Differences in male and female cognitive abilities: Sexual selection or division of labor?

1996 ◽  
Vol 19 (2) ◽  
pp. 254-255
Author(s):  
Michael T. Ghiselin
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Sexual Dimorphism ◽  
Division Of Labor ◽  
Cognitive Abilities ◽  
Reproductive Competition ◽  
Male And Female ◽  
Males And Females

AbstractIn Darwinian terminology, “sexual selection” refers to purely reproductive competition and is conceptually distinct from natural selection as it affects reproduction generally. As natural selection may favor the evolution of sexual dimorphism by virtue of the division of labor between males and females, this possibility needs to be taken very seriously.

scholarly journals Ontogenetic allometry in the foot size of Oligoryzomys flavescens (Waterhouse, 1837) (Rodentia, Sigmodontinae)

2015 ◽  
Vol 75 (2) ◽  
pp. 435-441 ◽  
Author(s):  
R. Maestri ◽  
R. Fornel ◽  
TRO. Freitas ◽  
JR. Marinho
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Sexual Dimorphism ◽  
Encounter Rate ◽  
Allometric Growth ◽  
Positive Allometry ◽  
Rate Of Growth ◽  
Ontogenetic Allometry ◽  
Males And Females ◽  
Oligoryzomys Flavescens

Ontogenetic allometry is the study of how the size or shape of certain structures changes over the course of an animal’s development. In this study, using Huxley's formula of allometric growth (1932), we assessed the changes in the rate of growth of the feet size of the sigmodontine rodent Oligoryzomys flavescens during its ontogeny and compared differences between males and females. We find evidence of a change of polarity during the ontogenetic development of the species, with the presence of positive allometry during pregnancy and negative allometry in adulthood. Moreover, we note the presence of sexual dimorphism in the size of the feet, in which males of the species have a higher rate of growth than females. This growth pattern is positively related to escape from predators in childhood in both sexes and, in adulthood, provides a higher encounter rate of females by males, due to the larger displacement of the latter. We suggest that both the forces of natural selection and sexual selection have acted to shape the evolution of foot size in this species.

Sex, Difference, and Desire

2020 ◽  
pp. 177-232
Author(s):  
Ben Bradley
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Evolutionary Psychology ◽  
Evolutionary Biology ◽  
Racial Politics ◽  
Sexual Agency ◽  
Human History ◽  
Male And Female ◽  
Males And Females ◽  
Descent Of Man

The parts of The Descent of Man dealing with sexual desire and difference have sparked more controversy and misrepresentation than any of Darwin’s other publications. Crucial to Descent’s arguments is the derivation of sexual selection from the dramas of display and desire observed among animals. The book describes four plotlines structuring the theatre of sexual agency in animals, each having different implications for the roles played by males and females. When Descent extends these plotlines to humans, they alter and modulate into an even more varied array of scenarios, again, each with its own distinctive roles for women and men. A mirror-dynamic figures centrally in both animal and human sex—the need to recognize or predict others’ desires so as to act in a way to arouse them. However, several nodes of concern disturb Darwin’s presentation of human sex: tensions between his three epochs of human history; Victorian racial politics; Victorian ideas about male and female superiority; and the imperatives of propriety. The chapter illustrates some of the muddles that result from these concerns, including: confirmation bias; aporia in argument; grammatical kinks; and overlap between sexual and natural selection. Finally, the chapter instances some of the main resonances in more recent scholarship of Darwin’s discussion of sex, instancing debates in feminism, about anthropomorphism, in evolutionary biology, and evolutionary psychology.

4. Sex roles and stereotypes

2018 ◽  
pp. 52-68
Author(s):  
Leigh W. Simmons
Keyword(s):  
Sexual Selection ◽  
Mate Choice ◽  
Sexual Behaviour ◽  
Sex Roles ◽  
Animal Species ◽  
Male And Female ◽  
Mating Competition ◽  
Characteristic Behaviour ◽  
Males And Females ◽  
Female Roles

‘Sex roles and stereotypes’ examines the notion, implicit in many of the original ideas about sexual selection, that males and females have natural ‘roles’ with characteristic behaviour associated with each sex. It also explores further the reasons behind deviations from the ‘typical’ sex roles in mate choice and in mating competition. Are there ‘standard’ male and female roles in both humans and other animal species? One version of sex roles holds that males are generally dominant and females submissive, stemming from the way that sexual selection favours different behaviours in each sex. This could mean that sexual selection dictates particular behaviours in males and females. But in fact, sexual behaviour is extraordinarily varied in nature.

scholarly journals Does sexual selection explain human sex differences in aggression?

