Up until very recently it was thought to have no use in humans – it was thought to be a ‘left over’ from evolution, where it’s original function was possibly to aid digestion of plant matter (leaves, grasses and other really fibrous things) when we were still monkeys living in trees.
More recently, research has suggested that it may serve as a ‘safe house’ of sorts for the friendly bacteria that live in your gut. When you have a gut problem, the good bacteria can be flushed out of your system leaving you exposed to infection by more harmful species. The idea is that the appendix keeps a small number of the friendly bacteria safe during the period of illness, which allows them to ‘re-populate’ the gut when the illness passes. This is still up for debate however, so don’t take it as hard fact!
Stuart – I didn’t know about the bacteria theory! I had thought the appendix had had some previous function and fell into disuse. That’s pretty interesting. I got mine taken out when I was 15 – so I’ve a cool scar, but no appendix!