The Ape That Thought It Was a Peacock: Does Evolutionary Psychology Exaggerate Human Sex Differences?

Synthesis of sexual selection: a systematic map of meta-analyses with bibliometric analysis

Sexual selection has been a popular subject within evolutionary biology because of its central role in explaining odd and counterintuitive traits observed in nature. Consequently, the literature associated with this field of study became vast. Meta-analytical studies attempting to draw inferences from this literature have now accumulated, varying in scope and quality, thus calling for a synthesis of these syntheses. We conducted a systematic literature search to create a systematic map with a report appraisal of meta-analyses on topics associated with sexual selection, aiming to identify the conceptual and methodological gaps in this secondary literature. We also conducted bibliometric analyses to explore whether these gaps are associated with the gender and origin of the authors of these meta-analyses. We included 152 meta-analytical studies in our systematic map. We found that most meta-analyses focused on males and on certain animal groups (e.g. birds), indicating severe sex and taxonomic biases. The topics in these studies varied greatly, from proximate (e.g. relationship of ornaments with other traits) to ultimate questions (e.g. formal estimates of sexual selection strength), although the former were more common. We also observed several common methodological issues in these studies, such as lack of detailed information regarding searches, screening, and analyses, which ultimately impairs the reliability of many of these meta-analyses. In addition, most of the meta-analyses' authors were men affiliated to institutions from developed countries, pointing to both gender and geographical authorship biases. Most importantly, we found that certain authorship aspects were associated with conceptual and methodological issues in meta-analytical studies. Many of our findings might simply reflect patterns in the current state of the primary literature and academia, suggesting that our study can serve as an indicator of issues within the field of sexual selection at large. Based on our findings, we provide both conceptual and analytical recommendations to improve future studies in the field of sexual selection.

Inter-sexual Mate Competition in Humans: A Historical Example from Seventeenth Century Portugal

Inter-sexual mate competition occurs any time opposite-sex individuals simultaneously seek to acquire or maintain exclusive access to the same sexual partner. This underappreciated form of mate competition has been anecdotally documented in several avian and mammalian species, and systematically described among Japanese macaques and humans. Here, we extend the concept of inter-sexual mate competition by reassessing a remarkable series of Portuguese letters, penned in 1664 and later discovered and translated by Mott and Assunção (J Homosex 16:91-104, 1989). The letters comprise one side of a correspondence between two males, former lovers who were scrutinized by the Portuguese Inquisition. After ending the relationship, the recipient of the letters was betrothed to a woman, which provoked a jealous response from his jilted male lover and pleas to reunite. We argue that the letters portray a prolonged sequence of inter-sexual mate competition in which a male and female competitor vied for the same man. An established taxonomy of mate competition tactics was applied to the behavior of both competitors illustrating many parallels with contemporary examples of inter-sexual mate competition. Through this comparison, we show that modern mate competition taxonomies can be fruitfully applied to historical texts and that inter-sexual mate competition occurred hundreds of years before the present. Other examples of inter-sexual mate competition are likely to exist in the historical record, providing a rich source of scientific information if appropriate theoretical frameworks are employed. Indeed, any time individuals are attracted to sexual partners who behave in a bisexual manner, then inter-sexual mate competition can ensue with members of the other sex.

The Role of Accurate Self-Assessments in Optimizing Mate Choice

Individuals are thought to seek the best possible romantic partner in exchange for their own desirability. We investigated whether individuals' self-evaluations were related to their partner choices and whether the accuracy of these self-evaluations was associated with mating outcomes. Participants (N = 1,354) took part in a speed-dating study where they rated themselves and others on mate value and indicated their willingness to date each potential partner. Individuals were somewhat accurate in their self-evaluations, and these self-evaluations were associated with individuals' revealed minimum and maximum standards for a potential partner, but not the number of partners they were interested in. Participants who overestimated their mate value were accepted by an equivalent number of partners compared with under-estimators, but the over-estimators were choosier and thus ended up with fewer (but similarly attractive) reciprocal matches. Results support social exchange theory and the matching hypothesis, and contrast findings that self-enhancement facilitates positive social outcomes.

Love songs and serenades: a theoretical review of music and romantic relationships

In this theoretical review, we examine how the roles of music in mate choice and social bonding are expressed in romantic relationships. Darwin's Descent of Man originally proposed the idea that musicality might have evolved as a sexually selected trait. This proposition, coupled with the portrayal of popular musicians as sex symbols and the prevalence of love-themed lyrics in music, suggests a possible link between music and attraction. However, recent scientific exploration of the evolutionary functions of music has predominantly focused on theories of social bonding and group signaling, with limited research addressing the sexual selection hypothesis. We identify two distinct types of music-making for these different functions: music for attraction, which would be virtuosic in nature to display physical and cognitive fitness to potential mates; and music for connection, which would facilitate synchrony between partners and likely engage the same reward mechanisms seen in the general synchrony-bonding effect, enhancing perceived interpersonal intimacy as a facet of love. Linking these two musical functions to social psychological theories of relationship development and the components of love, we present a model that outlines the potential roles of music in romantic relationships, from initial attraction to ongoing relationship maintenance. In addition to synthesizing the existing literature, our model serves as a roadmap for empirical research aimed at rigorously investigating the possible functions of music for romantic relationships.