2009 ◽  
Vol 32 (3-4) ◽  
pp. 249-266 ◽  
Author(s):  
John Archer
Keyword(s):  
Sex Differences ◽  
Sexual Selection ◽  
Physical Aggression ◽  
Role Theory ◽  
Social Roles ◽  
Social Role ◽  
Conflicts Of Interest ◽  
Reproductive Competition ◽  
Threat Displays ◽  
Males And Females

AbstractI argue that the magnitude and nature of sex differences in aggression, their development, causation, and variability, can be better explained by sexual selection than by the alternative biosocial version of social role theory. Thus, sex differences in physical aggression increase with the degree of risk, occur early in life, peak in young adulthood, and are likely to be mediated by greater male impulsiveness, and greater female fear of physical danger. Male variability in physical aggression is consistent with an alternative life history perspective, and context-dependent variability with responses to reproductive competition, although some variability follows the internal and external influences of social roles. Other sex differences, in variance in reproductive output, threat displays, size and strength, maturation rates, and mortality and conception rates, all indicate that male aggression is part of a sexually selected adaptive complex. Physical aggression between partners can be explained using different evolutionary principles, arising from the conflicts of interest between males and females entering a reproductive alliance, combined with variability following differences in societal gender roles. In this case, social roles are particularly important since they enable both the relatively equality in physical aggression between partners from Western nations, and the considerable cross-national variability, to be explained.

scholarly journals Sexual selection is a form of social selection

2012 ◽  
Vol 367 (1600) ◽  
pp. 2266-2273 ◽  
Author(s):  
Bruce E. Lyon ◽  
Robert Montgomerie
Keyword(s):  
Sexual Selection ◽  
Social Interactions ◽  
Social Selection ◽  
Reproductive Competition ◽  
Selection Theory ◽  
Males And Females ◽  
Female Roles ◽  
Comprehensive Framework ◽  
Natural And Sexual Selection ◽  
Lines Of Evidence

Social selection influences the evolution of weapons, ornaments and behaviour in both males and females. Thus, social interactions in both sexual and non-sexual contexts can have a powerful influence on the evolution of traits that would otherwise appear to be detrimental to survival. Although clearly outlined by West-Eberhard in the early 1980s, the idea that social selection is a comprehensive framework for the study of ornaments and weapons has largely been ignored. In West-Eberhard's view, sexual selection is a form of social selection—a concept supported by several lines of evidence. Darwin's distinction between natural and sexual selection has been useful, but recent confusion about the limits of sexual selection suggests that some traits are not easily categorized as naturally or sexually selected. Because social selection theory has much to offer the current debates about both sexual selection and reproductive competition in females, it is sometimes viewed, narrowly, to be most useful when considering female roles. However, social selection theory encompasses much more than female reproductive competition. Our goal here was to provide that broader perspective.

Sexual dimorphism in the claws of the European terrapin (Emys orbicularis): potential implications for the reproductive fitness of the species.

2019 ◽  
Author(s):  
Gonzalo Alarcos ◽  
Jaime Madrigal-González ◽  
Miguel Lizana ◽  
Fabio Flechoso
Keyword(s):  
Sexual Selection ◽  
Comparative Analysis ◽  
Sexual Dimorphism ◽  
Reproductive Success ◽  
Sexual Maturity ◽  
Reproductive Fitness ◽  
Emys Orbicularis ◽  
Future Studies ◽  
Different Populations ◽  
Males And Females

There are many biometric differences between the males and females of the European pond turtle (Emys orbicularis) as regards their size, colouring, the shape of the plastron, tail, etc. The males use their claws to grasp the female during copulation and hence sexual selection should favour the males that have larger claws, which allow them to grasp the female better. Here, we address this type of sexual dimorphism in a comparative analysis of indices obtained from claw length, the length of the carapace and the locality where individuals were sampled. The results show that the curvature of the claws differs between the two sexes, being longer in males and increasing with age, size, and hence, the state of sexual maturity, than in females. Greater claw length could confer advantages for males when grasping the carapace of females, and hence, improve their reproductive fitness. Importance in the reproductive success that might have this feature in males could originate future studies that will relate the shape, thickness, length and other measures of the claws in males with their reproductive success in different populations, genetic variety, and most importantly, viability of populations. 

A Shape to Die for?

2021 ◽  
pp. 481-510
Author(s):  
Graham Mitchell
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Surface Water ◽  
Alternative Hypothesis ◽  
Natural Habitat ◽  
Large Body ◽  
Male And Female ◽  
Large Size ◽  
Selection For ◽  
Competition For Resources

The product of natural selection over at least 15 million years is the elongated, slender shape of giraffes that fits the natural habitat giraffes now occupy. What selection pressures operated to produce their shape? Their shape is partly the product of gravity and could have been an accidental by-product of selection for a large body mass and the protection from predation that large size brings, but the prevailing explanation is that their shape confers a browsing advantage. Preferred browse is concentrated at a height easily reached by giraffes but not by other browsers and natural selection would have favored those giraffes that could reach it. An alternative hypothesis is that their shape confers thermoregulatory benefits in addition to improved vigilance. Another hypothesis is that a long neck evolved to counter long legs allowing giraffes to drink surface water. An attractive hypothesis is that their shape is a product of ‘runaway’ sexual selection by females for males with long heavy necks, but analysis of this hypothesis has shown that the morphology of male and female giraffe does not differ. Nevertheless, all these possibilities could have contributed. A consequence of selection for their shape is over-specialization: giraffes seem to be inextricably dependent on a narrow diet, a diet that is subject to the vagaries of climate and competition for resources. The greatest threat to their survival is, therefore, their shape.

