Corruption Drives the Emergence of Civil Society

Peer punishment of free-riders (defectors) is a key mechanism for promoting cooperation in society [1, 2, 3, 4, 5]. However, it is highly unstable since some cooperators may contribute to a common project but refuse to punish defectors. Centralized sanctioning institutions (for example, tax-funded police and crimi-nal courts) can solve this problem by punishing both defectors and cooperators who refuse to punish. These institutions have been shown to emerge naturally through social learning and then displace all other forms of punishment, includ-ing peer punishment [6, 7]. However, this result provokes a number of questions. If centralized sanctioning is so successful, then why do many highly authoritar-ian states suffer from low levels of cooperation? Why do states with high levels of public good provision tend to rely more on citizen-driven peer punishment? And what happens if centralized institutions can be circumvented by individual acts of bribery? Here, we consider how corruption influences the evolution of cooperation and punishment. Our model shows that the effectiveness of central-ized punishment in promoting cooperation breaks down when some actors in th