That's the theory from surgeons and immunologists at Duke University Medical School, published online in a scientific journal this week.
For generations, the appendix has been dismissed as superfluous. Doctors figured it had no function. Surgeons removed them routinely. People live fine without them.
And, when infected, the appendix can turn deadly. It gets inflamed quickly, and some people die if it isn't removed in time. Two years ago, 321,000 Americans were hospitalized with appendicitis, according to the Centers for Disease Control and Prevention.
The function of the appendix seems related to the large amount of bacteria populating the human digestive system, according to the study in the Journal of Theoretical Biology. There are more bacteria than human cells in the typical body. Most of it is good and helps digest food.Storyunteller: Surgery professor Bill Parker, Duke University Medical School
Appendix is a refuge for good germs, study says
Story research: David Tyler
The human appendix - from rags to riches