## SuperCooperaters
It's easy to understand evolution as competition, so why does cooperation exist? Nowak wants to explain why, and his experiments take him from Vienna to Princeton to Harvard and from game theory to viruses to group selection.The best part was Nowak's explanation of what happened when he punched strategies for solving the prisoner's dilemma into computer models. At first, tit for tat (if you cooperate, I will too, but if you defect, I will too) is successful. But as the programs become more complex, the results become more interesting. As a general rule, selfish defectors get off to a hot start but are nearly always overcome by cooperative strategies. There are circumstances, however, in which cooperators become complacent and defectors manage to tear everything down. These models are metaphors for human interaction, so I reminded myself that Nowak was a theoretical modeller. Still, I found I couldn't look away from each game and who won.