Examining the interplay of cooperation and conflict through the lens of Pan

Across taxa, social groups compete for territories and the resources they provide, engaging in interactions that pose significant fitness risks. Yet, the outcomes of intergroup conflicts are not fixed; individuals can mitigate these risks through within-group cooperation, allowing groups to gain the benefits of conflict while minimizing associated costs. As such, intergroup conflict is considered as a strong selective pressure, shaping the social dynamics, cooperation, and cognition of social species. Despite its significance, the evolutionary role of intergroup conflict in influencing social and cooperative attitudes is rarely examined, limiting our understanding of these processes. Chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), as a pair, offer a unique opportunity to explore this question. These two closely related species share similar history trajectories, social environments, and cognitive capacities, but have also diverged in distinct ways. Chimpanzees live in a male-dominated society characterized by hostility towards out-groups, whereas bonobo are known for their high female-status society and relatively tolerant intergroup interactions. In this talk, I will examine how these contrasting behaviors in our closest living relatives provide insights into the evolution of social strategies and the role of intergroup interactions in shaping their societies. By leveraging and evaluating the similarities and differences between them, I will explore how in-group/out-group identities and pairwise versus collective cooperation manifest in the two species, and their potential link to hostile or peaceful out-group attitudes. I will evaluate the conditions and mechanisms underlying violence and cooperation, focusing on the importance of differentiated social relationships and bonds in guiding cooperative exchanges.