What is the point of an appendix?

Question

Why do we have an appendix? I've met one person who actually had their appendix removed but anyways, why do we have an appendix?

Answer 1

The appendix is the remnant of a part of the cecum that probably helped our ancestors digest cellulose (plant material).  

In the other animals, the appendix is much larger and exists as a pouch off the main intestinal tract.  The appendix in these other animals allows cellulose to be trapped and subjected to prolonged digestion.

Answer 2

Loren G. Martin, a professor of physiology at Oklahoma State University, argues that the appendix has a function in fetuses and adults. Endocrine cells have been found in the appendix of 11 week old fetuses that contribute to "biological control (homeostatic) mechanisms." In adults, Martin argues that the appendix acts as a lymphatic organ. The appendix is experimentally verified as being rich in infection-fighting lymphoid cells, suggesting that it might play a role in the immune system. Zahid suggests that it plays a role in both manufacturing hormones in fetal development as well as functioning to 'train' the immune system, exposing the body to antigens in order that it can produce antibodies. He notes that doctors in the last decade have stopped removing the appendix during other surgical procedures as a routine precaution, because it can be successfully transplanted into the urinary tract to rebuild a sphincter muscle and reconstruct a functional bladder.

The most common explanation is that the appendix is a vestigial structure with no absolute purpose.

One potential ancestral purpose put forth by Darwin[3] was that the appendix was used for digesting leaves as primates. Over time, we have eaten fewer vegetables and have evolved, over millions of years, for this organ to be smaller to make room for our stomach. It may be a vestigial organ of ancient man that has degraded down to nearly nothing over the course of evolution. Evidence can be seen in herbivorous animals such as the Koala. The cecum of the koala is attached to the juncture of the small and large intestines and is very long, enabling it to host bacteria specific for cellulose breakdown. Early man’s ancestor must have also relied upon this system and lived on a diet rich in foliage.

Answer 3

It is an evolutionary leftover.  Oddly enough, it is difficult to evolve it away altogether because if it got any narrower, it would get blocked off and dangerously inflamed more often.

There is evidence that it is now evolving some function in the immune system.  It is not uncommon for something evolved for one purpose to end up being used for another; for example the bones in your inner ear, which are descended from the compound jawbones of the common ancestors of mammals and reptiles.

Answer 4

Well there was a belief that it was once a second stomach for us, and that as we evolved it became useless.

Answer 5

We have no reason for an appendix. however in animals like dears they are used to digest foods with heavy cell walls like oats, Humans due to their diet have lost the function of theirs.