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A given man's phenotype embodies cues of his ancestral ability to effectively defend himself and his kin from harm, to survive adverse conditions, and to acquire status and mating opportunities. In this review, we explore the hypothesis that a man's phenotype also embodies cues to fertility or the probability that an ejaculate will fertilize ova. Female mate choice depends on the ability to discern the quality of a male reproductive partner through his phenotype, and male fertility may be among the traits that females have evolved to detect. A female who selects as mates males that deliver higher quality ejaculates will, on average, be more fecund than her competitors. Data on several non-human species demonstrate correlations between ejaculate quality and secondary sexual characteristics that inform female mate choice, suggesting that females may select mates in part on the basis of fertility. While the non-human literature on this topic has advanced, the human literature remains limited in scope and there is no clear consensus on appropriate methodologies or theoretical positions. We provide a comprehensive review and meta-analysis of this literature, and conclude by proposing solutions to the many issues that impede progress in the field. In the process, we hope to encourage interest and insight from investigators in other areas of human mating and reproductive biology.
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Humans perform copulatory behaviors that do not contribute directly to reproduction (e.g., cunnilingus, prolonged copulation). We conducted a content analysis of pornography to investigate whether such behaviors might contribute indirectly to reproduction by influencing ejaculate volume—an indicator of ejaculate quality. We coded 100 professional pornography scenes depicting the same male actor copulating with 100 different females, affording control for between-male differences in estimated ejaculate volume. Coders visually estimated ejaculate volume and recorded the time the actor spent engaged in cunnilingus, penile-vaginal penetration, and in any physical contact with his partner. We found support for the hypothesis that a man who spends more time performing cunnilingus produces an ejaculate with greater estimated volume, even after controlling statistically for the age and attractiveness of the actress, and time spent in physical contact with his partner. Additionally, we tested the ejaculate adjustment hypothesis for prolonged copulation and found no support. Prolonged copulation does not facilitate production of an ejaculate with greater estimated volume, even after controlling statistically for time spent in physical contact with a partner. This research is the first to use content analysis to document that pre-ejaculatory copulatory behavior predicts estimated ejaculate volume and also is the first to document a relationship between the time spent performing cunnilingus and ejaculate quality.
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Objective This study investigated the relationship between perceived mate value discrepancy (i.e., the difference between an individual's mate value and their partner's mate value) and perceived frequency of mate retention performed by an individual relative to his or her partner. Method In two studies, participants in long-term, exclusive, sexual, heterosexual relationships reported their own, and their partner's, mate value and mate retention. Samples included 899 community members (Study 1) and 941 students and community members (Study 2). Results In Study 1, we documented that individuals with higher self-perceived short-term mate value, and who perceive their partner to have lower (vs. higher) short-term mate value, perform less frequent Benefit-Provisioning mate retention, controlling for the partner's Benefit-Provisioning mate retention. In Study 2, we documented that individuals who perceive that they could less easily replace their partner, and who perceive their partner could more (vs. less) easily replace them, perform more frequent mate retention (Benefit-Provisioning and Cost-Inflicting), controlling for the partner's mate retention. Conclusion These results highlight the importance of assessing perceived discrepancies in mate value (notably, regarding the replaceability of self and partner with another long-term mate) and perceived mate retention behaviors of self, relative to partner, between men and women in long-term relationships.
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Sexual selection may have shaped male visual sensitivity to characteristics that provide information about female mate quality. Indeed, men judge certain facial and bodily configurations of women to be attractive, possibly because those configurations signal health and fertility. Most of this evidence derives from the study of women's facial and body photographs. We tested the hypothesis that attractive female dancers receive greater visual attention from men than do unattractive dancers. Twenty-nine men viewed video pairs of pre-categorized high and low attractive female dancers. Their eye gaze was tracked and they also provided ratings of attractiveness, femininity, and dance movement harmony. High attractive dancers received greater visual attention than did low attractive dancers and men's visual attention correlated positively with their judgments of attractiveness, femininity, and dance movement harmony. We discuss our findings in the context of the ‘beauty captures the mind of the beholder’ hypothesis and the role of dance movements in human mate selection.
