Mate Choice

In polygynous mating systems, sexual selection can drive the evolution of male characters beneficial to winning fights for mates (intrasexual selection), for improving the mating success of males through mate choice (intersexual selection), or both. However, it may be difficult to disentangle the relative contributions of intra and intersexual selection on multiple traits that may be of dual utility. We used field arena trials to determine which morphological traits best explained male fighting ability and male mating success in 2 species of chameleons in Madagascar, Furcifer labordi and Furcifer verrucosus. In F. labordi, male fighting success was best predicted by body size and size-corrected shorter rostral appendages and male mating success was best predicted by width of the rostral appendage and body size. In F. verrucosus, we found strong intrasexual selection for increased male body size and fewer counted dorsal cones, a trait that may correspond to increased age and experience. Although females in this species are generally passive toward courting males, male mating success with potentially receptive females is highly variable. Fewer counted dorsal cones and larger size-corrected casque height best explained male mating success; traits that may be selected by the female and/or correlated with increased age and experience. Although difficult to determine the relative contributions of intra and intersexual selection on traits with dual benefits (both fighting and mate choice), we documented both types of selection on body size and secondary sexual characters in these 2 chameleon species.

Carotenoid-dependent plumage displays are widely assumed to be honest indicators of individual health or quality, which are used as cues during mate choice and/or agonistic signalling. Despite the fact that red, yellow and orange pigmentation of bills is common, and also variable between individuals, comparatively little is known about bill colouration as a condition-dependent trait. Furthermore, many studies of avian colouration are confounded by the lack of objective colour quantification and the use of overly simplistic univariate techniques for analysis of the relationship between the condition-dependent trait and individual quality variables. In this study, we correlated male blackbird bill colour (a likely carotenoid-dependent sexually selected trait) with body/condition variables that reflect male quality. We measured bill colour using photometric techniques, thus ensuring objectivity. The data were analysed using the multivariate statistical techniques of canonical ordination. Analyses based on reflectance spectra of male blackbird bill samples and colour components (i.e. hue, chroma and brightness) derived from the reflectance spectra were very similar. Analysing the entire reflectance spectra of blackbird bill samples with Redundancy Analysis (RDA) allowed examination of individual wavelengths and their specific associations with the body/condition variables. However, hue, chroma and brightness values also provided useful information to explain colour variation, and the two approaches may be complimentary. We did not find any significant associations between male blackbird bill colour and percent incidence of ectoparasites or cloaca size. However, both the colour component and full spectral analyses showed that culmen length explained a significant amount of variation in male blackbird bill colour. Culmen length was positively associated with greater reflectance from the bill samples at longer wavelengths and a higher hue value (i.e. more orange-pigmented bills). Larger males may have larger territories or be better at defending territories during male-male interactions, ensuring access to carotenoid food sources. Future studies should elucidate the relationship between bill colour and behavioural measures such as aggressiveness, territory size, song rate and nest attendance.

The evolutionary divergence of a single species into two has never been directly observed in nature, primarily because speciation can take a long time to occur. A ring species, in which a chain of intergrading populations encircles a barrier and the terminal forms coexist without interbreeding, provides a situation in which variation in space can be used to infer variation in time. Here we reconstruct the pathway to speciation between two reproductively isolated forms of greenish warbler (Phylloscopus trochiloides). These two taxa do not interbreed in central Siberia but are connected by a long chain of intergrading populations encircling the Tibetan Plateau to the south. Molecular data and climatic history imply that the reproductively isolated taxa came into contact following expansions northward around the western and eastern sides of the plateau. Parallel selection pressures for increased song complexity during the northward expansions have been accompanied by divergence in song...

