title: Why mutual helping in most natural systems is neither conflict-free nor based on maximal conflict.
abstract: Mutual helping for direct benefits can be explained by various game theoretical models, which differ mainly in terms of the underlying conflict of interest between two partners. Conflict is minimal if helping is self-serving and the partner benefits as a by-product. In contrast, conflict is maximal if partners are in a prisoner's dilemma with both having the pay-off-dominant option of not returning the other's investment. Here, we provide evolutionary and ecological arguments for why these two extremes are often unstable under natural conditions and propose that interactions with intermediate levels of conflict are frequent evolutionary endpoints. We argue that by-product helping is prone to becoming an asymmetric investment game since even small variation in by-product benefits will lead to the evolution of partner choice, leading to investments by the chosen class. Second, iterated prisoner's dilemmas tend to take place in stable social groups where the fitness of partners is interdependent, with the effect that a certain level of helping is self-serving. In sum, intermediate levels of mutual helping are expected in nature, while efficient partner monitoring may allow reaching higher levels.
authors.affiliation: Institute of Biology, University of Neuchâtel, Emile-Argand 11, Neuchâtel 2000, Switzerland redouan.bshary@unine.ch.
authors.forename: Redouan
authors.initials: R
authors.lastname: Bshary
authors.affiliation: Institute of Biology, University of Neuchâtel, Emile-Argand 11, Neuchâtel 2000, Switzerland.
authors.forename: Klaus
authors.initials: K
authors.lastname: Zuberbühler
authors.affiliation: Anthropological Institute and Museum, University of Zürich, Winterthurerstrasse 190, Zürich 8057, Switzerland.
authors.forename: Carel P
authors.initials: CP
authors.lastname: van Schaik
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D005075:Biological Evolution; D003220:Conflict, Psychological; D003299:Cooperative Behavior; D017753:Ecosystem; D005260:Female; D005716:Game Theory; D006379:Helping Behavior; D008297:Male; D008954:Models, Biological; D000068956:Prisoner Dilemma
keywords: biological market; by-product mutualism; cooperation; mutualism; prisoner's dilemma; pseudo-reciprocity