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.

They also protect the important organs inside you ... Most of us have the same kind of body parts in the same places. You have a head and a neck. You have arms, elbows, hands and fingers.

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.