Randy Thornhill - Academia.edu (original) (raw)

Papers by Randy Thornhill

Journal of Comparative Psychology; …, Jan 1, 1994

We hypothesized from the parasite theory of sexual selection that men (Homo sapiens) would prefer... more We hypothesized from the parasite theory of sexual selection that men (Homo sapiens) would prefer averageness and symmetry in women's faces, that women would prefer averageness and symmetry in men's faces, and that women would prefer largeness (not averageness) of the secondary sexual traits of men's faces. We generated computer images of men's and women's faces and of composites of the faces of each sex, and then had men and women rate opposite-sex faces for 4 variables (attractive, dominant, sexy, and healthy). Symmetry, averageness, and the sizes of facial features were measured on the computerized faces. The hypotheses were supported, with the exception of the hypothesized effects of averageness of female and male faces on attractiveness ratings. This is the first study to show that facial symmetry has a positive influence on facial attractiveness ratings.

Biological Reviews, Jan 1, 2007

Current theoretical and empirical findings suggest that mate preferences are mainly cued on visua... more Current theoretical and empirical findings suggest that mate preferences are mainly cued on visual, vocal and chemical cues that reveal health including developmental health. Beautiful and irresistible features have evolved numerous times in plants and animals due to sexual selection, and such preferences and beauty standards provide evidence for the claim that human beauty and obsession with bodily beauty are mirrored in analogous traits and tendencies throughout the plant and animal kingdoms. Human beauty standards reflect our evolutionary distant and recent past and emphasize the role of health assessment in mate choice as reflected by analyses of the attractiveness of visual characters of the face and the body, but also of vocal and olfactory signals. Although beauty standards may vary between cultures and between times, we show in this review that the underlying selection pressures, which shaped the standards, are the same. Moreover we show that it is not the content of the standards that show evidence of convergence -it is the rules or how we construct beauty ideals that have universalities across cultures. These findings have implications for medical, social and biological sciences.

Evolution and Human …, Jan 1, 1999

Evidence has accumulated in recent years supporting the hypothesis that both facial and bodily ph... more Evidence has accumulated in recent years supporting the hypothesis that both facial and bodily physical attractiveness in humans are certifications of developmental and hormonal health. Such evidence indicates that physical attractiveness is an honest or Zahavian signal of phenotypic and genetic quality. The hypothesis that physical beauty connotes health was first proposed by Westermarck and was discussed later by Ellis and Symons. It has been suggested that facial attractiveness in women is a deceptive signal of youth, unrelated to phenotypic and genetic quality. This sensory-bias or super-stimulus hypothesis is not supported by this study of men's ratings of the attractiveness of photographs of 92 nude women. Independent ratings of photographs of faces, fronts with faces covered, and backs of the same women are significantly, positively correlated. The correlation between the ratings of different photos implies that women's faces and external bodies comprise a single ornament of honest mate value, apparently constructed during puberty by estrogen and also probably by developmental adaptations for symmetry. Thus, women's physical attractiveness in face and body honestly signal hormonal and perhaps developmental health.

Journal of Comparative …, Jan 1, 2001

Animal Behaviour, Jun 1, 1998

Males play a variable parental role in reproduction, ranging from no male parental care to extens... more Males play a variable parental role in reproduction, ranging from no male parental care to extensive male care. Females may acquire either direct or indirect fitness benefits from their mate choice, and direct fitness benefits include male parental care. Theoreticians have traditionally emphasized direct fitness benefits to females in species with extensive male parental care. We review the literature and show extensive variation in the patterns of male care, related to the attractiveness of males to females. At one extreme of this continuum, females invest differentially in parental care, investing more when paired with attractive males. The costs of female parental care and other aspects of parental investment may be balanced by benefits in terms of more attractive sons and/or more viable offspring. At the other extreme, in species with extensive direct fitness benefits, males with preferred sexual phenotypes provide the largest relative share of parental care. A comparative study of birds revealed that the extent of the differential female parental investment was directly related to the frequency of extra-pair paternity. Since extra-pair paternity may arise mainly as a consequence of female choice for indirect fitness benefits, this result supports our prediction that differential parental investment is prevalent in species where females benefit indirectly from their mate choice. The consequences for sexual selection theory of these patterns of male care in relation to male attractiveness are emphasized.

