Question

From a reciprocal altruism point of view, suggest what the reproductive/survival costs and benefits of opposite-sex and same-sex friendships might be in humans. Answer this question in six parts (use Chapters 7 & 8 in Alcock and lecture notes to do so; you may also want to read: Friends with Benefits: The Evolved Psychology of Same- and Opposite-Sex Friendship, by Lewis, Conroy-Beam, Al-Shawaf, Raja, DeKay and Buss, sent as a scan early in the semester): male-male friendship benefits male-male friendship costs female-female friendship benefits female-female friendship costs female-male friendship benefits female-male friendship costs

Answer 1

• An evolutionary perspective yields fresh insights into the nature of human friendships and the emotions associated with these relationships. This approach sheds light on how specific types of friendship would have benefited ancestral humans in the currency of natural selection—reproductive success—as well as in the currency of subjective well-being.
• This chapter outlines hypothesized ancestral functions of friendship, and discusses why immersion in friendships results in positive emotions such as happiness. We also review the empirical literature on different friendship types, drawing attention to the unique profiles of costs and benefits that characterize each type of friendship.
• In light of the various fitness-benefits and challenges that these relationships can pose, we propose evolutionarily inspired strategies for individuals to reap the benefits of friendships while simultaneously minimizing the costs they impose.
• In this way, we can hope that an evolutionary approach not only augments our basic scientific understanding of these fundamental social relationships, but also contributes to the practical objective of enhancing friendships and maximizing their happiness yield.
• Friendships are fundamental to human social life. People direct great effort toward both the formation and maintenance of friendships, investing time, energy, money, and emotional resources. Across cultures, friendship is reliably linked to the experi-ence of positive emotions such as happiness an association that is present in both same-sex and cross-sex friendships (Argyle1999), and which holds from early adulthood (Demir and Weitekamp 2007) through old age (Larson et al. 1986). Why are friendships so important to our happiness?
• An evolutionary perspective may shed light on this issue. Friendships were almost certainly recurrently linked to survival and reproduction during human evolutionary history, and the specific benefits that accrue to individuals in different types of friendship may offer unique insight into the evolutionary impetuses for these relationships. An evolutionary perspective can offer insight into how specific types of friendship would have benefitted ancestral humans in both the currency of natural selection—reproductive success—and the currency of subjective well-being and happiness.
• An Evolutionary Approach to Friendship and Happiness
• An evolutionary approach may yield valuable insight into why friendships and immersion in quality social relationships are consistently linked to happiness (Corneau 2009; Demir et al. 2013). It suggests that positive emotions such as happiness are produced by motivational programs that evolved because of their ability to guide ancestral humans to repeat behaviors associated with increased survival and reproductive success (Cosmides and Tooby 2000; Hill et al. 2013; Kenrick et al. 2010).
• Having friends would have dramatically increased ancestral humans’ likelihood of survival and reproduction (Tooby and DeVore 1987). Consequently, selection could have favored mechanisms that produced happiness in response to such friendships to the extent that this subjective experience motivated ancestral humans to form and maintain these beneficial relationships. In the following section, we briefly outline several different evolutionary pathways by which psychological adaptations to form and maintain friendships could have evolved.
• Evolutionary Models of Friendship
• Reciprocal Altruism
• Non-evolutionary research has investigated friendship as a means of social exchange in which individuals select friends on the basis of the costs and benefits associated with these friendships (Befu 1977; Emerson 1976; Homans 1958). Although these hypotheses about friend preferences and selection do not articulate the specific benefits exchanged in these friendships, an evolutionary perspective can illuminate how such social exchange relationships could have evolved.
• The theory of reciprocal altruism postulates that altruistic tendencies toward non-relatives can evolve when the delivery of benefits is reciprocated at some point in the future (Axelrod 1984; Cosmides and Tooby 1992; Trivers 1971).
• Such exchange relation-ships can result in net fitness benefits for both parties involved—a condition economists refer to as a “gain in trade” (Kemp 1995). Selection could thus have led to the evolution of mechanisms that motivate individuals to form and maintain these highly beneficial social exchange relationships.
• To illustrate how such exchange relationships could have evolved, consider the adaptive problem our ancestors faced of hunting large game to acquire meat. Ancestral humans rarely hunted large game alone due to the risky and costly nature of hunting dangerous prey (Milton 1999; Tooby and DeVore 1987).
• Ancestral humans who formed friendships and coalitions in the service of solving this adaptive problem would have experienced improved survival and reproductive rates, as these coalitions incur fewer costs and enjoy greater success in the hunt for dangerous game (Buss 2004; Hill and Hurtado 1996; Tooby and DeVore 1987). Because individuals who hunted together were more likely to secure nutritious food, over many generations, selection would have favored mechanisms that motivated individuals to form friendships and coalitions to achieve these goals.
• The key concept illustrated here is that friendships relationships may have delivered unique sets of benefits linked to ancestral humans’ survival and reproduction. It is likely that our ancestors benefitted greatly from these kinds of relationships, and that reciprocal exchange formed the basis not only for many ancestral friendships, but for the mechanisms that lead to friendships in modern environments as well.
• The Alliance Model of Friendship
• Another recent evolutionary perspective suggests that human friendship is based on evolved computational systems for building alliances (DeScioli and Kurzban 2012, 2009). The alliance-building model is distinct from the theory of reciprocal altruism, as it is not based on exchange, but rather on concerns about interpersonal conflict. These concerns are a central feature of the alliance-building model, but do not feature prominently in reciprocal altruism models of human friendship.
• The central premise of the alliance model is that humans habitually get into conflicts with one another. Having a supportive network of alliances is crucial to successfully navigating these problems and emerging on the “winning” side of direct interpersonal conflicts. Crucially, the likelihood of winning such conflicts depends not only on one’s own wit, agility, and physical formidability, but also on one’s ability to mobilize other individuals—friends—to support one in such conflicts.
• The alliance-building model of friendship proposes that humans have evolved computational systems dedicated to cognitively representing different friends’ degree of loyalty to oneself, because those who are most loyal are most likely to provide support in future disputes. DeScioli and Kurzban (2012) insightfully note that “individuals frequently have relationships with both sides in a conflict, particularly because human social networks are locally dense” (p. 216). This suggests that ancestral humans needed to be able to determine whom they would support in any possible pairwise within-group conflict—including one between two close friends.
• As the authors suggest, one way to do this is to rank one’s allies, prioritizing certain friendships over others. The most important aspect of this hypothesis is that an individual (let’s call him Tom) should count among his closest friends those who rank him as one of their closest friends. The logic is that those who consider Tom a very close friend are those who are most likely to be fiercely loyal to him and support him in future.