Dimorphism In Humans Research Articles

Pelvic shape change in adult Japanese macaques and implications for childbirth at old age

Pelvic morphology exhibits a particular sexual dimorphism in humans, which reflects obstetrical constraints due to the tight fit between neonates and mothers. Huseynov et al. [Proc. Natl. Acad. Sci. U.S.A. 113, 5227-5232 (2016)] showed that in humans, pelvic sexual dimorphism is greatest around the age of highest fertility, and it becomes less marked in association with menopause in females. They proposed that this reflects changes of obstetrical versus locomotor functional demands in females. It remains unknown whether such developmental adjustment of the pelvic morphology is unique to humans. Macaques exhibit human-like cephalopelvic proportions, but they lack menopause and usually maintain fertility throughout adulthood. Here, we track pelvic development in Japanese macaques from neonate to advanced ages using computed tomography-based data. We show that female pelvic morphology changes throughout adult life, reaching the obstetrically most favorable shape at advanced ages rather than around primiparity. We hypothesize that pelvic morphology in Japanese macaques is developmentally adjusted to childbirth at advanced ages, where obstetrical risks are potentially higher than at younger ages. Our data contribute to the growing evidence that the female primate pelvis changes its morphology during the whole lifespan, possibly adjusting for changing functional demands during adulthood.

Architectural anatomy of the human tibialis anterior presents morphological asymmetries between superficial and deep unipennate regions.

The tibialis anterior muscle plays a critical role in human ambulation and contributes to maintaining the upright posture. However, little is known about its muscle architecture in males and females. One hundred and nine physically active males and females were recruited. Tibialis anterior muscle thickness, pennation angle, and fascicle length were measured at rest in both unipennate regions of both legs using real-time ultrasound imaging. A linear mixed model was used with muscle thickness, pennation angle, or fascicle length as the dependent variables. All models were carried out with and without total leg lean mass and shank length as covariates. Causal mediation analysis was computed to explore the effect of muscle thickness on the relationship between fascicle length and pennation angle. There were no significant differences between dominant and nondominant legs regarding muscle architecture. Muscle thickness and pennation angle were greater in the deep than the superficial unipennate region in males (1.9 mm and 1.1°, p < 0.001) and women (3.4 mm and 2.2°, p < 0.001). However, the fascicle length was similar in both regions for both sexes. The differences remained significant after accounting for differences in leg lean mass and shank length. In both regions, muscle thickness was 1-3 mm greater in males and superficial pennation angle 2° smaller in females (both, p < 0.001). After accounting for leg lean mass and shank length, sex differences remained for muscle thickness (1.6 mm, p < 0.05) and pennation angle (3.4°, p < 0.001) but only in the superficial region. In both regions, leg lean mass and shank-adjusted fascicle length were 1.4 mm longer in females than males (p < 0.05). The causal mediation analysis revealed that the estimation of fascicle length was positive, suggesting that a 10% increase in muscle thickness would augment the fascicle length, allowing a 0.38° pennation angle decrease. Moreover, the pennation angle increases in total by 0.54° due to the suppressive effect of the increase in fascicle length. The estimated mediation, direct, and total effects were all significantly different from zero (p < 0.001). Overall, our results indicate that the architectural anatomy of the tibialis anterior shows sexual dimorphism in humans. Tibialis anterior presents morphological asymmetries between superficial and deep unipennate regions in both sexes. Lastly, our causal mediation model identified a suppressive effect of fascicle length on the pennation angle, suggesting that increments in muscle thickness are not always aligned with increments in fascicle length or the pennation angle.

Morphometric Analysis of Greater Palatine Foramen and the Adjacent Structures: Forensic Odontology Study using CBCT

