What is humor? Why do we laugh? And why is the root of a good joke almost always error? Good jokes, bad jokes, clever jokes, dad jokes--the desire to laugh is universal. But why do we find some gags hilarious, whilst others fall flat? Why does explaining a joke make it less amusing rather than more so? Why is laughter contagious, and why did it evolve in the first place? Using the oldest jokes and the latest science,...