Pour les questions liées à la division du travail dans les sociétés paléolithiques, j’ai créé une nouvelle page.
Expanding the evolutionary explanations for sex differences in the human skeleton
Holly M. Dunsworth
Evolutionnary anthropology, 2020
While the anatomy and physiology of human reproduction differ between the sexes, the effects of hormones on skeletal growth do not. Human bone growth depends on estrogen. Greater estrogen produced by ovaries causes bones in female bodies to fuse before males’ resulting in sex differences in adult height and mass. Female pelves expand more than males’ due to estrogen and relaxin produced and employed by the tissues of the pelvic region and potentially also due to greater internal space occupied by female gonads and genitals.
False dichotomies and human sexual size dimorphism: A comment of Dunsworth (2020)
Font & Carazo
Evolution and human behavior, 2020
Sexual dimorphism in human arm power and force: implications for sexual selection on fighting ability
Morris et al.
Journal of experimental biology, 2020
our results indicate the presence of pronounced male-biased sexual dimorphism in muscle performance for protracting the arm to propel the fist forward. We also compared overhead pulling force between males and females, to test the alternative hypothesis that sexual dimorphism in the upper body of humans is a result of selection on male overhead throwing ability. We found weaker support for this hypothesis, with less pronounced sexual dimorphism in overhead arm pulling force. The results of this study add to a set of recently identified characters indicating that sexual selection on male aggressive performance has played a role in the evolution of the human musculoskeletal system and the evolution of sexual dimorphism in hominins.
Three‐dimensional analysis of sexual dimorphism in ribcage kinematics of modern humans
Garcia-Martinez et al.
American journal of physical anthropology, 2019
Our results show significant size differences between males and females both in inspiration and expiration (p < .01) as well as significant shape differences, with males deforming more than females during inspiration, especially in the mediolateral dimension of the lower ribcage. Finally, dummy regressions of shape on kinematic status showed a small but statistically significant difference in vectors of breathing kinematics between males and females (14.78°; p < .01).
We support that sex‐related differences in skeletal ribcage kinematics are discernible, even when soft tissues are not analyzed. We hypothesize that this differential breathing pattern is primarily a result of more pronounced diaphragmatic breathing in males, which might relate to differences in body composition, metabolism, and ultimately greater oxygen demand in males compared to females. Future research should further explore the links between ribcage morphological variation and basal metabolic rate.
Cochlear shape reveals that the human organ of hearing is sex-typed from birth
Braga et al.
Nature scientific reports, 2019
Sex differences in behavioral and neural characteristics can be caused by cultural influences but also by sex-based differences in neurophysiological and sensorimotor features. Since signal-response systems influence decision-making, cooperative and collaborative behaviors, the anatomical or physiological bases for any sex-based difference in sensory mechanisms are important to explore.
[…] We conclude that the human cochlea is sex-typed from an early post-natal age.
[…] Our observed sex-typed cochlear shape from birth is likely associated with complex evolutionary processes in modern humans for reasons not yet fully understood.
Sexual dimorphism in Homo erectus inferred from 1.5 Ma footprints near Ileret, Kenya
Villmoare et al.
Nature scientific reports, 2019
Our results indicate that East African Homo erectus was more dimorphic than modern Homo sapiens, although less so than highly dimorphic apes, suggesting that the Ileret footprints offer a unique window into an important transitional period in hominin social behavior.
The Performance Gap in Sport Can Help Determine Which Movements Were Most Essential to Human Evolution
Frontiers in physiology, 2019
This difference suggests that general sexual dimorphism does not explain why female performance is relatively closer to male performance at some track and field events than others. We hypothesize that this trend can be explained by the presence of sex-blind musculoskeletal adaptations (SBMA’s), which accumulate over generations to reduce the size of the PG in certain movements. We conclude that the selection trend favoring in humans should be explored further to determine whether the PG in sport can indeed be used to determine movements to which the human body is adapted.
Sexual Dimorphism in Hominin Ancestors
J. Michael Plavcan
The international encyclopedia of anthropology, 2018
The fossil record suggests that the earliest known hominin—Ardipithecus ramidus—showed little size or canine dimorphism. Later australopithecines show modest to strong dimorphism, with dimorphism approaching modern human levels in Homo erectus and Homo heidelbergensis. Behavioral inferences based on dimorphism are uncertain, but strong dimorphism in Australopithecus suggests polygynous mating, with strong male competition. Changes in dimorphism and body size suggest changes in female life history and associated patterns of male competition. Finally, the reevolution of dimorphism in hominins suggests that the modern human condition is derived and not inherited from the common ancestor of Homo and Pan.