Polygamous Interest in a Mononormative Nation: The Roles of Sex and Sociosexuality in Polygamous Interest in a Heterosexual Sample from the UK

Polygamy is a form of "one-sided" consensually non-monogamous relationship where one person has multiple committed partners, each of whom is only involved with that one person. It was likely a reoccurring feature of ancestral mating that posed adaptive problems for our ancestors. Yet polygamy, and multi-partnering more generally, is understudied in Western cultures, raising questions about the existence of polygamous interest and whether this is calibrated adaptively to personal conditions. In two studies, we examined polygamous interest in two heterosexual online samples from the UK. In Study 1 (N = 393), modest interest was found for polygamous relationships overall. Men were six times more open to polygyny than women, but there was little sex difference in openness to polyandry. Further analysis revealed that all forms of multi-partnering were undesirable relative to singlehood and monogamy; however, consensual multi-partner relationships were less undesirable than non-consensual ones. Sex differences were largest for polygyny and arrangements where men had agreed access to a casual partner alongside a committed one, yet these were two of the most acceptable forms of multi-partnering when men and women's responses were combined. Sociosexuality positively predicted interest in most forms of multi-partnering. Study 2 (N = 735) focused on polygyny and added status-linked traits as predictors. The results of Study 1 were broadly replicated, though the status-linked traits did not predict polygynous interest specifically. Instead, sociosexuality and male intrasexual competitiveness uniquely predicted general interest in multi-partner relationships. Overall, interest in polygamy appears to emerge despite social discouragement and sex differences in interest track the relative costs and benefits associated with it. However, there is no strong evidence that polygamous interest is uniquely calibrated to personal conditions when compared to other forms of multi-partnering.

The Role of Humor Production and Perception in the Daily Life of Couples: An Interest-Indicator Perspective

In established relationships, are couples who are funny more satisfied with each other, or are satisfied couples more able to see the funny side of their partners? Much research has examined the evolutionary function of humor in relationship initiation, but not in relationship maintenance. Using a dyadic daily-diary study composed of college students from Singapore, results showed that relationship quality was positively associated with same-day humor production and perception. Importantly, and consistent with an interest-indicator perspective in which humor exchanges communicate relationship interest, relationship quality was also positively associated with next-day humor production and perception, and across both sexes. Results also indicated some support for a sexual-selection perspective in which humor exchanges predicted only same- and next-day satisfaction, but not commitment. Our findings suggest that humor can ultimately function as a strategy to monitor and maintain established relationships.

Nocturnal selective pressures on the evolution of human musicality as a missing piece of the adaptationist puzzle

Human musicality exhibits the necessary hallmarks for biological adaptations. Evolutionary explanations focus on recurrent adaptive problems that human musicality possibly solved in ancestral environments, such as mate selection and competition, social bonding/cohesion and social grooming, perceptual and motor skill development, conflict reduction, safe time-passing, transgenerational communication, mood regulation and synchronization, and credible signaling of coalition and territorial/predator defense. Although not mutually exclusive, these different hypotheses are still not conceptually integrated nor clearly derived from independent principles. I propose The Nocturnal Evolution of Human Musicality and Performativity Theory in which the night-time is the missing piece of the adaptationist puzzle of human musicality and performing arts. The expansion of nocturnal activities throughout human evolution, which is tied to tree-to-ground sleep transition and habitual use of fire, might help (i) explain the evolution of musicality from independent principles, (ii) explain various seemingly unrelated music features and functions, and (iii) integrate many ancestral adaptive values proposed. The expansion into the nocturnal niche posed recurrent ancestral adaptive challenges/opportunities: lack of luminosity, regrouping to cook before sleep, imminent dangerousness, low temperatures, peak tiredness, and concealment of identity. These crucial night-time features might have selected evening-oriented individuals who were prone to acoustic communication, more alert and imaginative, gregarious, risk-taking and novelty-seeking, prone to anxiety modulation, hedonistic, promiscuous, and disinhibited. Those night-time selected dispositions may have converged and enhanced protomusicality into human musicality by facilitating it to assume many survival- and reproduction-enhancing roles (social cohesion and coordination, signaling of coalitions, territorial defense, antipredatorial defense, knowledge transference, safe passage of time, children lullabies, and sexual selection) that are correspondent to the co-occurring night-time adaptive challenges/opportunities. The nocturnal dynamic may help explain musical features (sound, loudness, repetitiveness, call and response, song, elaboration/virtuosity, and duetting/chorusing). Across vertebrates, acoustic communication mostly occurs in nocturnal species. The eveningness chronotype is common among musicians and composers. Adolescents, who are the most evening-oriented humans, enjoy more music. Contemporary tribal nocturnal activities around the campfire involve eating, singing/dancing, storytelling, and rituals. I discuss the nocturnal integration of musicality's many roles and conclude that musicality is probably a multifunctional mental adaptation that evolved along with the night-time adaptive landscape.

Porn use and men's and women's sexual performance: evidence from a large longitudinal sample

BACKGROUND

We examined whether young men and women differ in the relation between porn use and sexual performance (sexual self-competence, sexual functioning, and partner-reported sexual satisfaction).

METHODS

We conducted a three-wave longitudinal study (spanning 2015-16-17) that involved a very large number of men and women in their early 20s (100 000 + French-speaking individuals; 4000 + heterosexual couples).

RESULTS

The results revealed a twofold phenomenon. Among men, a higher frequency of porn use (wave 1) and increased porn use over time (waves 1-3) were associated with lower levels of sexual self-competence, impaired sexual functioning, and decreased partner-reported sexual satisfaction. In contrast, among women, higher and increasing frequencies of porn use were associated with higher levels of sexual self-competence, improved sexual functioning, and enhanced partner-reported sexual satisfaction (for some aspects).

CONCLUSIONS

The findings reveal the irony that porn - a male-dominated industry that targets a male-dominated audience - is associated with the erosion of the quality of men's sex lives and the improvement of women's sex lives.

The sexual selection of creativity: A nomological approach

Cultural innovations, such as tools and other technical articles useful for survival, imply that creativity is an outcome of evolution. However, the existence of purely ornamental items obfuscates the functional value of creativity. What is the functional or adaptive value of aesthetic and intellectual ornaments? Recent evidence shows a connection between ornamental creativity, an individual's attractiveness, and their reproductive success. However, this association is not sufficient for establishing that creativity in humans evolved by sexual selection. In this critical review, we synthesize findings from many disciplines about the mechanisms, ontogeny, phylogeny, and the function of creativity in sexual selection. Existing research indicates that creativity has the characteristics expected of a trait evolved by sexual selection: genetic basis, sexual dimorphism, wider variety in males, influence of sex hormones, dysfunctional expressions, an advantage in mating in humans and other animals, and psychological modules adapted to mating contexts. Future studies should investigate mixed findings in the existing literature, such as creativity not being found particularly attractive in a non-WEIRD society. Moreover, we identified remaining knowledge gaps and recommend that further research should be undertaken in the following areas: sexual and reproductive correlates of creativity in non-WEIRD societies, relationship between androgens, development, and creative expression, as well as the impact of ornamental, technical and everyday creativity on attractiveness. Evolutionary research should analyze whether being an evolved signal of genetic quality is the only way in which creativity becomes sexually selected and therefore passed on from generation to generation. This review has gone a long way toward integrating and enhancing our understanding of ornamental creativity as a possible sexual selected psychological trait.

