Humans are not cooperative breeders but practice biocultural reproduction

Context: Alloparental care and feeding of young is often called "cooperative breeding" and humans are increasingly described as being a cooperative breeding species. Objective: To critically evaluate whether the human offspring care system is best grouped with that of other cooperative breeders. Methods: (1) Review of the human system of offspring care in the light of definitions of cooperative, communal and social breeding; (2) re-analysis of human lifetime reproductive effort. Results: Human reproduction and offspring care are distinct from other species because alloparental behaviour is defined culturally rather than by genetic kinship alone. This system allows local flexibility in provisioning strategies and ensures that care and resources often flow between unrelated individuals. This review proposes the term "biocultural reproduction" to describe this unique human reproductive system. In a re-analysis of human life history data, it is estimated that the intense alloparenting typical of human societies lowers the lifetime reproductive effort of individual women by 14-29% compared to expectations based upon other mammals. Conclusion: Humans are not cooperative breeders as classically defined; one effect of the unique strategy of human biocultural reproduction is a lowering of human lifetime reproductive effort, which could help explain lifespan extension.