Sex differences are insufficient evidence of ecological adaptations in human females
Behavioral and Brain Sciences, 2022
Benenson et al. postulate that human females evolved unique survival adaptations to facilitate ma... more Benenson et al. postulate that human females evolved unique survival adaptations to facilitate maternal and grandmaternal care. This hypothesis is consistent with the broader hypothesis that female phenotypes are more ecologically optimal, but further evidence is needed to make a compelling case that sex differences in self-protection are not primarily the result of more intense sexual selection on males.
Unlike men, heterosexual women's genital arousal is gender nonspecific, such that heterosexual wo... more Unlike men, heterosexual women's genital arousal is gender nonspecific, such that heterosexual women show relativelysimilar genital arousalto sexual stimuli depicting menand women but typically report greater subjective arousal to male stimuli. Based on the ovulatory-shift hypothesis-that women show a mid-cycle shift in preferences towards more masculine features during peak fertility-we predicted that heterosexual women's genital and subjective arousal would be gender specific (more arousal towards male stimuli) during peak fertility. Twentytwo naturally-cycling heterosexual women were assessed during the follicular and luteal phases of their menstrual cycle to examine the role of menstrual cycle phase in gender specificity of genital and subjective sexual arousal. Menstrual cycle phase was confirmed with salivary hormone assays; phase at the time of first testing was counterbalanced. Women's genital and subjective sexual arousal patterns were gender nonspecific, irrespective of cycle phase. Cycle phase at first testing session did not influence genital or subjective arousal in the second testing session. Similar to previous research, women's genital and subjective sexual arousal varied with cues of sexual activity, but neither genital nor subjective sexual arousal varied by gender cues, with the exception of masturbation stimuli, where women showed higher genital arousal to the stimuli depicting male compared to female actors. These data suggest that menstrual cycle phase does not influence the gender specificity of heterosexual women's genital and subjective sexual arousal.
Polymorphisms in the dopamine D4 receptor (DRD4) have previously been shown to associate with a v... more Polymorphisms in the dopamine D4 receptor (DRD4) have previously been shown to associate with a variety of human behavioral phenotypes, including ADHD pathology, alcohol and tobacco craving, financial risk-taking in males, and broader personality traits such as novelty seeking. Recent research has linked the presence of a 7-repeat (7R) allele in a 48bp variable number of tandem repeats (VNTR) along exon III of DRD4 to age at first sexual intercourse, sexual desire, arousal and function, and infidelity and promiscuity. We hypothesized that carriers of longer DRD4 alleles may report interest in a wider variety of sexual behaviors and experiences than noncarriers. Participants completed a 37-item questionnaire measuring sexual interests as well as Cloninger's Temperament and Character Inventory, and were genotyped for the 48-bp VNTR on exon III of DRD4. Based on our final genotyped sample of female (n = 139) and male (n = 115) participants, we found that 7R carriers reported interest in a wider variety of sexual behaviors (r = 0.16) within a young adult heterosexual sample of European descent. To our knowledge, this is the first reported association between DRD4 exon III VNTR genotype and interest in a variety of sexual behaviors. We discuss these findings within the context of DRD4 research and broader trends in human evolutionary history.
The difficulty of inducing orgasm in women, its variability between women, and the lack of an obv... more The difficulty of inducing orgasm in women, its variability between women, and the lack of an obvious relationship with women’s reproductive success have led some researchers to conclude that female orgasm is a nonfunctional by-product of developmental pathways that women share with men. Other researchers have presented evidence that orgasm is an adaptation in women. In this chapter, we review the evidence for these opposing points of view and find that a functional hypothesis receives greater support. First, we discuss the phenomenological, anatomical, and neurological correlates of women’s orgasm, which are generally inconsistent with the idea that female orgasm is a by-product. We then present evidence that female orgasm enhances the likelihood of conception, and we summarize evidence that female orgasm functions as a mechanism for choosing mates of high genetic quality, investment potential, or both. Finally, we outline directions for future research that will help to resolve the debate about the functionality of orgasm in women.
Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a... more Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a larger role than female choice. In a sample of men (N = 164), we sought to provide further evidence on the effects of men's physical dominance and sexual attractiveness on mating success and hence in sexual selection. Objective measures and subjective ratings of male sexually dimorphic traits purportedly under sexual selection (height, vocal and facial masculinity, upper body size from 3D scans, physical strength, and baseline testosterone) and observer perceptions of physical dominance and sexual attractiveness based on self-presentation video recordings were assessed and associated with mating success (sociosexual behaviour and number of potential conceptions) in a partly longitudinal design. Results from structural equation models and selection analyses revealed that physical dominance, but not sexual attractiveness, predicted mating success. Physical dominance mediated associations of upper body size, physical strength, as well as vocal and facial physical dominance and attractiveness with mating success. These findings thus suggest a greater importance of intrasexual competition than female choice in human male sexual selection.
Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a... more Recent evidence suggests that in sexual selection on human males, intrasexual competition plays a larger role than female choice. In a sample of men (N = 164), we sought to provide further evidence on the effects of men's physical dominance and sexual attractiveness on mating success and hence in sexual selection. Objective measures and subjective ratings of male sexually dimorphic traits purportedly under sexual selection (height, vocal and facial masculinity, upper body size from 3D scans, physical strength, and baseline testosterone) and observer perceptions of physical dominance and sexual attractiveness based on self-presentation video recordings were assessed and associated with mating success (sociosexual behaviour and number of potential conceptions) in a partly longitudinal design. Results from structural equation models and selection analyses revealed that physical dominance, but not sexual attractiveness, predicted mating success. Physical dominance mediated associations of upper body size, physical strength, as well as vocal and facial physical dominance and attractiveness with mating success. These findings thus suggest a greater importance of intrasexual competition than female choice in human male sexual selection.
