Sexual Dimorphism In Population Research Articles

Sexual Dimorphism: The Interrelation of Shape and Color

Sex-typicality displayed as sexual dimorphism of the human face is a key feature enabling sex recognition. It is also believed to be a cue for perceiving biological quality and it plays an important role in the perception of attractiveness. Sexual dimorphism of human faces has two main components: sexual shape dimorphism of various facial features and sexual color dimorphism, generally manifested as dimorphism of skin luminance, where men tend to be darker than women. However, very little is known about the mutual relationship of these two facets. We explored the interconnection between the dimorphism of face shape and dimorphism of face color in three visually distinct populations (Cameroonian, Czech, and Vietnamese). Our results indicated that populations which showed a significant dimorphism in skin luminance (Cameroon, Vietnam) had low levels of sexual shape dimorphism, while a population with higher levels of sexual shape dimorphism (Czech Republic) did not exhibit a significant dimorphism of skin luminance. These findings suggest a possible compensatory mechanism between various domains of sexual dimorphism in populations differing in the levels of shape and color dimorphism.

Influence of climatic stress on nonmetric sexually dimorphic features of the skull and pelvis.

Human sexual dimorphism is frequently assessed through skull and pelvic size and shape. Researchers suggest that climatic variation and the associated stress may be significant factors in sexual dimorphism's etiology. However, little research has specifically investigated climatic effects on nonmetric skeletal indicators of sex. To further appreciate the plasticity of human biology, a comparative study of standard skull and pelvic nonmetric sex indicators is presented. A Native Alaskan archeological sample (n=104) and a component of the Terry collection (n=99) represent populations originating from different climatic environments in recent history. These sex-balanced groups are compared through Tukey-Kramer's method and Greene's t-test to determine any variation in degree of sexual dimorphism within and between samples. The results reinforce the complex and multifaceted relationship between climate and sexual dimorphism. The Terry sample demonstrated a greater degree of sexual dimorphism with statistically significant differences in robusticity of the mastoid process and nuchal crest compared with the Native Alaskans. A more "male" morphotype and reduced dimorphism are appreciated in the pelves of Native Alaskans than the Terry sample. This research highlights a reduction in sexual dimorphism in populations under greater climatic stress and contributes to the production of more accurate skeletal assessments in future investigations. Discussion of confounding factors suggest more research is necessary to untangle climate and human morphology's complex relationship. This study contributes to a greater appreciation of human biological plasticity, ecogeographic variation, and the evolution of modern human diversity.

The Morphometric Examination of Head Area of Black Headed Gulls (Larus Ridibundus) from Marmara Region

The Black-headed gull (Larus ridibundus), a gull species commonly seen on shores of Küçükçekmece lake located in Marmara Region, does not exhibit sexual dimorphism as it has monomorphic feather traits like the other gull species. In order to perform sex discrimination in gulls, the effective discriminant function analysis (DFA) method is used for the measurements based on the external morphology and determining the variables discriminating the two sex groups. The head morphological measurements and the body weights of 28 adult Black-headed gulls were obtained. One discriminant function was determined based on the results. The accuracy rate in two sexes was determined to be 82.1% (85.7% female, 78.6% male) using the formula we obtained as a result of the discriminant function analysis in which the head length, determined to be more significant compared to the other variables, was used. The aim of the study is to assess the sexual dimorphism in population of Black-headed gull in Küçükçekmece Lake and its surrounding located in Marmara Region and represent a reliable method to make a sex discrimination along with discriminant analysis.

Проявления полового диморфизма в популяциях Южной Сибири: внутригрупповой анализ

Проявления полового диморфизма в популяциях Южной Сибири: внутригрупповой анализ

Metacarpal lengths & ratios as a marker of sexual dimorphism in population of Haryana and Jammu & Kashmir. A radiological study

