Evolutionary Dynamics Within and Among Competing Groups

TL;DR

This paper extends evolutionary game theory to multilevel systems, analyzing how within- and among-group mechanisms influence cooperation and competition, with implications for biological evolution and social resource management.

Contribution

It develops a multilevel evolutionary framework using nested processes and PDEs, revealing how different population structures affect cooperation and competition outcomes.

Findings

Population structures promoting cooperation differ between single and multiple scales.

Among-group selection can produce second-best solutions balancing individual and collective incentives.

Multiscale models apply broadly, from microbial metabolite production to resource management.

Abstract

Biological and social systems are structured at multiple scales, and the incentives of individuals who interact in a group may diverge from the collective incentive of the group as a whole. Mechanisms to resolve this tension are responsible for profound transitions in evolutionary history, including the origin of cellular life, multi-cellular life, and even societies. Here we synthesize a growing literature that extends evolutionary game theory to describe multilevel evolutionary dynamics, using nested birth-death processes and partial differential equations to model natural selection acting on competition within and among groups of individuals. We apply this theory to analyze how mechanisms known to promote cooperation within a single group -- including assortment, reciprocity, and population structure -- alter evolutionary outcomes in the presence of competition among groups. We find that population structures most conducive to cooperation in multi-scale systems may differ from those most conducive within a single group. Likewise, for competitive interactions with a continuous range of strategies we find that among-group selection may fail to produce socially optimal outcomes, but it can nonetheless produce second-best solutions that balance individual incentives to defect with the collective incentives for cooperation. We conclude by describing the broad applicability of multi-scale evolutionary models to problems ranging from the production of diffusible metabolites in microbes to the management of common-pool resources in human societies.