Ethology and Sociobiology, 1983

Human evolutionary history was apparently one of polygyny. Polygyny favors the use of different r... more Human evolutionary history was apparently one of polygyny. Polygyny favors the use of different reproductive options by human males with different competitive abilities. These options or alternatives collectively represent a single conditional strategy; which alternatives are employed depend on conditions encountered during a man's life history. It is hypothesized that human rape is an evolved facultative alternative that is primarily employed when men are unable to compete for resources and status necessary to attract and reproduce successfully with desirable mates. According to thii hypothesis males that cannot effectively compete may employ rape as the only behavioral alternative, or depending on circumstances of relative status and family composition, they may incorporate rape into a repertoire of other behavioral patterns, including low commital pairbonding with one or more females and/or investing available resources toward sister's offspring. The evolutionary view of rape we propose is completely testable. The view provides predictions about the rapist's and victim's behavior and about rape laws and taboos, several of which we attempt to test. This study indicates that an evolutionary view promises considerable understanding of rape and related phenomena.

Springer eBooks, Oct 14, 2006

John Wiley & Sons, Inc. eBooks, Sep 8, 2015

Normally ovulating women have been found to report greater sexual attraction to men other than th... more Normally ovulating women have been found to report greater sexual attraction to men other than their own partners when near ovulation relative to the luteal phase. One interpretation is that women possess adaptations to be attracted ...

Journal of Evolutionary Biology, 1997

A. P. Moller’.* and R. Thornhill’ ‘Laborutoire d’Ecologie, CNRS URA 258, UniversitB Pierre et Mur... more A. P. Moller’.* and R. Thornhill’ ‘Laborutoire d’Ecologie, CNRS URA 258, UniversitB Pierre et Murie Curie, B&. A, 7w Parsons, 1990) and discussion at the developmental stability workshop mentioned below. Furthermore, some workers in developmental stability have claimed that there should not be any heritability of stability (e.g., Zakharov, 1989; Palmer and Strobeck, 1992, p. 59). We have read the commentaries addressing our paper on the heritability of developmental instability with great interest. Between the two of us we have published 340 papers and 7 books. We have received many pointed criticisms of our work in the spirit of promoting better science, but we have never received comments of hidden agenda or deception. The negative emotional tone of certain commentaries is interesting in itself, leading us to wonder what is actually at stake. Clearly the issue of heritability of developmental instability is more than just a scientific question to some commentators. In science, no one should feel threatened by others working in “their field”. We are newcomers to the study of developmental instability (only nine (A.P.M.) and seven (R.T.) years, respectively, working on this subject as a primary research interest) and have tremendous respect for the ground work laid by some commentators. Certain commentators claim to be experts on our motivations for doing the meta-analysis. They allege that we had an agenda of wanting to prove fluctuating asymmetry’s heritability in order to support a view that sexual selection operates by favoring individuals with genes that code for offspring viability (so-called good genes). Our motivation was scientific. At the workshop organized by T. A. Markow in Tempe, Arizona in June 1993 there was intense discussion about whether fluctuating asymmetry is heritable. Each side of the argument used one or two

Elsevier eBooks, 1998

Publisher Summary This chapter examines the role of stress-related attraction and attractiveness ... more Publisher Summary This chapter examines the role of stress-related attraction and attractiveness in the three major areas of human social behavior: mating, nepotism, and reciprocity. It addresses the stresses of the home environment during girls' upbringing and how this may functionally mold the development of women's sexuality, particularly the variation among women in sexual arousal. There is considerable evidence that women raised in low-resource settings exhibit different sexual tactics than women raised in settings with more resources. The former women show early maturity and age of copulation, more sex partners, less stable pair-bonds, and less emotional warmth toward mates. The chapter also examines the stresses on human parents surrounding parental investment in babies with focuses on postpartum depression of mothers and on infants' crying. The chapter proposes and tests the hypothesis that postpartum depression is an evolved manifestation of discriminative parental solicitude, which motivates mothers to eliminate newborn babies under ecological situations that are not conducive to infant survival in human evolutionary history. The baby's cry is hypothesized to be an evolved, honest signal of offspring reproductive value. Data bearing on this hypothesis are also reviewed in the chapter.