IntroductionThis study was designed to compare and detect possible differences between the metacarpal length (MCL) and all metacarpal length ratios in left - and right hands of female and male individuals of Haryanvi and J&K populations. Materials and methodsMetacarpal lengths (MCL) of 143 subjects were measured after obtaining X-ray of both the hands, followed by calculating the ratio of each digit to the others (1MCL:2MCL, 1MCL:3MCL, 1MCL:4MCL, 1MCL:5MCL, 2MCL:3MCL, 2MCL:4MCL, 2MCL:5MCL, 3MCL:4MCL, 3MCL:5MCL, and 4MCL:5MCL). ResultsAll the metacarpals can arranged according to their mean digit lengths in increasing order there to obtain formulae i.e MCL1(49.77) < MCL5(57.21) < MCL4(61.67) < MCL3(69.74) < MCL2(72.46) & MCL1(49.40) < MCL 5(57.21) < MCL4(61.31)< MCL3(68.33) < MCL2(72.31) for right and left hands of north Indian males respectively. MCL1(45.67) < MCL5(51.81) < MCL4(56.47) < MCL3(64.26) < MCL2(66.60) & MCL1(45.42) < MCL5(51.26) < MCL4(56.09) < MCL3(63.25) < MCL2(66.21) for right and left hands of females respectively. DiscussionMetacarpal length is known to enhance potential, particularly in sporting activities Male and females of north Indian population have difference MCL for their both the hands, hence dimorphism is established. It is especially necessary to measure metacarpal length of the hand for practical reasons. In handball and basketball, the longer is the metacarpal length, the better the accuracy of the shot or throw. Longer metacarpals may help to stabilize digits when throwing objects, and this would increase throwing accuracy. In turn, this would give more of an advantage in sporting activities.

The tale of the shrinking weapon: seasonal changes in nutrition affect weapon size and sexual dimorphism, but not contemporary evolution.

Sexually selected traits are often highly variable in size within populations due to their close link with the physical condition of individuals. Nutrition has a large impact on physical condition, and thus, any seasonal changes in nutritional quality are predicted to alter the average size of sexually selected traits as well as the degree of sexual dimorphism in populations. However, although traits affected by mate choice are well studied, we have a surprising lack of knowledge of how natural variation in nutrition affects the expression of sexually selected weapons and sexual dimorphism. Further, few studies explicitly test for differences in the heritability and mean-scaled evolvability of sexually selected traits across conditions. We studied Narnia femorata (Hemiptera: Coreidae), an insect where males use their hind legs as weapons and the femurs are enlarged, to understand the extent to which weapon expression, sexual dimorphism and evolvability change across the actual range of nutrition available in the wild. We found that insects raised on a poor diet (cactus without fruit) are nearly monomorphic, whereas those raised on a high-quality diet (cactus with ripe fruit) are distinctly sexually dimorphic via the expression of large hind leg weapons in males. Contrary to our expectations, we found little evidence of a potential for evolutionary change for any trait measured. Thus, although we show weapons are highly condition dependent, and changes in weapon expression and dimorphism could alter evolutionary dynamics, our populations are unlikely to experience further evolutionary changes under current conditions.

Morphology and sexual dimorphism ofAcanthochelys spixii(Testudines, Chelidae) in Brazil

Body size is an important parameter for ecology, reproduction, evolution, and development of animal species, besides understanding their taxonomic relationships and to establishing the relationships between individual size and shape. We evaluated the variation in body size traits, sexual dimorphism in populations of a turtle species Acanthochelys spixii across its distribution in Brazil and we described sex ratio in those populations. Description of the size-classes on these populations was also provided. We sampled 86 adults (16 in Minas Gerais (MG) and 70 in Rio Grande do Sul (RS)). The sex ratio was 1:1 in both sampling areas. Females were larger than males, and specimens from RS were larger than those from MG. The posterior-lobe width (PLW) was deemed the most significant sexing variable in a linear discriminant analysis of specimens within each state. Two variables, PLW and maximum carapace width, together distinguished the four groups (males and females in MG and RS) with 77% accuracy. Overall, most...

Sexual dimorphism of the mandible in a contemporary Chinese Han population

A present limitation of forensic anthropology practice in China is the lack of population-specific criteria on contemporary human skeletons. In this study, a sample of 203 maxillofacial Cone beam computed tomography (CBCT) images, including 96 male and 107 female cases (20–65 years old), was analyzed to explore mandible sexual dimorphism in a population of contemporary adult Han Chinese to investigate the potential use of the mandible as sex indicator. A three-dimensional image from mandible CBCT scans was reconstructed using the SimPlant Pro 11.40 software. Nine linear and two angular parameters were measured. Discriminant function analysis (DFA) and logistic regression analysis (LRA) were used to develop the mathematics models for sex determination. All of the linear measurements studied and one angular measurement were found to be sexually dimorphic, with the maximum mandibular length and bi-condylar breadth being the most dimorphic by univariate DFA and LRA respectively. The cross-validated sex allocation accuracies on multivariate were ranged from 84.2% (direct DFA), 83.5% (direct LRA), 83.3% (stepwise DFA) to 80.5% (stepwise LRA). In general, multivariate DFA yielded a higher accuracy and LRA obtained a lower sex bias, and therefore both DFA and LRA had their own advantages for sex determination by the mandible in this sample. These results suggest that the mandible expresses sexual dimorphism in the contemporary adult Han Chinese population, indicating an excellent sexual discriminatory ability. Cone beam computed tomography scanning can be used as alternative source for contemporary osteometric techniques.

