Unselfish behaviour spreads through society in a way that most benefits the hubs in the network
Once cooperators occupy a hub and some surrounding nodes, the hub gains a large payoff and is likely to disseminate its offspring (i.e., cooperators) to the neighbors. This event further increases the payoff of the hub, and the cooperation on the hub is stabilized. In contrast, defection on a hub is not stable because the hub does not gain a large payoff if the defector hub disseminates its offspring to the neighbors. Cooperators are propagated from hubs to the entire network.