Background. While the evolution of reciprocal cooperation has attracted an enormous attention, the proximate mechanisms underlying the ability of animals to cooperate reciprocally are comparatively neglected. Symmetry-based reciprocity is a hypothetical proximate mechanism that has been suggested to be widespread among cognitively unsophisticated animals. Methods. We developed two agent based models of symmetrybased reciprocity (one relying on an arbitrary tag and the other on interindividual

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... oximity) and tested their ability both to reproduce significant emergent features of cooperation in group living animals and to promote the evolution of cooperation. Results. Populations formed by agents adopting symmetry-based reciprocity showed differentiated "social relationships" and a positive correlation between cooperation given and received, two common aspects of animal cooperation. However, when reproduction and selection across multiple generations were added to the models, agents adopting symmetry-based reciprocity were outcompeted by selfish agents that never cooperated. Discussion. In order to evolve, hypothetical proximate mechanisms must be able to stand competition from alternative strategies. While the results of our simulations require confirmation using analytical methods, we provisionally suggest symmetry-based reciprocity is to be abandoned as a possible proximate mechanism underlying the ability of animals to reciprocate cooperative interactions. PeerJ reviewing PDF | (Manuscript to be reviewed 21 ABSTRACT 22 Background. While the evolution of reciprocal cooperation has attracted an enormous attention, 23 the proximate mechanisms underlying the ability of animals to cooperate reciprocally are 24 comparatively neglected. Symmetry-based reciprocity is a hypothetical proximate mechanism 25 that has been suggested to be widespread among cognitively unsophisticated animals. 26 Methods. We developed two agent based models of symmetry-based reciprocity (one relying on 27 an arbitrary tag and the other on interindividual proximity) and tested their ability both to 28 reproduce significant emergent features of cooperation in group living animals and to promote 29 the evolution of cooperation. 30 Results. Populations formed by agents adopting symmetry-based reciprocity showed 31 differentiated "social relationships" and a positive correlation between cooperation given and 32 received, two common aspects of animal cooperation. However, when reproduction and selection 33 across multiple generations were added to the models, agents adopting symmetry-based 34 reciprocity were outcompeted by selfish agents that never cooperated. 35 Discussion. In order to evolve, hypothetical proximate mechanisms must be able to stand 36 competition from alternative strategies. While the results of our simulations require confirmation 37 using analytical methods, we provisionally suggest symmetry-based reciprocity is to be 38 abandoned as a possible proximate mechanism underlying the ability of animals to reciprocate 39 cooperative interactions. 40 PeerJ reviewing PDF | (