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Previous research documents that men and women can accurately judge male physical strength from gait, but also that the sexes differ in attractiveness judgments of strong and weak male walkers. Women’s (but not men’s) attractiveness assessments of strong male walkers are higher than for weak male walkers. Here, we extend this research to assessments of strong and weak male walkers in Chile, Germany, and Russia. Men and women judged videos of virtual characters, animated with the walk movements of motion-captured men, on strength and attractiveness. In two countries (Germany and Russia), these videos were additionally presented at 70% (slower) and 130% (faster) of their original speed. Stronger walkers were judged to be stronger and more attractive than weak walkers, and this effect was independent of country (but not sex). Women tended to provide higher attractiveness judgments to strong walkers, and men tended to provide higher attractiveness judgments to weak walkers. In addition, German and Russian participants rated strong walkers most attractive at slow and fast speed. Thus, across countries men and women can assess male strength from gait, although they tended to differ in attractiveness assessments of strong and weak male walkers. Attractiveness assessments of male gait may be influenced by society-specific emphasis on male physical strength.
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Coalitional mate retention (CMR) occurs when individuals request assistance from a friend to minimize the risk of partner infidelity. We secured reports from men and women in a committed, heterosexual relationship to investigate associations between CMR requests and the sex and personality traits of individuals who request CMR and the sex of their friends. Consistent with our hypothesis, individuals scoring higher in Honesty–Humility requested CMR less frequently. We also documented that individuals higher in Extraversion and lower in Conscientiousness requested CMR more frequently. We address limitations of the research and future research directions, including tests of the hypothesis that CMR involves duplicitous behaviors that are less typical of individual mate retention.
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Human dance may have originated from selection to display quality in courtship. This proposal is based on comparative investigation of variation in motor skills in relation to mate preference and selection. However, scholars have also proposed that dance has evolved as a by-product of imitative proficiency. In this view, imitative proficiency plays a central role in dance learning and performance and facilitates movement synchronization among dancers and thus social bonding. Here we comment on a recent paper (Laland et al. in Current Biology, 26, R5–R9, 2016 ), which favors the latter perspective. We suggest that social bonding through dance has evolved in consequence of the adaptive problem of assessing mate qualities and other social information from body movement. This information may then have been used in strengthening social cohesion.
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In women with lightly pigmented skin in particular, facial skin color homogeneity decreases with age, primarily due to chronic exposure to solar ultraviolet radiation (UVR), leading to a decrease in perceived health and attractiveness. Perception of female skin may be influenced by continuous exposure to, and thus familiarity with, age-related changes in visible skin condition in a given society. Men and women of two traditional societies, the Maasai (Tanzania) and the Tsimane’ (Bolivia), unfamiliar with lighter colored skin, judged images of British women’s facial skin for age, health, and attractiveness. In both samples, images with homogeneous skin color (from the cheeks of younger women) were judged to be younger and healthier and received a stronger preference than corresponding images with heterogeneous skin color (from older women). We suggest that (i) human sensitivity for quality-related information from facial skin color distribution is universal and independent of any known age-dependent variation in skin in a given population and (ii) skin discoloration is universally associated with less positive judgment.
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Background Evolutionary psychology suggests that skin signals aspects of mate value, yet only limited empirical evidence exists for this assertion. Objectives We sought to study the relationship between perception of skin condition and homogeneity of color/chromophore distribution. Methods Cropped skin cheek images from 170 girls and women (11-76 years) were blind-rated for attractiveness, healthiness, youthfulness, and biological age by 353 participants. These skin images and corresponding melanin/hemoglobin concentration maps were analyzed objectively for homogeneity. Results Homogeneity of unprocessed images correlated positively with perceived attractiveness, healthiness, and youthfulness (all r > 0.40; P < .001), but negatively with estimated age (r = −0.45; P < .001). Homogeneity of hemoglobin and melanin maps was positively correlated with that of unprocessed images (r = 0.92, 0.68; P < .001) and negatively correlated with estimated age (r = −0.32, −0.38; P < .001). Limitations Female skin only was studied. Conclusions Skin color homogeneity, driven by melanin and hemoglobin distribution, influences perception of age, attractiveness, health, and youth.
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Olfactory communication is very common amongst animals, and since the discovery of an accessory olfactory system in humans, possible human olfactory communication has gained considerable scientific interest. The importance of the human sense of smell has by far been underestimated in the past. Humans and other primates have been regarded as primarily ‘optical animals’ with highly developed powers of vision but a relatively undeveloped sense of smell. In recent years this assumption has undergone major revision. Several studies indicate that humans indeed seem to use olfactory communication and are even able to produce and perceive certain pheromones; recent studies have found that pheromones may play an important role in the behavioural and reproduction biology of humans. In this article we review the present evidence of the effect of human pheromones and discuss the role of olfactory cues in human sexual behaviour.
