Infidelity Reconsidered
As a society, we should not presume to judge the relationships of others based on our own moral code.
On September 19th, Instagram model Sumner Stroh released a TikTok alleging that she’d had a year-long affair with American pop star, Adam Levine. The Maroon 5 frontman subsequently issued a statement in which he admitted to sending inappropriate messages but denied an affair. Since then, several other women have claimed that they received flirty messages from him. In a previous interview, when Levine was asked why men cheat, he blithely responded, “Monogamy is not in our genetic makeup. People cheat. I have cheated.” Is there any truth to this, or is it just an expedient excuse invented by people—particularly men—to justify their philandering?
The institution of marriage exists worldwide, but maintaining an intimate relationship is difficult and some of us breach the sexual exclusivity of our intimate commitments by engaging in infidelity. In the US, infidelity is frequent, occurring in 20–40 percent of married couples, and in 70 percent of dating couples. But high rates of infidelity are by no means exclusive to US couples; a study conducted across 53 nations found that mate poaching—a tactic used to attract a partner already in a committed relationship—was committed by 56.9 percent of men and 34.9 percent of women. Another study conducted across 160 cultures worldwide found that marital infidelity was the most frequently reported reason for divorce. In the West, it has been estimated that half of marriages end this way (the average US divorce rate is 50 percent). Infidelity is not only a leading cause of divorce or separation, it can also contribute to the spread of STIs, harsh social and professional consequences, and even intimate-partner violence and homicide. With so much at stake, it is worth re-examining why we cheat.
In monogamous partnerships, it is mutually agreed that the benefits of such an arrangement (sexual contact and gratification, emotional and financial support, intimacy) may only be shared within that union. Each partner is expected to provide the benefits necessary to satisfy the needs and desires of the other. Those who feel that those needs and desires are being neglected expect to cheat in the future and expect their partners to do the same. Boredom, a lack of emotional support, and poor communication can also lead to infidelity. When personal needs are not being met, people may be more motivated to pursue extra-pair relationships. From this perspective, dissatisfied partners may seek a new experience rather than a new romantic partner. In that sense, affairs may serve as a means of exploration, self-discovery, and personal growth, as well as a search for a new identity and transformation. A loss of sexual satisfaction, particularly a decline in the frequency of sex, can lead to infidelity, especially in men. Research also suggests that the risk of infidelity increases after seven years of marriage. In addition, certain developmental stages in a marriage, including pregnancy and postpartum may be highly sensitive times for infidelity in men.
However, because some people cheat regardless of how happy they are in their relationship, it seems that novelty-seeking may be a key driver in pursuing extramarital affairs. It is said that when President Coolidge and the First Lady visited a government farm in Kentucky, Mrs. Coolidge asked the guide why there was only one cockerel but so many hens. When the guide explained that the cockerel could copulate many times a day, the First Lady replied, “Tell that to Mr. Coolidge.” When the guide further explained that it was with a different hen every time, the president said, “Tell that to Mrs. Coolidge.” This story coined the “Coolidge effect,” which refers to the male tendency to be aroused by sexual novelty, a phenomenon observable in several species.
For example, when male Norway rats are housed with a single female, they reach sexual satiation after about 1.5 hours. But males can be kept sexually active for almost 8 hours with the introduction of novel females. Among humans, men were found to rate faces as less attractive after being exposed to them twice, further suggesting that men are attracted to novelty rather than familiarity. This may help explain why men also prefer variety in short-term mating (casual dating, one-night stands). Indeed, a study found that when men are exposed to a new woman, they experience a significant decrease in ejaculation time and an increase in sperm count compared to when they are exposed to the same woman six times.
So, why did sexual novelty evolve as a male-typical mating strategy? Parental Investment Theory holds that men are not obliged to invest as much in parenthood as women—the consequences of having a child are costlier for women in terms of time and energy investment (for example, pregnancy and postpartum) than for men who are only required to provide sperm. Men are therefore less choosy than women about who they mate with in the short term. Long-term mating, on the other hand, is typically marked by heavy investment, love, and the dedication of time and resources.
