Researchers have spent decades investigating factors in attraction; biological variables, cultural norms, and social pressures have all had their time in the spotlight. Humans are complicated animals and each of these realms have shown measurable effects. However, evolutionary approaches provide a unifying theory that subsumes and explains each of these factors and how they interact to create intricate yet predictable patterns in human mating behavior. In this chapter, we give a brief summary of major factors influencing attractiveness as perceived by men, including biological factors such as age and ovulatory status but also social factors such as exposure to highly attractive, or simply novel, women. Understanding how attractiveness can vary over time and within relationships can be useful, not only to research but also in applied clinical fields such as couples’ and marital therapy.

Despite a tendency to form socially monogamous pair-bonds that carry expectations of sexual exclusivity, infidelity has been a recurrent feature of human mating across societies. The attitudes, social cognition, affect, and behavior associated with infidelity vary in patterned ways between women and men. In the current chapter, we use an evolutionary perspective to make sense of the historical and cross-cultural ubiquity of extradyadic behavior, as well the adaptative costs and benefits of men’s infidelity. Specifically, we review theory and research pertaining to men’s extra-pair mating and consider salient individual differences, romantic relationship dynamics, and social–ecological factors that influence mating strategies and extradyadic involvement. Following other scholars, we argue that men have evolved adaptations for short-term mating that facilitate opportunistic extra-pair behavior in a “quantity-over-quality” reproductive strategy. Consequently, on average, men are predicted to express a stronger desire to engage in sexual infidelity and to have more permissive attitudes toward extradyadic involvement than women. However, only particular men appear to execute a mixed mating strategy involving a long-term mate and an extra-pair partner, such as those with greater mate value. Satisfaction with and commitment to the relationship appear to be crucial in preventing men’s infidelity, and socio-ecological factors, including cultural dynamics (e.g., norms surrounding infidelity) and sex ratios that create conditions of mate scarcity, are inextricably tied to men’s extra-pair mating.

The present chapter advances the view that women’s mate preferences can be grouped into at least two overarching domains: competitiveness and fatherhood. Theoretical and empirical considerations suggest that female mate preferences evolve in contexts of male competitiveness and often amplify the effects of male–male competition. Evidence for the importance of male–male competition and female choice for competitiveness in humans is reviewed. Evidence is likewise offered for the importance of human fatherhood as an additional domain of female choice outside of male competitiveness. Implications of more inclusive mate preferences for the evolution of cognitive architecture are discussed alongside the social and ethical implications of female choice for competitiveness.

Despite the extensive empirical exploration of sexual desire, only one field explains the proper biological function of this phenomenon—evolutionary psychology. This chapter reviews women’s copulatory urgency—individual differences in the experience or intensity of sexual desire—from an evolutionary psychological perspective. An evolutionary psychological perspective of the function of sexual desire can shed light on how deficits in this motivational force may emerge, which may be useful for clinicians when helping patients understand the etiology of sexual desire concerns. An evolutionary psychological perspective of sexual desire further reveals: (1) why men and women differ in their experiences of sexual desire, (2) how natural selection produces individual differences in sexual desire, and (3) how extremes in sexual desire may be associated with hypersexuality, paraphilias, or an evolutionary mismatch between the adaptive problems faced during our species’ past and the challenges we face today. I begin the chapter by presenting a brief history of research on sexual desire and highlighting the limitations of early models of sexual responding. Next, I discuss the difficulties of measuring sexual desire, and explain how evolutionary meta-theory can be fruitful when examining context-dependent individual differences in sexual desire. I then describe the impact of several important contextual factors (e.g., age, relationship length, parental effort, partner habituation) on variation in women’s sexual desire responses and highlight avenues for future research. The chapter ends by discussing the qualities of compulsive sexual behavior and proposing that extreme variations in sexual desire as we currently understand them may be the result of an evolutionary mismatch. In sum, I suggest that scientists distinguish between sexual desire and sexual arousal, consider evolutionary meta-theory when thinking about context-dependent variation in sexual desire, and be cognizant of potential confounds when examining women’s sexual desire responses.

