Biology & Philosophy

, Volume 26, Issue 4, pp 517-531

First online:

Efficient social contracts and group selection

  • Simon M. HutteggerAffiliated withDepartment of Logic and Philosophy of Science, University of California, Irvine
  • , Rory SmeadAffiliated withDepartment of Philosophy and Religion, Northeastern University Email author 

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We consider the Stag Hunt in terms of Maynard Smith’s famous Haystack model. In the Stag Hunt, contrary to the Prisoner’s Dilemma, there is a cooperative equilibrium besides the equilibrium where every player defects. This implies that in the Haystack model, where a population is partitioned into groups, groups playing the cooperative equilibrium tend to grow faster than those at the non-cooperative equilibrium. We determine under what conditions this leads to the takeover of the population by cooperators. Moreover, we compare our results to the case of an unstructured population and to the case of the Prisoner’s Dilemma. Finally, we point to some implications our findings have for three distinct ideas: Ken Binmore’s group selection argument in favor of the evolution of efficient social contracts, Sewall Wright’s Shifting Balance theory, and the equilibrium selection problem of game theory.


Cooperation Equilibrium selection Group selection Haystack model Prisoner’s Dilemma Shifting balance Stag Hunt