Resources,attractiveness, family commitment; reproductive decisions in human mate choice

This study of reproductive decisions in human mate selection used data from "lonely hearts" advertisements to examine a series of predictions based on the mate preferences of male and females relating to age; physical appearance; financial condition and socioeconomic status; family commitment and personal traits; short- and long-term mating; and marital status and preexisting children. The sample consisted of 1000 personal advertisements (500 male) placed in two daily, national papers between February and October 1994 in Hungary. The research procedure included a pilot study of 150 advertisers (75 male) to refine the categories examined. Analysis was performed using 1) a matrix with one axis referring to offers and the other to demands of males and females separately; 2) a matrix of offers only to derive correlated traits of claims by males and females; and 3) a matrix with columns describing sex, offers, demands, advertiser's age, and required age and a row for each of the 1000 samples. It was found that men preferred younger mates, while women preferred older ones. Men were more likely to seek physical attractiveness, while women were more likely to seek financial resources (ranked 7th) and high status (ranked 6th). Women strongly preferred male domestic virtue and family commitment, and twice as many women as men demanded long-term relationships. Women more frequently declared preexisting children, and men exhibited a reluctance to accept these children. Both males and females employed "trade-off" strategies, making greater demands if they felt they had attractive offers.     

Lonely hearts advertisements reflect sexually dimorphic mating strategies

Lonely hearts personal advertisements (LHPA) became popular during the 1980s and now appear in nearly every major newspaper. They appear to reflect common male and female reproductive themes. Our analyses of 49 advertisements written by males and 49 advertisements written by females indicate that males offer resources to females and ask for youth and attractiveness, and that females offer youth and attractiveness and ask for resources. When subjects judge these advertisements on a 5-point scale, advertisements are easily grouped into three levels of attractiveness. The attributes of preferred advertisements are defined by those things offered not those things sought. Words or phrases extracted from these advertisements are readily categorized by subjects along a 5-point dimension of desirability. Males and females generally agree on the degree of preference for these 105 words or phrases (r = 0.94), yet differ in degree of preference on 39. Words or phrases preferred by females focus on commitment (e.g., “loving,” “monogamous,” “unattached”). Those preferred by males focus on sexual qualities (e.g., “good figure,” “sexy,” “young”). Individuals of both sexes who indicate a high level of self-confidence prefer words or phrases indicating adventuresome and outgoing qualities. Lack of self-confidence is related to preference for inward-directed qualities. When advertisements are artificially constructed from these words or short phrases, the rating of the advertisements corresponds to the desirability of the individual words. A factor analysis of the words reveals three major factors: (1) words that males prefer; (2) words that females prefer; (3) words that neither males nor females prefer. More highly rated words appear in Factors 1 and 2 than in Factor 3. A survey of 91 lonely hearts advertisement writers demonstrate the same sex differences in what individuals seek and what they offer. Males seek attractivity and offer resources; females seek resources and offer attractivity. After the numerous responses are categorized, only about eight categories for solicitations and eight categories of offers are evident. Interests in resources and attractivity prevail and show sexual dimorphism. Interests in the six remaining categories are nearly identical for the two sexes. Males receive fewer responses to their advertisements than do females. Lengthy advertisements do better for males and shorter ones do better for females. LHPA appear to reflect sexual differences in reproductive concerns. They offer an obvious entry into the motivational systems underlying sexual interactions.     

Mate choice differences according to sex and age

We used 7,415 advertisements published in Spain to analyze traits sought/offered by men and women from different age groups. Findings regarding age, socioeconomic status, and physical attractiveness requirements support evolutionary predictions about mate preferences. However, changes in trait preferences among women under 40 appear to be contingent on Spain’s socioeconomic transformation. Women under 40 seek mainly physical attractiveness in men, whereas those over 40 seek mainly socioeconomic status. The trait most sought by men in all age groups is physical attractiveness. Traits sought and offered by advertisers may be conditioned by the personal situation of the advertiser. Mean age of advertisers (around their forties) and Spain’s social indicators suggest that the majority of advertisers have been unsuccessful in the mating arena at the conventional age.     

