Humans are an ultrasocial species. This sociality, however, cannot be fully explained by the canonical approaches found in evolutionary biology, psychology, or economics. Understanding our unique social psychology requires accounting not only for the breadth and intensity of human cooperation but also for the variation found across societies, over history, and among behavioral domains. Here, we introduce an expanded evolutionary approach that considers how genetic and cultural evolution, and their interaction, may have shaped both the reliably developing features of our minds and the well-documented differences in cultural psychologies around the globe. We review the major evolutionary mechanisms that have been proposed to explain human cooperation, including kinship, reciprocity, reputation, signaling, and punishment; we discuss key culture–gene coevolutionary hypotheses, such as those surrounding self-domestication and norm psychology; and we consider the role of religions and marriage systems. Empirically, we synthesize experimental and observational evidence from studies of children and adults from diverse societies with research among nonhuman primates.
From the Discussion
Understanding the origins and psychology of human cooperation is an exciting and rapidly developing enterprise. Those interested in engaging with this grand question should consider three elements of this endeavor: (1) theoretical frameworks, (2) diverse methods, and (3) history. To the first, the extended evolutionary framework we described comes with a rich body of theories and hypotheses as well as tools for developing new theories, about both human nature and cultural psychology. We encourage psychologists to take the formal theory seriously and learn to read the primary literature (McElreath & Boyd 2007). Second, the nature of human cooperation demands cross-cultural, comparative and developmental approaches that integrate experiments, observation, and ethnography. Haphazard cross-country cyber sampling is less efficient than systematic tests with populations based on theoretical predictions. Finally, the evidence makes it clear that as norms evolve over time, so does our psychology; historical differences can tell us a lot about contemporary psychological patterns. This means that researchers need to think about psychology from a historical perspective and begin to devise ways to bring history and psychology together (Muthukrishna et al. 2020).