The evolutionary and psychological origins of reciprocal cooperation

If only those behaviours evolve that increase the actor’s own survival and reproductive success, then it might come as a surprise that cooperative behaviours, i.e. providing benefits to others, are a widespread phenomenon. Many animals cooperate even with unrelated individuals in various contexts, like providing care or food. One possibility to explain these behaviours is reciprocity. Reciprocal cooperation, i.e. helping those that were helpful before, is a ubiquitous and important trait of human sociality. Still, the evolutionary origin of it is largely unclear, mainly because it is believed that other animals do not exchange help reciprocally. Consequently, reciprocity is suggested to have evolved in the human lineage only. In contrast to this, I propose that reciprocity is not necessarily cognitively demanding and likely to be widespread. In my talk, I will first shed light on the mechanisms of reciprocal cooperation in Norway rats (Rattus norvegicus). In a series of studies, my colleagues and I have demonstrated that Norway rats reciprocally exchange goods and services between and within different commodities and independent of kinship. Furthermore, to understand the evolutionary origins of human reciprocity, and whether it is shared with other animals, I will then discuss evidence for reciprocity in non-human primates, which are our closest living relatives. A thorough analysis of the findings showed that reciprocity is present and, for example, not confined to unrelated individuals, but that the choice of commodities can impact the likelihood of reciprocation. Based on my findings, I conclude that reciprocal cooperation in non-human animals is present but largely neglected and not restricted to humans. In order to deepen our understanding of the evolutionary origins of reciprocity in more general, future studies should investigate when and how reciprocity in non-human animals emerged and how it is maintained.