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The original was posted on /r/biology by /u/gslysz on 2025-09-12 11:34:25+00:00.

1. What We Thought for ages: The appendix was dismissed as a useless, vestigial leftover from evolution, prone to inflammation and often surgically removed without much regret. It seemed like a quirky appendage with no real purpose beyond causing appendicitis trouble. But why preserved in many primates and rodents?
2. What Is New: -The appendix turns out to be a shielded sanctuary for good gut bacteria at the gut junction between the small and large bowel. It protects these species with biofilms, mucus, and IgA antibodies creating a safe zone from infections, antibiotics, or inflammation. -Acts like a microbial Noah’s Ark, reseeding the gut after wipeouts like diarrhea or meds. -Removal doubles the chance of stubborn C. difficile infections, higher odds of colorectal cancer or Crohn’s, plus lingering issues like IBS, digestive woes, anxiety, or brain fog.

In a nutshell, the appendix is a backup reservoir for much needed bacteria after wipe-out events. It’s time to question those ‘since we are here’ appendectomies.

Citation: Sagor, M. S., Islam, T., Tamanna, N. T., Bappy, M. K. I., Danishuddin, Haque, M. A., & Lackner, M. (2025). The functional landscape of the appendix microbiome under conditions of health and disease. Gut Pathogens, 17(1), 38. https://doi.org/10.1186/s13099-025-00696-2 (PubMed: ncbi.nlm.nih.gov/39375776/)