Evolution experiments with social microbes allow us to watch the evolution of cooperation and conflict in real time. The social bacterium Myxococcus xanthus engages in cooperative motility, predation and fruiting body formation. With brief forays into data from natural M. xanthus populations and lab populations that evolved novel forms of social motility, I will primarily tell the story of how one laboratory lineage of M. xanthus evolved from being a cooperator in fruiting body development to a cheater and back again to a competitively dominant cooperator. This series of evolutionary changes illustrate how bacteria can allow us to not only directly observe qualitative evolutionary transitions in social strategies, but also uncover the mutational and mechanistic bases of such heritable social change.