It turns out that the appendix appears to have two related functions. The first function is supporting the immune system. The appendix has a high concentration of immune tissue, so it's acting to help the immune system fight any bad things in the gut.

The second function that it serves is what we refer to as the safe house. So this was a hypothesis that was put forward by a team from Duke University in 2007. And they argued that the appendix may serve as a safe reservoir for the beneficial gut bacteria that we have.