On the basis of the presence of the appendix, what might you infer about dietary habits of our evolutionary antecedents? Solution The main function of the appendix is to hydrolyze cellulose and indigestible plant material but it is present in mammals that includes rodents and primates which are not eating cellulose as food souce but may be in past they used to eat that so still it is there, Although there is no main function of this organ and known as vestigial organ but there is some report that it having some role in immune system. Some herbivorous animals, such as rabbits, have a terminal vermiform appendix..