system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What was the appendix used for before it became obsolete?
gpt
The current best theory is that it isn't entirely obsolete. It functions as a place where various microorganisms that live in your gut can survive even if you have diarrhea, or if you eat something that has antibiotic properties. Those microorganisms can be pretty important to proper digestion and good health (you don't want to have just any old random bunch living inside you), so having an internal refuge for them is useful.