Environmental Predictors of Geographic Variation in Human Mating Preferences

Sexual selection theory classically posits consistent and directional mate-preferences for male traits that provide benefits to females. However, flexible mate-choice tactics may persist within a species when males display multiple desirable features that confer different benefits to females under variable environmental conditions. Ecological factors such as population density, resource demand, and sex ratio can influence the value that female animals place on certain male characteristics across mating environments. In this study, I used human mate-preference data from `lonely hearts' advertisements in the newspapers of 23 cities in the USA to assess geographic differences in female preferences for male traits (e.g. physical attributes, resource-holding potential, emotional characteristics, personal interests) in relation to these ecological parameters. I found that females placed more emphasis on the resource-accruing ability of prospective mates in densely populated cities and cities having greater resource demands (higher cost of living). In contrast, women from densely populated or resource-demanding cities placed less emphasis on the emotional aspects or personal interests of males. Preferences for physical features were not environmentally linked, but instead were a function of the degree to which females advertised their own physical attractiveness. Collectively, these results suggest that certain mate-choice criteria employed by women are sensitive to variation in local environmental conditions and that variable levels of resource or mate availability may favor different mating tactics across human populations.     

Sex differences in mate selection strategies: Content analyses and responses to personal advertisements in Brazil

We studied mate selection strategies as revealed in heterosexual personal advertisements published in a Brazilian newspaper, analyzing both the ads' content, with respect to the attributes that men and women offered and sought, and predictors of the number of responses that each ad received. Demands made for a prospective partner changed as a function of the age of the advertiser in predictable sex-differentiated ways: women became less demanding as they aged, whereas men became more demanding. The number of responses received by men and women as a function of age followed a similarly sex-differentiated pattern, with older women receiving fewer responses than younger women, and older men receiving more responses than younger men. In general, results of the present study provided support for our predictions. People who used personal advertisements, a relatively recent unconventional way for selecting mates, expressed conventional preferences, suggestive of evolved psychological mechanisms.     

Sexually dimorphic mate preference in Japan

Lonely hearts advertisements (LHA) published in Japan were examined in a comparative study on sexually dimorphic mate preference. I analyzed 944 LHA written by Japanese (730 by males and 214 by females) seeking short-term relationships and 780 LHA (577 by males and 203 by females) seeking long-term relationships. Some universal patterns of mate preference were confirmed and others were not. Female advertisers in both categories sought more traits than they offered; they also sought more traits than male advertisers. Males tended to offer their financial and social status, and females tended to seek those traits. More females requested family commitment than males. While there was no sex difference in offering and seeking physical appearance and health, females tended to request photographs of their potential mates. Males were more likely than females to be willing to accept children from previous relationships, although there was no significant difference in refusing such children. More females seeking long-term mates requested family commitment than females seeking short-term mates. In both males and females, more advertisers seeking long-term mates offered family commitment than advertisers seeking short-term mates. Some predictions for contingent preference were also examined. One prediction confirmed was that females offering physical appearance and health sought more traits than those not doing so. However, males offering financial and social status did not make higher demands than those who did not, which does not support one prediction. This paper was presented in a meeting of a team research project on "Mating systems, mate choice, and evolution by sexual selection in humans" by the International Research Center for Japanese Studies. I appreciate Professor Takeru Akazawa and other members inviting me to the project. Ryo Oda obtained his Ph.D. from the University of Tokyo for the study of lemur vocal communication. He is a lecturer at Nagoya Institute of Technology, and his current work focuses on the evolution of human behavior and language.     

Different impacts of resources on opposite sex ratings of physical attractiveness by males and females

Parental investment hypotheses regarding mate selection suggest that human males should seek partners featured by youth and high fertility. However, females should be more sensitive to resources that can be invested on themselves and their offspring. Previous studies indicate that economic status is indeed important in male attractiveness. However, no previous study has quantified and compared the impact of equivalent resources on male and female attractiveness. Annual salary is a direct way to evaluate economic status. Here, we combined images of male and female body shape with information on annual salary to elucidate the influence of economic status on the attractiveness ratings by opposite sex raters in American, Chinese and European populations. We found that ratings of attractiveness were around 1000 times more sensitive to salary for females rating males, compared to males rating females. These results indicate that higher economic status can offset lower physical attractiveness in men much more easily than in women. Neither raters' BMI nor age influenced this effect for females rating male attractiveness. This difference explains many features of human mating behavior and may pose a barrier for male engagement in low-consumption lifestyles.     

