Singles of both sexes expedite reproduction: Shifts in sexual-timing strategies before and after the typical age of female menopause

https://doi.org/10.1016/j.evolhumbehav.2019.08.001Get rights and content

Abstract

How do singles' strategies for engaging in sexual activity with a new partner vary across the adult lifespan? Using three large and independent demographically representative cross-sectional samples of heterosexual single adults in the U.S., we found that females approaching the typical age of menopause became less likely to establish relationship exclusivity prior to sexual activity with a new partner. However, after the typical age of menopausal onset, females returned to earlier levels of commitment choosiness. These changes in commitment choosiness surrounding the age of menopause were consistent across two studies (including a larger dataset combining two samples). Findings suggest that single females approaching menopause—a major life history milestone—alter their behavior to achieve reproductively relevant partnering goals but abandon this mating strategy once the typical reproductive period has ended. Males exhibited similar, though attenuated, changes in expected relationship commitment before sexual activity during midlife as well. Age-related changes in commitment corresponded with the amount of stress expressed regarding one's “biological clock”. However, reduced commitment choosiness did not vary with frequency of sexual thoughts, frequency of sexual behaviors, or external pressures to find a romantic partner. Results are discussed in terms of life history theory and sex differences in sexuality.

Introduction

The “Closing Time” effect (Pennebaker et al., 1979) holds that over the course of an evening in a bar, patrons rate one another as more attractive as closing time approaches. This result highlights the influence of diminishing opportunity on decision making, even on social interactions that take place over the course of just a few hours. However, it is less understood what happens when the time scale is expanded. Do diminishing opportunities have similar effects on romantic and sexual decision making over longer durations, such as over years or across the lifespan?

A few studies have attempted to address questions related to the effects of age on partner preferences and choice. Most have been couched in terms of individual value on mating markets, with age-related declines in fecundity (reproductive capacity) associated with diminishing value and hence decreasing market competitiveness and selectivity (e.g. Fales et al., 2016; Kenrick & Keefe, 1992). In research on newspaper personal ads, for instance, both older women and relatively less attractive women tended to be less demanding than their younger and more attractive counterparts (Pawlowski & Dunbar, 1999; Waynforth & Dunbar, 1995). The decline in demands may be due to female age being negatively correlated with the number of suitor responses a woman receives, be it in newspaper ads (Baize & Schroeder, 1995) or online dating markets, where men contrastingly receive greater interest with age (Bruch & Newman, 2018). However, it remains unclear whether women of an older age are more generally exhibiting shifts in their behavioral strategies to accommodate diminishing mating opportunities. Furthermore, considerably less work has been done on age-related shifts or changes in men's sexual behavior (e.g. DeLamater, 2012; Gray & Garcia, 2012). The current study explores these questions of shifting mating strategies across the adult life course in two separate studies of adult singles in the United States.

Animals with a limited breeding season provide comparison cases that can reveal wider evolutionary patterns regarding diminishing mating opportunities. Reproductive senescence occurs across a variety of sexually reproducing species (Alberts et al., 2013; Nussey, Froy, Lemaitre, Gaillard, & Austad, 2013), and female choosiness (that is, selectivity for a mate) often decreases when reproductive time is limited. In polygynous killifish [Austrolebias reicherti], for example, females prefer larger males, but this preference decreases by the end of the breeding season (Passos, Tassino, Reyes, & Rosenthal, 2014). In cockroaches [Nauphoeta cinerea], females who are prevented access to males early in the lifespan subsequently require dramatically less courtship prior to mating (Moore & Moore, 2001). Theory predicts generalized expedited courtship and lowered mating standards as time diminishes for other species as well: Computational simulations have shown that animals with a limited breeding season and mutual mate choice should optimally become less choosy over time as the number of mating prospects and quality of remaining mates decreases (Crowley et al., 1991; Johnstone, 1997), provided mate quality changes over time (but see a counter-example from a species with biparental care in Kvarnemo & Forsgren, 2000).

