Human violence reaches way back into our evolutionary past and is usually about the same things that are important to chimps: resources, territory, and sexual access to females. Humans are exquisitely attuned to dominance. Body language and facial expressions underlie a host of social interactions and are very effective at communicating important information about a person, particularly social rank. By assessing “competency,” people can predict, with almost 70 percent accuracy, winners of U. S. Senate races based on a one-second glimpse of the candidates’ faces. People can accurately assess dominant and submissive traits in others by seeing photographs of them for only 4/100ths of a second, so-called thin-slice judgments.