Sexes of a monomorphic species differ in preference for mates with a novel trait

We investigated the different roles of the sexes in the originationof novel traits in the sexually monomorphic Javanese mannikinLonchura leucogastroides. We introduced a red feather as anevolutionarily novel trait in both sexes and tested their preferencesfor prospective mates with this trait. Males rejected femalesbearing the red feather and preferred to court unadorned females.In contrast, females partly preferred adorned males. Specifically,previously unattractive males gained in attractiveness and could increasetheir reproductive success when bearing the ornament, whereas previouslyattractive males lost in attractiveness, but this did not affect theirreproductive success. We introduced two other novel traits inmales and investigated the females' response to these in matechoice tests. Each of the three new traits interacted with thenatural attractiveness of males. The more attractive a malewas before ornamentation, the more it lost in attractiveness afterornamentation and vice versa. Thus, the position of the traitdid not affect the interaction. Because males rejected adornedfemales and females partly preferred adorned males, novel traitsmight evolve by intersexual selection in males rather than infemales. This can lead to a sexual dimorphism with conspicuoustraits in males. Our study reveals a new insight into the mechanismof the evolution from monomorphism to dimorphism with ornamentaltraits in males.     

Alternative hypotheses linking the immune system and mate choice for good genes

Why do males often have extravagant morphological and behavioural traits, and why do females prefer to mate with such males? The answers have been the focus of considerable debate since Darwin''s The descent of man, and selection in relation to sex appeared in 1871. Recently the broadening of investigation to include fields outside evolutionary biology has shed new light on mate choice and sexual selection. Here, we focus on a specific set of hypotheses relating the biology of resisting disease-causing organisms with the production of condition-dependent sexual signals (advertisements). We present a framework that distinguishes three different hypotheses about trade-offs within the immune system that affect general condition. Hamilton and Zuk''s original hypothesis suggests that hosts fight off disease through resistance to particular pathogens, which consequently lowers resistance to other pathogens. Changes in pathogens over evolutionary time in turn favours changes in which genes confer the best resistance. Alternatively, the immunocompetence hypotheses suggests that the energetic costs of mounting a response to any pathogen compete for resources with other things, such as producing or maintaining advertisements. Finally, improving resistance to pathogens could increase the negative impacts of the immune system on the host, via immunopathologies such as allergies or autoimmune diseases. If both disease and immunopathology affect condition, then sexual advertisements could signal a balance between the two. Studies of hypothesized links between genes, condition, the immune system and advertisements likely will require careful consideration of which hypothesis is being considered, and may necessitate different measures of immune system responses and different experimental protocols.     

Male Courtship Behavior and Weapon Trait as Indicators of Indirect Benefit in the Bean Bug,Riptortus pedestris

Females prefer male traits that are associated with direct and/or indirect benefits to themselves. Male–male competition also drives evolution of male traits that represent competitive ability. Because female choice and male–male competition rarely act independently, exploring how these two mechanisms interact is necessary for integrative understanding of the evolution of sexually selected traits. Here, we focused on direct and indirect benefits to females from male attractiveness, courtship, and weapon characters in the armed bug Riptortus pedestris. The males use their hind legs to fight other males over territory and perform courtship displays for successful copulation. Females of R. pedestris receive no direct benefit from mating with attractive males. On the other hand, we found that male attractiveness, courtship rate, and weapon size were significantly heritable and that male attractiveness had positive genetic covariances with both courtship rate and weapon traits. Thus, females obtain indirect benefits from mating with attractive males by producing sons with high courtship success rates and high competitive ability. Moreover, it is evident that courtship rate and hind leg length act as evaluative cues of female choice. Therefore, female mate choice and male–male competition may facilitate each other in R. pedestris. This is consistent with current basic concepts of sexual selection.     

INBREEDING AND ADVERTISEMENT CALLING IN THE CRICKET TELEOGRYLLUS COMMODUS: LABORATORY AND FIELD EXPERIMENTS

If sexually selected traits reveal a male's heterozygosity or condition to females, then such traits should exhibit declines with inbreeding. We tested this by examining the effect of inbreeding on advertisement calling in male crickets Teleogryllus commodus. We investigated the effect of one generation of full‐sibling mating on calling effort and fine‐scale call structure. Inbreeding reduced calling effort but had no effect on call structure. We then compared the attractiveness of inbred and outbred calls in the field by monitoring how many wild females were attracted to each call type. From the field data, we conducted a selection analysis to identify the major axes of linear and nonlinear multivariate sexual selection on call structure. A comparison of multivariate attractiveness of inbred and outbred calls along each major axis of selection revealed no difference in attractiveness. Our results suggest that inbred male calls have a fine‐scale structure that is no less attractive to females than that of outbred calls. However, because inbred males call less often, and female T. commodus prefer males with a higher calling effort, inbred males will suffer reductions in mating success. Females who base mate choice on call rate are therefore using a signal correlated with male heterozygosity and/or condition.     

