scholarly journals Sex differences in ocular morphology in Caucasian people: a dubious role of sexual selection in the evolution of sexual dimorphism of the human eye

2020 ◽  
Vol 74 (10) ◽  
Author(s):  
Dariusz P. Danel ◽  
Sławomir Wacewicz ◽  
Karel Kleisner ◽  
Zdzisław Lewandowski ◽  
Mariska E. Kret ◽  
...  
Keyword(s):  
Sex Differences ◽  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Facial Attractiveness ◽  
Total Surface Area ◽  
Sexually Dimorphic ◽  
Human Eye ◽  
Eye Morphology ◽  
Caucasian Men

Abstract The horizontal size of the exposed depigmented sclera in Caucasians has been previously suggested to be sexually dimorphic, and the significance of this phenomenon remains unclear. Here we build on a previous study and extend it by (i) examining sex differences in other measures of ocular morphology and (ii) exploring the link between eye morphology and biometric markers of facial attractiveness. We used facial photographs of 100 Caucasians (50 men) from Eastern-Central Europe and digitally measured four ocular features. Eye measurements were tested for sex differences and associations with morphometric data on facial averageness and sexual shape dimorphism. We found that sclera surface is more horizontally exposed in men, even though the total surface area is similar in both sexes. We also found that eye fissures are rounder (less rectangular) in women than in men and that irises are brighter in women. We did not find any relationship between the examined eye features and two aspects of facial attractiveness: facial averageness and sexual dimorphism in facial shape. Despite being sexually dimorphic, eye features may be loosely linked with the development of facial sexual ornamentation. The role of sexual selection in the evolution of the observed phenomena is disputable. Significance statement It is often argued that because of their physical appearance, human eyes are crucial to interpersonal and social interactions. In many aspects, however, the significance of the human eye architecture is unclear. In this study, we examine sex differences in eye morphology and explore the link between ocular features and biometric measures of facial attractiveness in Caucasian men and women. We found that despite being sexually dimorphic, eye features may be loosely linked with biometric markers of facial attractiveness. We argue that the role of sexual selection in the evolution of the observed sex differences is disputable.

scholarly journals Regulatory Role of Sex Hormones in Cardiovascular Calcification

2021 ◽  
Vol 22 (9) ◽  
pp. 4620
Author(s):  
Holly J. Woodward ◽  
Dongxing Zhu ◽  
Patrick W. F. Hadoke ◽  
Victoria E. MacRae
Keyword(s):  
Cardiovascular Disease ◽  
Sex Differences ◽  
Sexual Dimorphism ◽  
Aortic Stenosis ◽  
Sex Hormones ◽  
Sex Hormone ◽  
Increased Risk ◽  
Male Sex ◽  
Primary Male

Sex differences in cardiovascular disease (CVD), including aortic stenosis, atherosclerosis and cardiovascular calcification, are well documented. High levels of testosterone, the primary male sex hormone, are associated with increased risk of cardiovascular calcification, whilst estrogen, the primary female sex hormone, is considered cardioprotective. Current understanding of sexual dimorphism in cardiovascular calcification is still very limited. This review assesses the evidence that the actions of sex hormones influence the development of cardiovascular calcification. We address the current question of whether sex hormones could play a role in the sexual dimorphism seen in cardiovascular calcification, by discussing potential mechanisms of actions of sex hormones and evidence in pre-clinical research. More advanced investigations and understanding of sex hormones in calcification could provide a better translational outcome for those suffering with cardiovascular calcification.

scholarly journals The evolution of sexual dimorphism in parasitic cuckoos: sexual selection or coevolution?

2007 ◽  
Vol 274 (1617) ◽  
pp. 1553-1560 ◽  
Author(s):  
O Krüger ◽  
N.B Davies ◽  
M.D Sorenson
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Parental Care ◽  
Brood Parasitism ◽  
Selection Pressure ◽  
Life Histories ◽  
Exceptional Case ◽  
Evolutionary Pathways ◽  
Common Situation

Sexual dimorphism is ubiquitous in animals and can result from selection pressure on one or both sexes. Sexual selection has become the predominant explanation for the evolution of sexual dimorphism, with strong selection on size-related mating success in males being the most common situation. The cuckoos (family Cuculidae) provide an exceptional case in which both sexes of many species are freed from the burden of parental care but where coevolution between parasitic cuckoos and their hosts also results in intense selection. Here, we show that size and plumage differences between the sexes in parasitic cuckoos are more likely the result of coevolution than sexual selection. While both sexes changed in size as brood parasitism evolved, we find no evidence for selection on males to become larger. Rather, our analysis indicates stronger selection on parasitic females to become smaller, resulting in a shift from dimorphism with larger females in cuckoos with parental care to dimorphism with larger males in parasitic species. In addition, the evolution of brood parasitism was associated with more cryptic plumage in both sexes, but especially in females, a result that contrasts with the strong plumage dimorphism seen in some other parasitic birds. Examination of the three independent origins of brood parasitism suggests that different parasitic cuckoo lineages followed divergent evolutionary pathways to successful brood parasitism. These results argue for the powerful role of parasite–host coevolution in shaping cuckoo life histories in general and sexual dimorphism in particular.