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The ratio between 2nd and 4th digit length (2D:4D) may be a negative correlate of prenatal testosterone. This possibility has led to a number of studies of 2D:4D and its relationship with sexual orientation and other sex-dependent traits. At first, 2D:4D ratio was calculated from measurements made directly on the fingers but recently a number of studies have used measurements from photocopies of the hands. Here, we compared finger lengths (2D, 3D, 4D, and 5D) and ratios obtained from these two measurement techniques. Our sample consisted of 30 homosexual men and 50 men and 70 women who were not selected for their sexual orientation. We found evidence that (1)2D:4D from photocopies tended to be lower than that from direct measurements, (2) there were differences in finger lengths such that 2D from photocopies tended to be shorter or equal in length to direct measurements, while 4D from photocopies tended to be longer or equal in length to direct measurements, (3) the sex differences in 2D:4D tended to be stronger for photocopy measurements, and (4) the pattern for length differences across 2D to 5D appeared to be different for homosexual men compared to men and women recruited without regard to sexual orientation. We conclude that there are differences in digit ratios obtained from photocopies and direct measurements, and these differences arise from length differences recorded from the different protocols. Therefore, 2D:4D ratios obtained from photocopies and direct measurements should not be combined within one study nor should they be used together in comparative studies. We suggest that finger length differences between the two techniques could result from the shapes of fat-pads at the tips of the fingers and these may be dependent on sex and sexual orientation.
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Previous studies showed that male faces with extreme features that are likely to be associated with testosterone (T) are perceived as dominant and masculine. Women were reported to prefer masculinized male faces, as they may consider T markers to be an “honest” indication of good health. However, it is also likely that female preferences for certain male faces arise from the fact that dominant- and masculine-looking males are signaling characteristics which may be beneficial in intrasexual conflict, and thereby also indicate potential achievers of high status, an important factor in female mate selection. Although numerous studies were built on this assumption, nothing is known about the relationship between perceived facial dominance and physical strength in men. We measured hand-grip strength, as a measure of overall physical strength, in a sample of 32 male students, and recorded age, body weight, and height. Seventy-nine women rated facial images of these men for dominance, masculinity, and attractiveness. After controlling for age and body weight, hand-grip strength was found to correlate significantly positively with all three measures. The present data thus support the supposition that a male's physical strength is also signaled via facial characteristics of dominance and masculinity, which are considered attractive by women.
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Evolutionary psychologists have proposed that preferences for facial characteristics, such as symmetry, averageness, and sexual dimorphism, may reflect adaptations for mate choice because they signal aspects of mate quality. Here, we show that facial skin color distribution significantly influences the perception of age and attractiveness of female faces, independent of facial form and skin surface topography. A set of three-dimensional shape-standardized stimulus faces—varying only in terms of skin color distribution due to variation in biological age and cumulative photodamage—was rated by a panel of naive judges for a variety of perceptual endpoints relating to age, health, and beauty. Shape- and topography-standardized stimulus faces with the homogeneous skin color distribution of young people were perceived as younger and received significantly higher ratings for attractiveness and health than analogous stimuli with the relatively inhomogeneous skin color distribution of more elderly people. Thus, skin color distribution, independent of facial form and skin surface topography, seems to have a major influence on the perception of female facial age and judgments of attractiveness and health as they may signal aspects of underlying physiological condition of an individual relevant for mate choice. We suggest that studies on human physical attractiveness and its perception need to consider the influence of visible skin condition driven by color distribution and differentiate between such effects and beauty-related traits due to facial shape and skin topography.
