"Telling me to relax or smile when I'm angry is like bringing a birthday cake into an ape sanctuary. You're just asking to get your nose and genitals bitten off."

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Though the man-apes often fought and wrestled one another, their disputes very seldom resulted in serious injuries. Having no claws or fighting canine teeth, and being well protected by hair, they could not inflict much harm on one another. In any event, they had little surplus energy for such unproductive behavior; snarling and threatening was a much more efficient way of asserting their points of view.

— Arthur C. Clarke