Past work demonstrates that humans behave differently towards women across their menstrual cycles... more Past work demonstrates that humans behave differently towards women across their menstrual cycles, even after exclusively visual exposure to women's faces. People may look at women's faces differently as a function of women's menstrual cycles. Analyses of participants' scanpaths (eye movement patterns) while they looked at women at different phases of their menstrual cycles revealed that observers exhibit more consistent scanpaths when examining women's faces when women are in a menstrual cycle phase that typically corresponds with peak fertility, whereas they exhibit more variable patterns when looking at women's faces when they are in phases that do not correspond with fertility. A multivariate classifier on participants' scanpaths predicted whether they were looking at the face of a woman in a more typically fertile-versus non-fertile-phase of her menstrual cycle with above-chance accuracy. These findings demonstrate that people look at women's faces differently as a function of women's menstrual cycles, and suggest that people are sensitive to fluctuating visual cues associated with women's menstrual cycle phase.
Adaptive human behavior and physiology, Feb 14, 2018
Prior work suggests that women's preferences for sexually dimorphic traits, such as preferences f... more Prior work suggests that women's preferences for sexually dimorphic traits, such as preferences for masculine facial and vocal characteristics, may be modulated by a multitude of factors related to reproductive potential including breastfeeding status. In the present study, we investigated women's preferences for a highly sexually dimorphic vocal characteristic, voice pitch, across a sample of nulliparous (n = 65) and breastfeeding (n = 63) women in Manila, Philippines. We examined whether preferences for pitch were related to breastfeeding status, age, relationship status, self-rated attractiveness, or salivary steroid hormone concentrations. Both nulliparous and breastfeeding women displayed preferences for feminized, rather than masculinized, pitch. The strength of this preference was negatively associated with age and negatively associated with self-rated attractiveness, but was unrelated to breastfeeding and relationship status. Estradiol and progesterone positively interacted in predicting pitch preferences, such that estradiol tended to negatively predict preferences for masculinized pitch when progesterone was low, and to positively predict preferences when progesterone was high. Our findings reinforce the notion that reproductive potential predicts preferences for sexually dimorphic traits, and emphasize importance of assessing measures of reproductive potential when evaluating mate preferences.
Women's mating psychology may have evolved to track reproductive conditions, including conception... more Women's mating psychology may have evolved to track reproductive conditions, including conception risk, across and between ovulatory cycles. Alternatively, withinwoman correlations between mating psychology and ovarian hormones may be byproducts of between-women relationships. Here, we examined associations between steroid hormones and two facets of sexual psychology with putatively different adaptive functions, sociosexual orientation and general sexual desire, in a sample of naturally cycling women (NC; n = 348, 87 of whom completed 2 sessions) and hormonally contracepting women (HC; n = 266, 65 of whom completed 2 sessions). Across two sessions, increases in estradiol predicted elevated sociosexual desires in NC women, and this relationship was stronger in women whose progesterone simultaneously decreased across sessions. Changes in hormones were not associated with changes in general sexual desire. Between-subjects differences in testosterone robustly, positively predicted sociosexuality and general sexual desire among NC women. Hormones were not consistently related to changes or differences in sexual psychology among HC women. The present results are consistent with testosterone contributing to individual differences, or modulating relatively long-term changes, in women's mating psychology. Further, our within-woman findings are consistent with the hypothesis that shifts in women's mating psychology may function to secure genetic benefits, and that these shifts are not byproducts of between-women associations.
Personality and Social Psychology Bulletin, Nov 21, 2016
A few years ago, actor Mel Gibson's mistress became pregnant with their child. His marriage ended... more A few years ago, actor Mel Gibson's mistress became pregnant with their child. His marriage ended, and he eventually married his mistress. It had been rumored for some time that Gibson had engaged in extramarital affairs, but it seemed to be the mistress' pregnancy that prompted his wife to end their 31-year marriage (Sacks, 2011). Infidelity can lead to several negative outcomes, including relationship dissolution (Amato & Previti, 2003; Buunk, 1995). The costs of infidelity may be particularly high if the infidelity occurs with a woman who is near the fertile phase of her ovulatory cycle. If the mistress becomes pregnant, the emotional and psychological costs of infidelity would be compounded by the threat of the man's time, money, and other resources being diverted away from his primary partner to the mistress and child. The present studies tested the hypothesis that women demonstrate more mate guarding and jealousy toward other women who are in the fertile phase of their ovulatory cycle than toward women who are not in the fertile phase of their cycle.
The ratio of the lengths of the second and fourth fingers (2D:4D) may serve as a marker for prena... more The ratio of the lengths of the second and fourth fingers (2D:4D) may serve as a marker for prenatal androgen signaling. Because people are typically unaware of their 2D:4D, its use allows possible effects of early sex hormone regimes and socialization to be disentangled. We conducted a meta-analysis on relationships between 2D:4D and sexual orientation in men and women in 18 independent samples of men and 16 independent samples of women. Collectively, these samples comprised 1,618 heterosexual men, 1,693 heterosexual women, 1,503 gay men, and 1,014 lesbians. In addition to identifying the normative heterosexual sex difference in 2D:4D for both hands, we found that heterosexual women had higher (more feminine) left-and right-hand 2D:4D than did lesbians, but we found no difference between heterosexual and gay men. Moderator analyses suggested that ethnicity explained some between-studies variation in men. These results add to a literature suggesting that early sex hormone signaling affects sexual orientation in women, and highlight the need for further research exploring the relationships among 2D:4D, sexual orientation, and ethnicity in men.
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