Human adults also decrease in reproductive ability over the lifespan, meaning one might expect corresponding lowered standards for a potential reproductive partner (reduced mate choosiness) as age advances. All else being equal, individuals should be choosy in their partner choices overall, as there are a variety of social, economic, sexual, reproductive, and survival benefits that can result (directly or indirectly) from good partnering decisions. The sexes vary in this pattern: Women are relatively more choosy in mate choice than men, having more demanding preferences for a mate (Schwarz & Hassebrauck, 2012) and preferring to wait longer prior to engaging in sexual intercourse with a new partner (Buss & Schmitt, 1993). Women also decline in fecundity faster than men, experiencing reproductive cessation with the onset of menopause, a transitional process that consistently begins around the ages of the late 40s and early 50s (recent biomedical reproductive technology interventions notwithstanding). Menopause, therefore, represents a significant temporal boundary in direct reproductive fitness for women—that is, a reproductive deadline or milestone, but crucially one that does not typically occur at the end of life. Despite the importance of this life history event, relatively little is known about the consequences of reproductive decline on women's mate choice strategies and choosiness.

As with other species, reduced choosiness in response to diminishing reproductive opportunity may be advantageous for women as menopause approaches. When younger, the benefits of being romantically and sexually discriminating are large, because one can choose a good partner with whom to have and raise multiple offspring in the years ahead. But being choosy also comes with costs: Being more restrictive in partner choice typically results in some good opportunities being lost, more time passing (thus delaying partnering and/or reproduction), and potentially increasing intrasexual competition with other choosy individuals attempting to attract the same mates. When the reproductive window begins to close, the cost-benefit scales tip with respect to individual reproductive potential, particularly for women, making it more advantageous to relax their choosiness towards sexual partners.

Just such a pattern was found by Easton, Confer, Goetz, and Buss (2010)—in their study, women ages 27–45 years (i.e. those typically nearing or experiencing a decline in fecundity) reported more frequent sexual fantasies and more willingness to have sex with a partner they had known for a short period of time than women ages 46+ (i.e. approaching menopause or post reproductive deadline) or women younger than 27 (i.e. no immediate reproductive deadline). The authors dubbed the effect reproduction expediting— a tendency for women (both nulliparous women and those with children) nearing the onset of menopause to engage in behaviors and thoughts promoting additional sexual activity. While theory predicts this particular pattern for women, their study did not include men, leaving unexamined additional questions around the sex-specific nature of the reproduction-expediting effect. Schmitt et al. (2002) also found that women, but not men, experience a sexual peak in in the early 30s, hypothesizing it could increase fertility in long-term monogamous relationships. These results are in line with an evolutionary prediction that women nearing menopause have facultative changes in sexual desires and engage in sexual activities that promote increased potential of sexual intercourse, conception, and ultimately reproduction.

Most past research has focused on what happens to women's mating strategies as they approach menopause, but that is only a portion of the lifetime story of women's partner choices. Humans tend to engage in pair-bonding and reproduction throughout much of the adult life course and enter partnerships not just to reproduce, but also for companionship and recreational sex, among numerous other reasons. Cross-cultural and biological evidence indicates that older adults generally remain sexually active, with older women even showing increased sexual satisfaction (Gray, Garcia, & Gesselman, 2018), even though sexual activity (and reproductive output) generally declines with increased age (DeLamater, 2012; Gray & Garcia, 2012; Winn & Newton, 1982). After menopause, when sexual reproduction is no longer as substantial a factor in women's partner choice, other factors such as companionship, resources, and health benefits remain important, and individuals should again attempt to choose a high-quality partner—but based on these other aspects of a mate not necessarily tied to their reproductive possibility. As a result, the cost-benefit comparison can shift back in favor of the benefits of greater choosiness in the relationship domain. Thus, we hypothesize a general U-shaped pattern for women's romantic/sexual partner choosiness, predicting a steep decline in choosiness before the typical age of menopausal onset (reproduction-expediting), and a return to greater choosiness after menopause.

Choosiness can be defined as an acceptable threshold level for some valued trait in a mate. Individuals value many traits in a mate, which differ in relative importance. We here focus on a single trait that is typically valued by women: commitment (see Discussion for additional consideration of choosiness based on other important traits). We measure choosiness regarding commitment in terms of the length of time one expects to wait prior to having sex with a potential new romantic or sexual partner (one's sexual-timing strategy1), such that waiting longer indicates greater choosiness. Therefore, we expect:

H1

: While women approaching the typical age of menopausal transition are likely to use sexual-timing strategies that reduce their partner commitment choosiness, women beyond that age will be more likely to use strategies requiring greater partner commitment, increasing commitment choosiness to levels similar to those before menopause.

Testing this hypothesis involves replicating the reproduction-expediting pattern observed by Easton et al. (2010) in a larger and more diverse national sample with a greater range of sexual choice behaviors.

