The edge of neutral evolution in social dilemmas

TL;DR

This paper explores how fluctuations and neutral evolution influence cooperation and defection in social dilemmas, revealing an 'edge of neutral evolution' that affects the persistence of cooperation.

Contribution

It introduces a method to distinguish regimes of neutral and Darwinian evolution in social dilemmas using mean extinction times, highlighting the role of fluctuations.

Findings

Neutral regimes significantly maintain cooperation.

Classical evolutionary game theory predictions hold in Darwinian regimes.

Fluctuations can partly resolve social dilemmas.

Abstract

The functioning of animal as well as human societies fundamentally relies on cooperation. Yet, defection is often favorable for the selfish individual, and social dilemmas arise. Selection by individuals' fitness, usually the basic driving force of evolution, quickly eliminates cooperators. However, evolution is also governed by fluctuations that can be of greater importance than fitness differences, and can render evolution effectively neutral. Here, we investigate the effects of selection versus fluctuations in social dilemmas. By studying the mean extinction times of cooperators and defectors, a variable sensitive to fluctuations, we are able to identify and quantify an emerging 'edge of neutral evolution' that delineates regimes of neutral and Darwinian evolution. Our results reveal that cooperation is significantly maintained in the neutral regimes. In contrast, the classical predictions of evolutionary game theory, where defectors beat cooperators, are recovered in the Darwinian regimes. Our studies demonstrate that fluctuations can provide a surprisingly simple way to partly resolve social dilemmas. Our methods are generally applicable to estimate the role of random drift in evolutionary dynamics.