Most animals for whom we have data treat their kin differently from non-kin. When food resources are scarce, or a hungry predator appears in the midst of an animal group, it’s often relatives who help each other out. This makes good evolutionary sense: when one animal aids another who shares its genes, it boosts the chances that its own genes will be long-lived.
Nowadays, however, as I study and write about the expression of emotion in a variety of mammals, I have come to realise that this perspective is too limiting. If we make the biology of kinship the primary motivator for an animal’s behaviour, we might be slow to explore the nature of its other social relationships. Indeed, some scientists have begun to describe the close bonds between non-kin relatives as ‘friendships’, in species ranging from chimpanzees and elephants to domestic and farm animals. This is an encouraging trend. I think we can go further, especially by borrowing a new concept from anthropology that Marshall Sahlins calls mutuality of being.
Mutuality of being refers to a special type of relationship, one that overlaps with friendship but has its own distinct qualities. To qualify as friends, two animals must engage in positive social interactions beyond the context of mating and reproduction. In her pioneering field study Sex and Friendship in Baboons (1985), Barbara Smuts used grooming and proximity to decide which male and female baboons were friends. More broadly, the anthropologists Robert Seyfarth and Dorothy Cheney, professors at the University of Pennsylvania, define friendships as close, enduring social bonds, including those that form between males and between females.
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