In the earthworm Lumbricus terrestris L., mating occurs on the soil surface, but partners remain anchored in their burrow and mating is preceded by repeated mutual burrow visits between neighbors. This study focuses on body size as one possible trait that earthworms may assess during these burrow visits. Size-related mate choice is predicted to result in size-assortative mating, which we found in one field sample (n ϭ 90 pairs), but not in a second (n ϭ 102). We discovered that when mates separate, one of them can be pulled out of its burrow. This was more likely for small individuals or those mating across wide distances. In a subsequent greenhouse experiment, we allowed focal individuals to mate with two neighbors of different sizes. Relative size affected neither mating rate nor primary preference, but focals mated sooner with the same-sized neighbor than with a differently sized one. Small focals visited large neighbors more often than small ones. We conclude that size influences mate choice as well as the outcome of mating and discuss how the ''tug-of-war'' that ends a mating contributes to this result. Precopulatory visits may involve assessment as well as enticement to lure the partner closer to the individual's own burrow, in order to minimize the risk when mating with a partner that is large or far away.

Animals acquire skills and knowledge from other animals, and ¢sh are no exception. There is now strong experimental evidence that many species of ¢sh exhibit social learning and traditional behaviours. Here, we review the literature pertaining to social learning in ¢sh, focusing on (i) antipredator behaviour, (ii) migration and orientation, (iii) foraging, (iv) mate choice and (v) eavesdropping.

The mbuna cichlids of Lake Malawi are a diverse, monophyletic, and recently derived clade. Sexual selection is thought to have accelerated their rapid diversification, though the mechanism by which this has occurred remains unknown. In this study, we examine the effect that male-male interactions have on female preference. We first used a short interaction experiment as a proxy for male dominance. We then measured female preference for (1) a single, isolated male; (2) a group of three, highly ranked males, relative to a group of lower ranked males; and (3) a group of three, mixed-ranked males against a similar group of mixed-rank males. We found that male dominance was highly correlated with male standard length. Female preference for male standard length and for dominance rank was significant in both isolated and group interactions. However, females only showed preference for groups of interacting males when males were segregated by dominance rank, not when groups were composed of both dominant and subordinate males. The results suggest that male-male contests influence female mating decisions. By investigating the rules that dictate the outcomes of such interactions we can elucidate the role that behavior plays in the diversification of this species-rich lineage.

Although researchers have suggested that adult women who experienced early puberty may demonstrate particularly strong preferences for masculine men, evidence for such an association is equivocal. Here we show that adult women's preferences for masculinized male voices (i.e., male voices with lowered pitch) are negatively associated with the age at which they experienced first menses (i.e., age at menarche). Moreover, this relationship was independent of women's stated preference for long-versus short-term relationships, suggesting that the relationship does not necessarily reflect individual differences in women's preferred type of relationship. We discuss alternative mechanisms for the relationship between early puberty and women's masculinity preferences, focusing on the possibility that girls who experience early puberty might learn to associate masculinity with desirable mates because of exposure to particularly masculine males during adolescence.

Animals that communicate acoustically must compete for acoustic space in order to convey their signals effectively. Tropical rainforest birds live in an extremely diverse acoustic community consisting of other birds, mammals, frogs, and many insects. Insects are notable for often producing continuous bands of sound energy at constant frequencies, which vary between species and across habitats. We examined how green hylia (Hylia prasina) song frequencies correlate to insect-generated spectral profiles of ambient noise. We also examined how the environment influenced song frequency by using remote sensing to quantify environmental variables. Using path analysis, we assessed the relative effects of elevation, tree cover, precipitation, and insect sounds on green hylia song frequency. Environmental variables were found to directly influence green hylia song frequencies.

Many animals use coloration to communicate with other individuals. Although the signalling role of avian plumage colour is relatively well studied, there has been much less research on coloration in avian bare parts. However, bare parts could be highly informative signals as they can show rapid changes in coloration. We measured bill colour (a ubiquitous bare part) in over 1600 passerine species and tested whether interspecific variation in carotenoid-based coloration is consistent with signalling to potential mates or signalling to potential rivals in a competitive context. Our results suggest that carotenoid bill coloration primarily evolved as a signal of dominance, as this type of coloration is more common in species that live in social groups in the nonbreeding season, and species that nest in colonies; two socio-ecological conditions that promote frequent agonistic interactions with numerous and/or unfamiliar individuals. Additionally, our study suggests that carotenoid bill c...

