According to surgeons and immunologists at Duke University Medical School, as published online in a scientific journal this week, the purpose of the appendix is to aide the growth of healthy digestive bacteria:
Diseases such as cholera or amoebic dysentery would clear the gut of useful bacteria. The appendix's job is to reboot the digestive system in that case.So underuse may increase the risk of infection and appendicitis.
The appendix "acts as a good safe house for bacteria," said Duke surgery professor Bill Parker, a study co-author. Its location -- just below the normal one-way flow of food and germs in the large intestine in a sort of gut cul-de-sac -- helps support the theory, he said.
Also, the worm-shaped organ outgrowth acts like a bacteria factory, cultivating the good germs, Parker said. That use is not needed in a modern industrialized society, Parker said.
If a person's gut flora dies, it can usually be repopulated easily with germs they pick up from other people, he said. But before dense populations in modern times and during epidemics of cholera that affected a whole region, it wasn't as easy to grow back that bacteria and the appendix came in handy.
In less developed countries, where the appendix may be still useful, the rate of appendicitis is lower than in the U.S., other studies have shown, Parker said.