Women in consensually non-monogamous relationships reported earlier pubertal development; CNM individuals also reported more social and ethical risk-taking, less aversion to germs, and greater interest in short-term mating

Life History and Multi-Partner Mating: A Novel Explanation for Moral Stigma Against Consensual Non-monogamy. Justin K. Mogilski et al. Front. Psychol., January 21 2020. https://doi.org/10.3389/fpsyg.2019.03033

Abstract: Life history theory (LHT) predicts that individuals vary in their sexual, reproductive, parental, familial, and social behavior according to the physical and social challenges imposed upon them throughout development. LHT provides a framework for understanding why non-monogamy may be the target of significant moral condemnation: individuals who habitually form multiple romantic or sexual partnerships may pursue riskier, more competitive interpersonal strategies that strain social cooperation. We compared several indices of life history (i.e., the Mini-K, the High-K Strategy Scale, pubertal timing, sociosexuality, disease avoidance, and risk-taking) between individuals practicing monogamous and consensually non-monogamous (CNM) romantic relationships. Across several measures, CNM individuals reported a faster life history strategy than monogamous individuals, and women in CNM relationships reported earlier pubertal development. CNM individuals also reported more social and ethical risk-taking, less aversion to germs, and greater interest in short-term mating (and less interest in long-term mating) than monogamous individuals. From these data, we discuss a model to explain how moral stigma toward non-monogamy evolved and how these attitudes may be mismatched to the modern environment. Specifically, we argue that the culture of sexual ethics that pervades contemporary CNM communities (e.g., polyamory, swinging) may attenuate risky interpersonal behaviors (e.g., violent intrasexual competition, retributive jealousy, partner/child abandonment, disease transmission) that are relatively more common among those who pursue multi-partner mating.

Discussion

We compared self-report indices of life history across men and women within monogamous, open, and multi-partner romantic relationships. Collectively, our results suggest that pursuit of CNM is associated with a faster life history strategy. Individuals within open and multi-partner relationships reported lower scores (i.e., a faster life history) on the Mini-K than those in monogamous relationships. Open individuals also reported lower scores on the HKSS than both monogamous and multi-partner individuals, who were no different from one another.

That individuals within CNM relationships report a faster life history makes sense in light of previous research on the association between faster life histories and promiscuous mating systems. CNM individuals’ preference for multiple sexual and romantic partners has been documented across several samples (Morrison et al., 2013; Rodrigues et al., 2016, 2017, 2019; Mogilski et al., 2017, 2019; Balzarini et al., 2018b) and is replicated again in this study using an alternative measure of sociosexuality (i.e., the MMSO) that separately measures affinity toward short- and long-term partnerships. We found that those in multi-partner relationships reported a more STMO than those in open and monogamous relationships, and open individuals reported a more STMO than monogamous people. Interestingly, those in multi-partner relationships also reported less interest in long-term committed romantic relationships than monogamous, but not open, individuals. It is possible that CNM individuals, and particularly those that maintain several concurrent romantic relationships, form fewer enduring partnerships than those in monogamous relationships. However, this is not consistent with prior research. Séguin et al. (2017) found that individuals within polyamorous relationships reported longer relationships than those in monogamous and open relationships, and all three relationship types reported similar levels of partner commitment. Similarly, Mogilski et al. (2017) compared relationship length between monogamous and CNM individuals’ primary and secondary relationships. Although they found that monogamous relationships tended to be older than secondary relationships, CNM primary relationships tended to be older than monogamous relationships. This suggests that those in CNM relationships regularly form long-term enduring relationships but are perhaps selective about with whom they maintain those relationships. That is, people who form multi-partner relationships may desire and actively seek a variety of intimate partners, but only maintain partnerships if they are of high quality. Balzarini et al. (2017) reported that primary partnerships tend to entail more commitment than secondary partnerships, and Mitchell et al. (2014) likewise found that polyamorous individuals report greater commitment to one partner than the other. Alternatively, LTMO may differ across different types of CNM. We did not collect data to distinguish different types of multi-partner relationships, but individuals interested in polyamory (i.e., multiple emotionally intimate relationships) may be more oriented toward long-term relationships than those interested in exclusively sexual extradyadic relationships.

