In his book Grooming, Gossip and the Evolution of Language, biologist Robin Dunbar (1997) proposes a new way of looking at the evolution of language. According to this view, language evolved to provide a new social bonding mechanism: Gossiping. This allows humans to live in larger groups than other primates, which increasing predation risks forced our ancestors to do. We use a computational multi-agent model to test the internal workings of this hypothesis, with interesting results. Our work provides a fundamentally new kind of evidence for Dunbars theory, by experimentally demonstrating that greater group sizes can stimulate the evolution of language as a tool for social cohesion.