On The Evolution of The Sex Differences in Throwing: Throwing is a Male Adaptation in Humans
Lombardo & Deaner
The quarterly review of biology, 2018
The development of the ability to throw projectiles for distance, speed, and accuracy was a watershed event in human evolution. We hypothesize that throwing first arose in threat displays and during fighting and later was incorporated into hunting by members of the Homo lineage because nonhuman primates often throw projectiles during agonistic interactions and only rarely in attempts to subdue prey. Males, who threw more often than females in both combat and hunting, would have been under stronger selection than females to become proficient at the ability to throw, intercept, and dodge projectiles as throwing skills became critical to success in combat and hunting. Therefore, we predict that males, more than females, should display innate anatomical and behavioral traits associated with throwing. We use data from a variety of disciplines to discuss: the sex differences in throwing speed, distance, and accuracy; sex differences in the development of the throwing motion; inability of training or cultural influences to erase the sex differences in throwing; sex differences in the use of throwing in sports, combat, and hunting; and sex differences in anatomical traits associated with throwing that are partly responsible for male throwing superiority. These data contradict the view held by many commentators that socialization rather than innate sex differences in ability are primarily responsible for male throwing superiority. We suggest that throwing is a male adaptation.
Lower limb articular scaling and body mass estimation in Pliocene and Pleistocene hominins
Ruff et al.
Journal of human evolution, 2018
Sexual dimorphism in body mass is greatest in Australopithecus afarensis (log[male/female] = 1.54), declines in Australopithecus africanus and Paranthropus robustus (log ratio 1.36), and then again in early Homo and middle and late Pleistocene archaic Homo (log ratio 1.20–1.27), although it remains somewhat elevated above that of living and middle/late Pleistocene anatomically modern humans (log ratio about 1.15).
Opposite molecular signatures of depression in men and women
Seney et al.
Biological psychiatry, 2018
Of the 706 genes differentially expressed in men with MDD and 882 genes differentially expressed in women with MDD, only 21 were changed in the same direction in both sexes. Notably, 52 genes displayed expression changes in opposite directions between men and women with MDD. Similar results were obtained using a threshold-free approach, where the overall transcriptional profile of MDD was opposite in men and women. Gene ontology indicated that men with MDD had decreases in synapse-related genes, whereas women with MDD exhibited transcriptional increases in this pathway. Cell type-specific analysis indicated that men with MDD exhibited increases in oligodendrocyte- and microglia-related genes, while women with MDD had decreases in markers of these cell types.
The brain transcriptional profile of MDD differs greatly by sex, with multiple transcriptional changes in opposite directions between men and women with MDD.
Mori et al.
Encyclopedia of Animal Cognition and Behavior, 2017
https://www.researchgate.net/profile/Emiliano_Mori/publication/319275172_Sexual_Dimorphism/links/59a179d9aca2726b90162578/Sexual-Dimorphism.pdf(lien non cliquable, copier l’URL)
Homo sapiens shows an adult male-to-female body weight of about 1.1–1.2; on average, males are taller than females, with a ratio of 1.06 ; they are also more muscular, have larger heart and lungs, a greater number of red cells in blood, and a beard (Dixon2009). Also, males with a broad chest and shoulders, narrow hips, and a muscular torso tend to be considered attractive partners by females, so that sexual selection comes into play. Conversely, females invest more in the production and storage of fat, mainly deposited around buttocks, hips, thighs, and breast, as a result of estrogen action, when they become mature reproductively (Pond1998). In fact, fat reserves are crucial for reproduction and it makes sense their positive selection in evolutionary terms, as they are honest signals of reproductive potential. There are quite a few other signs of sexual dimorphism inHomo sapiens, relevant to skin color, craniofacial traits, and voice pitch, some of them dependent on differential hormone actions during development. All these features make the human species a remarkably dimorphic one.
Gorillas in Our Midst? Human Sexual Dimorphism and Contest Competition in Men
Hill et al.
On human nature, 2017
The literature on human sexual selection has historically focused on the role of female mate choice, but cumulating experimental, correlational, and cross-cultural evidence suggests that male contest competition may have been more influential in shaping men’s phenotypes. Cross-species comparison has shown similarities between humans and our closest extant phylogenetic relatives, the Great Apes, in male–male aggression, and archeological evidence also indicates a great antiquity for male–male violence. Compared to women, men possess substantially greater muscle mass, strength, cranial robusticity, physical aggression, pain tolerance, risk-taking, weapons use, and participation in coalitional aggression. Men also exhibit displays of physical prowess and acuity to the formidability of male conspecifics, as well as possessing a suite of traits, such as facial hair and low vocal pitch, that increase perceptions of dominance. These traits are consistent with having been shaped by contest competition over mates: they are sexually dimorphic, appear at sexual maturity, and predict success in male contests as well as success in mating and reproduction. While alternative explanations for some of these sexually dimorphic traits are possible, contest competition among males throughout human evolutionary history is the most parsimonious.
Sexual competition among women : a review of theory and supporting evidence
Arnocky & Vaillancourt
The oxford handbook of women and competition, 2017
The biology of human gender
Manning et al.
Encyclopedia Evolutionary Psychological Science, 2017
The development of human gender identity may be inﬂuenced by organizational effects of prenatal hormones. This includes physical and neural development. Digit ratio (or 2D:4D) is a proxy of fetal hormones that correlates negatively with prenatal testosterone and positively with prenatal estrogen. Studies investigating associationsbetween 2D:4D and sex-dependent traits suggest that in addition to genetics, prenatal hormonescontribute to the determination of gender.
Long-term patterns of body mass and stature evolution within the hominin lineage
Will et al.