Our complementary findings suggest that life history differences between monogamous and CNM individuals extend beyond sociosexuality. Women within multi-partner, but not open, relationships reported earlier sexual debut than women within monogamous relationships. There were no differences in self-reported pubertal timing among men. This is consistent with research showing that early sexual maturity is associated with a faster life history in women (Byrd-Craven et al., 2007; James et al., 2012; also see Hehman and Salmon, 2019), particularly within western industrialized societies (Sear et al., 2019). Scores on the PVDS also revealed that individuals within CNM and monogamous relationships did not differ in their perceived infectability. However, monogamous individuals reported greater germ aversion than both multi-partner and open individuals, while the latter were equally averse. This is consistent with work showing that those who score higher on the Mini-K (i.e., slow life history) report greater pathogen, sexual, and moral disgust than those who score lower (Frederick et al., 2018). For slow strategists, this aversion may motivate protective avoidance of risks that threaten long-term well-being. For fast strategists, a higher threshold for disgust would allow them to capitalize on opportunities despite possible risks (e.g., exposure to disease, interpersonal exploitation). However, these individuals may likewise fail to avoid sexual disease risk, which may become a community health issue. Finally, we also observed that those in multi-partner and open relationships scored higher than monogamous people on social and ethical (though not health) risk-taking. This suggests that CNM individuals may be more likely to disregard how their behaviors are perceived by or affect the well-being of others, but supports research showing that those in CNM relationships tend to be conscientious about sexual health (Conley et al., 2012, 2013b). Collectively, these findings suggest that differences in life history between monogamous and CNM individuals do not merely reflect differences in sociosexuality. Rather, people who are interested in pursuing a CNM relationship may be predisposed to a faster life history strategy.

CNM, Morality, and Sexual Ethics

Knee-jerk condemnation of CNM can produce wrongful discrimination that harms personal and community well-being. For instance, those in CNM relationships typically report being more secretive about their non-primary (or pseudo-non-primary) partners (Balzarini et al., 2019), presumably to avoid third-party punishment. Indeed, Conley et al. (2012) found that women who fear condemnation are less willing to accept an offer of casual sex that they would otherwise enjoy pursuing. This fear of judgment can cause anxiety that prevents those who practice CNM from seeking sexual health services (e.g., STD testing), particularly within rural communities where reputation can be more easily tracked (Kirkman et al., 2015). Moreover, therapists and clinicians who assume that monogamy is a universal relationship ideal may inadvertently marginalize or mistreat patients who are oriented toward multi-partner mating (see Finn et al., 2012; Brandon, 2016; van Tol, 2017; Cassidy and Wong, 2018). In fact, Schechinger et al. (2018) found that CNM individuals reported that therapy was more helpful when therapists were more affirmative about their relationship structure (e.g., did not make an issue of their relationship structure when it was not relevant).

It is possible that moral stigma toward CNM (see Moors et al., 2013) stems from aversion to the high-risk, competitive interpersonal strategies that are characteristic of a fast life history (see Wang et al., 2009; Figueredo and Jacobs, 2010; Kruger, 2010; Griskevicius et al., 2011). Commitment to a faster life history strategy can lead to greater risk-taking (Hampson et al., 2016; Mishra et al., 2017), impulsivity (Frankenhuis et al., 2016; Maner et al., 2017), and aggression against others (Figueredo et al., 2018). Also, robust indicators of faster life history, such as paternal absenteeism and adolescent fertility, predict national rates of criminal violence (Minkov and Beaver, 2016), child maltreatment, and homicide (Hackman and Hruschka, 2013). Moral condemnation of multi-partner mating may thereby occur when condemners believe that monogamy prevents competitive contests for mates, enhancing cooperation within groups and reducing negative physical and mental health outcomes. In other words, though fast life history traits can help individuals cope with an unpredictable environment (Figueredo and Jacobs, 2010; Frankenhuis et al., 2016; Young et al., 2018), they may conflict with the optimal social strategy pursued by slow life history strategists. Baumard and Chevallier (2015) argue that fast life history behaviors may be moralized to the extent that slow strategists promote cooperation, self-regulation, and restricted sociosexuality, and condemn “fast” behaviors such as selfishness, conspicuous sexuality, and materialism. By espousing moral values that promote delayed gratification, sexual monogamy, and altruism, slow life history strategists may condemn multi-partner mating to create stable, cohesive communities that invest in long-term reciprocity and extended prosociality.

