Turns out the appendix may have a function after all:

The function of the appendix seems related to the massive 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.

But sometimes the flora of bacteria in the intestines die or are purged. 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.

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, they can usually repopulate it 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.

He said the appendix may be another case of an overly hygienic society triggering an overreaction by the body’s immune system.

Looks like a good application of Occam’s Razor to me. It makes more sense to think that humans have changed their conditions so as not to need the organ as frequently than it makes to think we evolved a distinct yet superfluous organ.