Age dependent sex allocation in the polygynous spotless starling

Theoretical and empirical evidence suggests that avian females are able to manipulate the offspring sex ratio at birth. Although mating with an attractive male may induce females to skew the sex ratio toward males, the balance between the benefits of producing attractive sons and the costs of competing with other females for mates could vary with female age, a possibility that had not been previously explored. In this paper we increment experimentally the attractiveness of males of the polygynous spotless starling (Sturnus unicolor) by adding green plants to their nests, a trait involved in courtship, and look for female age-differential effects on offspring primary sex ratio. Young and middle aged females produced more sons in experimental than in control nests, as expected, but old females showed the opposite tendency. To explain this novel result, we speculate that older females are limited to produce the most costly sex because the physiological drawbacks imposed by ageing reduce their ability to compete with younger ones for the non-shareable resources offered by males. We discuss that this evolutionary scenario may be widespread in avian polygynous systems.     

Chemoreception, symmetry and mate choice in lizards

Research on fluctuating asymmetry (FA)-mediated sexual selection has focused almost exclusively on visual signals and ignored chemical communication despite the fact that many species rely on chemical signals for attracting mates. Female mate choice based on visual traits appears to be rare in lizards. However, the femoral glands of male lizards produce pheromones which might transmit chemical information about an individual's developmental stability. Therefore, we hypothesized that mate choice may be based on chemical cues. We analysed the effect of the developmental stability levels of males on the attractiveness of males' scents to females in a laboratory experiment with the lizard Lacerta monticola. When we offered two males of similar body size, females preferentially associated with the scents of males with low FA in their femoral pores and also with the scents of males with a higher number of femoral pores. This suggested that the females were able to discriminate the FA of the males by chemical signals alone and that the females preferred to be in areas marked by males of high quality, thus increasing their opportunities of mating with males of high quality. We suggest that the quality and/or amount of male pheromones could communicate the heritable genetic quality of a male to the female and thereby serve as the basis for adaptive female choice in lizards.     

How to be an attractive male: floral dimorphism and attractiveness to pollinators in a dioecious plant

Background  

Sexual selection theory predicts that males are limited in their reproductive success by access to mates, whereas females are more limited by resources. In animal-pollinated plants, attraction of pollinators and successful pollination is crucial for reproductive success. In dioecious plant species, males should thus be selected to increase their attractiveness to pollinators by investing more than females in floral traits that enhance pollinator visitation. We tested the prediction of higher attractiveness of male flowers in the dioecious, moth-pollinated herb Silene latifolia, by investigating floral signals (floral display and fragrance) and conducting behavioral experiments with the pollinator-moth, Hadena bicruris.     

A comparison of heterosexual and homosexual mating preferences in personal advertisements

Human heterosexual mating preferences have been shown to conform to predictions drawn from evolutionary theory, with men and women adopting broadly distinct strategies. Attempts to reconcile sexual selection theory with homosexual behavior have been less consistent, however, and have largely focussed on addressing two alternative perspectives: (i) that gay men and lesbians display phenotypic traits in common with opposite sex heterosexual individuals or (ii) that homosexual individuals display sex-typical, or exaggerated sex-typical phenotypes. Testing these hypotheses is complicated by sampling issues involved in the study of human sexual orientation, since obtaining standardized and comparable samples of heterosexual and non-heterosexual mating preferences is a prerequisite to analysis. Here we present a comparison of homosexual and heterosexual mating strategies in men and women using a sample of 1733 personal (‘lonely hearts’) adverts gathered from a single source. We used principal components analysis in order to expose underlying structure of the advertisements, and identify three components involving relative emphasis placed on resources, physical attractiveness and personality when offering or seeking mate characteristics. While homosexual individuals are shown to resemble their own-sex heterosexual counterparts in terms of emphasis placed on partner physical attractiveness relative to partner personality, no clear pattern emerges in other aspects of advertisement strategy. Nevertheless, there we find no evidence in support of the hypothesis that homosexual men and women are intrinsically opposite-sex typical in terms of mate preferences.     