The population dynamics of a monogamous coral-reef fish were examined to test hypotheses of recruitment limitation, predation, and postrecruitment processes, and to determine their affects on the mating system. Valenciennea strigata are monogamous gobies that live in sand and rubble zones throughout the Indo-Pacific. Seasonal abundance was recorded in the summer and winter over 2.5 years. A subset of this population was tagged (n = 256) and followed to determine mortality and mobility. Valenciennea strigata were more abundant in summer than in winter, suggesting that a pulse of recruitment in the spring set the maximum population density. Growth rates derived from tagged fish support the hypothesis that recruitment peaked in the spring. Tagged fish experienced 88% mortality within six months; the annual mortality rate approached 100%. Evidence of predation, antipredatory behavior and strong site fidelity implicate predation as the primary source of mortality. Competition for space was not observed between adults, but may affect settlement and recruitment. Despite the lack of adult competition for space, both sexes guarded their mates and courted individuals of the opposite sex. Thus, although population size appears to be determined by nonequilibrium processes, the mating system is affected by competition for mates. Successful mate guarding by both sexes enforced monogamy.

Scientists have described myriad traits in mammalian and avian species that evolved to attract mates. But the brain mechanisms by which conspecifics become attracted to these traits is largely unknown. Yet mammals and birds express mate preferences and make mate choices, and data suggest that this "attraction system" is associated with the dopaminergic reward system. It has been proposed that intense romantic love, a cross-cultural universal, is a developed form of this attraction system. To determine the neural mechanisms associated with romantic love we used functional magnetic resonance imaging (fMRI) and studied 17 people who were intensely "in love" (Aron et al. [2005] J Neurophysiol 94:327-337). Activation specific to the beloved occurred in the right ventral tegmental area and right caudate nucleus, dopamine-rich areas associated with mammalian reward and motivation. These and other results suggest that dopaminergic reward pathways contribute to the "general arousal" component of romantic love; romantic love is primarily a motivation system, rather than an emotion; this drive is distinct from the sex drive; romantic love changes across time; and romantic love shares biobehavioral similarities with mammalian attraction. We propose that this attraction mechanism evolved to enable individuals to focus their mating energy on specific others, thereby conserving energy and facilitating mate choice-a primary aspect of reproduction. Last, the corticostriate system, with its potential for combining diverse cortical information with reward signals, is an excellent anatomical substrate for the complex factors contributing to romantic love and mate choice.

A major cost of social behavior is the increased risk of exposure to parasites and infection. Animals utilize social information, including chemical signals, to recognize and avoid conspecifics infected with either endoparasites or ectoparasites. Here, we briefly discuss the relations among odors, parasite recognition, and avoidance, and consider some of the associated hormonal, neural, and genomic mechanisms. In rodents, odor cues mediate sexual and competitive interactions and are of major importance in individual recognition and mate detection and choice. Female mice distinguish between infected and uninfected males by urinary odors, displaying aversive response to, and avoidance of, the odors of infected individuals. This reduces both the likelihood of the transmission of parasites to themselves and allows females to select for parasite-free males. This set of olfactory and mate choice responses can be further modulated by social factors such as previous experience and exposure to infected males and the mate choices of other females. Male mice, who also face the threat of infection, similarly distinguish and avoid parasitized individuals by odor, thus reducing their likelihood of infection. This recognition and avoidance of the odors of infected individuals involves genes for the neuropeptide, oxytocin (OT), and estrogenic mechanisms. Mice with deletions of the oxytocin gene [OT knockout mice (OTKO)] and mice whose genes for estrogen receptor (ER)-a or ER-h have been disrupted [ER knockout mice (ERKO), a-ERKO and h-ERKO] are specifically impaired in their recognition of, aversion to, and memory of the odors of infected individuals. These findings reveal some of the genes involved in the mediation of social recognition in the ecologically relevant context of parasite recognition and avoidance. D

