Duke University Medical Center researchers believe they have discovered why the appendix exists and what purpose it serves in modern humans.

They think it is used to 'reboot' the digestive system and produce the bacteria sometimes eliminated by disease. How is it that people have them removed and live normal lives afterward?

In modern times, it is relatively unimportant. In crowded areas people can easily replace lost bacteria from contact with others but in ancient times, when isolation was more common or when diseases such as cholera or amoebic dysentery struck and eliminated the stomach's good bacteria, the appendix was likely how the human body regenerated good bacteria.

They say this notion is born out by the fact that in developing nations, where the appendix may still be needed, there is much less appendicitis.

In that sense, modern hygiene makes it more likely that the under-utilized appendix will need to be removed.

Biofilms in the large bowel suggest an apparent function of the human vermiform appendix, R. Randal Bollingera, Andrew S. Barbasa, Errol L. Busha, Shu S. Lina, b and William Parker, doi:10.1016/j.jtbi.2007.08.032