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The evolutionary perspective on friendship

March 31, 2013

Yup. Robert M. Seyfarth and Dorothy L. Cheney explain our links with animals… and it makes a lot of sense. Useful for a bioliterary approach to adolescent fiction?

They explain: “Humans form close, enduring relationships and benefit from them. Having a strong social network reduces stress, lowers the risk of disease, and increases longevity (Berkman et al. 2004, Holt-Lunstad et al. 2010). Humans also classify relationships, giving them names like sisters, friends, lovers, allies, or rivals. Each name carries assumptions about the thoughts and emotions that underlie a relationship and reveals our expectations about how the individuals involved (including ourselves) will behave in the future, even in novel situations. Like forming relationships, recognizing and classifying the relationships that exist among others is adaptive because it helps us understand and predict peoples’ behavior.

There continues to be debate about the extent to which our social relationships are unique, requiring cognitive skills that appear to be limited to humans, such as language, planning, and the ability to anticipate events long into the future. There is growing evidence, however, that at least some aspects of human social relationships find parallels in the behavior and cognition of animals. In many species, individuals not only form close, enduring social bonds but also recognize these bonds in others.

Of course, scientists have known for years that males and females in many species form pair bonds in which partners cooperate in the care and feeding of offspring. The ecological and social factors that favor the evolution of monogamy are now well known (see Alcock 2009 for review). In birds, the behavior of partners is often beautifully synchronized, and bonds may persist for years. In barnacle geese (Branta leucopsis), pairs that maintain long-lasting pair bonds have higher lifetime reproductive success than those with shorter pair durations (Black 2001).

But what about the evolution of close, enduring social bonds that are not directly related to mating: bonds among females, for example, or among males? Here we review recent studies of these long-term relationships in animals. For simplicity, we call them “friendships” (Silk 2005). Our goal is to shed light on the evolution and adaptive value of human friendship. We focus primarily on nonhuman primates because of their close evolutionary relationship to humans and because the most abundant data come from monkeys and apes; however, we also discuss intriguing results from studies of hyenas, elephants, dolphins, and lions.” (p.154)

Ref; Robert M. Seyfarth and Dorothy L. Cheney (2012) The Evolutionary Origins of Friendship. Annu. Rev. Psychol. 2012. 63:153–77

Abstract: “Convergent evidence from many species reveals the evolutionary origins of human friendship. In horses, elephants, hyenas, dolphins, monkeys, and chimpanzees, some individuals form friendships that last for years. Bonds occur among females, among males, or between males and females. Genetic relatedness affects friendships. In species where males disperse, friendships are more likely among females. If females disperse, friendships are more likely among males. Not all friendships, however, depend on kinship; many are formed between unrelated individuals. Friendships often involve cooperative interactions that are separated in time. They depend, at least in part, on the memory and emotions associated with past interactions. Applying the term “friendship” to animals is not anthropomorphic:Many studies have shown that the animals themselves recognize others’ relationships. Friendships are adaptive. Male allies have superior competitive ability and improved reproductive success; females with the strongest, most enduring friendships experience less stress, higher infant survival, and live longer.” (p.153)

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