How exploitation launched human cooperation

Cooperation plays a crucial role in primate social life. However, the evolution of large-scale human cooperation from the cognitive fundamentals found in other primates remains an evolutionary puzzle. Most theoretical work focuses on positive reciprocity (helping) or coordinated punishment by assuming well-defined social roles or institutions (e.g., punishment pools), sophisticated cognitive abilities for navigating these, and sufficiently harmonious communities to allow for mutual aid. Here we explore the evolutionary and developmental origins of these assumed preconditions by showing how negative indirect reciprocity (NIR)-tolerated exploitation of those with bad reputations-can suppress misbehavior to foster harmonious communities, favor the cognitive abilities often assumed by other models, and support costly adherence to norms (including contributing to public goods). With minimal cognitive prerequisites, NIR sustains cooperation when exploitation is inefficient (victims suffer greatly; exploiters gain little), which is more plausible earlier in human evolutionary history than the efficient helping found in many models. Moreover, as auxiliary opportunities to improve one's reputation become more frequent, the communal benefits provided in equilibrium grow, although NIR becomes harder to maintain. This analysis suggests that NIR could have fostered prosociality across a broader spectrum of primate societies and set the stage for the evolution of more complex forms of positive cooperation. Significance statement The evolutionary origins of human cooperation and prosociality remain an evolutionary puzzle. Theoretical models exploring the dynamics which shaped our ancestors' interactions stimulate empirical investigations by anthropologists, primatologists, psychologists, archeologists and others, whose results in turn refine and direct theoretical inquiry. Common experience has focused this scholarly synergy on positive cooperation (cooperating by helping) and largely neglected the distinct and important challenge of negative cooperation (cooperating by not exploiting). Our contribution puts negative cooperation back in the spotlight. We outline what makes negative cooperation, especially negative indirect reciprocity, different and potentially more potent than positive cooperation, and present a simple model of how it emerges, shapes interactions, and can form a dynamic foundation that catalyzes more sophisticated forms of cooperation.