Examining the Sexual Double Standards and Hypocrisy in Partner Suitability Appraisals Within a Norwegian Sample

Sexual double standards are social norms that impose greater social opprobrium on women versus men or that permit one sex greater sexual freedom than the other. This study examined sexual double standards when choosing a mate based on their sexual history. Using a novel approach, participants (N = 923, 64% women) were randomly assigned to make evaluations in long-term or short-term mating contexts and asked how a prospective partner's sexual history would influence their own likelihood of having sex (short-term) or entering a relationship (long-term) with them. They were then asked how the same factors would influence the appraisal they would make of male and female friends in a similar position. We found no evidence of traditional sexual double standards for promiscuous or sexually undesirable behavior. There was some evidence for small sexual double standard for self-stimulation, but this was in the opposite direction to that predicted. There was greater evidence for sexual hypocrisy as sexual history tended to have a greater negative impact on suitor assessments for the self rather than for same-sex friends. Sexual hypocrisy effects were more prominent in women, though the direction of the effects was the same for both sexes. Overall, men were more positive about women's self-stimulation than women wee, particularly in short-term contexts. Socially undesirable sexual behavior (unfaithfulness, mate poaching, and jealous/controlling) had a large negative impact on appraisals of a potential suitor across all contexts and for both sexes. Effects of religiosity, disgust, sociosexuality, and question order effects are considered.

In the Heat of the Short-Term Moment: Evidence that Heightened Sexual Arousal Increases Short-Term Mating Motivation Among Men

Individual differences in men’s short-term mating interest are well studied, both at state and trait levels. Yet, the role of sexual arousal as a source of intra-individual variation has been neglected. This research represents the first attempt to integrate sexual arousal into the human mate plasticity literature. We argue that sexual arousal directly impacts the short-term mating motivation among men regardless of their personality, relationship status, and sociosexuality. Across four experiments, we found that heightened sexual arousal consistently increased men’s short-term mating motivation relative to participants in neutral and arousing control groups. Experiments 1 and 2 revealed that sexual arousal increased participants’ general short-term mating motivation and their preference for a short-term relationship over a long-term one. Experiment 3 replicated the findings of the first two experiments whilst also demonstrating that this effect was not moderated by personality (i.e., Dark Triad, Big Five) or relationship status. Heightened sexual arousal also led to decreased “state” long-term mating motivation. Finally, Experiment 4 showed that sexual arousal increased the participants’ preference for a short-term relationship over a long-term one, an effect that was not moderated by sociosexuality. Together, the results suggest that sexual arousal has a powerful effect on men’s short-term mating motivation, and that this effect is independent of intrasexual differences in personality, relationship status, and sociosexuality.

The mediating role of sexually selected traits in the association of androgynous tendencies with lower sexual activeness among Chinese youths

Androgynous tendencies and persistently low fertility rates have been observed in many countries, causing major social concerns. The theory of sexual selection suggests a possible mechanism between androgyny and decreased sexual activeness, as masculinity and femininity constitute an important aspect of reproductive strategies. This theory has also been proven by evolutionary and societal evidence. Therefore, we investigate the association between masculinity and femininity with sexual activeness, as well as the influence of gender-role conformity on the frequency of sexual intercourse through sexually selected traits among 42,492 Chinese youths. Sexual activeness was measured using sexual attitudes, experience, behaviors, and pleasure. Mediation analysis was employed to investigate the effects of sexually selected traits on the association between masculinity and femininity with sexual activeness, and gender-role conformity with the frequency of sexual intercourse. Low sexual activeness was found to be associated with low gender-role conformity. Our findings also suggest that physical attractiveness, sexual motivation, and interpersonal relationships may mediate the association between sexual activeness and gender-role conformity, supporting the males-compete/females-choose model.

Darwin’s sexual selection hypothesis revisited: Musicality increases sexual attraction in both sexes

A number of theories about the origins of musicality have incorporated biological and social perspectives. Darwin argued that musicality evolved by sexual selection, functioning as a courtship display in reproductive partner choice. Darwin did not regard musicality as a sexually dimorphic trait, paralleling evidence that both sexes produce and enjoy music. A novel research strand examines the effect of musicality on sexual attraction by acknowledging the importance of facial attractiveness. We previously demonstrated that music varying in emotional content increases the perceived attractiveness and dating desirability of opposite-sex faces only in females, compared to a silent control condition. Here, we built upon this approach by presenting the person depicted (target) as the performer of the music (prime), thus establishing a direct link. We hypothesized that musical priming would increase sexual attraction, with high-arousing music inducing the largest effect. Musical primes (25 s, piano solo music) varied in arousal and pleasantness, and targets were photos of other-sex faces of average attractiveness and with neutral expressions (2 s). Participants were 35 females and 23 males (heterosexual psychology students, single, and no hormonal contraception use) matched for musical background, mood, and liking for the music used in the experiment. After musical priming, females’ ratings of attractiveness and dating desirability increased significantly. In males, only dating desirability was significantly increased by musical priming. No specific effects of music-induced pleasantness and arousal were observed. Our results, together with other recent empirical evidence, corroborate the sexual selection hypothesis for the evolution of human musicality.

The Cocksure Conundrum: How Evolution Created a Gendered Currency of Corporate Overconfidence

Biological differences between men and women mandate that women’s obligatory investment in reproduction is significantly greater than that of men. As a result, women have evolved to be the “choosier” of the two sexes and men have evolved to compete for female choice. To the degree that overconfidence is an effective tool for attracting mates and driving away competitors, greater competition among men suggests that they should express more overconfidence than women. Thus, sexual selection may be the primary reason why overconfidence is typically more pronounced in men than it is in women. Sexual selection may also be a distal, causal factor in what we describe as a cult of overconfidence pervading modern organizations and institutions. Whereas overconfidence was once regulated and constrained by features of ancestral life, levels of social mobility and accountability in contemporary society and modern organizations make it increasingly difficult to keep this gendered bias in check.

