Freedom of choice supports social complexity in chimpanzees.

Fission-fusion sociality offers almost infinite options for individuals to make self-determined choices about how to range across space, spend time in different activities, and associate with conspecifics. Yet, how such freedoms contribute to the construction of functional social groups has received little attention. In this investigation, we found that sanctuary-living chimpanzees residing within spacious outdoor habitats with choice among a variety of social partners formed integrated communities that showed emergent properties of the fission-fusion social systems. Social network topology varied across communities, indicating species-typical intraspecific variation in social complexity. This variation was positively associated with indicators of behavioral diversity and wellbeing. Our results offer newfound understanding of the factors that facilitate fission-fusion societies, which, in turn, foster agency, social belonging, and culture that enable apes to thrive.