Although research on choosiness often focuses on the advantages for women, men also benefit from choosiness for a long-term partner and face age-related declines in fecundity. Therefore, men could also vary their degree of choosiness over the life course. Research has shown that men decrease in sexual motivation and sexual activity as they age (Gray et al., 2018; Lindau et al., 2007; Twenge, Sherman, & Wells, 2017). Men also risk declines in sexual function with advancing age, including erectile dysfunction (Feldman, Goldstein, Hatzichristou, Krane, & McKinlay, 1994), as well as reproductive aging (Vinicius, Mace, & Migliano, 2014), each of which directly impacts fecundity. However, the loss of reproductive function and age of onset is a variable risk for males (Lindau et al., 2007), not a near certainty as it is for menopausal women. Therefore, men do not face a clear cessation of reproduction, which lessens temporal pressure on men to find sexual partners and so also lessens the need to reduce their choosiness. Thus, for men, choosiness (at least for a committed romantic partner) remains beneficial throughout the lifespan.

The two sexes thus face different reproductive challenges, which may interact to influence choosiness. This is compounded by age variation in sexual partners. In a heterosexual context, men generally prefer younger partners with the preferred age gap increasing with the man's age, while women prefer men about 5 years older than themselves (Kenrick & Keefe, 1992). Actual sexual partners exhibit similar disparities in age across the lifespan, with men typically being around 2 to 3 years older than the women they have sex with, suggesting that age of sexual partners, like the frequency of sexual activity, appears to be driven by female sexual preferences (Antfolk et al., 2015). This suggests that men could also exhibit a reproduction-expediting pattern similar to women, following their lead in reduced commitment choosiness, but lagged by several years. However, in the relevant age range (in the 40s–50s), men's mate value also peaks (e.g. males become more demanding than women in personal ads—Waynforth & Dunbar, 1995), which could complicate the pattern of expediting in men.

These three factors—men's lack of acute temporal pressure to reproduce, women generally dictating when and with whom sex occurs, and men's improving mate value—may push in opposite directions in impacting men's overall mating strategy. Therefore, we hypothesize:

H2

: Men are likely to exhibit little variation in sexual-timing strategy over the lifespan.

Both sexes face several other proximate reproduction-related factors which could also contribute to changes in partner choosiness with age, complementary to ultimate evolutionary explanations. Sexual partnering decisions are not driven completely by reproductive motives but also conscious attitudes, societal norms, environmental context, and dyadic factors. Few of these variables are characterized over the course of life, let alone how they would interact with a drive to expedite reproduction. However, Easton et al. (2010) documented one relevant input—the frequency of women's sexual thoughts and activity, which are both elevated in reproduction-expediting women. Nevertheless, a more robust understanding of reproduction expediting requires investigation of other factors. Therefore, in addition to replicating Easton and colleagues' work on sexual thoughts and activity, we conduct exploratory analysis of two additional variables that are likely related to choosiness: internal concern over fecundity and external pressure to establish a romantic partnership.

Women's concern over reproducing as fecundity wanes (colloquially referred to as “the ticking of one's biological clock”) is associated with both internal factors (e.g. conscious awareness and physiological cues) and external factors (e.g. cultural norms and expectations regarding age at reproduction). Internal factors include sex-specific bodily changes and changes in thought processes, including greater attention to reproduction. For example, childless women nearing the end of peak fecundity (ages 27–33), regardless of their desire for children, recalled a greater number of baby-related items on a sentence-memory task than women experiencing or past menopause, suggesting greater reproductive-goal engagement by the former (Heckhausen, Wrosch, & Fleeson, 2001). Sexual behavior is also influenced by others, such as intra-sexual competition for desirable mates and judgements by one's peers. Childlessness is negatively stigmatized in Western societies (Miles, Keitel, Jackson, Harris, & Licciardi, 2009), meaning both sexes are likely to receive external social pressure from others to reproduce. Internal and external factors often work in concert, such that increased social pressure corresponds with enhanced stress over infertility (Miles et al., 2009), which could induce stronger behavioral change.

We expect that individuals with more internal stress over reproduction and recipients of more external cues about cultural norms to achieve a reproduction goal would exhibit stronger reproduction expediting. Overall, decreased fecundity, increased sexuality, heightened societal pressure to reproduce, and more salient internal stress over one's biological clock are likely driven in part by common factors, so they all may also covary with decreases in mating-related commitment choosiness.