Growth and sexual dimorphism in a population of hybrid macaques

AbstractGrowth and sexual dimorphism have long been the focus of investigation for researchers interested in the life history and socioecology of nonhuman primates. Previous research has shown that sex differences in the duration of growth, or bimaturism, are primarily responsible for the sexual dimorphism observed in anthropoid primates with multimale–multifemale social structure, such as macaques. The present study investigates sex differences in patterns of craniofacial and somatometric growth relative to head and body size and relative to dental development in a population of hybrid macaques (Cercopithecidae: Macaca) from Sulawesi, Indonesia. How these patterns may contribute to sexual dimorphism in this hybrid population is also examined. The results of the study suggest that there is no substantial effect on the levels of sexual dimorphism associated with hybridization in these macaques. Although sex differences in patterns of size‐related, or allometric, growth patterns play a significant role in the development of sexual dimorphism for some cranial dimensions in these hybrids, bimaturism seems to be the primary component in the ontogeny of sexual dimorphism in this hybrid population. The observed levels of hybrid dimorphism and the predominant ontogenetic pattern of bimaturism characterized by prolonged male growth are consistent with previously published reports on dimorphism and growth in other cercopithecine primates.

The causes and evolutionary consequences of a conflict between species and mate-quality recognition

Mate choice typically involves the identification of conspecifics (species recognition) and the identification of mates that provide females with enhanced fitness (mate-quality recognition). When high-quality conspecifics possess advertisement signals that resemble those of heterospecifics, however, females may be unable to engage in both species and mate-quality recognition simultaneously. This conflict between species and mate-quality recognition may require that females trade off the benefits of mating with high-quality males with the risk of heterospecific matings. In spadefoot toads, females face a conflict between species and mate-quality recognition because the advertisement calls of high-quality conspecifics resemble those of heterospecifics. Because of this conflict, females compromise on male quality to ensure conspecific matings. Moreover, this trade-off has seemingly caused spadefoot toads to evolve smaller body size, reduced fecundity, and different patterns of sexual dimorphism in populations where heterospecifics are present (sympatry) versus populations where heterospecifics are absent (allopatry). Thus, a conflict between species and mate-quality recognition can have profound impacts on how females use male advertisement signals to choose mates, sexual selection, and morphological evolution in different populations, and even the fitness of individuals in sympatry relative to those in allopatry.

A Measure of Sexual Dimorphism in Populations which are Univariate Normal Mixtures

Measures of sexual dimorphism have been used extensively to predict the social organization and ecology of animal and human populations. There is, however, no universally accepted measure of phenotypic differences between the sexes. Most indices of sexual dimorphism fail to incorporate all of the information contained in a random data set. In an attempt to have a better alternative, an index is proposed to measure sexual dimorphism in populations that are distributed according to a probabilistic mixture model with two normal components. The index calculates the overlap between two functions that represent the contribution of each sex in the mixture. In order to assess such an index, sample means, variances and sizes of each sex are needed. As a consequence, the sample information used is greater than that used by other indices that take intrasexual variability into account. By evaluating some examples, our proposed index appears to be a more realistic measure of sexual dimorphism than other measures currently used.

Dermatoglyphic sexual dimorphism in Middle Eastern Jews

Summary. — The dermatoglyphics of Jews of Middle Eastern extraction display, in general, the same features as do the majority of Caucasoid populations. In males there are more whorls and fewer ulnar loops than in females, and in correlation with this, a higher pattern intensity index, and higher total and absolute ridge counts. On the palms, where the image is more varied in diverse populations, the males of our sample, show more patterns in the left and right thenar areas and in the hypothenar area, especially on its left side. Some other palmar traits, as the line A exits and the a-b distance, present also significant differences between the sexes. Using only dermatoglyphic traits with high discriminant power (F > 4), discriminant analysis permits a correct classification by sex of 63,3 % of individuals, which is slightly better than in the North African but less than in East European or Yemenite Jewish groups. This indicates different levels of sexual dimorphism in populations otherwise possessing similar dermatoglyphic characteristics, and suggests the possible role of environmental prenatal factors in attainment of the dermatoglyphic sexual dimorphism level.