The evolutionary origin of human hyper-cooperation.

Area of Science:

• Evolutionary Anthropology
• Primatology
• Behavioral Ecology

Background:

• Proactive prosociality is fundamental to human hyper-cooperation, enabling complex cognition, morality, and cumulative culture.
• The evolutionary origins of human prosociality are poorly understood due to inconsistent primate testing methods.
• Existing data lack standardization for rigorous testing of functional hypotheses regarding prosociality.

Purpose of the Study:

• To investigate the evolutionary underpinnings of proactive prosociality across primate species.
• To identify key factors predicting interspecific variation in unsolicited prosocial behaviors.
• To test the hypothesis that cooperative breeding influences the evolution of prosocial motivations.

Main Methods:

• Conducted standardized prosociality experiments across 24 groups of 15 different primate species, including humans.
• Collected data on proactive prosocial behaviors using a consistent experimental paradigm.
• Analyzed interspecific variation in prosociality and correlated it with ecological and social factors, particularly cooperative breeding and allomaternal care.

Main Results:

• Extensive allomaternal care emerged as the strongest predictor of interspecific variation in proactive prosociality.
• Proactive prosocial motivations were found to systematically increase in species where selection favors cooperative breeding.
• Human prosociality data align with the general primate pattern, supporting a shared evolutionary trajectory.

Conclusions:

• The evolution of cooperative breeding provides a parsimonious explanation for the emergence of proactive prosociality and hyper-cooperation in humans.
• Allomaternal care is a critical factor driving the development of prosocial motivations across primate lineages.
• Understanding cooperative breeding offers key insights into the evolutionary foundations of uniquely human social behaviors.