As you have probably heard, most of human history, civility was not the default setting. Societies were rougher, hierarchies more brutal, and interpersonal interactions often governed by blunt displays of power and overt physical aggression rather than kind or cordial exchanges. In medieval societies, for instance, everyday interactions were far less restrained by norms of politeness. Status determined how you were treated, and those with power often exercised it quite openly. Rudeness, intimida...