The appendix is not a useless organ
by Mark Frauenfelder from on (#4SRGW)
The appendix has evolved in different animal species at least 29 times, according to this SciShow video, which means it probably serves a function. Scientists who studied appendixes in animals have come to the conclusion that it is a part of the immune system. In humans, the appendix is full of immune cells, including T cells, B cells, and natural killer cells, and good gut bacteria.