Royal society open science, 2017
our taxonomic analyses show that among Homo,younger species tend to be less variable in body size than older taxa (figure 8d), potentially associated with decreasing sexual dimorphism.
Predation by female chimpanzees: Toward an understanding of sex differences in meat acquisition in the last common ancestor of Pan and Homo
Gilby et al.
Journal of human evolution, 2017
There was no evidence that clinging offspring hampered female hunting. Instead, consistent with the hypothesis that females should be more risk-averse than males, females at all three sites specialized in low-cost prey (terrestrial/sedentary prey at Gombe; black and white colobus monkeys at Kanyawara).
[…] Although chimpanzees are not direct analogs of the last common ancestor (LCA) of Pan and Homo, these results suggest that before the emergence of social obligations regarding sharing and provisioning, constraints on hunting by LCA females did not necessarily stem from maternal care. Instead, they suggest that a risk-averse foraging strategy and the potential for losing prey to males limited female predation on vertebrates. Sex differences in hunting behavior would likely have preceded the evolution of the sexual division of labor among modern humans.
The landscape of sex-differential transcriptome and its consequent selection in human adults
Gershoni & Pietrokovski
BMC biology, 2017
Sex-differential expression (SDE) was tested in each of the 45 common tissues by comparing the individual expression values of 18,670 out of 19,644 informative protein-coding genes in men versus women.
[…] there are over 6500 protein-coding genes with significant SDE in at least one tissue. Most of these genes have SDE in just one tissue, but about 650 have SDE in two or more tissues, 31 have SDE in more than five tissues, and 22 have SDE in nine or more tissues
Nature Versus Nurture: Have Performance Gaps Between Men and Women Reached an Asymptote ?
Millard-Stafford et al.
Human kinetics journal, 2017
Men outperform women in sports requiring muscular strength and/or endurance, but the relative influence of “nurture” versus “nature” remains difficult to quantify. Performance gaps between elite men and women are well documented using world records in second, centimeter, or kilogram sports. However, this approach is biased by global disparity in reward structures and opportunities for women. Despite policies enhancing female participation (Title IX legislation), US women only closed performance gaps by 2% and 5% in Olympic Trial swimming and running, respectively, from 1972 to 1980 (with no change thereafter through 2016). Performance gaps of 13% in elite middistance running and 8% in swimming (∼4-min duration) remain, the 5% differential between sports indicative of load carriage disadvantages of higher female body fatness in running. Conversely, sprint swimming exhibits a greater sex difference than sprint running, suggesting anthropometric/power advantages unique to swim-block starts. The ∼40-y plateau in the performance gap suggests a persistent dominance of biological influences (eg, longer limb levers, greater muscle mass, greater aerobic capacity, and lower fat mass) on performance. Current evidence suggests that women will not swim or run as fast as men in Olympic events, which speaks against eliminating sex segregation in these individual sports.
Robust Sex Differences in Jigsaw Puzzle Solving—Are Boys Really Better in Most Visuospatial Tasks?
Kocijan et al.
Frontiers in behavioral neurosciences, 2017
Sex differences are consistently reported in different visuospatial tasks with men usually performing better in mental rotation tests while women are better on tests for memory of object locations. In the present study, we investigated sex differences in solving jigsaw puzzles in children. In total 22 boys and 24 girls were tested using custom build tablet application representing a jigsaw puzzle consisting of 25 pieces and featuring three different pictures. Girls outperformed boys in solving jigsaw puzzles regardless of the picture. Girls were faster than boys in solving the puzzle, made less incorrect moves with the pieces of the puzzle, and spent less time moving the pieces around the tablet. It appears that the strategy of solving the jigsaw puzzle was the main factor affecting differences in success, as girls tend to solve the puzzle more systematically while boys performed more trial and error attempts, thus having more incorrect moves with the puzzle pieces. Results of this study suggest a very robust sex difference in solving the jigsaw puzzle with girls outperforming boys by a large margin.
Morphological variation in Homo erectus and the origins of developmental plasticity
Anton et al.
Philosophical transactions of the Royal Society B, 2016
New footprints from Laetoli (Tanzania) provide evidence for marked body size variation in early hominins
Masao et al.
Our results are consistent with considerable body size variation and, probably, degree of sexual dimorphism within a single species of bipedal hominins as early as 3.66 million years ago.
Morphological and functional implications of sexual dimorphism in the human skeletal thorax
Garcia-Martinez et al.
American journal of physical anthropology, 2016
Males showed significantly larger thorax size (p < .01) and functional size (p < .05) than females. In addition, the 3D‐shape differed significantly between sexes (p < .01). Male rib cages were wider (particularly caudally) and shorter, with more horizontally oriented ribs when compared to females. While thorax widening and rib orientation were unrelated to allometry, thorax shortening showed a slight allometric signal.
Our findings are in line with previous research on sexual dimorphism of the respiratory system. However, we add that thorax shortening observed previously in males is the only feature caused by allometry. The more horizontally oriented ribs and the wider thorax of males may indicate a greater diaphragmatic contribution to rib cage kinematics than in females, and differences in functional size fit with the need for greater oxygen intake in males.
Sexual selection on male vocal fundamental frequency in humans and other anthropoids
Puts et al.