When searching for a mate, one must gather information to determine the mate value of potential partners. By focusing on individuals who have been previously chosen by others, one's selection of mates can be influenced by another's successful search-a phenomenon known as mate copying. We show mate copying in humans with a novel methodology that closely mimics behavioral studies with nonhuman animals. After observing instances of real mating interest in video recordings of speed-dates, both male and female participants show mate copying effects of heightened short-term and long-term relationship interest towards individuals in dates they perceived as successful. Furthermore, the relative attractiveness of observers and observed plays a mediating role in whom an individual will choose to copy.

spectral sensitivities of each of the zebra finch's single cone classes. This resulted in males that effectively had no UV (UV−), no short-wave (SW−), no medium-wave (MW−) or no long-wave (LW−) plumage reflection. Females preferred UV− and SW− males. LW− and MW− males were least preferred, suggesting that female zebra finches show the greatest response to the removal of longer wavelengths. Quantal catches of the single cone types viewing body areas of the male zebra finch are presented for each treatment. Our study suggests it is important to consider the role of the UV waveband in avian mate choice in conjunction with the rest of the avian visible spectrum.

The function of olfactory signalling in social species is less well understood than in asocial species. Consequently, we examined olfactory communication in the ringtailed lemur, a socially complex primate that retains a functional vomeronasal organ, has well-developed scent glands and shows a suite of scentmarking behaviour. To assess the information content of different types of scent gland secretions, we decoupled olfactory cues from the visual and behavioural modalities with which scent marking is normally associated. We presented male and female subjects (signal receivers) with a series of choice tests between odours derived from conspecific donors (signal senders) varying by sex, age, social status and reproductive condition. We additionally examined the influence of the receivers' reproductive state and familiarity with the signaller. The reproductive condition, social status and familiarity of senders and receivers affected signal transmission; specifically, male receivers attended most to the odours of conspecifics in breeding condition and to the odours of familiar, dominant animals. By contrast, females varied their responses according to both their own reproductive state and that of the sender. Based on male and female patterns of countermarking, we suggest that scent marking serves a function in intergroup spacing and intrasexual competition for both sexes, as might be expected in a female-dominant species. By contrast, minimal female interest in male odours counters a female mate choice function for scent marking in this species. Nevertheless, scent marks are critical to maleemale competition and, therefore, may be subject to sexual selection.

Women's preferences for facial structure vary over the menstrual cycle. Little is known, however, as to how preferences for behavior may be influenced by hormonal factors. Here, we demonstrate that social properties of facial motion influence attractiveness judgments in the absence of other cues, and that women's preferences for these displays vary over the menstrual cycle, as has been demonstrated for structural traits of men's faces in static stimuli. We produced shape-standardized facial models that were animated with male movement and assessed for flirtatiousness by 16 women and attractiveness by 47 women. In fertile phases of the menstrual cycle, women showed stronger preferences for flirtatious movement, but not for absolute movement. These data show that women (1) recognize specific mating-relevant social cues in male facial movement and (2) are differentially influenced by these cues at different phases of the menstrual cycle. This preference for flirtatiousness may promote the adaptive allocation of mating effort towards men who are, in turn, likely to respond positively.

Intraspecific variation in plumage may have a functional significance in mate choice. As a result, breeding birds are often paired assortatively with respect to colour. However, whether this within-pair correlation is a result of homotypic preference whereby individuals pick a mate that looks like themselves, or directional preference whereby all individuals have the same phenotypic preference, is often unknown. Using data collected between 1989 and 2006, we describe intraspecific variation in the striking white feathers on the leading edge of the wing, lesser coverts and mantle of 144 Spanish imperial eagles (Aquila adalberti), one of the most endangered birds of prey in the world. Females had, on average, more white than males, and pairs mated in a positive assortative fashion. Coloration was not related to age of the bird, food supply (i.e., territory quality) or breeding productivity. Our results are most consistent with the process of homotypic-preference assortative mating, and this may be a result of sexual imprinting, and function as a mechanism to optimize the degree of outbreeding. This pattern of mate selection may explain the rapid evolutionary divergence of A. adalberti from the continental population of imperial eagle A. heliaca.

