Evolution of cooperation: combining kin selection and reciprocal altruism into matrix games with social dilemmas.

Som B Ale,Joel S Brown,Amy T Sullivan,Attila Szolnoki

doi:10.1371/journal.pone.0063761

Abstract

Darwinian selection should preclude cooperation from evolving; yet cooperation is widespread among organisms. We show how kin selection and reciprocal altruism can promote cooperation in diverse 2×2 matrix games (prisoner’s dilemma, snowdrift, and hawk-dove). We visualize kin selection as non-random interactions with like-strategies interacting more than by chance. Reciprocal altruism emerges from iterated games where players have some likelihood of knowing the identity of other players. This perspective allows us to combine kin selection and reciprocal altruism into a general matrix game model. Both mechanisms operating together should influence the evolution of cooperation. In the absence of kin selection, reciprocal altruism may be an evolutionarily stable strategy but is unable to invade a population of non-co-operators. Similarly, it may take a high degree of relatedness to permit cooperation to supplant non-cooperation. Together, a little bit of reciprocal altruism can, however, greatly reduce the threshold at which kin selection promotes cooperation, and vice-versa. To properly frame applications and tests of cooperation, empiricists should consider kin selection and reciprocal altruism together rather than as alternatives, and they should be applied to a broader class of social dilemmas than just the prisoner’s dilemma.

Highlights

Darwinian selection precludes any action that increases the competitive ability of others at the expense of one’s self [1]
Prisoner’s Dilemma In the prisoner’s dilemma game, after many rounds of interactions, a portion r occurs with like-individuals while the portion 1-r occurs with randomly selected individuals, with the following outcomes (Table 2): Always-cooperate (All-C) strategy is the evolutionarily stable strategy (ESS) only when C played against C yields a higher payoff than D played against C, r(b2c)+(12r)(b2c).r(0)+(12r)(b)
Our model shows various ‘‘doses’’ of reciprocity and kin selection together can generate cooperation as the sole ESS, both cooperation and defection as local ESSs, cooperation and defection as mixed strategy ESS, and defection as the sole ESS

Summary

Introduction

Darwinian selection precludes any action that increases the competitive ability of others at the expense of one’s self [1]. Kinship fosters cooperation and common agendas help unrelated individuals to work together within and between species. The three standard motives for the evolution of cooperation include kin selection, reciprocity, and group selection [11,12,13,14,15]. Hamilton [16] formalized the idea of kinship in promoting the evolution of altruism. Supposing a cost to the altruist (c), a benefit to the recipient (b), and their genetic relatedness (r), Hamilton [16] showed that natural selection favours altruism among relatives when r.c/b. Sterile worker ants can accrue reproductive benefits by helping their relative, the queen. In so doing, their shared genes survive and get passed on to the generation

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