Abstract

One curious phenomenon of several social groups is that they are ‘redundant’ in the sense that they contain more cooperators than strictly needed to complete certain group tasks, such as foraging. Redundancy is puzzling because redundant groups are particularly susceptible to invasion by defectors. Yet, redundancy can be found in groups formed by a wide range of organisms, including insects and microbes. Birch ([2012]) has recently argued that coercive behaviours might account for redundancy using insect colonies as a case study. However, microbial examples suggest redundancy can evolve without coercive behaviours. This paper formulates an explanation for redundancy that does not require targeted punishment of defectors; instead, it proposes that redundancy might be due to ignorance. Specifically, it is suggested that redundancy evolves as a by-product of selection when group members have to opt whether to cooperate or not while being blind to the strategies of others. Accordingly, possessing information about the strategies of the group members might undermine rather than facilitate cooperation within groups.