Introduction: Sexual dimorphism plays a pivotal role in many instances, including solving medicolegal problems, anthropological studies, sorting out victims of natural calamities and man-made calamities. Among various parameters available for sexual dimorphism, structures of the oral cavity play an important role. The use of Cone Beam Computed Tomography (CBCT) is convenient and provides accurate measurements with the help of digital software. Aim: To determine the role of Greater Palatine Foramen (GPF), its Greater Palatine Canal (GPC) and relation with the adjacent structures like Naso-Palatine Foramen (NPF) and Lesser Palatine Foramen (LPF) in elucidating the level of sexual dimorphism using CBCT images, while enhancing the information on anatomy of Greater Palatine Foramen (GPF). Materials and Methods: This cross-sectional forensic odontology study was conducted in the Department of Oral Medicine and Radiology, CSI College of Dental Sciences and Research, Madurai, Tamil Nadu, India, and was performed using 50 males and 50 females CBCT images of patients between age 18 to 45. The CBCT data were collected from January 2021 till January 2022, and the obtained data were analysed from March 2022 till April 15, 2022. These were analysed using Planmeca imaging software. Measurements of GPF length, angulation with respect to Hard Palate (HP), relation between NPC and GPF, distance between GPC and Mid Maxillary Suture (MMS). Its relation to LPF and dimensions of GPF at opening of oral cavity were done. Finally, all measures were subjected to statistical analysis using IBM Statistical Package for the Social Sciences (SPSS), version 28.0. Independent t-test was used for analysis of difference between male and female measurements. Results: The GPC length on right (male:13.2570, female:12.3628) and left (male:12.8089, female:12.2780), angulation of GPC left (male: 61.1379, female: 57.4964), angle between GPF and NPC left (male: 28.6208, female: 26.5024), distance between GPC and MMS left (male: 15.1625, female: 14.5350) and Anteroposterior (AP) dimensions of GPF on right (male: 5.5402, female: 4.2314) and left-side (5.4934, female: 4.4576), Transverse (TR) dimension of GPF on right (male: 2.6752, female: 2.0528) and left (male: 5.4943, female: 4.4576) showed statistically significant difference between male and female CBCT images, while the measures were significantly higher in males. Conclusion: The CBCT images provided reliable measurements of the areas of interest. The present study results highlight a statistically significant difference between male and female, where males showed higher measurements in most instances. A more precise morphological measurement of GPF in relation to adjacent structures such as NPC, MMS proves to have sexual dimorphism in humans.

The sexual brain, genes, and cognition: A machine‐predicted brain sex score explains individual differences in cognitive intelligence and genetic influence in young children

Sex impacts the development of the brain and cognition differently across individuals. However, the literature on brain sex dimorphism in humans is mixed. We aim to investigate the biological underpinnings of the individual variability of sexual dimorphism in the brain and its impact on cognitive performance. To this end, we tested whether the individual difference in brain sex would be linked to that in cognitive performance that is influenced by genetic factors in prepubertal children (N = 9,658, ages 9–10 years old; the Adolescent Brain Cognitive Development study). To capture the interindividual variability of the brain, we estimated the probability of being male or female based on the brain morphometry and connectivity features using machine learning (herein called a brain sex score). The models accurately classified the biological sex with a test ROC–AUC of 93.32%. As a result, a greater brain sex score correlated significantly with greater intelligence (p fdr < .001, ηp2 = .011–.034; adjusted for covariates) and higher cognitive genome‐wide polygenic scores (GPSs) (p fdr < .001, ηp2 < .005). Structural equation models revealed that the GPS‐intelligence association was significantly modulated by the brain sex score, such that a brain with a higher maleness score (or a lower femaleness score) mediated a positive GPS effect on intelligence (indirect effects = .006–.009; p = .002–.022; sex‐stratified analysis). The finding of the sex modulatory effect on the gene–brain–cognition relationship presents a likely biological pathway to the individual and sex differences in the brain and cognitive performance in preadolescence.

Transcriptional progression during meiotic prophase I reveals sex-specific features and X chromosome dynamics in human fetal female germline.

During gametogenesis in mammals, meiosis ensures the production of haploid gametes. The timing and length of meiosis to produce female and male gametes differ considerably. In contrast to males, meiotic prophase I in females initiates during development. Hence, the knowledge regarding progression through meiotic prophase I is mainly focused on human male spermatogenesis and female oocyte maturation during adulthood. Therefore, it remains unclear how the different stages of meiotic prophase I between human oogenesis and spermatogenesis compare. Analysis of single-cell transcriptomics data from human fetal germ cells (FGC) allowed us to identify the molecular signatures of female meiotic prophase I stages leptotene, zygotene, pachytene and diplotene. We have compared those between male and female germ cells in similar stages of meiotic prophase I and revealed conserved and specific features between sexes. We identified not only key players involved in the process of meiosis, but also highlighted the molecular components that could be responsible for changes in cellular morphology that occur during this developmental period, when the female FGC acquire their typical (sex-specific) oocyte shape as well as sex-differences in the regulation of DNA methylation. Analysis of X-linked expression between sexes during meiotic prophase I suggested a transient X-linked enrichment during female pachytene, that contrasts with the meiotic sex chromosome inactivation in males. Our study of the events that take place during meiotic prophase I provide a better understanding not only of female meiosis during development, but also highlights biomarkers that can be used to study infertility and offers insights in germline sex dimorphism in humans.