Evolution of Artistic and Athletic Propensities: Testing of Intersexual Selection and Intrasexual Competition

Since Darwin proposed that human musicality evolved through sexual selection, empirical evidence has supported intersexual selection as one of the adaptive functions of artistic propensities. However, intrasexual competition has been overlooked. We tested their relative importance by investigating the relationship between the self-perceived talent/expertise in 16 artistic and 2 sports modalities and proxies of intersexual selection (i.e., mate value, mating and parenting efforts, sociosexuality, and number of sexual partners) and intrasexual competition (i.e., aggressiveness, intrasexual competitiveness) in heterosexuals. Participants were 82 Brazilian men, 166 Brazilian women, 146 Czech men, and 458 Czech women (Mage = 26.48, SD = 7.12). Factor analysis revealed five factors: Literary-arts (creative writing, humor, acting/theater/film, poetry, storytelling), Visual-arts (painting/drawing, sculpting, handcrafting, culinary arts, architecture design), Musical-arts (playing/instruments, singing, dance, whistling), Circus-arts (juggling, acrobatics), and Sports (individual, collective). Multivariate General Linear Model (GLM) showed more associations of the arts to intersexual selection in women and to intrasexual selection in men, and overall more relationships in women than in men. In women, literary and musical-arts were related to elevated inter- and intrasexual selections proxies, visual and circus-arts were related to elevated intersexual selection proxies, and sports were related to intrasexual selection proxies. In men, literary-arts and sports were related to elevated inter- and intrasexual selection proxies, musical-arts were related to intrasexual proxies, and circus-arts were related to intersexual proxies; visual-arts did not have predictors. Although present in both sexes, each sexual selection component has different relative importance in each sex. Artisticality functions to attract and maintain long/short-term partners, and to compete with mating rivals.

Enhanced Originality of Ideas in Women During Ovulation: A Within-Subject Design Study

The signaling theory suggests that creativity may have evolved as a signal for mates. Indeed, its aesthetic value might not have been necessary for survival, but it could have helped to attract a mate, fostering childbearing. If we consider creativity as such a signal, we should expect it will be enhanced in the context related to sexual selection. This hypothesis was tested mainly for men. However, both men and women display physical and mental traits that can attract a mate. Previous studies showed that women can be more creative during their peak fertility. We advanced these findings in the present study, applying reliable measures of menstrual cycle phases (examining saliva and urine samples) and the highly recommended within-subject design. We also introduced and tested possible mediators of the effect. We found women’s ideas to be more original during ovulation compared to non-fertile phases of the ovulatory cycle. The results are discussed in the context of signaling theory and alternative explanations are considered.

Intra- and Intersexual Mate Competition in Two Cultures : A Comparison of Women's Response to Mate Competition with Women and Gender-Nonbinary Males in Samoa and among the Istmo Zapotec

The present study examined women's mate competition tactics in response to female and feminine-male rivals in two cultures in which competition against both occurs. In Samoa and the Istmo Zapotec (Southern Mexico), women not only compete with other women (intrasexually) but also compete with rival feminine males (intersexually) in order to access/retain the same masculine men as sexual/romantic partners. Using a mixed-method paradigm, women were asked about their experiences of intra- and intersexual mate competition, and these narratives were recorded. The tactics reportedly employed by participants, and those attributed to mate competitors, were categorized according to established taxonomies of mate competition tactics, and their frequencies compared. Within-culture, the likelihood that participant women had ever experienced intra- and intersexual mate competition did not differ. Furthermore, participants reported a similar pattern of behavioral tactics whether their rival was another woman or a feminine male. These included benefit provisioning tactics during mate acquisition and cost-inflicting tactics during mate retention. Similarly, the mate competition tactics attributed to rival women and rival feminine males bore a striking resemblance, focused on enticing target men. Results highlight the mate competition tactics employed by women outside of a Euro-American context, and the way cultural factors impact mating landscapes presumed to be exclusively heterosexual. The presence of feminine males, alongside masculine men's willingness to engage in sexual activity with them, induces women in such cultures to compete intersexually in comparable ways to intrasexual competition with rival women.

Why and How Did Narrative Fictions Evolve? Fictions as Entertainment Technologies

Narrative fictions have surely become the single most widespread source of entertainment in the world. In their free time, humans read novels and comics, watch movies and TV series, and play video games: they consume stories that they know to be false. Such behaviors are expanding at lightning speed in modern societies. Yet, the question of the origin of fictions has been an evolutionary puzzle for decades: Are fictions biological adaptations, or the by-products of cognitive mechanisms that evolved for another purpose? The absence of any consensus in cognitive science has made it difficult to explain how narrative fictions evolve culturally. We argue that current conflicting hypotheses are partly wrong, and partly right: narrative fictions are by-products of the human mind, because they obviously co-opt some pre-existing cognitive preferences and mechanisms, such as our interest for social information, and our abilities to do mindreading and to imagine counterfactuals. But humans reap some fitness benefits from producing and consuming such appealing cultural items, making fictions adaptive. To reconcile these two views, we put forward the hypothesis that narrative fictions are best seen as entertainment technologies that is, as items crafted by some people for the proximate goal to grab the attention of other people, and with the ultimate goal to fulfill other evolutionary-relevant functions that become easier once other people's attention is caught. This hypothesis explains why fictions are filled with exaggerated and entertaining stimuli, why they fit so well the changing preferences of the audience they target, and why producers constantly make their fictions more attractive as time goes by, in a cumulative manner.

