Scientists Find More Evidence That Your Appendix Serves a Purpose

It’s time to stop picking on the appendix. A new article published in the journal Comptes Rendus Palevol supports the theory that the much-maligned organ may serve as a “safe house” for beneficial bacteria.

Your appendix is a little tube connected to the cecum (a pouch at the end of your large intestine) on the right side of your abdomen. Most of us know two things about the appendix: that infection there is dangerous, and that the organ itself is useless. The first statement is definitely true. A burst appendix is nobody’s idea of a good time. But useless? Perhaps not.

One scientific paper published in early 2016 found that removing an appendix-like structure in mice made them more susceptible to infection and inflammation. Other researchers have argued that the little tube acts as a reservoir for beneficial gut bacteria, keeping them safe even when infection damages the rest of the gut’s bacterial ecosystem. When the dust settles, the good guys in the appendix can start afresh, repopulating the gut with protective microbes.

Heather F. Smith researches the evolution of our bodies at Midwestern University Arizona College of Osteopathic Medicine. For her latest study, she and her colleagues compared the developmental history of the appendix in 533 mammal species.

The researchers found that, far from originating once in a single common ancestor, the appendix evolved independently more than 30 different times—a fact that suggests that it must do something.

The data also showed that species that have an appendix also have a higher concentration of lymphoid tissue, which supports immunity and the growth of beneficial bacteria, in the cecum. Taken all together, these findings support the theory that your appendix is there to help keep you safe and crawling with the right kind of microbes.

So it’s useful, yes. But do we need it? Not entirely. “In general,” Smith told TIME, “people who have had an appendectomy tend to be relatively healthy and not have any major detrimental effects.”

There may be some minor effects, though. People who’ve undergone appendectomies are slightly more prone to infection. “It may also take them slightly longer to recover from illness,” Smith said, “especially those in which the beneficial gut bacteria has been flushed out of the body.”