Proceedings of the Royal Society B, 2016
In many primates, including humans, the vocalizations of males and females differ dramatically, with male vocalizations and vocal anatomy often seeming to exaggerate apparent body size. These traits may be favoured by sexual selection because low-frequency male vocalizations intimidate rivals and/or attract females, but this hypothesis has not been systematically tested across primates, nor is it clear why competitors and potential mates should attend to vocalization frequencies. Here we show across anthropoids that sexual dimorphism in fundamental frequency (F0) increased during evolutionary transitions towards polygyny, and decreased during transitions towards monogamy. Surprisingly, humans exhibit greater F0 sexual dimorphism than any other ape. We also show that low-F0 vocalizations predict perceptions of men’s dominance and attractiveness, and predict hormone profiles (low cortisol and high testosterone) related to immune function. These results suggest that low male F0 signals condition to competitors and mates, and evolved in male anthropoids in response to the intensity of mating competition.
Elephants can determine ethnicity, gender, and age from acoustic cues in human voices
McComb et al.
Our results demonstrate that elephants can reliably discriminate between two different ethnic groups that differ in the level of threat they represent, significantly increasing their probability of defensive bunching and investigative smelling following playbacks of Maasai voices. Moreover, these responses were specific to the sex and age of Maasai presented, with the voices of Maasai women and boys, subcategories that would generally pose little threat, significantly less likely to produce these behavioral responses. Considering the long history and often pervasive predatory threat associated with humans across the globe, it is likely that abilities to precisely identify dangerous subcategories of humans on the basis of subtle voice characteristics could have been selected for in other cognitively advanced animal species.
Evolutionary perspectives on human height variation
Stulp & Barrett
Biological reviews, 2016
Here, we present a synthetic review of the literature on human height from an explicit evolutionary perspective, addressing its phylogenetic history, development, and environmental and genetic influences on growth and stature. In addition to presenting evidence to suggest the past action of natural selection on human height, we also assess the evidence that natural and sexual selection continues to act on height in contemporary populations. Although there is clear evidence to suggest that selection acts on height, mainly through life‐history processes but perhaps also directly, it is also apparent that methodological factors reduce the confidence with which such inferences can be drawn, and there remain surprising gaps in our knowledge. The inability to draw firm conclusions about the adaptiveness of such a highly visible and easily measured trait suggests we should show an appropriate degree of caution when dealing with other human traits in evolutionary perspective.
Evolution of early Homo: An integrated biological perspective
Anton et al.
Les chimpanzés mâles commettent plus de meurtres que les chimpanzés femelles. Les victimes sont plus souvent des mâles, mais les chimpanzés mâles tuent aussi des femelles. Ces chiffres sont assez proches de ce que l’on retrouve chez l’humain.
Lethal aggression in Pan is better explained by adaptive strategies than human impacts
Wilson et al.
Observations of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) provide valuable comparative data for understanding the significance of conspecific killing. Two kinds of hypothesis have been proposed. Lethal violence is sometimes concluded to be the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates1,2,3,4,5. Alternatively, it could be a non-adaptive result of human impacts, such as habitat change or food provisioning6,7,8,9. To discriminate between these hypotheses we compiled information from 18 chimpanzee communities and 4 bonobo communities studied over five decades. Our data include 152 killings (n = 58 observed, 41 inferred, and 53 suspected killings) by chimpanzees in 15 communities and one suspected killing by bonobos. We found that males were the most frequent attackers (92% of participants) and victims (73%); most killings (66%) involved intercommunity attacks; and attackers greatly outnumbered their victims (median 8:1 ratio). Variation in killing rates was unrelated to measures of human impacts. Our results are compatible with previously proposed adaptive explanations for killing by chimpanzees, whereas the human impact hypothesis is not supported.
A rapprocher de ce qu’on trouve chez les humains :
“I sing of arms and of a man…”: medial epicondylosis and the sexual division of labour in prehistoric Europe
Villotte & Knüsel
Journal of archeological science, 2014
This indicates that males, but not females, preferentially employed movements involving throwing motions in these hunter-gatherer and early farming groups. Based on this evidence we postulate the existence of a persistent sexual division of labour in these prehistoric European populations involving one or several strenuous activities linked to unilateral limb use.
Body Size, Size Variation, and Sexual Size Dimorphism in Early Homo
J. Michael Plavcan
Current anthropology, 2012
Modern humans show an unusual pattern of relatively modest body mass dimorphism (about 15%; Smith and Jungers 1997) but moderate “lean” body mass dimorphism (about 44%; Wang et al. 2001). This latter value reflects a proportionally greater amount of fat in human females (Plavcan 2012; Wang et al. 2001; Wells 2007, 2012). Skeletal dimorphism in modern humans is moderate and slightly greater than that of chimpanzees (Gordon, Green, and Richmond 2008), but when corrected for dimensionality it is proportional to lean body mass dimorphism in magnitude (Plavcan 2012). Cranial dimorphism in modern humans tends to be modest, being intermediate between body mass dimorphism and lean body mass dimorphism (Plavcan 2012).