Musicality in human vocal communication: an evolutionary perspective

Studies show that specific vocal modulations, akin to those of infant-directed speech (IDS) and perhaps music, play a role in communicating intentions and mental states during human social interaction. Based on this, we propose a model for the evolution of musicality-the capacity to process musical information-in relation to human vocal communication. We suggest that a complex social environment, with strong social bonds, promoted the appearance of musicality-related abilities. These social bonds were not limited to those between offspring and mothers or other carers, although these may have been especially influential in view of altriciality of human infants. The model can be further tested in other species by comparing levels of sociality and complexity of vocal communication. By integrating several theories, our model presents a radically different view of musicality, not limited to specifically musical scenarios, but one in which this capacity originally evolved to aid parent-infant communication and bonding, and even today plays a role not only in music but also in IDS, as well as in some adult-directed speech contexts. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part II)'.

Moderators of Sexual Interest in Opposite-sex Friends

The fact that men and women experience sexual attraction toward their opposite-sex friends has been evidenced in various studies. It has also been shown that there is a close parallel between preferences for opposite-sex friends and mate preferences, i.e., that men prioritize physical attractiveness of their OSFs, while women prioritize their male friends' ability to provide protection and economic resources. Although this mating activation hypothesis has been validated to an extent, there is hardly any research that points to moderating factors which would define the boundary conditions for these effects. We present two studies that involved heterosexual participants who were in a committed relationship and at the same time had a heterosexual opposite-sex friend. We investigated how both the qualities of one's current partner and the qualities of one's opposite-sex friend shape sexual interest in opposite-sex friends for men and women. Results mostly support the mating activation hypothesis. We show that within actual cross-sex friendships: 1) physical attractiveness of opposite-sex friends predicts sexual interest toward them, and this effect is stronger for men than women, 2) current partner's attractiveness, provided support, and relationship satisfaction moderate this effect only for women, and not men, 3) perceived financial resources of opposite-sex friends predict sexual interest toward them for highly sexually unrestricted women, and, surprisingly, for those who are in committed relationships with high-income men. The results reaffirm previous evidence indicating that perceptions of opposite-sex friends can be viewed as a manifestation of evolved human mating strategies.

The effects of sex and outcome expectancies on perceptions of sexual harassment

Using an outcome expectancy framework, this research sought to understand sex differences in the underlying beliefs that influence harassment perception. One hundred and ninety-six participants (52% women) read a series of vignettes depicting common examples of digital male-on-female sexual harassment. They were asked to what extent they thought each scenario constituted sexual harassment, and how likely the perpetrator would experience positive and negative outcomes. Consistent with predictions, women were more likely to consider the behaviours as harassment than men were. Both sexes harassment perceptions had significant relationships with their outcome expectancies, but we also found evidence of a sex specific moderation; the link between men's negative outcome expectancies was moderated by their positive ones. The results suggest that perceptions of harassment may have sexually asymmetrical underpinnings. Measuring the interplay between positive and negative outcome expectancies in relation to sexual harassment perception is a novel approach, that may have implications for the development of anti-sexual harassment interventions. Implications for theory and future research directions are discussed.

Phenotypic Signals of Sexual Selection and Fast Life History Dynamics for the Long-Term but Not Short-Term Mating

Mating patterns are crucial for understanding selection regimes in current populations and highly implicative for sexual selection and life history theory. However, empirical data on the relations between mating and reproductive outcomes in contemporary humans are lacking. In the present research we examined the sexual selection on mating (with an emphasis on Bateman's third parameter - the association between mating and reproductive success) and life history dynamics of mating by examining the relations between mating patterns and a comprehensive set of variables which determine human reproductive ecology. We conducted two studies (Study 1: N = 398, Study 2: N = 996, the sample was representative for participants' sex, age, region, and settlement size). The findings from these studies were mutually congruent and complementary. In general, the data suggested that short-term mating was unrelated or even negatively related to reproductive success. Conversely, long-term mating was positively associated with reproductive success (number of children in Study 1; number of children and grandchildren in Study 2) and there were indices that the beneficial role of long-term mating is more pronounced in males, which is in accordance with Bateman's third principle. Observed age of first reproduction mediated the link between long-term mating and number of children but only in male participants (Study 2). There were no clear indications of the position of the mating patterns in human life history trajectories; however, the obtained data suggested that long-term mating has some characteristics of fast life history dynamics. Findings are implicative for sexual selection and life history theory in humans.

Singing is not associated with social complexity across species

Based on their social bonding hypothesis, Savage et al. predict a relation between "musical" behaviors and social complexity across species. However, our qualitative comparative review suggests that, although learned contact calls are positively associated with complex social dynamics across species, songs are not. Yet, in contrast to songs, and arguably consistent with their functions, contact calls are not particularly music-like.

The evolution of perennially enlarged breasts in women: a critical review and a novel hypothesis

The possession of permanent, adipose breasts in women is a uniquely human trait that develops during puberty, well in advance of the first pregnancy. The adaptive role and developmental pattern of this breast morphology, unusual among primates, remains an unresolved conundrum. The evolutionary origins of this trait have been the focus of many hypotheses, which variously suggest that breasts are a product of sexual selection or of natural selection due to their putative role in assisting in nursing or as a thermoregulatory organ. Alternative hypotheses assume that permanent breasts are a by-product of other evolutionary changes. We review and evaluate these hypotheses in the light of recent literature on breast morphology, physiology, phylogeny, ontogeny, sex differences, and genetics in order to highlight their strengths and flaws and to propose a coherent perspective and a new hypothesis on the evolutionary origins of perennially enlarged breasts in women. We propose that breasts appeared as early as Homo ergaster, originally as a by-product of other coincident evolutionary processes of adaptive significance. These included an increase in subcutaneous fat tissue (SFT) in response to the demands of thermoregulatory and energy storage, and of the ontogenetic development of the evolving brain. An increase in SFT triggered an increase in oestradiol levels (E2). An increase in meat in the diet of early Homo allowed for further hormonal changes, such as greater dehydroepiandrosterone (DHEA/S) synthesis, which were crucial for brain evolution. DHEA/S is also easily converted to E2 in E2-sensitive body parts, such as breasts and gluteofemoral regions, causing fat accumulation in these regions, enabling the evolution of perennially enlarged breasts. Furthermore, it is also plausible that after enlarged breasts appeared, they were co-opted for other functions, such as attracting mates and indicating biological condition. Finally, we argue that the multifold adaptive benefits of SFT increase and hormonal changes outweighed the possible costs of perennially enlarged breasts, enabling their further development.