Sex-Related Differences in Cerebrospinal Fluid Plasma-Derived Proteins of Neurological Patients.

Background and aims: Cerebrospinal fluid (CSF) protein content presents a sexual dimorphism in humans. We investigated sex-related differences in CSF IgG levels and in the quantification of intrathecal IgG synthesis (IIS). Methods: CSF, serum albumin and IgG were measured in 1519 neurological patients and both linear and hyperbolic formulas were used for the quantification of IIS. CSF-restricted oligoclonal IgG bands (OCBs) were used as “gold standard”. Results: The linear IgG Index showed a weak agreement with OCBs in males and females (k = 0.559, k = 0.587, respectively), while the hyperbolic Reiber’s formulas had a moderate agreement with OCBs in females (k = 0.635) and a weak agreement in males (k = 0.565). Higher CSF albumin and IgG levels were found in men than in women in the whole population and in subjects without IIS after adjusting for age and for serum concentrations of albumin and IgG, respectively (Quade statistics, p < 0.000001). CSF and serum albumin and IgG levels positively correlated to age in both sexes. CSF total protein content did not correlate with CSF leukocyte numbers but was higher in patients with marked pleocytosis. Conclusions: In neurological patients, men have higher levels of CSF serum-derived proteins, such as albumin and IgG.

Sex Differences in Genomic Drivers of Adipose Distribution and Related Cardiometabolic Disorders: Opportunities for Precision Medicine.

This review focuses on the human genetics, epidemiology, and molecular pathophysiology of sex differences in central obesity, adipose distribution, and related cardiometabolic disorders. Distribution of fat is important for cardiometabolic health, with peripheral fat depots having a protective effect and central visceral fat depots conferring a detrimental effect on health. There are important sex differences in fat distribution that are masked when studying body mass index as a measure of obesity. From epidemiological, murine, and in vitro studies, several mechanisms have been proposed to explain the sex differences in adipose distribution, including sex hormonal effects, cell-intrinsic properties, and the microenvironment in fat depots. More recently, human genetics have revealed hundreds of loci for central obesity providing disruptive opportunities for mechanistic discoveries and clinical translation. A striking feature is that over one-third of these loci have reproducible but poorly understood sexual dimorphic associations with central obesity, most having stronger effects in women. Understanding the genetic and molecular mechanisms of adipose distribution and its sexual dimorphism in humans provides a unique opportunity to promote the use of precision medicine for early identification of at-risk individuals, and the development of novel therapeutic strategies for central obesity and related cardiometabolic disorders.

SNPs Associated With Testosterone Levels Influence Human Facial Morphology.

Many factors influence human facial morphology, including genetics, age, nutrition, biomechanical forces, and endocrine factors. Moreover, facial features clearly differ between males and females, and these differences are driven primarily by the influence of sex hormones during growth and development. Specific genetic variants are known to influence circulating sex hormone levels in humans, which we hypothesize, in turn, affect facial features. In this study, we investigated the effects of testosterone-related genetic variants on facial morphology. We tested 32 genetic variants across 22 candidate genes related to levels of testosterone, sex hormone-binding globulin (SHGB) and dehydroepiandrosterone sulfate (DHEAS) in three cohorts of healthy individuals for which 3D facial surface images were available (Pittsburgh 3DFN, Penn State and ALSPAC cohorts; total n = 7418). Facial shape was described using a recently developed extension of the dense-surface correspondence approach, in which the 3D facial surface was partitioned into a set of 63 hierarchically organized modules. Each variant was tested against each of the facial surface modules in a multivariate genetic association-testing framework and meta-analyzed. Additionally, the association between these candidate SNPs and five facial ratios was investigated in the Pittsburgh 3DFN cohort. Two significant associations involving intronic variants of SHBG were found: both rs12150660 (p = 1.07E-07) and rs1799941 (p = 6.15E-06) showed an effect on mandible shape. Rs8023580 (an intronic variant of NR2F2-AS1) showed an association with the total and upper facial width to height ratios (p = 9.61E-04 and p = 7.35E-04, respectively). These results indicate that testosterone-related genetic variants affect normal-range facial morphology, and in particular, facial features known to exhibit strong sexual dimorphism in humans.