Nutritional effects on male calling behaviour in the variable field cricket

In the variable field cricket, Gryllus lineaticeps, females prefer higher chirp rates and longer chirp durations in male calling song. Higher chirp rates are energetically more expensive to produce, but the energetic cost of calling does not vary with chirp duration. We tested the hypothesis that nutrition affects male chirp rate and chirp duration. Full-sibling brothers of similar age were placed on high- and low-nutrition feeding regimes. There was no effect of feeding regime on male weight; neither group showed a significant change in weight, and the two groups did not differ from each other in weight change. However, males on the high-nutrition feeding regime both called more frequently and called at higher chirp rates when they did call. The two groups did not differ in chirp duration, the duration of pulses within chirps or chirp dominant frequency. These results suggest that females select mates based on one nutrition-dependent call character (chirp rate) and one nutrition-independent call character (chirp duration). In addition, because males in the two groups did not show significant differences in weight change, and because males on the high-nutrition feeding regime engaged in energetically more expensive calling, these results suggest that males invest any excess energy above their basic maintenance requirements in the production of call types that increase their attractiveness to females. The absence of a relationship between body condition and calling song structure for males in the field may be a consequence of this pattern of energy allocation. Copyright 1999 The Association for the Study of Animal Behaviour.     

Modulation of sexual signalling by immune challenged male mealworm beetles (Tenebrio molitor, L.): evidence for terminal investment and dishonesty

Organisms partition resources into life-history traits in order to maximise fitness over their expected lifespan. For the males of many species fitness is determined by qualitative and quantitative aspects of costly sexual signals: The notion that epigamic traits are costly forms the cornerstone of those theories that propose parasites drive sexual selection. Consequently studies examining this notion assume sexual signalling is honest (i.e. driven by cost) when they seek to identify correlations or causal links between male immune function and attractiveness. We demonstrate that immune challenged males of the mealworm beetle, Tenebrio molitor, increased their investment in epigamic pheromone signals: these males became significantly more attractive to females whilst increasing the activity of a key immune effector system. In other words males increase terminal reproductive effort (invest in attractiveness) in response to a survival threat (immune insult). Consequently the signal preferred by the female is dishonest when considering the male's condition.     

Early Developmental Conditions and Male Attractiveness in Zebra Finches

Traits used in mate choice are often costly to produce or maintain, and thus can reflect an individual’s current condition. Mate choice, however, might not only be influenced by the current condition of a potential partner, but also by the condition it had experienced during its early development which can have strong and long‐lasting effects on various traits. Here we studied the effects of different early developmental conditions, imposed by brood size manipulations (small, medium and large broods), on male attractiveness as measured by female choice experiments in zebra finches (Taeniopygia guttata). In three different experiments, we allowed females to choose between males that had been raised in different experimental brood sizes. In none of the experiments, females showed a significant preference for males which had experienced better developmental conditions, i.e. were raised in the relatively smaller experimental broods. Song rate was higher in males coming from small than large broods, but females did not prefer males that sang more. These results suggest that sexual attractiveness either was not affected by our experimental treatment or that males subsequently had compensated in their overall attractiveness for negative effects of early developmental conditions.     

Paternity and multiple signaling: effects of a secondary sexual character and song on paternity in the barn swallow

ABSTRACT Multiple signals may evolve because they provide independent information on the condition of a signaler. Females should pay attention to male characters relative to their reliability as signals of male attractiveness or quality. Since behavioral traits are flexible and, therefore, subject to strong environmental influences, females should weigh stable morphological signals higher in their choice of mates for genetic benefits than flexible behavioral traits, for example, by paying particular attention to phenotypically plastic traits when produced in combination with an exaggerated morphological signal. Consistent with this prediction, female barn swallows Hirundo rustica, which are known to prefer males with the longest tail feathers (a secondary sexual character), also preferred males with extreme expressions of a behavioral trait (song rate), as determined from patterns of paternity assessed by microsatellites. However, a statistical interaction between tail length and song rate implied that song rate was relatively unimportant for males with a short tail but more important for longtailed males. Since song rate is a flexible behavioral trait, females appear to have responded to this flexibility by devaluing the importance of song rate in assessment of unattractive sires.     

Sex differences in smiling and other photographed traits: a theoretical assessment

Many studies have shown that females smile more than males do in social situations. The present study extends this research by examining a large sample of high school yearbook photographs. In addition to assessing the degree of smiling, ratings were obtained of the following traits for each photograph: hair length, hair colour, masculine-feminine appearance and physical attractiveness. Results reconfirmed earlier research showing that females smile more than males do while they are being photographed. Other findings were that smiling was positively correlated with hair length, femininity and physical attractiveness for females but not for males. When a multivariate analysis was performed, none of these traits predicted smiling in males, and only femininity was significant in predicting smiling in females. Although social learning theories of smiling can account for some of these findings, a recently proposed neurohormonal theory seems to best explain why femininity is related to smiling in females but not in males.