Although men and women are both motivated to use long-term and short-term strategies in dating, there are important sex differences in the qualities people look for in a partner. For example, in long-term mating, men tend to look for signals of fertility and reproductive value, such as youth and physical appearance, whereas women tend to look for signals of status and resources. The sexes also differ in their motivations for pursuing short-term partners. Men tend to be motivated by adaptive desires for sexual variety, and tend to consent to sex more readily than women. Women, on the other hand, pursue men with access to material resources, and who indicate good genes (fitness, masculinity) which can be passed on to their offspring. However, given the asymmetry in obligatory parental investment, women have less to gain in reproductive output by engaging in short-term mating than men.
Short-term seeking men can produce a hundred offspring by mating with a hundred women in a year, while a monogamous man will only be able to father one child with their partner during that time. So, from an evolutionary perspective, there should be a strong selective pressure for men to prefer sexual variety. Indeed, in our ancestral past, men could reap many adaptive benefits from securing multiple sexual partners. In many societies, children of non-marital unions survive to maturity without the assistance of the father, owing to support provided by family, the community, or the government. But short-term mating can also provide men with increased social status and self-esteem. Moreover, the societal penalties for unfaithful men in most cultures are relatively minor compared to women. So long as the potential reproductive benefits from mating with numerous partners are much higher for men than for women, it appears that adaptive desires for sexual variety will motivate some men to seek novelty through short-term mating.
Nevertheless, the gender gap in infidelity is closing, meaning that women now cheat almost as much as men. This could be due to social changes, including rising female economic and reproductive independence. But infidelity dates to our egalitarian hunter-gatherer ancestors, and anthropologists theorize that it was the agricultural revolution that moved humans from an egalitarian culture to a sexually possessive one. This introduced the concept of property, while religion turned sex into property through marriage (lifelong monogamy). From this perspective, humans aren’t meant for monogamy and are programmed to cheat. Indeed, our hunter-gatherer ancestors were serial monogamists who typically switched partners once children reached the age of six. So perhaps this explains the trend of increased infidelity after seven years of marriage.
Does all this mean that we should simply scrap the institution of marriage and move on to consensual non-monogamy (CNM), a relationship model in which both partners permit sexual relations with other people? Instead of restricting or coercing partners into being faithful, CNM couples create their own guidelines to minimize the consequences of sexual contact with others. The most common forms of CNM are swinging, open, and polyamorous relationships. In the US and Canada, up to 25 percent of adults have had a CNM relationship in their lifetime and between three and seven percent of adults report being in CNM relationships. These alternative relationship models are more likely among men and people who identify as gay, lesbian, or bisexual. The main advantage of CNM relationships is that they provide an alternative to infidelity by acknowledging rather than hiding sexual attraction to others, thereby allowing partners to openly discuss and establish healthy boundaries.
However, polyamorous marriage may have negative societal implications, as this model can lead to many unmarried “leftover” men, increasing the risk of male competition which can lead, in turn, to violence and crime. Therefore, although the institution of monogamous marriage may indeed run contrary to our evolved nature, it can provide multiple benefits including our own and our children’s wellbeing. The biggest problem with cheating is the deceit. Today, no one should feel the need to cheat and the violation of trust that involves. If we can’t control our sexual impulses, we should openly address our urges in conversation with our partner. Whether we choose to be in monogamous or consensually non-monogamous relationships, each couple must agree defined rules. An exclusive relationship is not enough to ensure that partners share the same values when it comes to infidelity—assuming that a partner will always be faithful without talking about it is not only naïve but makes failure more likely.
We don’t know enough about Adam Levine’s relationship with his wife to judge his behavior. And as a society, we should not presume to judge the relationships of others based on our own moral code. Rather, we should have a more honest discussion about sexuality and relationships, and appreciate that intimate relationships and marriage aren’t as much about sex as they are about qualities that are much more profound and enduring, especially once children are involved. The unrealistic expectation of everlasting passion in marriage is causing unnecessary suffering and can ultimately lead to disappointment and divorce. If we want to increase marital stability and preserve the institution of marriage, we need to develop a more tolerant and rational understanding of human sexuality and use this knowledge to approach our intimate relationships realistically, with more sympathy and compassion.
