The appendix sometimes seems to be more trouble than useful, kind of like tonsils. You don’t even hear about the appendix before it becomes inflamed, unless you’ve studied medicine. Once it becomes inflamed, there’s the risk of the organ bursting and spreading bacteria throughout the abdomen, causing severe pain and even death in some cases. Still, it can be quite easily removed through surgery, and its removal has no apparent effect on the body. So if it’s so dispensable, yet causes so much problems, why do we have an appendix?

The general belief, until very recently, was that the appendix has no useful function whatsoever, and it’s actually rather hazardous for one’s health. Fifty years ago, for example, if you asked any doctor about the purpose of the appendix, the answer would have been a clear “no”, said with all certainty. Moreover, in the United States, approximately seven percent of the population have an appendectomy during their lifetime, and apparently suffer no ill effects. Therefore, the appendix was considered just a “leftover” of evolution, useful in some mammals, but not humans. Indeed, in some mammals the appendix helps digest cellulose, a major component of grass, as well as the stems and leaves of many plants. Primates, however, don’t eat grass.

On the other hand, recent research has discovered that the appendix has its role after all. Immunologists performed the study based on how many bacteria in our intestines do we need for survival. These bacteria play a play a great role in breaking down food so that it can be used by our bodies, and researchers have found evidence that the appendix in fact provides a place for these essential bacteria to live. In some cases, diseases that are accompanied with extreme diarrhea cause such extreme emptying of the intestines that the populations of bacteria are substantially depleted. The hypothesis therefore is that when bacteria are depleted, the appendix serves as a reservoir of useful bacteria, releasing them into the intestines and speeding recovery. So according to this new theory, people can survive without an appendix because it is seldom used, and one can still recover even without it.

Still, even with this hypothesis, we have a use for the appendix, but the risks associated with appendicitis are greater than the benefits of having an appendix. So even if it is useful after all, everyone agrees that an inflamed appendix should be removed.