We studied the reproductive behavior of wild caught and captive-born, first generation offspring of the Lake Malawi fish, Tramitichromis intermedius (Teleostei, Cichlidae), held in aquaria. Spawning behavior includes an exchange of actions with dominant males performing bower construction and courtship behaviors while females focus on oviposition and mouthbrooding. Egg counts per oviposition and brooding and interbrooding periods of wild caught T. intermedius follow records of other mouthbrooding cichlid fishes. Observation of circling behavior suggests this behavioral trait may be used in mate choice as longer circling, indicating a secure territory and thus male dominance, leads to more oviposition events and hence the potential for larger broods. Comparisons of clutch size and total length of young at release from full-sized females vs. first spawners reveal smaller clutches and young from the younger females, most likely stemming from differences in body size. Investigation of spawning photoperiodicity also noted distinctions between the two groups with wild caught T. intermedius spawning activity peaking in the middle of the light cycle and captive-born, first spawners exhibiting no significant peak in activity. The trend to spawn midday is most likely influenced by predation factors, while the lack of a spawning periodicity in the offspring may be explained by developmental processes, the absence of environmental cues or the tendency for smaller males to be opportunistic in spawning events. The details of spawning behavior recorded in this study provide a database to investigate species differences and to indicate changes due to chemical and physical disturbances.

Symmetrical human faces are attractive and it has been proposed that humans have a specialized mechanism for detecting symmetry in faces and that sensitivity to symmetry determines symmetry preferences. Here, we show that symmetry preferences are influenced by inversion, whereas symmetry detection is not and that within individuals the ability to detect facial symmetry is not related to preferences for facial symmetry. Taken together, these findings suggest that symmetry preferences are indeed driven by a mechanism that is independent of conscious detection. A specialized mechanism for symmetry preference independent of detection may be the result of specific pressures faced by human ancestors to select high-quality mates and could support a modular view of mate choice. Unconscious mechanisms determining face preferences may explain why the reasons behind attraction are often difficult to articulate and demonstrate that detection alone cannot explain symmetry preferences.

Fluctuating asymmetry in male ornaments may be related to male quality and therefore may be used by females as a guide in mate choice. Experiments on different species have shown female preferences for symmetry, but few previous studies have addressed preferences for symmetry in coloration. Using the bluethroat, Luscinia s. svecica, a passerine with a conspicuous blue and chestnut throat patch, as a model species, we devised an experiment in which the females could choose between males with either symmetric or asymmetric coloured leg bands. The females associated more with symmetric than asymmetric males, indicating a preference for symmetry.

This study tested the differences between restrained and nonrestrained eaters' attractiveness perceptions of female line drawings, of their own figures, and the ideal female figure. Female line drawings varied systematically in body weight and in waist and hip circumference. Forty-six female undergraduate students, 23 nonrestrainers and 23 restrainers, rated stimuli in attractiveness, identified the figure which best represented their own body type (PAF), and the ideal body figure (IF) according to the Restraint Scale [RS; Herman, C. P., & Polivy, J. (1980). Restrained eating. In: A. Stunkard (Ed.), Obesity (pp. 208-225). Philadelphia, PA: Saunders].

Female waist-to-hip ratio (WHR) has been proposed by evolutionary psychologists to be an important component of human male mate choice, because this trait is thought to provide a reliable cue to a woman's reproductive value. Based largely on work conducted in industrialized societies, the claim has been made that preferences for low WHR are culturally invariant. Presumably, the preferences evolved before the advent of agriculture, making foraging populations the best place to test the hypothesis. This was done with the Hadza of Tanzania, who were shown figures of females that varied by weight and waist-to-hip ratio. Low WHR was not preferred. Hadza men did not consider waist-to-hip ratio when expressing preferences for mates. Instead, they were most interested in the weight of potential partners. Research by others with subjects who practice swidden agriculture also revealed that low WHR was not preferred. The data from the Hadza coupled with the information derived from this horticultural group bring into question whether preferences for low WHR are culturally invariant.

