Question

Why is the appendix non functional in humans?

Answer 1

No that fact is wrong!
New studies says that Appendix is functional in humans. The purpose of appendix is to provide immunity to the body.
This was observed when the persons who had their appendix removed were found to have less immunity than those who didn't remove their appendix.
After the long, slow and continuous process of evolution humans have developed other organs for immunity and their WBC has developed antibodies (transferred from parent to a child), and so the appendix is has become less functional but not disfunctional.

Answer 2

Answer:

Some studies suggest that as ancient humans were predominantly herbivorous, they used their appendixes for digestion. However, as humans evolved, they started to include more easily digestible food in their diet and the appendix eventually lost it function.