Behavioral and Brain Sciences, Dec 1, 1985

In most cultures, extramarital sex is highly restricted for women. In most of those cultures, men... more In most cultures, extramarital sex is highly restricted for women. In most of those cultures, men transfer wealth to their own sons (patrilineal inheritance). In some cultures extramarital sex is not highly restricted for women, and in most of those cultures, men transfer wealth to their sisters' sons (matrilineal inheritance). Inheritance to sisters' sons ensures a man's biological relatedness to his heirs, and matrilineal inheritance has been posited as a male accommodation to cuckoldry-a paternity strategy-at least since the 15th century. However, longitudinal analysis of the cumulative effect of female extramarital sex indicates that matrilineal inheritance is most advantageous for women and would be more accurately considered a grandmaternity strategy. That is, if the probability that men's putative children are their biological children (p = probability of paternity) is less than 1, the probabilistic degree of relatedness between a female and her matrilineal heirs is higher than her corresponding relatedness to her patrilineal heirs. The same holds true for men only if p is very low (< 0.46). The upshot is that for moderate levels of female extramarital sex, matrilineal inheritance, relative to patrilineal inheritance, is highly advantageous for women and disadvantageous for men. Consideration of female variance in reproductive success beyond the first generation, and of a man's network of obligation to the inclusive fitness of his relatives, suggests that although the establishment of matrilineal inheritance may require extremely high levels of female extramarital sex, once established, it is likely to be maintained at levels of p that reasonably characterize many societies in the ethnographic record. New analysis of previously published data shows a strong association between matrilineal inheritance and moderate to low probability of paternity, and an even stronger relationship between patrilineal inheritance and high probability of paternity.

Journal of Comparative Psychology, 1991

In earlier papers we discussed a hypothesis for the evolutionary significance of psychological pa... more In earlier papers we discussed a hypothesis for the evolutionary significance of psychological pain. In the present paper we discuss briefly the hypothesis and its application to the psychological pain experienced by rape victims. We have hypothesized that psychological pain reflects a psychological adaptation that is designed to focus on individual's full attention on fitness-reducing social circumstances, allowing correction of the pain causing events and their future avoidance. Psychological pain following rape is proposed to accomplish a focus of victims' attention on the fitness reducing circumstances of rape. Using a data-set comprised of 790 rape victims in the U.S. whose postrape psychological trauma was assessed, we evaluate the effects of rape by strangers, friends and family members. The victims in the sample are most likely to be raped by strangers; this is especially the case for women as opposed to prereproductive-aged girls. Prereproductive-aged girls were more likely to be raped by family members than were women. Rape by strangers is the most psychologically traumatizing of the three rape-offender categories and family-member rape the least. The importance of victim's age and marital status as predictive factors in the degree of psychological trauma following rape-with reproductive-aged and married victims showing significantly more trauma than pre-or post-reproductive-aged and unmarried victims (see N. W. Thornhill and R. Thornhill 1990)-is not confounded by the type of rape perpetrator.

Behavioral Ecology, Nov 1, 1998

Developmental stability reflects the ability of individuals to cope with their environment during... more Developmental stability reflects the ability of individuals to cope with their environment during ontogeny given their genetic background. An inability to cope with environmental and genetic perturbations is reflected in elevated levels of fluctuating asymmetry and other measures of developmental instability. Both trait size and symmetry have been implicated as playing an important role in sexual selection, although their relative importance has never been assessed. We collected information on the relationship between success in sexual competition and size and asymmetry, respectively, to assess the relative importance of these two factors in sexual selection. Studies that allowed comparison of the relationships for the same traits' size and symmetry and success in sexual competition constituted the data, which totaled 73 samples from 33 studies of 29 species. The average sample-size weighted correlation coefficients between mating success or attractiveness and size and asymmetry, respectively, were used as measures of effect size in a meta-anatysis. Analysis was conducted on samples, studies, and species separately. We found evidence of an overall larger effect of symmetry at the species level of analysis, but similar effects at the sample or study levels. The difference in effect size for character size and character symmetry was larger for secondary sexual characters than for ordinary morphological characters at the level of analysis of samples. The results lend support to the conclusion that symmetry plays an important general role in sexual selection, especially symmetry of secondary sexual characters.

