This week we’ve looked at body parts considered useless evolutionary leftovers. And I’ve saved the classic example for last—the appendix.

You know, Darwin believed this organ was a useless leftover and so many doctors would just cut it out and throw it away without much thought. But, eventually, researchers decided to actually study it. And, not surprising to those who reject evolution, it has a function!

The appendix is a “safe house” for good gut bacteria when bad bacteria temporarily out-compete them. Although we can live without it, the appendix is an important part of our immune system—not an evolutionary leftover.