Because most cranial, dental, and postcranial traits are normally or at least unimodally distributed in males and females, the effect of dimorphism is to simultaneously increase the total sample variance and generate bimodality
Sexual Size Dimorphism, Canine Dimorphism, and Male-Male Competition in Primates
J. Michael Plavcan
Human nature, 2012
What Are the Causes of Size Dimorphism in Modern Humans?The evolutionary origins of the prominent secondary sexual characteristics of humansare potentially diverse. Sexual ornamentation and size dimorphism in humans arehypothesized to have evolved for signaling to attract mates, to indicate mate quality(genetic quality in both sexes, and fecundity in particular in females) or age, to signaldominance, or even to reduce a sense of threat (Sefcek et al.2006). The greater bodysize and strength of males has been thought to give males competitive advantage foraccess to mates, or to be attractive to females, to signal male quality (Cashdan1996;Dixson2009; Sefcek et al.2006), or to reflect the sexual division of labor for huntingor between-group competition (Frayer1980). Body mass dimorphism also might reflect smaller female body size selected to increase or decrease female fecundity(Dixson2009; Ralls1976). Alternatively, human size and stature dimorphism may bea product of sexual selection from the recent past that persists in modern humans(Dixson2009; Rogers and Mukherjee1992; Wade and Shuster2004).
The importance of physical strength for males
Sell et al.
Human nature, 2012
Fighting ability, although recognized as fundamental to intrasexual competition
in many nonhuman species, has received little attention as an explanatory variable
in the social sciences. Multiple lines of evidence from archaeology, criminology,
anthropology, physiology, and psychology suggest that fighting ability was a crucial
aspect of intrasexual competition for ancestral human males, and this has contributed to the evolution of numerous physical and psychological sex differences. Because fighting ability was relevant to many domains of interaction, male psychology should have evolved such that a man’s attitudes and behavioral responses are calibrated according to his formidability. Data are reviewed showing that better fighters feel entitled to better outcomes, set lower thresholds for anger/aggression, have self-favoring political attitudes, and believe more in the utility of warfare. New data are presented showing that among Hollywood actors, those selected for their physical strength (i.e., action stars) are more likely to believe in the utility of warfare.
Short stature in African pygmies is not explained by sexual selection
Becker et al. (Priscille Touraille)
Evolution and human behaviour, 2012
Altogether, our results demonstrate that stature influences mate choice in pygmies, and we argue that, if of any influence for sexual selection, mate choice should have favored tallness rather than shortness in our pygmy population. Consequently, this study establishes that sexual selection is a very unlikely candidate to account for the evolution of pygmies’ short stature.
Le dimorphisme sexuel au XXIe siècle
Junien et al.
En ce début du XXIe siècle, une redéfinition du dimorphisme sexuel s’impose. Elle se doit d’incorporer conjointement non seulement les hormones sexuelles et le formatage socio culturel spécifique du genre, mais aussi l’importance des gènes localisés sur les chromosomes sexuels. Ces différentes composantes ont des effets indé-pendants et parallèles et qui interagissent dès la conception et tout au long de la vie. Des mécanismes épigénétiques assurent la mise en place de marques spécifiques du sexe qui modulent l’expression des gènes sans changer leur séquence. Ces marques représentent une sorte de mémoire pour se « souvenir » de son sexe, mais aussi pour « archiver » les impacts de l’environnement, selon l’expérience. Dans tous les tissus, ces marques et d’autres à venir, façonnées en fonction du sexe et du genre au gré de l’environnement, établissent des réseaux de gènes différents chez le mâle et la femelle, tant au niveau basal que pour les réponses immédiates et futures.
Osteological clues for the presence of a sexual division of labour in the Eurasian Middle Paleolithic
Leiden university, 2011
In this bachelor thesis I investigate whether Neanderthals had a sexual division of labour or not. I established three hypotheses: 1) Neanderthals had a sexual division of labour where males hunt and females gather plant foods and perform other activities, 2) Neanderthals had a sexual division of labour where males and females hunt but males perform the most dangerous tasks, 3) there was no sexual division of labour and males and females hunted and gathered in equal amounts. To find out if Neanderthals had a sexual division of labour, a meta-study of two osteological analyses applied to Neanderthal bones was performed. The first methods that was used was a comparison of the shape and robusticity of male and female Neanderthal limb bones compared to samples of modern human hunter-gatherers and sedentary populations. Secondly the distribution of trauma across the skeletons of male and female Neanderthals was compared. In both of the analyses the evidence pointed towards the first hypothesis. The evidence however was too limited. The small sample size of sexable Neanderthals was the largest issue. I concluded that according to the data gathered in this thesis hypothesis 1 is the most likely. However, none of the three hypotheses can be rejected confidently due to the limited evidence.