Ethology and Sociobiology, May 1, 1990

Ethology, Apr 26, 2010

Certain loud call\ made by female red junglefoivl and Lapland longspurs arc given most freq~ientl... more Certain loud call\ made by female red junglefoivl and Lapland longspurs arc given most freq~iently immediately after egg laving, when a copulation should have the highest probability of fertilizing the next egg to be laid. In these species there is considerable male-male interaction for access to tertilizablc h a l e s , and males are attracted t o o r folloa females making these calls. Based o n our interpretation of these c~l l s , we develop a general hypothesis to predict the pattern of occurrence of fertility advertisement both within and among bird species. We hypothesize that certain loud calls given by female birds before and during the egg-laying period are designed to advertise fertility and thereby incite male-male competition. This hypothesis predicts that calls advertising female fertility should most often occur soon after an egg is laid (i.e. during the period of highest fertility) but may also occur at any time during the female's fertilizable period. Such calls are unlikely to be given by females in strictly monogamous species (especially those n i t h long-term pair bonds) because in these species each female usually mates with only a single male and extra-pair copulations are avoided. Although reports of loud female calls associated with copulation are rare in the literature, the 18 exaniples we found (including iunglefo\vl and longspurs) n e r e predominantly (15/18) in species adopting mating systems other than strict monogamy, and these calls were most commonly and disproportionately reported in multi-male mating system:;. This form of "estrus" in birds may be \x idespread because fe\v species appear t o be strictly monogamous, but it will be difficult to study because the period of high fertility for female birds is so short. '-= no information was available; ? = this is our interpretation of vague information; = the most common situation. 'AM = apparent monogamy (see text); M O = monogamy; PG = polygyny; MM = multi-male (i.e. >1 adult male per social group); LE = lek; PR = promiscuity; D A = dense aggregation. ' E = prior to and/or during egg-laying period; I = during incubation period; N = during nestling period. ' e = shortly after egg laying; n = on nest or after nest departures; c = during courtship and/or copulation. F = males follow or approach female; I = males ignore or avoid female; A = male-male aggression; (A) = male-male aggression recorded during courtship but not necessarily in response to female vocalizations.

Animal Behaviour, Feb 1, 1992

Field-collected males of the scorpionfly Panorpa vulgaris (Inseeta: Mecoptera: Panorpidae) were s... more Field-collected males of the scorpionfly Panorpa vulgaris (Inseeta: Mecoptera: Panorpidae) were separated on the basis of whether or not they could produce salivary nuptial food during matings in the laboratory. Adult males must feed to secret salivary nuptial gifts. Males who could secrete saliva during mating were designated nutritionally 'high' and males who could not were designated nutritionally 'low'. This designation may reflect differences in the ability of the two types of males to compete with conspecifies for food in the habitat. Nutritionally high and nutritionally low fathers were paired haphazardly with virgin mates, all of whom were full siblings. The adult sons of nutritionally high fathers won significantly more fights and mates than the sons of nutritionally low fathers when the two were placed in competition for food. The adult daughters of nutritionally high fathers won significantly more fights in competition with adult daughters of nutritionally low fathers. These sire effects on offspring performance were not confounded by body size differences of contestants. Bilateral symmetry is heritable, differs significantly between the two sire categories and between the offspring of the sire categories, and nutritionally low sires and their offspring are more bilaterally asymmetrical. The genetic paternal effects on offspring fitness components may give rise to female choice based on genetic quality of potential sires.