Sex Differences in Voyeuristic and Exhibitionistic Interests: Exploring the Mediating Roles of Sociosexuality and Sexual Compulsivity from an Evolutionary Perspective

Sociosexuality and sexual compulsivity predict sex differences in voyeuristic interest in the population. In this study, we used a sample of 1113 participants from the UK (46% men) to consider whether sociosexuality and sexual compulsivity interacted to explain these sex differences and whether this relationship extended to the related domain of exhibitionism. In doing so, we tested novel predictions derived from an evolutionary perspective which views voyeuristic and exhibitionistic interest as manifestations of a short-term mating strategy. Participants reported their levels of repulsion toward voyeurism and exhibitionism and their interest in performing such acts under different levels of risk. There were clear sex differences in voyeuristic and exhibitionistic repulsion that were partially mediated by the serial combination of sociosexuality and sexual compulsivity. Examining the sexes separately revealed qualitatively different relationships between sociosexuality and sexual compulsivity when predicting exhibitionistic, but not voyeuristic, repulsion. Combined, sociosexuality and sexual compulsivity also mediated the sex difference in willingness to commit acts of voyeurism, but not exhibitionism, which was equally low for both sexes. The results highlight the role sociosexuality plays in voyeuristic and exhibitionistic interest, which coupled with an evolutionary perspective, may have implications for how we view courtship disorders.

Ethnoscientific expertise and knowledge specialisation in 55 traditional cultures

People everywhere acquire high levels of conceptual knowledge about their social and natural worlds, which we refer to as ethnoscientific expertise. Evolutionary explanations for expertise are still widely debated. We analysed ethnographic text records (N = 547) describing ethnoscientific expertise among 55 cultures in the Human Relations Area Files to investigate the mutually compatible roles of collaboration, proprietary knowledge, cultural transmission, honest signalling, and mate provisioning. We found relatively high levels of evidence for collaboration, proprietary knowledge, and cultural transmission, and lower levels of evidence for honest signalling and mate provisioning. In our exploratory analyses, we found that whether expertise involved proprietary vs. transmitted knowledge depended on the domain of expertise. Specifically, medicinal knowledge was positively associated with secretive and specialised knowledge for resolving uncommon and serious problems, i.e. proprietary knowledge. Motor skill-related expertise, such as subsistence and technological skills, was positively associated with broadly competent and generous teachers, i.e. cultural transmission. We also found that collaborative expertise was central to both of these models, and was generally important across different knowledge and skill domains.

Sex differences in sexual attraction for aesthetics, resources and personality across age

Because sexual attraction is a key driver of human mate choice and reproduction, we descriptively assess relative sex differences in the level of attraction individuals expect in the aesthetic, resource, and personality characteristics of potential mates. As a novelty we explore how male and female sexual attractiveness preference changes across age, using a dataset comprising online survey data for over 7,000 respondents across a broad age distribution of individuals between 18 and 65 years. In general, we find that both males and females show similar distribution patterns in their preference responses, with statistically significant sex differences within most of the traits. On average, females rate age, education, intelligence, income, trust, and emotional connection around 9 to 14 points higher than males on our 0-100 scale range. Our relative importance analysis shows greater male priority for attractiveness and physical build, compared to females, relative to all other traits. Using multiple regression analysis, we find a consistent statistical sex difference (males relative to females) that decreases linearly with age for aesthetics, while the opposite is true for resources and personality, with females exhibiting a stronger relative preference, particularly in the younger aged cohort. Exploring non-linearity in sex difference with contour plots for intelligence and attractiveness across age (mediated by age) indicates that sex differences in attractiveness preferences are driven by the male cohort (particularly age 30 to 40) for those who care about the importance of age, while intelligence is driven by females caring relatively more about intelligence for those who see age as very important (age cohort 40 to 55). Overall, many of our results indicate distinct variations within sex at key life stages, which is consistent with theories of selection pressure. Moreover, results also align with theories of parental investment, the gender similarities hypothesis, and mutual mate choice-which speaks to the fact that the broader discipline of evolutionary mate choice research in humans still contains considerable scope for further inquiry towards a unified theory, particularly when exploring sex-difference across age.

The More Fertile, the More Creative: Changes in Women's Creative Potential across the Ovulatory Cycle

Creative thinking is a defining human feature. It provides novel solutions and as such undoubtedly has contributed to our survival. However, according to signaling theory, creativity could also have evolved through sexual selection as a potential fitness indicator. In our study, we tested one implication of this theory. Specifically, we hypothesized that if creativity can serve as a signal of women’s fitness, then we should observe an increase in creative thinking in the fertile phase of the ovulatory cycle compared to other non-fertile phases. In our study (N = 751), we tested creative potential throughout the ovulatory cycle. We found a positive correlation between the probability of conception and both creative originality and flexibility. Importantly, we also tested the mediating role of arousal in the relationship between the probability of conception and creative thinking. The results of our study are discussed in terms of signaling theory, through which women advertise their fitness with their creativity.

Proximate and Ultimate Perspectives on Romantic Love

Romantic love is a phenomenon of immense interest to the general public as well as to scholars in several disciplines. It is known to be present in almost all human societies and has been studied from a number of perspectives. In this integrative review, we bring together what is known about romantic love using Tinbergen’s “four questions” framework originating from evolutionary biology. Under the first question, related to mechanisms, we show that it is caused by social, psychological mate choice, genetic, neural, and endocrine mechanisms. The mechanisms regulating psychopathology, cognitive biases, and animal models provide further insights into the mechanisms that regulate romantic love. Under the second question, related to development, we show that romantic love exists across the human lifespan in both sexes. We summarize what is known about its development and the internal and external factors that influence it. We consider cross-cultural perspectives and raise the issue of evolutionary mismatch. Under the third question, related to function, we discuss the fitness-relevant benefits and costs of romantic love with reference to mate choice, courtship, sex, and pair-bonding. We outline three possible selective pressures and contend that romantic love is a suite of adaptions and by-products. Under the fourth question, related to phylogeny, we summarize theories of romantic love’s evolutionary history and show that romantic love probably evolved in concert with pair-bonds in our recent ancestors. We describe the mammalian antecedents to romantic love and the contribution of genes and culture to the expression of modern romantic love. We advance four potential scenarios for the evolution of romantic love. We conclude by summarizing what Tinbergen’s four questions tell us, highlighting outstanding questions as avenues of potential future research, and suggesting a novel ethologically informed working definition to accommodate the multi-faceted understanding of romantic love advanced in this review.