The Relative Sexual Dimorphism of Human Incisor Crown and Root Dimensions

Teeth are unusual structures in that theirdimensions are sexually dimorphic even though theyform early in life, several years before steroid-mediatedadolescence. These size differences make teeth attractiveas indicators of a specimen’s sex. Alternatively, themagnitude of sexual dimorphism in humans is low, sothere is considerable overlap in sizes between the twosexes. Prior studies suggest that tooth root dimensionsare more dimorphic than crown dimensions, so rootswould be more useful for sex determination. Toexplore this, we measured the four incisor tooth typesfrom standardized periapical radiographs in a sample(n = 148) of living American white adolescents. Rootlengths are somewhat more dimorphic than crownsizes in this sample (ca. 6% vs. 2%), and this translatesinto somewhat higher discriminatory power. Thehindrance, however, is that all crown and root sizesare positively intercorrelated, so there is effectivelyjust one dentition-wide axis of “tooth size” variation.Statistically, at least for these incisor tooth types, thereis no added discriminatory power in the crown sizesonce root dimensions have been accounted for, thoughthe addition of data from other tooth types mightimprove discrimination somewhat.

Sex differences in psychiatric disorders: what we can learn from sex chromosome aneuploidies.

The study of sexual dimorphism in psychiatric and neurodevelopmental disorders is challenging due to the complex interplay of diverse biological, psychological, and social factors. Males are more susceptible to neurodevelopmental disorders including intellectual disability, autism spectrum disorder, and attention-deficit activity disorder. Conversely, after puberty, females are more prone to major depressive disorder and anxiety disorders compared to males. One major biological factor contributing to sex differences is the sex chromosomes. First, the X and Y chromosomes have unique and specific genetic effects as well as downstream gonadal effects. Second, males have one X chromosome and one Y chromosome, while females have two X chromosomes. Thus, sex chromosome constitution also differs between the sexes. Due to this complexity, determining genetic and downstream biological influences on sexual dimorphism in humans is challenging. Sex chromosome aneuploidies, such as Turner syndrome (X0) and Klinefelter syndrome (XXY), are common genetic conditions in humans. The study of individuals with sex chromosome aneuploidies provides a promising framework for studying sexual dimorphism in neurodevelopmental and psychiatric disorders. Here we will review and contrast four syndromes caused by variation in the number of sex chromosomes: Turner syndrome, Klinefelter syndrome, XYY syndrome, and XXX syndrome. Overall we describe an increased rate of attention-deficit hyperactivity disorder and autism spectrum disorder, along with the increased rates of major depressive disorder and anxiety disorders in one or more of these conditions. In addition to contributing unique insights about sexual dimorphism in neuropsychiatric disorders, awareness of the increased risk of neurodevelopmental and psychiatric disorders in sex chromosome aneuploidies can inform appropriate management of these common genetic disorders.

Sexual Dimorphism in Humans from the Palatal Rugae Pattern

Sexual Dimorphism in Humans from the Palatal Rugae Pattern

Sexual dimorphism in two mediaeval Muslim populations from Spain

Sexual dimorphism in humans is mainly observed as a difference in the anatomy of genitals and breasts. There are also some differences in the stature and metric or morphological traits of the skeleton. Degree of sexual dimorphism varies among populations and depends on their genetic composition and various cultural and environmental factors. In this study, two Mediaeval Muslim populations from Granada, Spain, were compared, testing whether differences in living environment (urban vs. rural) would result in distinct degrees of sexual dimorphism of long bones. We studied skeletal material from urban (Sahl ben Mālik, Granada, Spain) and rural (La Torrecilla, Arenas del Rey, Granada, Spain) cemeteries. Only adult individuals (66 from Sahl ben Mālik and 72 from La Torrecilla) were selected for the study. Maximum length, minimum circumference of the shaft and maximum widths of the proximal and distal epiphyses were measured in each bone. The index of sexual dimorphism (ISD) was calculated for each variable and each population. The degree of sexual dimorphism was greater in La Torrecilla. These results indicate that Muslim women in large urban centres may have played a more active role in social and working life in comparison to their rural counterparts and may have enjoyed superior living conditions, which contributed to enhancing the body development of women and reducing sexual dimorphism. We conclude that living in an urban or a rural environment may influence the degree of sexual dimorphism.

Determination of sexual dimorphism in humans by measurements of mandible on digital panoramic radiograph.

