The significance of reciprocal cooperation to the functioning and stability of human societies has been recognised in many academic disciplines. Reciprocity is a widespread practice in our species (Bowles et al., 1997). It forms the basis for economic transaction and trade (Frank et al., 2018). As an ethical imperative, it is central to many world religions (Neusner & Chilton, 2008). Reciprocity is also a trait that emerges early in our ontogeny, as children at the age of 3 years reliably reciprocate (Warneken & Tomasello, 2013), suggesting evolutionary conservation (Warneken & Tomasello, 2009). Further, it has been described in human foragers (Jaeggi & Gurven, 2013), whose socio-ecology is probably closest to the conditions of early humans (Tooby & Cosmides, 2015). Even though reciprocity seems ubiquitous and significant in our species, its proximate mechanisms and ultimate causes are still not well understood. The purpose of this special issue is to explore the principle of reciprocity in a diverse way by employing theoretical and empirical research as well as presenting observational and experimental evidence while featuring a multitude of species from invertebrates to humans.

Schweinfurth, M.K. (2024) Interdisciplinary perspectives on the principle of reciprocation. Ethology 130: 13445.