Laughter to begin with was probably glee at the misfortunes of others. The baring of the teeth in laughter hints at its savage ancestry. Animals have no malice, hence also no laughter. They never savor the sudden glory of Schadenfreude. It was its infectious quality that made of laughter a medium of mutuality.
Between the Devil and the Dragon: The Best Essays and Aphorisms of Eric Hoffer (ed. HarperCollins Publishers, 1982)