Social structure of primate interaction networks facilitates the emergence of cooperation

Abstract

Animal cooperation has puzzled biologists for a long time as its existence seems to contravene the basic notion of evolutionary biology that natural selection favours 'selfish' genes that promote only their own well-being. Evolutionary game theory has shown that cooperators can prosper in populations of selfish individuals if they occur in clusters, interacting more frequently with each other than with the selfish. Here we show that social networks of primates possess the necessary social structure to promote the emergence of cooperation. By simulating evolutionary dynamics of cooperative behaviour on interaction networks of 70 primate groups, we found that for most groups network reciprocity augmented the fixation probability for cooperation. The variation in the strength of this effect can be partly explained by the groups' community modularity-a network measure for the groups' heterogeneity. Thus, given selective update and partner choice mechanisms, network reciprocity has the potential to explain socially learned forms of cooperation in primate societies.

Conditional cooperation can hinder network reciprocity

“…In particular for the latter, theoretical models show positive effects on cooperation levels (17)(18)(19)(20)(21). Congruent with this theoretical work, evolutionary simulations based on social networks of nonhuman primates show that, for example, these natural networks have the appropriate static structure to potentially support cooperation (8). By using social network analysis, we can now investigate not only the effects on the evolution of cooperative behavior, but also the existing social network properties and their effects on the individual's behavior (22).…”

“…15). Homogenous networks are generally not found in nature; instead, natural social networks are usually heterogeneous networks (8,16). In particular for the latter, theoretical models show positive effects on cooperation levels (17)(18)(19)(20)(21).…”

“…In addition, in many other social species, interactions between individual behavior and population-level structure have been identified as important ecological factors (7,8). In general, the network structure poses a significant ecological factor for the evolution of cooperative behavior.…”

Evolution and maintenance of cooperation via inheritance of neighborhood relationship

“…Different from the traditional well-mixed population, individuals interact only with some neighbors in a structured population. In such a heterogeneous environment, cooperators could survive by forming cooperative clusters to resist the invasion and exploitation of defectors [27,28]. The above network effect is called network reciprocity.…”

Social dynamics, network structure, and information diffusion in fish shoals.

“…This occurred even in the presence of ties that connected otherwise "socially distant" individuals, thereby allowing clusters of cooperators to be more easily invaded by defectors. Turning to real-life networks, simulations using 70 nonhuman primate social networks found that primate social structure often-though not always-facilitated cooperation (Voelkl & Kasper, 2009). …”