Mate Rivalry in Friendships: A Lifespan-Evolutionary Perspective

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According to evolutionary psychology, friendships enhance genetic fitness because they offer support in times of sickness and rejoice in times of happiness. Recent research continues to demonstrate the benefits of friendships for health (e.g., Mukerjee, 2013; Tay, Tan, Diener, & Gonzalez, 2013). However, friendships may have adverse consequences for genetic fitness if a poor match is chosen. For example, having a close friend who is highly similar in terms of intrapersonal traits (e.g., values, interests) and choice of mates would pose a reproductive threat, particularly if the friend interacts regularly with one’s romantic partner. From an evolutionary standpoint, individuals are therefore expected to select friends who have dissimilar mate preferences (Bleske & Shackelford, 2001). Based on evolutionary psychology, we predicted that individuals would be less likely to have close friends with similar mate preferences, especially as they get older and/or involved in a serious romantic relationship (e.g., get married, have children). Participants were 1,142 ethnically diverse individuals recruited from university participant pools. Participants completed a mixed-method online survey with quantitative and qualitative questions. The quantitative questions assessed demographic characteristics, mate rivalry, friendship intimacy, and friendships throughout the lifespan. Open-ended questions asked participants to qualitatively describe their own and best friends’ mate preferences and feelings associated with their relationship at various points. Our hypothesis was supported: Individuals were more likely to report having friends with similar mate preferences when they were younger and/or less seriously involved with a romantic partner. Friendship intimacy also declined with age. We discuss our findings according to evolutionary psychology and suggest possibilities for future research.