Reducing global inequality increases local cooperation: a simple model of group selection with a global externality

Abstract

Group-structured models often explain the evolution of prosocial activities in terms of selection acting at both individual and group levels. Such models do not typically consider how individuals' behaviours may have consequences beyond the boundaries of their groups. However, many behaviours affect global environmental variables, including climate change and ecosystem fragility. Against this background, we propose a simple model of multi-level selection in the presence of global externalities. In our model, group members can cooperate in a social dilemma with the potential for group-level benefits. The actions of cooperators also have global consequences, which can be positive (a global good) or negative (a global bad). We use simulations to consider scenarios in which the effects of the global externality either are evenly distributed, or have stronger influences on either the rich or the poor. We find that the global externality promotes the evolution of cooperation only if it either disproportionately benefits the poor or disproportionately reduces the payoffs of the rich. If the global externality primarily harms the poor, it undermines the evolution of prosocial behaviour. Understanding this effect is important given concerns that poorer households are more vulnerable to climate change impacts. This article is part of the theme issue ‘Evolution and sustainability: gathering the strands for an Anthropocene synthesis’.

Long-distance social relationships can both undercut and promote local natural resource management

“…Polycentric institutions offer one potential solution to the costs imposed by long-distance relationships and are especially important to successful management of global commons in the Anthropocene, which will require institutions of different scope and scale working together [13,17]. Given the ease with which long-distance relationships can be formed and maintained via online social networks and other technologies, long-distance relationships may offer a powerful tool for building these polycentric systems [11,31]-even more so given the diversity of identities and group allegiances on which 'community' can be built when large CPRs are located in cities or are transnational [11].…”

“…However, this local turn also promotes a tendency to ignore connections between resources and between the people who use them [12], connections which are only becoming more common in the Anthropocene. When community-based cooperation fails, it creates externalities that can undermine multi-level collective action with global-scale implications [3,[13][14][15].…”

Characteristic processes of human evolution caused the Anthropocene and may obstruct its global solutions

“…The population structure problem should be formally tested. New models could build on multilevel selection models with environmental resource constraints [24,131], ETI models with environmental patchiness [102,116] and cultural adaptation models with population size constraints [21,132]. These can enable new questions to be tested.…”