Background:Identification of sex is the first step in forensic science obtained from skeletal remains. Mandible, being a strong bone that is difficult to damage and disintegrate, is an important tool in sex determination. The present study is aimed to assess, compare, and evaluate the mandibular measurements as seen on digital panoramic radiographs to analyze their use in sexual dimorphism assessment.Materials and Methods:This retrospective study was conducted using digital panoramic images of 100 each in both genders. Mandibular measurements were carried out utilizing RadiAnt DICOM Viewer 2.2.9 (32 bit) software (Medixant Company, Poland) and subjected to statistical analysis.Results:Descriptive statistics for all the parameters on the right and left sides of mandible in both males and females were analyzed. Inferential statistics were performed using t-test to compare males and females with different variables. A statistical significance of P < 0.001 has been demonstrated for all the variables (except linear measurement of mandibular foramen). All variables showed increased measurements in males than in females. The accuracy of sex determination in mandibular ramus measurements is 79.5% on right side and 77% on left side, where as, in linear mandibular measurements it is 76% on right side and 79.5% on left side.Conclusion:Mandibular measurements on digital radiograph are useful in sex determination, and this study can be compared with other similar studies.

Genetic Architecture of Sexual Dimorphism in Humans.

Males and females differ across a broad spectrum of morphological, physiological, and behavioral characters. In fact, sexually dimorphic traits typically contribute the largest component of phenotypic variance in most taxa that use sex to reproduce. However, we know very little about the mechanisms that maintain these dimorphic states and how these sexually dimorphic traits evolve. Here, we review our current knowledge of the underlying genetic basis of sexual dimorphism in humans. First, we briefly review the etiology of sex differences starting from sex determination's initial switch early in embryogenesis. We then survey recent sex-biased transcriptomic expression literature in order to provide additional insight into the landscape of sex-biased gene expression in both gonadal and non-gonadal tissues: from overall prevalence to tissue specificity to conservation across species. Finally, we discuss implications of sex-biased genetic architecture to human health and disease in light of the National Institute of Health's recently proposed initiative to promote study samples from both sexes.

Does Patient Sex Influence Cartilage Surgery Outcome?

Background: Sexual dimorphism in humans has already been documented at different levels, and preliminary findings also suggest the importance of patient sex on clinical outcome in the treatment of cartilage lesions. Purpose: To document and analyze the influence of sex on clinical outcome in a large cohort of patients treated with a cartilage regenerative procedure for knee chondral lesions and prospectively followed at midterm follow-up. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 250 knees were treated with matrix-assisted autologous chondrocyte transplantation (MACT) and prospectively evaluated with International Knee Documentation Committee (IKDC), EuroQol visual analog scale (EQ-VAS), and Tegner scores at 1-, 2-, and minimum 5-year follow-ups to compare results obtained in men and women. The lesions were focal International Cartilage Repair Society grade III-IV chondral knee defects involving femoral condyles, trochleae, and patellae. Two homogeneous groups of 56 male patients and 56 female patients were then selected by a blinded statistician for a matched-pair analysis. Results: A statistically significant improvement in all the scores in both men and women was observed in the general population. The IKDC subjective score showed better results for men at all follow-up times: at 5 years, the mean IKDC subjective score was 79.5 ± 18.6 versus 64.3 ± 20.2 for men and women, respectively (P < .0005), and the same trend was confirmed with the EQ-VAS and Tegner scores. The matched-pair analysis confirmed the difference of final results achieved (74.1 ± 19.8 vs 63.7 ± 20.2, respectively; P = .006). However, men and women started with different preoperative levels, and the analysis of the improvement obtained was not significantly different. Finally, when scores were standardized for each patient, according to the mean score typical for the corresponding age and sex category in a healthy population, a sex-related difference was not confirmed at any of the follow-ups. Etiological factors, lesion site, and preinjury activity level differed in women and men of the general population and were the confounding factors responsible for the different outcome not confirmed by the analysis of homogeneous cohorts of patients. Conclusion: Women have a different knee chondral lesion pattern and more often have unfavorable conditions related to the cause of injury, site, and activity level, and they also have lower raw, not standardized, scores. However, a matched-pair analysis with data standardized for the specific patient categories showed that, on equal terms, women have the same possibilities for successful outcome as men after surgical treatment for knee cartilage regeneration.

