Limitations and Future Directions in the Evolutionary Study of Romantic Relationships

Sex differences are interesting because they reveal how sexual selection may have shaped the ever-changing, culture-contingent milieu of phenotypes that males and females of a species employ to resolve the adaptive challenges of sexual conflict. A more fundamental distinction may be predator and prey, or that may be more broadly conceptualized as zero-sum competitive encounters (i.e., win–lose social exchanges; Różycka-Tran et al., 2015). The risks of succumbing to predation, such as physical injury, theft, coerced compliance, or death may be a more ancient set of adaptive problems than those crafted after the evolution of anisogamy—though coevolution would have undoubtedly occurred (e.g., Rankin et al., 2011). Studying adaptations to predation may help disentangle the considerable overlap in men’s and women’s relationship motives, desires, and preferences, such as interest in partner honesty and fidelity (Mogilski et al., 2019; Mogilski et al., 2014). Doing so may reveal adapted strategies in both men and women for establishing trust, negotiating interdependence, and avoiding interpersonal manipulation. Likewise, research on dark personality (i.e., individual differences in the willingness to exploit others for personal gain) (see Marcus et al., 2018) could reveal the motivational computation underlying intimate predation (see Zeigler-Hill & Jonason, 2018), such as sexual assault (Koscielska et al., 2020), intimate partner violence (Plouffe et al., 2020), and stalking (March et al., 2020).

In consensual nonmonogamy (CNM), partners distinguish extra-pair interactions from infidelity. In these relationships, infidelity may more broadly be understood as lying or withholding information about extra-pair interactions that a partner would deem relevant to the in-pair relationship (Mogilski et al., this volume) or whether a partner violates an agreed-upon relationship boundary (see Andersson, 2022).

Distinguishing infidelity and extra-pair interaction in this way could help make sense of researching showing that CNM and monogamy report similar relationship quality and satisfaction (Rubel & Bogaert, 2015) and that people who open an existing relationship report more sexual satisfaction than those who do not (Murphy et al., 2021). People who take precaution to communicate with a partner about their extra-pair attractions, regulate their jealousy, or otherwise mitigate the harms of extra-pair relationships may successfully avoid the recurrent adaptive problems of multipartner mating. Relationship science and social policy (Stein, 2020) could benefit from accounting for recent or understudied intimate relationship practices (see Brady & Baker, 2021).

Relationships may be better viewed as alliances for achieving shared goals (Conroy-Beam et al., 2015; Orehek et al., 2018). Sex and intimacy are defining features of romance, but intimate partners routinely collaborate to produce and/or raise offspring, mutually advance their social status, provide physical and emotional caregiving to each other, share resources, create or preserve social networks (e.g., union of families), or otherwise coordinate to pursue shared goals. Studying romantic relationships as alliances could help to reveal how individuals manage third-party conflicts (Aoki, 1984) and coalitional rivalries (Gimeno, 2004), build and maintain a reputation with their partners (Ebbers & Wijnberg, 2010), negotiate social hierarchy (Gavrilets et al., 2008), or deal with commitment uncertainty (Thomas & Trevino, 1993).

This volume reviews the historic and contemporary developments in evolutionary social sciences that have transformed how researchers study the intimate relationship process. Understanding the functional mechanisms that guide human mating has revealed previously unknown features of relationship initiation, maintenance, and dissolution. Just as a mechanic might use architectural knowledge of a car to troubleshoot its performance, relationship scientists who consider evolutionary design features equip themselves with technical knowledge of how environment-gene interactions, domain specificity, and adaptationism (see Nettle & Scott-Phillips, 2021) have shaped the relationship processes observed in humans. We anticipate that this approach will continue to inspire novel research for generations to come.