The Bible's lex talionis – "Eye for eye, tooth for tooth, hand for hand, foot for foot" (Exodus 21:24-27) – has captured the human imagination for millennia.

Tyler Ryan learned the importance of taking care of your feet, and how an insert can change your life - or at least legs ...

Several other body parts used to be important for humans' survival, but they have since become useless. Some of them can be removed, and their absence does not lower people's quality of life.