Identifying and explaining apparent universal sex differences in cognition and behavior
Personality and individual differences, 2011
With growing recognition that there are universal sex differences in cognition and behavior, four theories have been proposed to account for these differences: the founder effect theory, the social structuralist theory, the evolutionary theory, and the evolutionary neuroandrogenic (ENA) theory. The latter of these theories is described in considerable detail as offering an explanation for most of 65 recently identified apparent universal sex differences (AUSDs) in cognition and behavior. Regarding “ultimate causes” (why), ENA theory asserts that (a) evolutionary-genetic factors incline females to bias their mate choices toward males who are loyal and competent provisioners of resources and (b) males are merely a genetic variant on the female sex selected for responding to female mating biases. In terms of “proximate causes” (how), the theory maintains that high exposure to androgens has evolved to alter the male brain functioning in two specific ways relative to most female brains: (a) suboptimal arousal and (b) a rightward shift in neocortical functioning. These two functional patterns are described and hypothesized to incline males and females to learn differently in many respects. The most fundamental differences involve males learning ways of either complying with or circumventing female mate preferences. Numerous universal sex differences in cognition and behavior are hypothesized to result from these evolved neurohormonal factors, including most of the 65 AUSDs herein summarized in seven categorical tables.
Sex differences in chimpanzees’ use of sticks as play objects resemble those of children
Kahlenberg & Wrangham
Current Biology, 2010
Sex differences in children’s toy play are robust and similar across cultures 1, 2. They include girls tending to play more with dolls and boys more with wheeled toys and pretend weaponry. This pattern is explained by socialization by elders and peers, male rejection of opposite-sex behavior and innate sex differences in activity preferences that are facilitated by specific toys . Evidence for biological factors is controversial but mounting. For instance, girls who have been exposed to high fetal androgen levels are known to make relatively masculine toy choices . Also, when presented with sex-stereotyped human toys, captive female monkeys play more with typically feminine toys, whereas male monkeys play more with masculine toys . In human and nonhuman primates, juvenile females demonstrate a greater interest in infants, and males in rough-and-tumble play. This sex difference in activity preferences parallels adult behavior and may contribute to differences in toy play . Here, we present the first evidence of sex differences in use of play objects in a wild primate, in chimpanzees (Pan troglodytes). We find that juveniles tend to carry sticks in a manner suggestive of rudimentary doll play and, as in children and captive monkeys, this behavior is more common in females than in males.
Sex-related variation in human behavior and the brain
Trends in cognitive science, 2010
Male and female fetuses differ in testosterone concentrations beginning as early as week 8 of gestation. This early hormone difference exerts permanent influences on brain development and behavior. Contemporary research shows that hormones are particularly important for the development of sex-typical childhood behavior, including toy choices, which until recently were thought to result solely from sociocultural influences. Prenatal testosterone exposure also appears to influence sexual orientation and gender identity, as well as some, but not all, sex-related cognitive, motor and personality characteristics. Neural mechanisms responsible for these hormone-induced behavioral outcomes are beginning to be identified, and current evidence suggests involvement of the hypothalamus and amygdala, as well as interhemispheric connectivity, and cortical areas involved in visual processing.
Costs and benefits of fat-free muscle mass in men: relationship to mating success, dietary requirements, and native immunity
Lassek & Gaulin
Evolution and human behavior, 2009
Despite claims of reduced levels of sexual dimorphism in the genus Homo (e.g., compared to Australopithecus) (McHenry, 1994, Plavcan, 2001), muscle mass and resulting muscular strength are very sexually dimorphic traits in contemporary humans. On average, men have approximately 61% more total muscle mass than women (Illner et al., 2000, Kim et al., 2004, Phillips, 1995, Shen et al., 2004, Wetter & Economos, 2004). Relatively more of this muscle mass is allocated to the upper body, with men having about 75% more arm muscle mass than women (Abe et al., 2003, Fuller et al., 1992, Gallagher et al., 1997, Nindl et al., 2002). Not surprisingly, this latter difference translates into approximately 90% greater upper body strength in men
Why are women smaller than men? When anthropology meets evolutionary biology
Priscille Touraille et Pierre-Henri Gouyon
Nature preceedings, 2008 (non reviewé)
There are large variations of size among humans but in all populations, men are larger on average than women. For most biologists this fact can be easily explained by the same processes that explain the size dimorphism in large mammals in general and in apes in particular. Due to fights between males for the possession of females, sexual selection has favoured bigger males. Indeed, this factor certainly explains why males are selected for being large but lets aside the question of selection on the female side. Actually, it has been shown that larger females are also favoured by natural selection. This is particularly relevant for women because their probability of dying when giving birth is then reduced. In this paper, the common view that size dimorphism in humans results from the fact that the advantage of being big is stronger for men than for women is challenged by another hypothesis, namely that the difference results from a difference of cost rather than from a difference of benefits. The cost of being big would be higher in women simply because, under gender hierarchical regimes found in all cultures, men are allocated the best food. The interaction between evolutionary forces and cultural practices could then lead to this disadaptive situation.
Male chimpanzees exchange political support for mating opportunities
Duffy et al.
Current biology, 2007
Male chimpanzees, Pan troglodytes, differ from males in most other mammalian taxa because they remain in their natal communities throughout their lives, form close bonds with one another, and cooperate in a range of activities . However, males also compete fiercely for status within their groups 2, 3, and high rank enhances male reproductive success 4, 5. Males rely partly on coalitions to achieve and maintain status 2, 3, 6, 7, 8, 9, and shifts in male alliances can have dramatic political effects 2, 3, 6. It is not known what benefits are obtained by low-ranking coalition partners. Here we report that the highest-ranking (alpha) male in one well-studied community of chimpanzees rewarded his allies by allowing them preferential access to mates.
