None! The appendix is an organ designed to break down cellulose (look away now Creationalists - I'm about to use some facts) i.e. it would originally they were more dependant on a vegetable based diet. Since human beings are omnivorous (eat both meat and veg) the dependency on extracting quite so much nutrition from one source lessened and in humans the organ attrophied. In rabbits for instance, it is an essential part of the digestive process. That why they can remove it if they get inflamed.