In seabirds, colors of feathers and external tissues have only recently been studied, and ultraviolet (UV) color has not yet been detected. Using live individuals as well as museum skins, we found UV peaks of reflectance in two large Aptenodytes species, King (A. patagonicus) and Emperor (A. forsteri) Penguins. UV reflectance did not occur on the feathers, claws, or skin of these species, nor did we find UV reflectance in five other genera of penguins (11 species). UV peaks overlapped with spots of color on the lower beak that appeared orange for human observers, and beak spots differed slightly in location between the two species. Adults of both sexes possessed these UV markings, but they were lacking in juveniles, as was the orange color of the beak spot, and auricular patches used for selecting mates. Finally, measure-Manuscript

This lecture and the accompanying game, The Mating Game, is suitable for advanced high school or undergraduate courses such as AP Biology, Animal Behavior, Introductory Biology, or Evolutionary Biology.

Overall learning goal of this lecture: Understand how sexual selection shapes reproductive behavior

Specific learning goals:
1.  Understand how differences in parental investment lead to differences in sexual activity.
2.  Explain how survival-decreasing traits can evolve via sexual selection.
3.  Know ways in which males compete for mates.
4.  Evaluate theories of female choice.

Please read the accompanying publication in American Biology Teacher that describes The Mating Game by Moore, Holbrook, Meadows, and Taylor.

Individuals tend to choose mates who are sufficiently genetically dissimilar to avoid inbreeding. As facial attractiveness is a key factor in human mate preference, we investigated whether facial preferences were related to genetic dissimilarity. We asked female volunteers to rate the attractiveness of men from photographs and compared these results with individual genotypes at the major histocompatibility complex (MHC). In contrast to previously reported preferences based on odour, we found a non-significant tendency for women to rate MHC-similar faces as more attractive, suggesting a preference for cues to a self-similar MHC in faces. Further analysis revealed that male faces received higher attractiveness scores when rated by women who were MHC-similar than by MHC-dissimilar women. Although unexpected, this MHC-similar facial preference is consistent with other studies documenting assortative preferences in humans, including for facial phenotype.

The enhancement of physical attractiveness through body modifications, such as tattoos is evident in a wide range of cultures and has recently become popular also in Westernized societies. Evolutionary psychologists have suggested that these invasive body modifications could possibly act as handicap signals in sexual selection. However, knowledge about the actual signalling quality of body modification and its perception is still scarce. In this present study a sample of 278 men and women rated images of tattooed and non-tattooed virtual ...

Darwin envisioned a scientific revolution for psychology. His theories of natural and sexual selection identified two classes of struggles-the struggle for existence and the struggle for mates. The emergence of evolutionary psychology and related disciplines signals the fulfillment of Darwin's vision. Natural selection theory guides scientists to discover adaptations for survival. Sexual selection theory illuminates the sexual struggle, highlighting mate choice and same-sex competition adaptations. Theoretical developments since publication of On the Origin of Species identify important struggles unknown to Darwin, notably, within-families conflicts and conflict between the sexes. Evolutionary psychology synthesizes modern evolutionary biology and psychology to penetrate some of life's deep mysteries: Why do many struggles center around sex? Why is social conflict pervasive? And what are the mechanisms of mind that define human nature?

Literature in evolutionary psychology suggests that mate choice has been the primary mechanism of sexual selection in humans, but this conclusion conforms neither to theoretical predictions nor available evidence. Contests override other mechanisms of sexual selection; that is, when individuals can exclude their competitors by force or threat of force, mate choice, sperm competition, and other mechanisms are impossible. Mates are easier to monopolize in two dimensional mating environments, such as land, than in three-dimensional environments, such as air, water, and trees. Thus, two-dimensional mating environments may tend to favor the evolution of contests. The twodimensionality of the human mating environment, along with phylogeny, the spatial and temporal clustering of mates and competitors, and anatomical considerations, predict that contest competition should have been the primary mechanism of sexual selection in men. A functional analysis supports this prediction. Men's traits are better designed for contest competition than for other sexual selection mechanisms; size, muscularity, strength, aggression, and the manufacture and use of weapons probably helped ancestral males win contests directly, and deep voices and facial hair signal dominance more effectively than they increase attractiveness. However, male monopolization of females was imperfect, and female mate choice, sperm competition, and sexual coercion also likely shaped men's traits. In contrast, male mate choice was probably central in women's mating competition because ancestral females could not constrain the choices of larger and more aggressive males through force, and attractive women could obtain greater male investment. Neotenous female features and body fat deposition on the breasts and hips appear to have been shaped by male mate choice.

