According to Darwin, the appendix was a useless biological remnant, the remains of a larger structure called the cecum, which was used by now-extinct ancestors for digestion. Researchers have now found that not only does the appendix appear in nature much more frequently than previously acknowledged, but that it actually serves a critical function. According to researchers at Duke University Medical Center, the tiny organ provides a safe haven where good bacteria can hang out until they are needed to repopulate the gut after, for example, a bout of diarrhea (Science Daily, August 21, 2009). The presence of a reservoir of good bacteria provides more proof that homo sapiens lives in symbiotic relationship with gut bacteria. What we’d like to know is what antibiotic use does to the appendix—does it promote appendicitis, or lead to exhaustion through overuse?