The appendix has long been supposed to be a vestigial, useless organ. But a 2007 study suggests that it might have had — and may still have in many developing countries — an important role in digestion. It may provide a refuge for helpful, commensal bacteria to repopulate our guts after we purge when we get sick (Bollinger et al., 2007):
… the human appendix is well suited as a “safe house” for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal tract are purged following exposure to a pathogen.
— Bollinger et al., 2007: Biofilms in the large bowel suggest an apparent function of the human vermiform appendix in the Journal of Theoretical Biology.
Why do they think that? What’s the evidence?
The shape of the appendix is perfectly suited as a sanctuary for bacteria: Its narrow opening prevents an influx of the intestinal contents, and it’s situated inaccessibly outside the main flow of the fecal stream.
–Glausiusz (2008): And Here’s Why You Have an Appendix in Discover Magazine.
And thinking about supposedly useless bits of biology, there’s a bunch of interesting papers coming out about so-called “junk” DNA.