It has been hypothesized that female orgasm evolved to facilitate recruitment of high-quality genes for offspring. Supporting evidence indicates that female orgasm promotes conception, although this may be mediated by the timing of female orgasm in relation to male ejaculation. This hypothesis also predicts that women will achieve orgasm more frequently when copulating with high-quality males, but limited data exist to support this prediction. We therefore explored relationships between the timing and frequency of women's orgasms and putative markers of the genetic quality of their mates, including measures of attractiveness, facial symmetry, dominance, and masculinity. We found that women reported more frequent and earlier-timed orgasms when mated to masculine and dominant men-those with high scores on a principal component characterized by high objectively-measured facial masculinity, observer-rated facial masculinity, partner-rated masculinity, and partner-rated dominance. Women reported more frequent orgasm during or after male ejaculation when mated to attractive men-those with high scores on a principal component characterized by high observer-rated and self-rated attractiveness. Putative measures of men's genetic quality did not predict their mates' orgasms from self-masturbation or from non-coital partnered sexual behavior. Overall, these results appear to support a role for female orgasm in sire choice.

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) ...

The recent incorporation of sexual selection theories into the rubric of Evolutionary Psychology has produced an important framework from which to examine human mating behavior. Here we review the extant empirical and theoretical work regarding heterosexual human mating preferences and reproductive strategies. Initially, we review contemporary Evolutionary Psychology's adaptationism, including the incorporation of modern theories of sexual selection, adaptive genetic variation, and mate choice. Next, we examine women's and men's mating preferences focusing on the adaptive significance of material, genetic and fertility benefits, and their relationship to environmental characteristics. Following this, we consider human mate choice in relation to non-adaptive preferences. This discussion ends with a look at context effects for individual differences in mate-preferences and reproductive strategies.

Attachment theory has been extremely successful at stimulating research on the formation and quality of emotional bonds and the complex interplay between individual-level and relationship-level processes in all phases of the lifespan . In this chapter, we review and assess some of the empirical findings and propose integrative ideas concerning both normative and individual-difference aspects of personal relationships in adulthood. First, we present a theoretical model of the activation and psychodynamics of the attachment behavioral system in adulthood and describe the intrapsychic and interpersonal manifestations of the sense of attachment security and the regulatory strategies of hyperactivation and deactivation. Next, we focus on romantic relationships, the site of some of the most important emotional bonds in adulthood, and explore implications of variations in attachment-system functioning for the formation and maintenance of these relationships. Specifically, we discuss (a) the contribution of these variations to relationship quality in different stages of a romantic relationship (initiation, consolidation, and maintenance) and (b) the interpersonal processes that explain this contribution. Finally, we extend our theoretical analysis to other kinds of relationships, such as relationships within family systems, friendships, therapeutic relationships, and both intra-and intergroup relations.

A substantial body of work demonstrates that women's mate preferences change across the ovulatory cycle. When fertile in their cycles, women are especially attracted to masculine features (e.g., faces, voices, bodies), socially dominant behavior, and male scents associated with body symmetry and social dominance. Women may also find intelligent men particularly attractive when fertile, though findings are mixed. Related research shows that, on average, romantically-involved women report stronger sexual attraction to men other than their pair-bond partners, but not partners, when fertile, and especially when their partners lack features fertile women prefer (e.g., symmetry). In the current study, we examined whether women's patterns of sexual interests across the cycle are similarly moderated by partners' facial masculinity, facial attractiveness, and intelligence. Results revealed predicted effects of male partners' facial masculinity but none for partners' intelligence. Facial attractiveness may have effects, but we find no evidence that it does so independently of facial masculinity.

