For over 25 years, primatologists have speculated that intelligence, at least in monkeys and apes, evolved as an adaptation to the complicated social milieu of hard-won friendships and bitterly contested rivalries. Yet the Balkanization of animal research has prevented us from studying the same problem in other large-brained, long-lived animals, such as hyenas and elephants, bats and sperm whales. Social complexity turns out to be widespread indeed...