Brain and Body

It Turns Out the Appendix May Serve an Important Biological Function After All

January 10, 2017 | Kelly Tatera

Photo credit: Hellerhoff/Wikimedia Commons (CC by SA 3.0)

New research “confidently rejects” the notion that the appendix has no adaptive value or function — it may help the immune system.

One of the first things taught in basic biology is that the appendix, a pouchlike structure of the colon, has no known purpose.

Or does it?

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Researchers at Midwestern University conducted an analysis on the appendix over the past 11 million years, tracing the appearance, disappearance, and reemergence of the organ in several mammal species.

Publishing the new research in the journal Comptes Rendus Palevol, the team found that the the appendix evolved independently in a number of mammal lineages, over 30 separate times. Once the appendix appears, the analysis revealed that it almost never disappears, suggesting that the organ likely serves an adaptive purpose.

“We can confidently reject the hypothesis that the appendix is a vestigial structure with little adaptive value or function among mammals,” the researchers wrote in the study.

Many researchers posit that the evolutionary reason the human body never got rid of the appendix is that, since it doesn’t doesn’t harm most people, there’s simply little evolutionary pressure to eliminate the body part. But perhaps the appendix has been quietly fulfilling an important role in our bodies that has been long overlooked.

Zeroing in on some factors like diet, climate, social aptitude, and where a species lives, the researchers were able to reject several previous hypotheses which linked the appendix to dietary or environmental factors, according to the study press release.

LEARN MORE: Where You Live Shapes Your Immune System More Than Your Genes

Instead, the analysis showed that species with an appendix have higher concentrations of immune (lymphoid) tissue in the cecum — part of the large intestines — thereby suggesting that the appendix could serve as a secondary immune organ.

Further, lymphatic tissue can stimulate the growth of beneficial gut bacteria, so the appendix might also function as a “safe house” for helpful gut bacteria, as the press release explains.

Future studies are needed to confirm these new findings, but we may have jumped the gun on writing off our appendixes.

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