The penguin vs. the leviathan -- Nature vs. culture : the evolution of human cooperation -- Stubborn children, New York city doormen, and why obesity is contagious : psychological and social influences on cooperation -- I/you, us/them : empathy and group identity in human cooperation -- Why don't we sit down and talk about it? -- Equal halves : fairness in cooperation -- What's right is right or at least normal : morals and norms in cooperation -- For love or money : rewards, punishments, and motivation -- The business of cooperation -- How to raise a penguin.