Sexual Size Dimorphism, Canine Dimorphism, and Male-Male Competition in Primates

Sexual size dimorphism is generally associated with sexual selection via agonistic male competition in nonhuman primates. These primate models play an important role in understanding the origins and evolution of human behavior. Human size dimorphism is often hypothesized to be associated with high rates of male violence and polygyny. This raises the question of whether human dimorphism and patterns of male violence are inherited from a common ancestor with chimpanzees or are uniquely derived. Here I review patterns of, and causal models for, dimorphism in humans and other primates. While dimorphism in primates is associated with agonistic male mate competition, a variety of factors can affect male and female size, and thereby dimorphism. The causes of human sexual size dimorphism are uncertain, and could involve several non-mutually-exclusive mechanisms, such as mate competition, resource competition, intergroup violence, and female choice. A phylogenetic reconstruction of the evolution of dimorphism, including fossil hominins, indicates that the modern human condition is derived. This suggests that at least some behavioral similarities with Pan associated with dimorphism may have arisen independently, and not directly from a common ancestor.

Pelvic dimorphism in relation to body size and body size dimorphism in humans

Many mammalian species display sexual dimorphism in the pelvis, where females possess larger dimensions of the obstetric (pelvic) canal than males. This is contrary to the general pattern of body size dimorphism, where males are larger than females. Pelvic dimorphism is often attributed to selection relating to parturition, or as a developmental consequence of secondary sexual differentiation (different allometric growth trajectories of each sex). Among anthropoid primates, species with higher body size dimorphism have higher pelvic dimorphism (in converse directions), which is consistent with an explanation of differential growth trajectories for pelvic dimorphism. This study investigates whether the pattern holds intraspecifically in humans by asking: Do human populations with high body size dimorphism also display high pelvic dimorphism? Previous research demonstrated that in some small-bodied populations, relative pelvic canal size can be larger than in large-bodied populations, while others have suggested that larger-bodied human populations display greater body size dimorphism. Eleven human skeletal samples (total N: male = 229, female = 208) were utilized, representing a range of body sizes and geographical regions. Skeletal measurements of the pelvis and femur were collected and indices of sexual dimorphism for the pelvis and femur were calculated for each sample [ln(M/F)]. Linear regression was used to examine the relationships between indices of pelvic and femoral size dimorphism, and between pelvic dimorphism and female femoral size. Contrary to expectations, the results suggest that pelvic dimorphism in humans is generally not correlated with body size dimorphism or female body size. These results indicate that divergent patterns of dimorphism exist for the pelvis and body size in humans. Implications for the evaluation of the evolution of pelvic dimorphism and rotational childbirth in Homo are considered.

Effect of gender differences in distal femoral geometry on the clinical outcomes of total knee arthroplasty

Objective To investigate the effect of gender differences in distal femoral geometry on the clinical outcomes of total knee arthroplasty (TKA). Methods From March 2003 to October 2006, 213 cases with 294 osteoarthritic knees who had underwent primary TKA were involved in the study. The study included 87 men (118 knees) and 126 women (176 knees) who had a mean age of 64.4 years. All the cases were assessed with the knee-rating system of Knee Society, the knee range of flexion (ROF), corrected posterior offset (PCO) and anterior condylar offset (ACO) based on sex. Results Each patient had a Minimum of 2 years follow-up. The preoperative Knee Society scores and ROF, the two-year postoperative changes of stability scores and walking ability had no differences between the two groups. While greater improvements of postoperative pain scores and stair-climbing ability were seen in male. Men had better intraoperative ROF than women had ones, but there were no gender differences with regard to the two-year postoperative improvement of ROF. Corrected PCO decreased more markedly in female than in male. Corrected ACO decreased equally in female and male. The difference in the posterior condylar offset after TKA was statistically correlated with the change in pain scores, stair climbing ability and intraoperative ROF, respectively. Conclusion Male had a better outcome than female did after TKA. Femoral components which designed in the light of Caucasian anatomic characteristics couldn't match the native anatomy of distal femurs of Chinese female. Sexual dimorphism in humans and anatomic variations in various ethnic groups should be seriously considered in total knee prosthesis design. Key words: Arthroplasty, replacement, knee; Gender identity; Prostheses and implants

Human sexual dimorphism, fitness display, and ovulatory cycle effects

AbstractSocial roles theorists claim that differences between the sexes are of limited consequence. Such misperceptions lead to misunderstanding the important role of sexual selection in explaining phenotypic differences both between species and within humans. Countering these claims, we explain how sexual dimorphism in humans affect expressions of artistic display and patterns of male and female aggression across the ovulatory cycle.

Why are women smaller than men? When anthropology meets evolutionary biology

AbstractThere 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.