Male provisioning ability may have evolved as a 'good dad' indicator through sexual selection, while male creativity may have evolved partly as a 'good genes' indicator. If so, women near peak fertility mid-cycle should prefer creativity over wealth, especially in short-term mating. Forty-one normally cycling women read vignettes describing creative but poor men versus non-creative but rich men. Women's estimated fertility predicted their short-term (but not long-term) preference for creativity over wealth, for both their desirability ratings of individual men (r = .40, p < .01), and their forced-choice decisions between men (r = .46, p < .01). These preliminary results are consistent with the view that creativity evolved at least partly as a good genes indicator through mate choice.

Female and male mate choice preferences in humans both vary according to the menstrual cycle. Women prefer more masculine, symmetrical and genetically unrelated men during ovulation compared with other phases of their cycle, and recent evidence suggests that men prefer ovulating women to others. Such monthly shifts in mate preference have been suggested to bring evolutionary benefits in terms of reproductive success.
New evidence is now emerging that taking the oral contraceptive pill might significantly alter both female and male mate choice by removing the mid-cycle change in preferences. Here, we review support for such conclusions and speculate on the consequences of pillinduced choice of otherwise less-preferred partners for relationship satisfaction, durability and, ultimately,reproductive outcomes.

Maternal hormones in bird eggs modulate not only offspring development, but recently it has also been shown that these effects can persist into adult life. A number of long-lasting effects concern traits of which the expression or development is modulated by androgens. This suggests that the nature of yolk hormonemediated maternal effects may be organizational. Maternal androgens may therefore play an important role in sexual selection, since the expression of sexually selected male characters is often androgen-dependent. We experimentally manipulated the yolk androgen concentrations of European Starling (Sturnus vulgaris) eggs. Subsequently we followed 49 unrelated males from hatching until year of first reproduction. We investigated the expression of multiple sexually selected male characters (song, beak color and throat feather characteristics), taking into account whether a trait is androgen-dependent. Elevated levels of yolk androgens affected the length of the embryonic period, but did not modify the expression of either androgen-dependent or androgen-independent sexually selected male characters including song phenotype at adulthood. Thus the most important function of yolk androgens in starlings and possibly other bird species may relate to the early developmental period. The outcome of our study together with the results of our meta-analysis indicates that the effects of yolk androgens on sexually selected male characters may be comparatively small. Our results suggest that this may relate to the numerous other environmental and/or genetic factors influencing the expression of sexually selected male characters.

A previous study by the authors showed that the body scent of men who have greater body bilateral symmetry is rated as more attractive by normally ovulating (non-pillusing) women during the period of highest fertility based on day within the menstrual cycle. Women in low-fertility phases of the cycle and women using hormone-based contraceptives do not show this pattern. The current study replicated these findings with a larger sample and statistically controlled for men's hygiene and other factors that were not controlled in the first study. The current study also examined women's scent attractiveness to men and found no evidence that men prefer the scent of symmetric women. We propose that the scent of symmetry is an honest signal of phenotypic and genetic quality in the human male, and chemical candidates are discussed. In both sexes, facial attractiveness (as judged from photos) appears to predict body scent attractiveness to the opposite sex. Women's preference for the scent associated with men's facial attractiveness is greatest when their fertility is highest across the menstrual cycle. The results overall suggest that women have an evolved preference for sires with good genes.

Male provisioning ability may have evolved as a “good dad” indicator through sexual selection, whereas male creativity may have evolved partly as a “good genes” indicator. If so, women near peak fertility (midcycle) should prefer creativity over wealth, especially in short-term mating. Forty-one normally cycling women read vignettes describing creative but poor men vs. uncreative but rich men. Women’s estimated fertility predicted their short-term (but not long-term) preference for creativity over wealth, in both their desirability ratings of individual men (r=.40, pr=.46, p