Biological anthropologist Chris Boehm at the University of Southern California studies the human revolutionary impulse and has been struck in particular by how it plays to a unique tension in the psychology of our species. On the one hand, humans are extremely hierarchical primates, readily picking leaders and assenting to their authority for the larger good of the community. On the other hand, our hunter-gatherer ancestors were a very egalitarian bunch, doing best when the group operated collectively, with dominance asserted only subtly. When one individual — usually a male — began to overreach, he was dealt with swiftly. That impulse — to challenge the bully and take him down — is one that stays with us today, and that we practice with great relish.

“The revolutionary urge is the universal reaction to power being exerted over us in an illegitimate way,” says Jonathan Haidt, a moral psychologist at the University of Virginia, whose own work parallels Boehm’s. “It’s absolutely thrilling and intoxicating to people.” How thrilling and intoxicating? “Put it this way,” says Haidt, “the flag of my state is an image of a woman warrior with a bared breast and her foot on a dead man, who represents tyranny. The state emblem is a murder.”

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