Although our data support the conclusion that CNM is associated with fast life history traits, it is important to note that our study assesses dispositional tendencies and not how these tendencies are modified by cultural practices within the CNM community. People who prefer multi-partner mating may have a proclivity toward pursuing a faster life history, but most modern CNM communities have well-developed guidelines for pursuing multi-partner relationships safely and ethically (see Anapol, 1997; Wosick-Correa, 2010; Deri, 2015; Hardy and Easton, 2017). Sexual ethics within CNM communities, including effective birth control methods, may help manage and diminish the traditional costs of competitive, high-risk, promiscuous mating environments. CNM individuals take precautions to attenuate distress caused by a partner’s extradyadic involvement (Jackson and Scott, 2004; McLean, 2004; Visser and McDonald, 2007). Those in CNM relationships are just as (or more) likely to practice safe sexual practices than people in monogamous relationships (Conley et al., 2012, 2013b; Lehmiller, 2015). They are also expected to practice open communication, honesty, emotional intimacy, and consent-seeking to reduce the threat of partner defection or resource diversion. Scoats and Anderson (2019) interviewed men and women who engaged in mixed-sex threesomes and found that open communication reduced feelings of exclusion. Similarly, Aguilar (2013) studied two communal living groups practicing polyamory and reported that both cultures discouraged aggression and competition among males within the community.

By reducing the social anxiety that accompanies multi-partner competition, individuals within CNM relationships may experience relationship and health outcomes on par with (or better than) those who pursue monogamy. Those within multi-partner relationships that include ethical treatment of and consent among partners typically experience more positive relationship and health outcomes than those who pursue non-consensual non-monogamy (i.e., adultery; Levine et al., 2018). Compared to those in monogamous relationships, CNM individuals report experiencing less emotional jealousy (Mogilski et al., 2019), and spend less time actively trying to retain their mate (Mogilski et al., 2017, 2019), which may alleviate conflict in relationships where one or both partners desire extradyadic intimacy. Indeed, people with an unrestricted sociosexuality report greater satisfaction within CNM relationships than they do in monogamous relationships (Rodrigues et al., 2016; Fairbrother et al., 2019), and report less preoccupation with constraining relationship forces (i.e., feeling obligation rather than desire toward a partner), which is associated with greater self-reported quality of life (Rodrigues et al., 2019). Stults (2018) also found that gay and bisexual men involved in multi-partner mating reported that the conflict resolution strategies of CNM improved their relationship satisfaction, communication, and trust. This suggests that CNM may improve, rather than dissolve, cooperation and well-being within certain populations – a feature that should be valued by those who fear how public acceptance of CNM might affect social cohesion.

Limitations and Future Directions

The most notable limitation of this research is that it does not assess the influence of measured morality or sexual ethics on behavior within CNM relationships, and these are constructs that should be examined further in future work. Our results should not be interpreted as support for condemnation against CNM. Rather, our data highlight how those with a proclivity toward CNM may possess personality traits that predispose them to take risks, pursue multi-partner mating, and disregard pathogens. CNM may therefore not foster these traits, but rather provide an environment where people can ethically express them. Without strict ethical guidelines for how to handle multiple concurrent romantic relationships, people may pursue multi-partner mating in a manner that produces social disharmony. For example, in sub-Saharan and Muslim populations where polygamy is socially acceptable, women in polygamous relationships experience more spousal mistreatment, abuse, and mental health concerns than those in monogamous relationships (Hassouneh-Phillips, 2001; Özer et al., 2013). Children from these polygynous families also report more mental health and social difficulties, poorer school achievement, and poorer paternal relationships than those from monogamous families (Al-Krenawi et al., 2002; Al-Krenawi and Slonim-Nevo, 2008). Within these populations, these negative outcomes seem to arise when there is competition, hostility, jealousy, and little communication among partners. However, when effort is invested into building respectful and congenial relationships among partners, these outcomes improve (Al-Krenawi, 1998). This suggests that the dynamic of a multi-partner relationship may be a better predictor of relationship functioning than its structure (Elbedour et al., 2002). CNM ethical practices may likewise reduce conflict among those who pursue multi-partner relationships. Specifically, CNM’s culture of compassionately enforced sexual ethics may provide an outlet for fast life history strategists to pursue their preferred strategy in a manner that reduces its negative impact on others’ well-being.

