Parker and his colleagues recently suggested that the appendix still served as a vital safehouse where good bacteria could lie in wait until they were needed to repopulate the gut after a nasty case of diarrhea. Past studies had also found the appendix can help make, direct and train white blood cells.
http://www.livescience.com/health/09...evolution.html

A good read. It's interesting that we are still learning about our bodies in this day and age.