on end, which would create a layer of warmth to help our ancestors survive. These days we just put on warm clothes and turn up the thermostat. Goose bumps serve somewhat of an emotional purpose, signifying feelings such as fear, pleasure or anger and can be a sign to others — and ourselves — when we're feeling heightened emotions.

7. Body hair: See above. We don't really need to keep warm using our hairy legs and other body parts. Besides, even if you're seriously hirsute, body hair is nothing like a nice wool blanket or down parka. And we spend way too much time waxing, shaving and otherwise getting rid of it.

8. Male nipples: Early on in the womb, all human fetuses develop nipples before they even know if they'll ever need them. Although nipples in men have no true function, some men can lactate and develop breast cancer.

9. Plica semilunaris: You know how sometimes you have a little sleeper in the corner of your eye? Look a little more closely. See that little fold of tissue in the inside corner of your eye? Many believe that is the remnants of a third eyelid. Yes. A third eyelid. These nictitating membranes are usually found in birds, reptiles and amphibians, but apparently our ancestors might have had them too. These days, the tissue still has some function. It helps drains your tears and sweeps foreign bodies from the eye.

Mary Jo DiLonardo Mary Jo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.