For decades, the appendix was considered a worthless, vestigial organ. The belief was so widespread that astronauts on long-term missions were once required to have it preventatively removed to avoid the risk of appendicitis in remote locations like space. But is this small organ truly disposable?

The appendix was long thought to be a remnant from our ancestors, who needed it to help digest a diet rich in tough plant cellulose. As the human diet evolved, the appendix shrank and seemingly lost its original digestive function. This led to its reputation as a “vestigial organ”—a part of the body we could do without.

Once dismissed as a relic, the appendix is now recognized for its important role in the immune system and gut health.

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Far from being useless, the appendix is an important part of our immune system. It acts as a lymphoid organ, helping mature white blood cells and produce antibodies that regulate our gut microbiota. It also contains its own diverse community of bacteria, distinct from the rest of the gut, suggesting a specialized role.

Removing the appendix can lead to a decrease in gut bacterial diversity and has been linked to an increased risk of certain infections and inflammatory bowel disease. Because of its newly understood role in regulating the microbiome, routine preventative removal is no longer recommended for astronauts or others. The potential long-term risks to our gut health are now seen to outweigh the benefits of avoiding appendicitis.