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Previous studies have shown that male faces with extreme features associated with testosterone are perceived as dominant and masculine. Women have been reported to prefer more masculinized male faces as they may consider testosterone markers to be an ‘honest’ indication of good health, and such considerations may underlie their aesthetic preferences. However, pronounced testosterone facial markers are also associated with dominance, and several negative personality traits. This suggests that female aesthetic preferences may be an adaptive compromise between positive attributes associated with higher than average testosterone, and negative attributes associated with more extreme masculinization. This current study attempts to clarify the role of hormone markers in female perceptions of dominance, masculinity and attractiveness, in male facial images. Recent evidence suggests that the relative length of the 2nd to 4th finger (2D : 4D ratio) is a pointer to prenatal testosterone levels and may thus serve as a window to the prenatal hormonal environment. We measured 2D : 4D in a sample of male college students and took salivary samples to analyse circulating levels of testosterone. Women rated facial images of these males for dominance, masculinity and attractiveness. Our results show that male 2D : 4D was significantly negatively related to perceived dominance and masculinity but not attractiveness. Circulating testosterone levels were not related to dominance, masculinity or attractiveness. These findings suggest that: (i) high prenatal levels of testosterone serve to ‘organize’ male facial features to subsequently reflect dominance and masculine characteristics presumably activated during puberty; and (ii) attractiveness is not directly related to testosterone levels. We conclude that facial dominance and masculinity reflect a male's perceived status rather than his physical attraction to women.
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The notion that surface texture may provide important information about the geometry of visible surfaces has attracted considerable attention for a long time. The present study shows that skin texture plays a significant role in the judgment of female facial beauty. Following research in clinical dermatology, the authors developed a computer program that implemented an algorithm based on co-occurrence matrices for the analysis of facial skin texture. Homogeneity and contrast features as well as color parameters were extracted out of stimulus faces. Attractiveness ratings of the images made by male participants relate positively to parameters of skin homogeneity. The authors propose that skin texture is a cue to fertility and health. In contrast to some previous studies, the authors found that dark skin, not light skin, was rated as most attractive.
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Current theoretical and empirical findings suggest that mate preferences are mainly cued on visual, vocal and chemical cues that reveal health including developmental health. Beautiful and irresistible features have evolved numerous times in plants and animals due to sexual selection, and such preferences and beauty standards provide evidence for the claim that human beauty and obsession with bodily beauty are mirrored in analogous traits and tendencies throughout the plant and animal kingdoms. Human beauty standards reflect our evolutionary distant and recent past and emphasize the role of health assessment in mate choice as reflected by analyses of the attractiveness of visual characters of the face and the body, but also of vocal and olfactory signals. Although beauty standards may vary between cultures and between times, we show in this review that the underlying selection pressures, which shaped the standards, are the same. Moreover we show that it is not the content of the standards that show evidence of convergence – it is the rules or how we construct beauty ideals that have universalities across cultures. These findings have implications for medical, social and biological sciences.
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The human face communicates an impressive number of visual signals. Although adults' ratings of facial attractiveness are consistent across studies, even cross-culturally, there has been considerable controversy surrounding attempts to identify the facial features that cause faces to be judged attractive or unattractive. Studies of physical attractiveness have attempted to identify the features that contribute to attractiveness by studying the relationships between attractiveness and (a) symmetry, (b) averageness, and (c) nonaverage sexually dimorphic features (hormone markers). Evolutionary psychology proposes that these characteristics all pertain to health, suggesting that humans have evolved to view certain features as attractive because they were displayed by healthy individuals. However, the question remains how single features that are considered attractive relate to each other, and if they form a single ornament that signals mate quality. Moreover, some researchers have recently explained attractiveness preferences in terms of individual differences that are predictable. This article briefly describes what is currently known from attractiveness research, reviews some recent advances, and suggests areas for future researchers' attention.
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Experimenters examining male facial attractiveness have concluded that the attractive male face is (1) an average male face, (2) a masculinized male face, or (3) a feminized male face. Others have proposed that symmetry, hormone markers, and the menstrual phase of the observer are important variables that influence male attractiveness. This study was designed to resolve these issues by examining the facial preferences of 42 female volunteers at two different phases of their menstrual cycle. Preferences were measured using a 40-s QuickTime movie (1200 frames) that was designed to systematically modify a facial image from an extreme male to an extreme female configuration. The results indicate that females exhibit (1) a preference for a male face on the masculine side of average, (2) a shift toward a more masculine male face preference during the high-risk phase of their menstrual cycle, and (3) no shift in other facial preferences. An examination of individual differences revealed that women who scored low on a “masculinity” test (1) showed a larger menstrual shift, (2) had lower self-esteem, and (3) differed in their choice of male faces for dominance and short-term mates. The results are interpreted as support for a hormonal theory of facial attractiveness whereby perceived beauty depends on an interaction between displayed hormone markers and the hormonal state of the viewer.