This research highlights the need to identify and quantify a formal taxonomy of CNM ethics. Although a number of popular guides exist (e.g., Anapol, 1997; Hardy and Easton, 2017), there is no unified scientific examination of the diverse strategies that CNM practitioners use to manage multi-partner relationships. The most obvious ethical guideline that differentiates CNM from other forms of non-monogamy is its namesake: consent. However, this is too broad a concept to capture the myriad of ethical considerations that may arise within a multi-partner relationship. For example, Peoples et al. (2019) presented case studies of two married men who pursued extramarital partnerships with and without the consent of their spouse. They documented that both men, regardless of spouse consent, engaged in antagonistic and exploitative relationship practices, such as deception, partner neglect, and divestment from childcare, which subsequently produced relationship conflict. This suggests that consent-seeking is a nominal feature of CNM relationships and that ethical pursuit of multi-partner mating may instead require a multifaceted approach that addresses the diverse array of anxieties and exploitations that can produce suffering within romantic and interpersonal relationships.

It may be fruitful to begin this investigation by examining how CNM practices complement the recurrent, domain-specific adaptive issues that have shaped humans’ evolved psychology. Natural selection has shaped psychological adaptations that protect against cuckoldry and partner abandonment (Buss and Schmitt, 1993, 2019), interpersonal exploitation (Buss and Duntley, 2008; Duntley, 2015), and infection by disease (Al-Shawaf et al., 2015; Tybur and Lieberman, 2016). Although these adaptations may have enhanced reproductive success, they do not necessarily enhance well-being (Kováč, 2012), nor may they function optimally within a modern environment (Li et al., 2018). It is possible that the sexual ethics of CNM, paired with modern sexual health technologies, reduce the need for humans to rely on psychological mechanisms of disgust and moral condemnation to regulate sexual risk-taking and other features of a faster life history. For example, proscribing hostility among partners within CNM relationships may reduce intrasexual competition and its consequences on public health (see Kruger, 2010; Tybur et al., 2012). Future research should compare CNM individuals who adhere or not to the ethical principles espoused by the greater community and assess whether adherence tends to improve relationship functioning, particularly among those who have a predisposition to disregard others’ well-being.

Another limitation of this study is that it did not examine a complete array of life history traits. It also relies exclusively on self-report measures, which are vulnerable to revisionism and faulty memory. The validity of the Mini-K and HKSS as self-report measures of life history variation is contested (see Dunkel and Decker, 2010; Figueredo et al., 2013, 2015; see also Copping et al., 2014; Richardson et al., 2017), though our complementary measures provide convergent evidence that CNM is associated with a faster life history. Nevertheless, future research should examine a wider collection of behavioral measures of life history within CNM populations and consider which features of a fast life history are most endemic to CNM populations. Research should also address whether life history features are invariant across different CNM populations and subcultures (e.g., swinging vs. polyamory vs. religious polygamy). People within polyamorous relationships are typically viewed as more moral and responsible than those in swinging and open relationships (Matsick et al., 2014). To the extent that polyamorous relationships are defined by multiple close, emotionally intimate bonds, these relationships (and the people within them) may be seen as less socially disruptive. Similarly, we did not assess whether our participants had children, which can substantially shape relationship behaviors and attitudes (e.g., Barbaro et al., 2016; Flegr et al., 2019).

Finally, there are several methodological issues that should be considered when interpreting this data. First, several of our measures had low Cronbach’s alphas, including the MMSO and the ethical, health/safety, and social risk-taking facets of the DOSPERT. Similarly, our measure of pubertal development relied on self-report responses, which may be biased by retrospection. Research designs that rely on alternative, well-validated measures of psychological and social functioning (e.g., psychophysiological assessment; social relations modeling) administered within laboratory or naturalistic settings may help to improve the quality of life history and CNM research more broadly.