Sexual dimorphism in Australopithecus afarensis revisited: How strong is the case for a human-like pattern of dimorphism ?
Plavcan et al.
Journal of human evolution, 2005
https://www.researchgate.net/profile/Michael_Lague/publication/7997310_Sexual_dimorphism_in_Australopithecus_afarensis_revisited_how_strong_Is_the_case_for_a_human-like_pattern_of_dimorphism/links/5c16cb164585157ac1c7b7cc/Sexual-dimorphism-in-Australopithecus-afarensis-revisited-how-strong-Is-the-case-for-a-human-like-pattern-of-dimorphism.pdf(pas de lien direct)
Stature of early Europeans
Sexual dimorphism in primate evolution
J. Michael Plavcan
American journal of physical anthropology, 2002
In contrast to the canine teeth, dimorphism inhominid body mass was apparently quite substan-tial. McHenry (1992, 1994a,b) provides data sug-gesting that body mass dimorphism in early homin-ids ranged from comparable to a chimpanzee inAustralopithecus robustus,to quite gorilla-like inA.boisei(Plavcan and van Schaik, 1997a). Interest-ingly, the data of McHenry (1992, 1994a,b) suggestthatHomo erectus,considered as a single species,could have shown substantial body size dimorphism.However, if traditionalH. erectusis split intoH.erectus sensu strictoandH. ergaster,then the levelsof dimorphism are reduced to levels more compara-ble to modern humans. Regardless, analyses of theface and skeletal elements of early hominids all sug-gest that body mass dimorphism in these animalswas substantial
Variation in human body size and shape
Annual review of anthropology, 2002
(Cité par Priscille Touraille)
Male strategies and Plio-Pleistocene archaeology
O’Connell et al.
Journal of human evolution, 2002
Archaeological data are frequently cited in support of the idea that big game hunting drove the evolution of early Homo, mainly through its role in offspring provisioning. This argument has been disputed on two grounds: (1) ethnographic observations on modern foragers show that although hunting may contribute a large fraction of the overall diet, it is an unreliable day-to-day food source, pursued more for status than subsistence; (2) archaeological evidence from the Plio-Pleistocene, coincident with the emergence of Homo can be read to reflect low-yield scavenging, not hunting. Our review of the archaeology yields results consistent with these critiques: (1) early humans acquired large-bodied ungulates primarily by aggressive scavenging, not hunting; (2) meat was consumed at or near the point of acquisition, not at home bases, as the hunting hypothesis requires; (3) carcasses were taken at highly variable rates and in varying degrees of completeness, making meat from big game an even less reliable food source than it is among modern foragers. Collectively, Plio-Pleistocene site location and assemblage composition are consistent with the hypothesis that large carcasses were taken not for purposes of provisioning, but in the context of competitive male displays. Even if meat were acquired more reliably than the archaeology indicates, its consumption cannot account for the significant changes in life history now seen to distinguish early humans from ancestral australopiths. The coincidence between the earliest dates for Homo ergaster and an increase in the archaeological visibility of meat eating that many find so provocative instead reflects: (1) changes in the structure of the environment that concentrated scavenging opportunities in space, making evidence of their pursuit more obvious to archaeologists; (2) H. ergaster‘s larger body size (itself a consequence of other factors), which improved its ability at interference competition.
Grosse synthèse du dimorphisme chez les primates, et de ses causes possibles.
Size, sexual dimorphism, and polygyny in primates
J. Michael Plavcan
Yearbook of physical anthropology, 2001
Sex differences in throwing: monkeys having a fling
Neil V. Watson
Trends in cognitive sciences, 2001
Fast and accurate throwing was undoubtedly important to ancestral hominids, and was subject to sexual-selection pressures that generated a male advantage in throwing accuracy that persists in modern humans. The balance of evidence, including that from a recent comparative study of throwing in humans and capuchin monkeys, suggests that high-performance throwing involves unique adaptations in the domains of spatial targeting, precision timing, and multi-joint motor control.
Une espèce très dimorphique ou deux espèces différentes ? Une des grosses difficultés quand on travaille sur des fossiles rares, anciens et incomplets.
Size variation and sexual dimorphism in Australopithecus afarensis and living hominoids
Richmond & Jungers
Journal of human evolution, 1995
. If the fossils from Hadar and Maka (and Laetoli) are assumed instead to be from one sexually dimorphic species, then the degree of sexual dimorphism of A. afarensis would have been at least as extreme as that of the most dimorphic living apes, the gorilla and orang-utan. It follows that a strictly monogamous social structure would have been highly unlikely.
Sexual dimorphism in relation to big-game hunting and economy in modern human populations
American journal of physical anthropology, 1993
the big‐game hunting (whaling) Eskimos had the lower multivariate dimorphism in the humerus, which could be expected to be the structure under greatest exertion by such hunting in males. While the exertions of the whale hunting economic activities led to high skeletal robusticity, as predicted by Frayer’s model, this was true of the females as well as the males, resulting in low sexual dimorphism in some features. Females are half the sexual dimorphism equation, and they cannot be seen as constants in any model of economic behavior.
