Why do humans have an appendix even though it is unnecessary?

 Why do humans have an appendix even though it is unnecessary?

The human cecal appendix is not completely unnecessary. 

In humans, the appendix is a small, dead-end tube that connects to the colon near where the small intestines feeds into the large intestines. 

Being a dead-end tube, the appendix can obviously not transport food and waste through the intestinal tract. 

Furthermore, many people have had their appendix removed and yet seem to suffer no symptoms at all from having no appendix. 

This fact may seem to indicate that the appendix is useless; an abandoned evolutionary relict of some ancient predecessor. But the appendix turns out to not be completely useless.