Keywords: Game theory Evolutionary dynamics

Extra-tag cooperation Prisoner’s dilemma Tag-based cooperation acti of the major transitions of evolution. Yet, as illustrated by the Prisoner’s dilemma, cooperative systems are fragile because cooperators can be exploited by defectors who reap the benefits of cooperation but do not reciprocate. This barrier to cooperation may be overcome if cooperators have a recognisable games in general, players in the Prisoner’s dilemma either cooperate ive a hen s the rator, for a of whether their co-player cooperates (T4R) or defects (P4S). Thus, Contents lists available at ScienceDirec