Sex-related Differences in Gene Expression in Salivary Glands of BALB/c Mice

2005 ◽  
Vol 84 (2) ◽  
pp. 160-165 ◽  
Author(s):  
N.S. Treister ◽  
S.M. Richards ◽  
M.J. Lombardi ◽  
P. Rowley ◽  
R.V. Jensen ◽  
...  
Keyword(s):  
Gene Expression ◽  
Sexual Dimorphism ◽  
Salivary Glands ◽  
Structure And Function ◽  
Differentially Expressed ◽  
Male And Female ◽  
Tissue Specific ◽  
Total Rna ◽  
Males And Females ◽  
And Function

Sex-related differences exist in the structure and function of the major glands in a variety of species. Moreover, many of these variations appear to be unique to each tissue. We hypothesized that this sexual dimorphism is due, at least in part, to gland-specific differences in gene expression between males and females. Glands were collected from male and female BALB/c mice (n = 5/sex/experiment), and total RNA was isolated. Samples were analyzed for differentially expressed mRNAs with CodeLink microarrays, and data were evaluated by GeneSifter. Our results demonstrate that significant (P < 0.05) sex-related differences exist in the expression of numerous genes in the major salivary glands, and many of these differences were tissue-specific. These findings support our hypothesis that sex-related differences in the salivary glands are due, at least in part, to tissue-specific variations in gene expression.

scholarly journals Sex Determination Using Inion-Opistocranium-Asterion (IOA) Triangle in Nigerians’ Skulls

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
C. N. Orish ◽  
B. C. Didia ◽  
H. B. Fawehinmi
Keyword(s):  
Sexual Dimorphism ◽  
Linear Regression ◽  
Coefficient Of Variation ◽  
Individual Identification ◽  
Male And Female ◽  
Gender Determination ◽  
Important Concern ◽  
Males And Females ◽  
The Right

Background. Determination of sex is an important concern to the forensic anthropologists as it is critical for individual identification. This study has investigated the existence of sexual dimorphism in the dimensions and the area of the IOA triangle. Methods. A total of 100 adult dry skulls, (78 males; 22 females) from departments of anatomy in Nigerian universities were used for this study. Automatic digital calliper was used for the measurement. Coefficient of variation, correlation, linear regression, percentiles, and sexual dimorphism ratio were computed from the IOA triangle measurements. The IOA triangle area was compared between sexes. Results. The male parameters were significantly (P<0.05) higher than female parameters. The left opistocranium-asterion length was 71.09±0.56 and 61.68±3.35 mm and the right opistocranium-asterion length was 69.73±0.49 and 60.92±2.10 mm for male and female, respectively. A total area of IOA triangle of 1938.88 mm2 and 1305.68 mm2 for male and female, respectively, was calculated. The left IOA indices were 46.42% and 37.40% in males and females, respectively, while the right IOA indices for males and females were 47.19% and 38.87%, respectively. Conclusion. The anthropometry of inion-opistocranium-asterion IOA triangle can be a guide in gender determination of unknown individuals.

scholarly journals Sexual dimorphism in the permeability response of coronary microvessels to adenosine

2005 ◽  
Vol 288 (4) ◽  
pp. H2006-H2013 ◽  
Author(s):  
Virginia H. Huxley ◽  
JianJie Wang ◽  
Stevan P. Whitt
Keyword(s):  
Sexual Dimorphism ◽  
Serum Albumin ◽  
Adult Male ◽  
Volume Regulation ◽  
Solute Flux ◽  
Male And Female ◽  
Porcine Serum ◽  
Males And Females ◽  
Gender Influences ◽  
Coronary Arterioles

Gender influences volume regulation via several mechanisms; whether these include microvascular exchange, especially in the heart, is not known. In response to adenosine (Ado), permeability ( Ps) to protein of coronary arterioles of female pigs decreases acutely. Whether Ado induces similar Ps changes in arterioles from males or whether equivalent responses occur in coronary venules of either sex has not been determined. Hypotheses that 1) basal Ps properties and 2) Ps responses to vasoactive stimuli are sex independent were evaluated from measures of Ps to two hydrophilic proteins, α-lactalbumin and porcine serum albumin (PSA), in arterioles and venules isolated from hearts of adult male and female pigs. Consistent with hypothesis 1, basal Ps values of both microvessel types were independent of sex. Contrary to hypothesis 2, Ps responses to Ado varied with sex, protein, and vessel type. Confirming earlier studies, Ado induced a ∼20% decrease in Ps to both proteins in coronary arterioles from females. In arterioles from males, Ado did not change Ps for α-lactalbumin ([Formula: see text], 3 ± 13%), whereas Ps for PSA ([Formula: see text]) decreased by 27 ± 8% ( P < 0.005). In venules from females, Ado elevated [Formula: see text] by 44 ± 20% ( P < 0.05), whereas in those from males, Ado reduced [Formula: see text] by 24 ± 5% ( P < 0.05). The variety of outcomes is consistent with transvascular protein and protein-carried solute flux being regulated by multiple sex-dependent mechanisms in the heart and provides evidence of differences in exchange homeostasis of males and females in health and, likely, disease.

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