Final answer:
The human appendix is considered a vestigial organ, implying it was functional in ancestors but not in modern humans. While our ancestors may have consumed plants rich in cellulose, the appendix does not play a significant role in digestion today. Instead, its immunological functions and role as a bacterial reservoir are highlighted.
Step-by-step explanation:
The appendix is a vestigial organ that does not have a direct role in digestion. It is a projection from the cecum of the colon and its function is uncertain. However, it may play a role in immunity and in the fetus, it seems to have an endocrine function. Some biologists speculate that the appendix may also store a sample of the colon's normal bacteria, which can repopulate the colon if necessary.
While the appendix does not aid humans in digesting complex cellulose like our herbivorous ancestors, some grazing animals such as cows and buffalos have bacteria in their appendix that help break down cellulose. This gives the appendix an important role in their digestive systems. Humans, on the other hand, rely on different mechanisms to digest cellulose.