This chapter focuses on the behaviors employed by men in the service of attracting mates, which we discuss as having emerged to solve specific reproductive problems faced by women. We consider behaviors employed by men to attract mates in short-term mating and long-term mating contexts, given the differential valuation on certain behavioral repertoire that emerge. In short-term mating, we specifically consider behavioral displays of dominance with their dispositional and situational antecedents before discussing men’s pursuit of distinctiveness and humor use, behaviors ostensibly indicative of good genes. In long-term mating, our discussion centers around the desirability of different resource displays and benevolence. We further discuss cues ostensibly diagnostic of paternal investment ability and an interest in monogamy. Our final section addresses how modern mating markets present adaptive problems for men (e.g., online dating, appearance enhancing behaviors) and how men seek to solve the new problems that have emerged.

Extrapair sex, although not a dominant human mating strategy, has been a part of our mating landscape throughout human history. Although prevalence rates vary across studies, a conservative estimate is that at least 1 out of 5 persons have cheated on a committed partner. In this chapter I discuss theories and evidence addressing extrapair interest and behavior (i.e., cheating on a committed partner) as produced by adaptations. Topics include the costs and benefits of extrapair behavior, comparisons to nonhuman animal extrapair behavior, sex differences, and purported female cyclical variations in extrapair orientation. I briefly discuss proximate factors that predict proclivity to cheat. I also touch on infidelity advertisement, cheating detection, forgiving a partner’s infidelity, and infidelity in popular culture. I conclude with some observations about the state of the field. Regardless of causes and correlates, infidelity can be costly, yet humans remain interested in and intrigued by the phenomenon.

Unlike extensive research conducted on courtship, foreplay, and intercourse, what happens after ejaculation is one of the most neglected dimensions of human sexual behavior. As described in this chapter, postejaculatory adaptations have important and diverse implications for such things as penis hypersensitivity, the refractory period, female infidelity, sperm competition, semen displacement, self-semen displacement, spousal rape, the risk of transmitting sexually transmitted diseases for uncircumcised men, and the incidence of nonpaternity. This chapter also outlines ways to test the Bruce effect in human females and provides a novel explanation for the absence of the Coolidge effect in women.

In this chapter we summarize and discuss the literature on human female romantic jealousy from an evolutionary perspective. We first define jealousy as a complex cognitive, affective, and motivational state that occurs in response to the threatened or actual loss of a valued relationship to a rival, and that can trigger different emotions. We further discuss different dimensions of jealousy, stressing both state and trait jealousy. We outline behavioral consequences of jealousy, such as mate guarding and mate retention, and we discuss how some qualities of rivals can trigger jealousy. The most frequently studied area in research on human jealousy is sex differences in sexual versus emotional jealousy, suggesting a robust and replicated finding of higher emotional jealousy in women, and higher sexual jealousy in men. We further discuss individual differences that explain variation in jealousy, such as higher overall jealousy among women, associations between women’s jealousy and their anxiety and self-esteem, developmental factors influencing jealousy, lower jealousy among non-monogamous individuals, and high jealousy among pathologically jealous individuals. We challenge the research on sex differences in jealousy with reference to intra-sexual variation among individuals of different sexual orientations. We show that female jealousy is influenced by hormonal and genetic factors, and we discuss examples of non-human species to show analogies to human jealousy. Throughout the chapter we stress the plasticity of jealous response depending on contextual factors, including environmental and sociocultural contexts. Human diversity in the manifestations of state jealousy does not contradict the evolved nature of jealousness. We conclude by considering the distal functions of jealousy, including maintenance of a valued relationship and self-esteem, mate-poaching, and mate-switching. We note several gaps in the literature of female jealousy, and we hope this chapter integrates the literature, informs newcomers, and inspires new evolutionary research.

Rape and sexual coercion have been recurrent adaptive challenges for women over human evolutionary history. There are many reproductive, physical, and psychological costs of sexual victimization, including mitigation of female sexual choice. The use of rape and coercion are well-documented behaviors in human males intended to circumvent female rejection. The intersexual conflict resulting from these deceptive and sometimes violent tactics likely generated selection pressures for a female defense system to protect reproductive choice. This chapter synthesizes a broad domain of research on the psychology of rape perpetration and avoidance to suggest that women may have evolved a specialized threat management system to mitigate their risk of rape and coercion. This system is hypothesized to be sensitive to inputs that signal either an increased likelihood of sexual victimization or greater costs of sexual victimization. Such inputs are expected to produce an emotional response, fear, that motivates avoidant behavior to preemptively avoid sexual victimization. Here, we discuss research in support of a precautionary psychological threat management system for rape avoidance, highlighting potential inputs to and outputs from this system.

