The human appendix has been assumed to be useless since Charles Darwin first suggested it was a vestigial organ—an evolutionary remnant from the time when our predecessors ate leaves and other now-indigestible foods. But new research suggests the organ had a much more vital function, LiveScience reports. It stored necessary bacteria with which to repopulate the stomach after diarrhea or vomiting, as well as helping to create and train white blood cells.
That’s why the appendix got its reputation, suggest Duke University immunology researchers: readily available clean drinking water and sewer systems mean contemporary humans spends a lot less time battling stomach ailments. It’s also what’s behind appendicitis—too little work for the organ renders it prone to inflammation. Rediscovering ways to challenge the appendix’s immune functions could lead to cures for autoimmune diseases like diabetes and lupus—and give a much-overlooked organ its due.