In the current investigation, using three large samples of single adults of all ages in the United States, we study how partner commitment choosiness and the corresponding use of different sexual-timing strategies changes with age in both sexes. Specifically, we assess whether the courtship period prior to sex with a new partner (sexual-timing strategy) is shortened before the typical start of menopausal transition for women (Easton and colleagues' reproduction expediting). We also analyze whether females past the transition return to former high levels of expected commitment (i.e. lengthened time before sexual activity with a new partner). While the original reproduction-expediting effect was studied using only three age groups of women for ease of testing (Easton et al., 2010), we use a finer timescale to reflect the variable age of onset and length of menopausal transition. Rather than divide participants into a ‘reproduction-expediting’ group and two pre- and post- comparison groups, we instead examine patterns holistically for overall trends. We also test whether males expedite reproduction with age and explore the influence of several relevant factors on both sexes' reproduction expediting and return to former sexual-timing strategies.

In Study 1, we examine the change in distribution of strategies for timing sex with a new partner over the life course for both sexes and the influence of proximal factors that may affect the prevalence of different strategies, including concern over one's biological clock and frequency of sexual acts and thoughts. In Study 2, we refine and replicate these findings of changes over the lifespan with a larger sample (consisting of two combined cross-sectional samples, samples 2A and 2B), including the reproduction-expediting effect and subsequent return to choosiness, and examine the influence of external stressors to find a romantic partner.

Section snippets

Procedure

Data were collected in 2011 as part of an annual study called Singles in America (SIA), sponsored by the relationship company Match; however, participants were not drawn from the Match or subsidiary site populations. Instead, participants were recruited exclusively by MarketTools (San Francisco, California), using independent opt-in Internet research panels for population-based cross-sectional survey. MarketTools draws panelists from their diverse pool of established participants who have been

Study 2

The previous results indicate that as people age, they alter their sexual-timing strategies. As expected, females typically decrease their use of high-commitment strategies until the end of menopause in a reproduction-expediting pattern and thereafter revert to waiting to have sex until greater relationship commitment or exclusivity (Fig. 1). Over the first half of the same age range, males also show decreasing use of high-commitment strategies, though the degree of this pattern is attenuated

Discussion

The current study examined sexual decision making over the adult lifespan using multiple large U.S. samples of heterosexual adult singles from diverse demographics and age cohorts. Evolutionary life history theory would predict that both men and women respond to aging using flexible sexual-timing strategies to establish and maintain pair-bonds to maximize reproductive output. Our results show that at midlife, as the female reproductive window shrinks and with it the relative benefits of

Conclusion

Women's menopausal transition appears to be a powerful motivator for shifting interpersonal commitment preferences and sexual behavior. Our findings show that both females and males approaching the typical age of female menopausal onset are more likely to engage in sexual activity sooner with a new partner. This behavior change may be driven by female concern about declining fecundity, rather than age-related changes in mate value. Our new results highlight the importance of studying sexuality

Declaration of interests

Singles in America (SIA) is funded by Match. J.R.G and H.E.F. have received funding from Match. Research findings from SIA are not subject to approval by Match or other sponsors prior to submission or publication.

References (43)

  • E.E. Bruch et al.

    Aspirational pursuit of mates in online dating markets

    Science Advances

    (2018)
  • D.M. Buss et al.

    Sexual strategies theory: An evolutionary perspective on human mating

    Psychological Review

    (1993)
  • B.P. Buunk et al.

    Age and gender differences in mate selection criteria for various involvement levels

    Personal Relationships

    (2002)
  • D. Conroy-Beam et al.

    Why is age so important in human mating?

    (2018)
  • P.H. Crowley et al.

    Mate density, predation risk, and the seasonal sequence of mate choices: A dynamic game

    The American Naturalist

    (1991)
  • J. DeLamater

    Sexual expression in later life: A review and synthesis

    Journal of Sex Research

    (2012)
  • P.W. Eastwick et al.

    Relational mate value: Consensus and uniqueness in romantic evaluations

    Journal of Personality and Social Psychology

    (2014)
  • R.M. Emerson

    Social exchange theory

    Annual Review of Sociology

    (1976)
  • S.W. Gangestad

    Sexual selection and physical attractiveness

    Human Nature

    (1993)
  • S.W. Gangestad et al.

    Toward an evolutionary history of female sociosexual variation

    Journal of Personality

    (1990)
  • S.W. Gangestad et al.

    The evolution of human mating: Trade-offs and strategic pluralism

    Behavioral and Brain Sciences

    (2000)
  • View full text