Men sometimes engage in noncopulatory sexual behaviors, such as cunnilingus and other kinds of sexual foreplay. Men involved in long-term romantic relationships, in particular, tend to provision their partners with oral sex. Potential adaptive functions of cunnilingus in humans are discussed with a focus on the hypothesis that men use oral sex provisioning as part of a general benefit-provisioning, long-term mating strategy. Other potential adaptive functions are also considered, including the infidelity detection hypothesis and several hypotheses concerning sperm competition adaptations. Some research has proposed the possibility that men may use oral sex as a form of infidelity detection, wherein they might be able to smell or taste the semen of rival males in their partner’s vagina. Other research has posited that men might perform cunnilingus in order to induce orgasm in their partners, thereby increasing the amount of sperm retained in her reproductive tract after ejaculation. Still others have suggested that men might perform cunnilingus to increase their own arousal, thus increasing their subsequent ejaculate volume. These adaptive perspectives are couched within the wider literature on oral sex, which includes data regarding the frequency of oral sex in adolescent, preindustrial and non-Western samples, as well as women’s desire for receiving oral sex. Regarding the relative infrequency of cunnilingus in preindustrial and non-Western samples, in particular, men’s provisioning of oral sex is considered as potentially being a part of an evolved cognition for benefit-provisioning mate retention in general, rather than oral sex itself serving a specific adaptive function. Specifically, oral sex may be one type of sexual favor that men, especially those in Western cultures, sometimes provide to their long-term partners. Additional data regarding the increased sexual and relationship satisfaction in women who engage in a wider variety of sexual practices and who more frequently experience orgasm further supports the mate retention hypothesis of men’s provisioning of oral sex. Nevertheless, the available literature investigating these potential adaptive functions is currently insufficient to draw any decisive conclusions. Finally, gaps in the current literature and suggestions for future research that may help determine the evolved nature of men’s oral sex provisioning are discussed.

Sexual fantasies refer to mental imagery of sexual activity with an emotional component that absorbs the fantasizer. These images are often sexually arousing and enjoyable, but they can elicit guilt and be unwanted and intrusive. Reported frequency of sexual fantasizing is subject to large individual differences. The present chapter reviews and discusses the role of motivational tendencies underlying sexual fantasies and the relationship between sexual functioning and sexual fantasies. Men report more frequent fantasies than women, but at least part of the difference is explained by greater frequency of masturbation accompanied by fantasies for men than women. Sexual desire does not require the experience of fantasies, but fantasy frequency is robustly related to sexual desire in the reproductive years. Tendency to experience sexual fantasies is related to imagery ability, in general, but the modest correlations suggest independent processes. Unlike sexual activity that requires compromise between partners’ desires, fantasies are unconstrained by physical and social reality; as such, they provide a window into sexual motivations that guide cognitions and behavior. Predictions of sex differences in fantasy contents based on evolutionary theory have been confirmed by many studies. Women are more likely than men to fantasize about sex with the current partner, and less likely than men to fantasize about group sex, sex with strangers, extradyadic relationships, and sex with (legally) much younger partners. This is interpreted as fantasies reflecting sex-differentiated mating strategies. However, a substantial proportion of women report fantasies of group sex, sex with unknown men, and sex with men other than their current partner. This suggests that a certain degree of sperm competition has occurred in human evolutionary history, which is corroborated by the relative size of men’s testes in comparison with other primates. Generally (and against expectations), women do not fantasize more about sex with much older partners and famous people. Fantasies involving sexual aggression are very common. Men fantasize more than women about forcing someone to have sex. Some studies report that women fantasize more about being forced to have sex, but others have failed to find this sex differences. Still, more women than men report that the fantasy of being forced to have sex is among their favorites. These fantasies are typically very sexually arousing, but they may challenge evolutionary explanations and the notion of fantasies revealing motivations, as rape is reported to be traumatic and revolting by victims. Several explanations are discussed. Rape fantasies might facilitate intercourse and sexual pleasure in circumstances of psychological ambivalence, when the environment is safe. In women, evidence of a relationship between sexual fantasies and sexual satisfaction is mixed. Sexual satisfaction is unrelated to female coital fantasies and to male fantasies, in general. Many variables that may cause fantasy-related dissatisfaction are discussed; these include fantasies provoking guilt feelings, preference for arousal solely induced by sensory and emotional stimulation, fantasies being used as escapes from relationship problems and other stressors of reality, and lack of adequate sleep leading to greater fantasy-induced arousal.