Is the Appendix Really a Vestigial Structure in Humans?

The appendix attached to the large intestine images

Vestigial structures are compelling evidence for evolution. The appendix is usually the first structure we think of that has no function in humans. But is the appendix really vestigial? A research team at Duke University says the appendix just might do something for the human body besides getting infected.

The research team traced the appendix back nearly 80 million years in evolutionary history. In fact, the appendix seems to have evolved two separate times in two separate lineages. The first line to see the appendix come into existence were some of the Australian Marsupials. Then, later on, the Geologic Time Scale, the appendix evolved in the mammalian line that humans belong to.

Even Charles Darwin said the appendix is vestigial in humans. He claimed it was leftover from when the cecum was its own separate digestive organ. The current studies show many more animals than previously thought have both a cecum and an appendix. This may mean the appendix isn't so useless after all. So what does it do?

It could be a sort of hiding place for your "good" bacteria when your digestive system is out of whack. Evidence suggests that this type of bacteria may actually move out of the intestines and into the appendix so the immune system does not attack them while trying to get rid of the infection. The appendix seems to safeguard and protect these bacteria from being found by the white blood cells.

While this seems to be a somewhat newer function of the appendix, researchers are still unsure about what the appendix's original function was in humans. It is not uncommon for organs that were once vestigial structures to pick up a new function as species evolve. 

Don't worry if you don't have an appendix, though. It still has no other known purpose and humans seem to do just fine without one if it's been removed. In fact, natural selection actually plays a part in whether or not you could possibly be inflicted with appendicitis. Typically, humans that have a smaller appendix are much more likely to get an infection in their appendix and require its removal. Directional selection tends to select for individuals with a larger appendix. Researchers believe this could be more evidence for the appendix not being as vestigial as previously thought.

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Scoville, Heather. "Is the Appendix Really a Vestigial Structure in Humans?" ThoughtCo, Aug. 27, 2020, Scoville, Heather. (2020, August 27). Is the Appendix Really a Vestigial Structure in Humans? Retrieved from Scoville, Heather. "Is the Appendix Really a Vestigial Structure in Humans?" ThoughtCo. (accessed June 3, 2023).