scholarly journals Artificial sexual selection alters allometry in the stalk-eyed fly Cyrtodiopsis dalmanni (Diptera: Diopsidae)

1993 ◽  
Vol 62 (3) ◽  
pp. 213-222 ◽  
Author(s):  
Gerald S. Wilkinson
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Body Length ◽  
Sexually Dimorphic ◽  
Selected Lines ◽  
Variable Intensity ◽  
High Line ◽  
Cumulative Selection ◽  
Selection For ◽  
Selection Of

SummarySelection for increased and decreased ratio of eye span to body length was exerted on male stalk-eyed flies (Cyrtodiopsis dalmanni) from Malaysia using replicate selected and unselected lines. Response to selection was symmetrical. After 10 generations high line male eye span increased to 1·3 body lengths while low line male eye span declined to 1·1 body lengths. Realized heritabilities for eye span to body length ratio, estimated using regressions of deviations from unselected controls on cumulative selection differentials, were greater than zero for all four selected lines with average h2 = 0·35 + 0·06. The static linear allometric relationship between eye span and body length diverged between selected lines and rotated among selected line males in the same direction as among males in other sexually dimorphic diopsid species. Crosses between lines after 13 generations of selection indicate that the genes which influence relative eye span combine additively and do not exhibit sex linkage or maternal effects. The genetic correlation between the sexes, 0·29 + 0·05 as estimated by the regression of female on male change in eye span, did not prevent sexual dimorphism in eye span from diverging between lines. These results suggest that the exaggerated eye span of male C. dalmanni is maintained by natural selection opposing sexual selection rather than by lack of or asymmetry in additive genetic variation. Furthermore, the variation in sexual dimorphism for eye span-body length allometry observed among extant diopsid species is consistent with sexual selection of variable intensity acting on relative eye span.

scholarly journals Sexual size dimorphism and sexual selection in artiodactyls

2020 ◽  
Vol 31 (3) ◽  
pp. 792-797
Author(s):  
Marcelo H Cassini
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Group Size ◽  
Sexual Size Dimorphism ◽  
Alternative Hypothesis ◽  
Mammalian Species ◽  
Generalized Least Squares ◽  
Size Dimorphism ◽  
Selection For

Abstract Sexual size dimorphism is biased toward males in most mammalian species. The most common explanation is precopulatory intramale sexual selection. Large males win fights and mate more frequently. In artiodactyls, previous tests of this hypothesis consisted of interspecific correlations of sexual dimorphism with group size as a surrogate for the intensity of sexual selection (Is). However, group size is not a proper measure of sexual selection for several reasons as is largely recognized in other mammalian taxa. I conducted an interspecific test on the role of sexual selection in the evolution of sexual dimorphism using the variance in genetic paternity as a proxy for the Is. I reviewed the literature and found 17 studies that allowed estimating Is= V/(W2), where V and W are the variance and mean number of offspring per male, respectively. A phylogenetic generalized least squares analysis indicated that dimorphism (Wm/Wf) showed a significant positive regression with the intensity of sexual selection but not group size (multiple r2= 0.40; F3,17= 12.78, P = 0.002). This result suggests that sexual selection may have played a role in the evolution of sexual size dimorphism in Artiodactyla. An alternative hypothesis based on natural selection is discussed.

scholarly journals Sex ratio variation shapes the ecological effects of a globally introduced freshwater fish

2015 ◽  
Vol 282 (1817) ◽  
pp. 20151970 ◽  
Author(s):  
David C. Fryxell ◽  
Heather A. Arnett ◽  
Travis M. Apgar ◽  
Michael T. Kinnison ◽  
Eric P. Palkovacs
Keyword(s):  
Sexual Dimorphism ◽  
Sex Ratio ◽  
Evolutionary Ecology ◽  
Natural Populations ◽  
Trophic Cascades ◽  
Zooplankton Abundance ◽  
Sexually Dimorphic ◽  
Ecosystem Responses ◽  
Ratio Variation

Sex ratio and sexual dimorphism have long been of interest in population and evolutionary ecology, but consequences for communities and ecosystems remain untested. Sex ratio could influence ecological conditions whenever sexual dimorphism is associated with ecological dimorphism in species with strong ecological interactions. We tested for ecological implications of sex ratio variation in the sexually dimorphic western mosquitofish, Gambusia affinis . This species causes strong pelagic trophic cascades and exhibits substantial variation in adult sex ratios. We found that female-biased populations induced stronger pelagic trophic cascades compared with male-biased populations, causing larger changes to key community and ecosystem responses, including zooplankton abundance, phytoplankton abundance, productivity, pH and temperature. The magnitude of such effects indicates that sex ratio is important for mediating the ecological role of mosquitofish. Because both sex ratio variation and sexual dimorphism are common features of natural populations, our findings should encourage broader consideration of the ecological significance of sex ratio variation in nature, including the relative contributions of various sexually dimorphic traits to these effects.

