Your appendix is not useless — it stores good bacteria

The appendix was long dismissed as a vestigial organ, but research published in 2007 suggests it acts as a 'safe house' for beneficial gut bacteria. After severe gut infections like cholera that flush out the intestinal microbiome, bacteria sheltered in the appendix repopulate the gut. People without an appendix take longer to recover from such infections — evidence that the organ has a genuine immune function.

Source: Randal Bollinger, R. et al., 'Biofilms in the large bowel suggest an apparent function of the human vermiform appendix', Journal of Theoretical Biology (2007)