Men, women and STEM: Why the differences and what should be done?

It is a well-known and widely lamented fact that men outnumber women in a number of fields in STEM (science, technology, engineering and maths). The most commonly discussed explanations for the gender gaps are discrimination and socialization, and the most common policy prescriptions target those ostensible causes. However, a great deal of evidence in the behavioural sciences suggests that discrimination and socialization are only part of the story. The purpose of this paper is to highlight other aspects of the story: aspects that are commonly overlooked or downplayed. More precisely, the paper has two main aims. The first is to examine the evidence that factors other than workplace discrimination contribute to the gender gaps in STEM. These include relatively large average sex differences in career and lifestyle preferences, and relatively small average differences in cognitive aptitudes – some favouring males, others favouring females – which are associated with progressively larger differences the further above the average one looks. The second aim is to examine the evidence suggesting that these sex differences are not purely a product of social factors but also have a substantial biological (i.e. inherited) component. A more complete picture of the causes of the unequal sex ratios in STEM may productively inform policy discussions.

The Effects of the Mating Market, Sex, Age, and Income on Sociopolitical Orientation : Insights from Evolutionary Theory and Sexual Economics Theory

Sociopolitical attitudes are often the root cause of conflicts between individuals, groups, and even nations, but little is known about the origin of individual differences in sociopolitical orientation. We test a combination of economic and evolutionary ideas about the degree to which the mating market, sex, age, and income affect sociopolitical orientation. We collected data online through Amazon's Mechanical Turk from 1108 US participants who were between 18 and 60, fluent in English, and single. While ostensibly testing a new online dating website, participants created an online dating profile and described people they would like to date. We manipulated the participants' popularity in the mating market and the size of the market (i.e., the number of ideal partners in the market) and then measured participants' sociopolitical attitudes. The sociopolitical attitudes were reduced to five dimensions via Principal Components Analysis (Sociosexuality, Benevolent Sexism, Wealth Redistribution, Nonconforming Behaviors, and Traditional Family Values). Both manipulations affected attitudes toward wealth redistribution but were largely not significant predictors of the other dimensions. Men reported more unrestricted sociosexual attitudes, and more support for benevolent sexism and traditional family values, than women did, and women supported wealth redistribution more than men did. There was no sex difference in accepting nonconforming behaviors. Younger people and people with lower incomes were more liberal than older people and people with higher incomes, respectively, regardless of sex. Overall, effects were largely not interactive, suggesting that individual differences in sociopolitical orientation may reflect strategic self-interest and be more straightforward than previously predicted.

A branded bandage is worth a thousand words: blood branded bandages signal men's generosity and morality

BACKGROUND AND OBJECTIVE

Recruiting and retaining male donors remain an ongoing challenge for blood collection agencies. Research suggests that interventions based on costly signalling theory that allows donors to unobtrusively but publicly signal their donor status may be effective. However, what functions as such a signal and how it is interpreted has not been determined.

MATERIALS AND METHODS

A total of 242 Australian residents (127 female; 115 male) recruited through an online research platform rated their perceptions of a male target wearing (a) no bandage, (b) a regular unmarked bandage or (c) a blood donor branded bandage.

RESULTS

The target wearing a blood donor branded bandage was rated as significantly more generous by female participants and moral compared to both the target who wore no bandage and the target wearing a regular unmarked bandage. The target wearing the unmarked bandage was perceived as significantly less healthy and competent compared to the target not wearing a bandage.

CONCLUSION

A public signal of public donor status conveys the generosity and morality of the wearer. The bandage applied to donors after they have donated can act as such an effective signal, but only when these bandages are clearly branded as resulting from donating blood.

Reactions to male-favouring versus female-favouring sex differences: A pre-registered experiment and Southeast Asian replication

Two studies investigated (1) how people react to research describing a sex difference, depending on whether that difference favours males or females, and (2) how accurately people can predict how the average man and woman will react. In Study 1, Western participants (N = 492) viewed a fictional popular-science article describing either a male-favouring or a female-favouring sex difference (i.e., men/women draw better; women/men lie more). Both sexes reacted less positively to the male-favouring differences, judging the findings to be less important, less credible, and more offensive, harmful, and upsetting. Participants predicted that the average man and woman would react more positively to sex differences favouring their own sex. This was true of the average woman, although the level of own-sex favouritism was lower than participants predicted. It was not true, however, of the average man, who - like the average woman - reacted more positively to the female-favouring differences. Study 2 replicated these findings in a Southeast Asian sample (N = 336). Our results are consistent with the idea that both sexes are more protective of women than men, but that both exaggerate the level of same-sex favouritism within each sex - a misconception that could potentially harm relations between the sexes.

Who are you talking about? Contrasting determinants of online disclosure about self or others

Purpose

This paper contrasts the determinants of online disclosures about self and others in social media.

Design/methodology/approach

Data from 216 respondents were collected through an online survey. The formal research model was tested with covariance based structural equation modeling.

Findings

The determinants of online disclosures vary whether the subject is self or others. Social networking site (SNS) users who self-disclose are also more likely to share information about others. Furthermore, there are significant gender effects in the influences of disclosure as revealed by multi-group SEM.

Research limitations/implications

Future research models should incorporate the construct of disclosure about others and examine the intertwining of different types of disclosure on SNS. Future work should include behavioral measures, as this study relied on self-report measures.