Sexual dimorphism in two savannah sparrow populations

1980 ◽  
Vol 58 (3) ◽  
pp. 412-415 ◽  
Author(s):  
Patrick J. Weatherhead
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Stabilizing Selection ◽  
Sexually Dimorphic ◽  
Mainland Population ◽  
Savannah Sparrow ◽  
Savannah Sparrows ◽  
Insular Population

Contrary to predictions, a monogamous, mainland population of savannah sparrows was found to be more sexually dimorphic than a polygynous, insular population. When only trophic characters were considered, the insular population fit the prediction of greater sexual dimorphism. Several explanations for increased sexual selection or decreased stabilizing selection in the more dimorphic population are considered. While none of the explanations seem readily applicable from the available evidence, further avenues of investigation are suggested.

scholarly journals How and why patterns of sexual dimorphism in human faces vary across the world

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Karel Kleisner ◽  
Petr Tureček ◽  
S. Craig Roberts ◽  
Jan Havlíček ◽  
Jaroslava Varella Valentova ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Mate Choice ◽  
Body Height ◽  
Human Populations ◽  
Sexually Dimorphic ◽  
Shape Variation ◽  
Cross Cultural Differences ◽  
Facial Shape ◽  
Human Faces

AbstractSexual selection, including mate choice and intrasexual competition, is responsible for the evolution of some of the most elaborated and sexually dimorphic traits in animals. Although there is sexual dimorphism in the shape of human faces, it is not clear whether this is similarly due to mate choice, or whether mate choice affects only part of the facial shape difference between men and women. Here we explore these questions by investigating patterns of both facial shape and facial preference across a diverse set of human populations. We find evidence that human populations vary substantially and unexpectedly in both the magnitude and direction of facial sexually dimorphic traits. In particular, European and South American populations display larger levels of facial sexual dimorphism than African populations. Neither cross-cultural differences in facial shape variation, sex differences in body height, nor differing preferences for facial femininity and masculinity across countries, explain the observed patterns of facial dimorphism. Altogether, the association between sexual shape dimorphism and attractiveness is moderate for women and weak (or absent) for men. Analysis that distinguishes between allometric and non-allometric components reveals that non-allometric facial dimorphism is preferred in women’s faces but not in faces of men. This might be due to different regimes of ongoing sexual selection acting on men, such as stronger intersexual selection for body height and more intense intrasexual physical competition, compared with women.

scholarly journals Sex Matters in Health and Disease: a review of biological sex differences with an emphasis on glioma

2019 ◽  
Author(s):  
Susan Christine Massey ◽  
Paula Whitmire ◽  
Tatum E Doyle ◽  
Joseph E Ippolito ◽  
Maciej M Mrugala ◽  
...  
Keyword(s):  
Sex Differences ◽  
Underlying Disease ◽  
Response To Treatment ◽  
Sexually Dimorphic ◽  
Biological Sex ◽  
Disease Outcomes ◽  
Broad Array ◽  
Health And Disease ◽  
Improve Patient

Humans are sexually dimorphic, with sex being the most persistent difference among humans over the course of our evolutionary history. Beyond the visible sex differences that can be considered true dimorphisms, there are also sex differences at the molecular and cellular scales. The role of these biological sex differences for human health, while being increasingly recognized, have long been underappreciated and underexplored. Frequently, these differences are only recognized in sex–specific diseases, such as genitourinary diseases and cancers. However, given the evidence for sex differences in the most basic aspects of human biology, including metabolism, cellular composition, and immune activity, these differences could have consequences for the etiology and pathophysiology of a majority of diseases. It is thus essential to consider the extent to which these differences may influence the various mechanisms underlying disease processes, response to treatment, and the maintenance of health in order to better improve patient outcomes. Here we review the evidence for a broad array of biological sex differences in humans and discuss how they may relate to observed sex differences in various diseases, with an emphasis on cancer, specifically glioblastoma. We further propose that mathematical approaches can be useful for exploring the extent to which sex differences affect disease outcomes and accounting for those in the development of therapeutic strategies.

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