Vestigial structures

Ouch. You can see the impacted wisdom teeth on the right. Why do we have them? Read on.
Courtesy of Ka-ho Chu

Today I’d like to have some fun showing you how you can trace your long, seamy ancestry through your own body. In the far distant past, your grandparents to the umpteenth power may have swam through murky swamps, warmed up on rocks, or jumped from tree to tree in the search of leaves. How can we figure this out? Through vestigial structures.

Vestigial structures are parts of you that have lost their function in your body, but have retained their function in many other animals.

What are some of your vestigial organs?
Everybody’s favorite example is the human appendix. It’s a little, worm shaped organ that hangs off of your large intestine. In humans, the appendix is famous for doing nothing- except for occasionally getting infected and necessitating it’s immediate removal. Some scientists claim that the appendix actually plays the small but important part of reintroducing beneficial bacteria back to your intestines after a bout of Montezuma’s Revenge.

In other animals, however, it plays a huge role. Animals that eat a lot of cellulose (an extremely starchy product of some plants) or toxic materials have huge appendixes. The Koala, the Australian marsupial famous for eating (highly poisonous) eucalyptus leaves, has an appendix over two meters long. Rats also have a large appendix, allowing them to eat pretty much anything.

Other good examples of vestigial traits in humans are: The coccyx- a remnant of the tails our distant relatives used to swing around on trees. The muscles attached to our ears- most small mammals use these muscles for directional hearing. Wisdom teeth- these teeth used to pushed others forward as people got older and started to lose their teeth. Thanks to better dentistry, present day wisdom teeth usually just impact and snaggle the jaw-line.

Do other animals have vestigial organs?
Yes, Virginia, other animals have vestigial organs. To show you one famous example, I’d like to go back to the whales. As I already discussed, the early ancestors of whales had legs and hips. Interestingly enough, they still do- they’re just embedded under layers of fat and muscle. Every so often, a little genetic accident occurs, and something amazing happens.

The letter "C" in this picture shows you a modern whale's hips and legs. Courtesy of Stefan Kühn