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Human marriage systems and sexual dimorphism in stature
Gaulin & Bauster
American Journal of Physical Anthropology, 1992
Contemporary populations of Homo sapiens are sexually dimorphic on a variety of traits. In terms of stature, men are reliably between 4% and 10% taller than women in well‐sampled human populations. Are cross‐cultural differences in the magnitude of sexual dimorphism consistent with expectations from sexual selection theory? Prior studies have provided conflicting answers to this question in part because they failed to agree on how the force of sexual selection should or could be operationalized. Here we offer a simple and unbiased method for operationalizing sexual selection and retest two separate predictions from earlier work (Alexander et al., 1979) about its expected impact on stature dimorphism in a sample of 155 societies. Neither prediction matches the observed cross‐cultural distribution of dimorphism. However, this is not the consequence of a random distribution of dimorphism across societies. Instead, the data exhibit a robust and unexpected pattern.
Female subsistence strategies among Ache hunter–gatherers of eastern Paraguay.
Hum Ecol. 1985
(cité par Priscille Touraille)
Size, Sexual Dimorphism, and Polygyny in Primates, in Size and Scaling in Primate Biology
Among primates, the extent of sexual dimorphism in body size ranges from species where mature females are slightly larger than mature males, as in some of the marmosets and tamarins (Ralls, 1976), through species where males are slightly larger than females, like many of the diurnal lemurs and the arboreal colobines, to those where males are nearly twice as heavy as females, as in the larger cercopithecines, the gorilla and the orang (Clutton-Brock and Harvey, 1978). The tendency for polygynous mammals to show greater size dimorphism than monogamous ones was originally noticed by Darwin (1871), and quantitative studies have subsequently confirmed that in primates (Gautier-Hion, 1975; Clutton-Brock et al., 1977; Clutton-Brock and Harvey, 1978)
(cité par Priscille Touraille)
Cross-cultural differences in sexual dimorphism: Is there any variance to be explained?
Gaulin & Boster
Ethology and sociobiology, 1985
Some argue that cross-cultural variation in sexual dimorphism is associated with marriage practices whereas others suggest it is a function of absolute size. We reject both explanations, noting that the degree of dimorphism in humans is very consistent and the observed variance is mainly a function of sample size.
(cité par Priscille Touraille)
Subsistence practices and human sexual dimorphism of stature
Wolfe & Gray
Journal of human evolution, 1982
Hypotheses recently advanced by Brace & Ryan (1980) and Frayer (1980) suggest links between changes in human sexual dimorphism and changes in technology and subsistence practices. In this paper we test these hypotheses using a sample of extant human groups. Results indicate that extant agriculturalists exhibit a greater degree of sexual dimorphism in stature than extant hunter-gatherers. Moreover, the data analysed in this paper do not indicate that a more equal division of labor is associated with a decrease in human height sexual dimorphism.
(cité par Priscille Touraille)
Sexual dimorphism and human tooth size differences
Brace & Ryan
Journal of human evolution, 1980
Late in the Pleistocene the development of food processing techniques led to the reduction of both male and female dental dimensions. Dental sexual dimorphism, however, was maintained until the very end of the Pleistocene when the hunting of large game animals by crude techniques was replaced by a focus on great numbers of small game caught by more sophisticated means and by an increasing utilization of plant foods. The subsequent reduction in dimorphism represents the actions of the Probable Mutation Effect operating under conditions of relaxed selection. The conclusion offered is that the smallest degree of sexual dimorphism visible in the modern world is to be found among those populations that are separated by the greatest interval of time from precursors who depended for their survival on a Pleistocene big game hunting mode of subsistence.
(cité par Priscille Touraille)
Sexual dimorphism and cultural evolution in the Late Pleistocene and Holocene of Europe
Journal of human evolution, 1980
Dental, cranial and body size data are reviewed for European Upper Paleolithic, Mesolithic and Neolithic males and females. Over these three periods there is a substantial decrease in the level of sexual dimorphism. From separate analysis of trends occurring between males and females, it is shown that the major cause for this decrease in sexual dimorphism is gracilization of the males between the Upper Paleolithic and Mesolithic. Reduction in males is related to shifting technological patterns associated with hunting and changes in the types of animals hunted. Further reduction in sexual dimorphism between the Mesolithic and Neolithic and from the Neolithic to modern European populations is shown to be more closely tied to changes occurring among females. Analysis of changing patterns of sexual dimorphism in Late Pleistocene and Holocene populations of Europe suggests an interrelationship between cultural and biological evolution.
(cité par Priscille Touraille)
Differences between ethnic groups in sex dimorphism of adult height
Phyllis B. Eveleth
Annals of human biology, 1974
An analysis has been made of sex dimorphism in adult height using data from 58 Negroid, 76 European, and 67 Amerindian populations. Regression analyses were carried out on the sex difference and sex average of male and female stature means. The greatest sex dimorphism was found in Amerindians and the least in Negroid populations. Data from 36 Asiatic and 27 New Guinea populations have also been considered. It seems that sex dimorphism in adult height has a strong genetic component, making it inappropriate as a measure by which to judge the health and nutritional status of a population.
Divers visuels non issus de publications scientifiques