Diversity, Specialization & Cooperation: Evolutionary Foundations from Ecosystems to Societies

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Diversity is ubiquitous in nature and comes in all shapes and sizes. Here we explore how diversity begets diversity in evolutionary processes. Based on evolutionary game theory (EGT) we study the relation between diverse interactions and the emergence and maintenance of diversity in terms of co-existence, specialization or social organization. 1. Diversity, Cooperation & Social Stratification Natural environments pose various challenges to individuals in the form of multiple, concurrent interactions. For example, microbes and humans alike engage in a variety of public goods interactions either through extra-cellular products or dwindling global resources. We extend traditional EGT to multiple interactions in order to determine the scaling of polymorphisms with the number (and types) of interactions as well as to delineate conditions under which specialization in particular tasks yields greater stability. However, for stochastic dynamics in finite populations of variable size, trait diversity is invariably lost, unless maintained by additional sources of variation, such as mutation or migration. This requires developing stochastic eco-evolutionary game theory and criteria to characterize evolutionary success and diversity based on transient configurations, in order to investigate the roots of social diversification. 2. Asymmetric Interactions & Structured Populations In nature, resources available to individuals typically vary based on environmental differences, phenotypic variation, or surpluses accumulated in the past, etc. Here we extend EGT to study effects of asymmetric interactions on the evolutionary success and diversity of behavioural traits. Of particular interest is evolved social behaviour that offsets resource inequalities to achieve fair and egalitarian outcomes, or, conversely, turns egalitarian configurations into unequal resource distributions, and hence causing asymmetric interactions. This reveals conditions for another approach to social diversification and stratification. Social networks are dynamical population structures that capture fleeting interaction patterns, which define societies. Following the principle form follows function we employ a novel framework based on actions, including cooperation, reward and punishment, to explore the evolutionary origins of social organization and formation of complex societies. 3. Behavioural Experiments & Empirical Analyses As an inspiring complement, we study concurrent interactions in human behavioural experiments and test whether participants succeed in coordinating their behaviour and specialize in different tasks to achieve more efficient outcomes - an essential aspect of division of labour as well as social stratification. In large-scale Internet experiments and using empirical data, we investigate social learning and the dynamics of social networks.