Practical implications

The current understanding of information sharing does not accommodate different forms of disclosure. Employers or systems administrators concerned about data sharing may need to tailor interventions to the subject of the disclosure. Furthermore, the significant gender differences in determinants of disclosure suggest that this should be considered in practical applications.

Originality/value

Disclosure about others has not been examined in prior work. This study contributes by offering empirical data on the contrasting determinants of disclosure as well as gender differences. It improves the understanding of online information sharing, a topic of particular relevance in today's information oriented society.

Automaticity of facial attractiveness perception and sex-specific mating strategies

The current literature shows mixed results regarding whether the perception of facial attractiveness is automatic, i.e. that it operates independently from attentional resources. We argue that an evolutionary perspective on mating strategies provides a comprehensive account of the findings. In two studies, we used the locus-of-slack logic in a psychological refractory period paradigm. Task 1 was a speeded judgment of tone pitch (low vs. high), and Task 2 was a speeded judgment of whether a face was attractive or unattractive on two difficulty levels. Male and female participants judged the attractiveness of opposite-sex faces (Study 1, n = 73) or same-sex faces (Study 2, n = 94) in this paradigm. Results indicate that men do not need attentional resources when processing female faces (Study 1), but require attentional resources when processing same-sex faces (Study 2). In contrast, women need attentional resources to process the attractiveness of opposite as well as same-sex faces.

Examining the link between religiousness and fitness in a behavioural ecological framework

In recent years there have been attempts to explain religiousness from an evolutionary viewpoint. However, empirical data on this topic are still lacking. In the present study, the behavioural ecological theoretical framework was used to explore the relations between religiousness, harsh environment, fitness (reproductive success and parental investment) and fitness-related outcomes (age at first birth, desired number of children and the romantic relationship duration). The data were collected from 461 individuals from a community sample who were near the end of their reproductive phase (54% females, Mage = 51.75; SD = 6.56). Positive links between religiousness, harsh environment, fitness and fitness-related outcomes were expected, with the exception of age at first birth, for which a negative association was hypothesized. Hence, the main assumption of the study was that religiousness has some attributes of fast life-history phenotypes - that it emerges from a harsh environment and enables earlier reproduction. The study findings partially confirmed these hypotheses. Religiousness was positively related to environmental harshness but only on a zero-order level. Religious individuals had higher reproductive success (this association was especially pronounced in males) but religiousness did not show associations with parental investment. Religiousness was positively associated with desired number of children and negatively associated with age at first birth, although the latter association was only marginally significant in the multivariate analyses. Finally, path analysis showed that desired number of children and age at first birth completely mediated the relation between religiousness and reproductive success. The data confirmed the biologically adaptive function of religiousness in contemporary populations and found the mediating processes that facilitate fitness in religious individuals. Furthermore, the findings initiate a more complex view of religiousness in a life-history context which could be fruitful for future research: a proposal labelled as 'ontogeny-dependent life-history theory of religiousness'.

Mate preference priorities in the East and West: A cross-cultural test of the mate preference priority model

OBJECTIVE

Mate choice involves trading-off several preferences. Research on this process tends to examine mate preference prioritization in homogenous samples using a small number of traits and thus provide little insight into whether prioritization patterns reflect a universal human nature. This study examined whether prioritization patterns, and their accompanying sex differences, are consistent across Eastern and Western cultures.

METHOD

In the largest test of the mate preference priority model to date, we asked an international sample of participants (N = 2,477) to design an ideal long-term partner by allocating mate dollars to eight traits using three budgets. Unlike previous versions of the task, we included traits known to vary in importance by culture (e.g., religiosity and chastity).

RESULTS

Under low budget conditions, Eastern and Western participants differed in their mate dollar allocation for almost every trait (average d = 0.42), indicating that culture influences prioritization. Despite these differences, traits fundamental for the reproductive success of each sex in the ancestral environment were prioritized by both Eastern and Western participants.

CONCLUSION

The tendency to prioritize reproductively fundamental traits is present in both Eastern and Western cultures. The psychological mechanisms responsible for this process produce similar prioritization patterns despite cross-cultural variation.

Unpacking mating success and testing Bateman's principles in a human population

Human marriage systems, characterized by long-term partnerships and extended windows of parental care, differ from the mating systems of pulsed or seasonally breeding non-human animals in which Bateman’s principles were originally tested. These features, paradigmatic of but not unique to humans, complicate the accurate measurement of mating success in evaluating Bateman’s three principles. Here, we unpack the concept of mating success into distinct components: number of partners, number of years partnered, the timing of partnerships, and the quality of partners. Drawing on longitudinal records of marriage and reproduction collected in a natural-fertility East African population over a 20-year period, we test and compare various models of the relationship between mating success and reproductive success (RS), and show that an accurate assessment of male and female reproductive behaviour requires consideration of all major components of mating success. Furthermore, we demonstrate that while Bateman’s third principle holds when mating success is defined in terms of years married, women’s fitness increases whereas men’s fitness decreases from an increase in the number of marriage partners, holding constant the total effective duration of marriages. We discuss these findings in terms of the distinct, sex-specific pathways through which RS can be optimized, and comment on the contribution of this approach to the broader study of sexual selection.

Near the Knuckle : How Evolutionary Logic Helps Explain Irish Traveller Bare-Knuckle Contests

Irish Travellers constitute a pre-demographic-shift population living among a post-demographic-shift one. Their socio-medico profile identifies them as largely on fast life-history trajectories. In addition, they are strongly religious (typically using no contraception), highly sexually behaviorally dimorphic, with strong traditions of male-male competition (bare-knuckle fighting) and quasi-symbolic bride capture ("grabbing"). Their male-male competitions thus allow for the comparative testing of a number of interesting theories pertaining to the nature and function of types of violence in society. As a pilot study, we used expert raters (some naive to the hypotheses) to analyze a number of real-life bare-knuckle competitions in terms of the support said spectacles offered to theories of this sort of violence as reinforcing ideas of antisociality, hierarchical promotion, intersexual signaling, or maintenance of within-group equality. We found good evidence to support theories of within-group, prosocial hierarchical functions for these contests. Limitations and implications for future research, such as direct measurement of fitness, are discussed.