Summary

The past decade has seen a marked convergence between evolutionary models of animal contests and the analysis of interstate war, or ‘militarised interstate disputes’ (MID). Since James Fearon's landmark paper in 1995 on war as a bargaining problem, the literature on ‘rationalist’ approaches to modelling war has burgeoned and become increasingly sophisticated. It has moved from a ‘Costly Lottery’ approach (in which the decision to cease bargaining and fight is a game-ending move with a costly, probabilistic outcome) to a ‘Costly Process’ approach, in which states continue to accumulate information on relative strength and motivation while fighting, and use this to inform their strategic decisions about whether to continue fighting or revert to bargaining. The Costly Process approach has much in common with the evolutionary analysis of animal conflict, and may stand to gain from incorporating some of its theoretical insights and approaches. The actors in evolutionary models are in a very similar strategic situation to those of rationalist models: they are unitary actors with imperfect information who have a range of behavioural options to facilitate mutual assessment and may have incentives to resolve conflicts short of lethal combat. The concept of rational utility maximisation is analogous to the assumption that, over evolutionary time, natural selection has honed behaviour such that it represents a game-theoretic equilibrium. Most importantly, the expectation that signallers will misrepresent their capabilities and intentions means that costly, inefficient actions will usually be required to stabilise the reliability of the signalling system. We discuss two key evolutionary models of conflict, comparing them with recent Costly Process models of war and suggesting how they could stimulate new theoretical and empirical research.