Does the appendix actually serve a purpose?

The answer

Long dismissed as a functionless evolutionary remnant, the human appendix has been re-evaluated by modern research. The leading current theory, proposed by Duke University researchers, suggests the appendix serves as a safe house for beneficial gut bacteria. Its narrow, dead-end shape and biofilm-coated interior protect a reservoir of commensal bacteria that can recolonize the gut after severe diarrheal illness flushes out the intestinal microbiome. Supporting this theory, the appendix has evolved independently at least 30 times across mammals, suggesting strong positive selection rather than mere vestigiality. The appendix is also rich in immune tissue (gut-associated lymphoid tissue), participating in immune surveillance and the maturation of B lymphocytes. However, in the modern developed world with access to clean water and antibiotics, the appendix's benefits may be reduced, which could explain why its removal (appendectomy) typically has no major health consequences.