Metric analysis of sex differences in South African black and white pelves

Sex determination of unknown skeletal material is one of the most vital determinations made by forensic anthropologists. Numerous studies have focussed on the differences, both osteometric and morphological, between the sexes of a particular racial phenotype and population. Previous work by a variety of researchers has underscored the necessity of population specific standards. The purpose of this research is to metrically assess sex differences in the pelvis of South African whites and blacks and develop standards tailored to these groups. Data were collected from 400 known sex/race skeletons from the Pretoria and Dart Collections. Nine measurements (traditional and newly developed) were taken and subjected to SPSS stepwise and direct discriminant analysis. Results indicated that there are significant differences (p < or = 0.001) between the sexes of both races for most measurements. Discriminant function analysis selected ischial length as the most sexually dimorphic dimension in whites (averaged 86% accuracy), while acetabulum diameter was most diagnostic in blacks (averaged 84% accuracy). Six functions were developed from the pelvic dimensions. Highest accuracy was achieved from Function 1 (including all dimensions) which averaged 95.5% correct classification in whites and 94% in blacks. Functions based on selected parts of the pelvis were not as effective and ranged from 73-86% in whites and 72-84% in blacks. This research provided evidence of the significant sex differences that exist between the pelves of South African whites and blacks whilst measurements used here for discriminant function analysis gave classifications with high accuracies. These results can be used to aid in the identification of human skeletal remains in South Africa.     

Metric determination of sex from the humerus in a Guatemalan forensic sample

The absence of population-specific standards for sex, age and stature estimation for rural Guatemala is problematic for the forensic analysis of skeletal remains recovered from clandestine graves attributed to the recent armed conflict in that country. In order to increase the reliability of the forensic analyses being undertaken in Guatemala, standards for metric determination of sex were developed. Data was collected on several bones; the results for the humerus are presented here. A sample of 118 complete humeri (68 male and 50 female) was studied; maximum length, maximum diameter of the head, circumference at midshaft, maximum diameter at midshaft, minimum diameter at midshaft and epicondylar breadth were measured and subjected to discriminant function analysis. The classification accuracies for the univariate functions range from 76.8% for the maximum diameter at midshaft to 95.5% for the maximum diameter of the head. The classification accuracy for the stepwise procedure was 98.2%.     

The efficiency of the demarking point of the femoral head as a sex determining parameter

The percentage of skeletal remains that can be sexed depends on the degree of completeness of the skeleton, the parameters that are used and the type of statistical analysis that is done. The objective of the present study was to assess the accuracy of the demarking point in sexing the femur of South African whites and blacks. One hundred pairs of femurs were randomly selected from the bone collections of each of the two racial groups. The bones were sexed by measuring the head diameters and comparing them with the corresponding demarking point values that had been previously determined. The sex that was so allocated to each bone was compared with its documented sex in the database in order to assess the accuracy of the method. The overall success rate of sex identification was 32% for both white and black populations, but the accuracy of sexing was 100%.     

Metric assessment of race from the pelvis in South Africans

It is well known that there are measurable differences between whites and blacks in the size and proportions of skeletal components. There are also metric differences among populations within these racial phenotypes. The population specific quantification of this variation can be used to aid in the identification of racial affinity in the absence of a more racially definitive skeletal element like the skull. Therefore, the purpose of this research is to quantify these differences in the pelvis of South African whites and blacks. A sample of 400, ostensibly healthy known sex/race os coxae was examined. Skeletal material was obtained from the Pretoria and Dart collections. A series of 13 measurements were taken Data were subjected to SPSS stepwise and direct discriminant function analysis. Pubic length was chosen as best for discriminating between races for males and iliac breadth as best in females. Highest average accuracies (Function 1) were 88% for males (pubic length, greater sciatic notch posterior width, acetabulum diameter, total height) and 85% for females (pubic length, greater sciatic notch posterior width, acetabulum diameter, iliac breath). In conclusion, this research resulted in the development of standards of identification tailored to this population and unquestionably demonstrates that race differences in the skeleton are highly significant and must be considered in all skeletal analyses.     

A study of sexual dimorphism in the femur among North Indians

Determination of sex of unknown skeleton remains is the most important step in the identification process. Racial and regional differences in the populations create and maintain specificity in their dimorphic characteristics. Moreover, considering continued secular changes in the population structure, constant revision of osteometric standards becomes mandatory. In an effort to establish osteometric standards for the femur of contemporary North Indian populations, 122 adult femora of known sex (M: 94; F: 28) were collected in the Department of Forensic Medicine, IMS, BHU, Varanasi. Eight standard parameters were measured and analyzed by discriminant function analysis using SPSS 16. The accuracy of sex prediction ranged from 70.5% to 83.6% with single variables. In stepwise analysis, epicondylar breadth, proximal breadth, and antero-posterior diameter of the lateral condyle were found to be the most discriminating variables providing an accuracy of 90.2%. The results clearly indicate the importance of the ends of femur in the determination of sex.     

Forearm bones and sexual variation in Turkish population

Forensic anthropologists are aware that there are considerable differences between human populations and therefore develop study models for each skeletal population. The purpose of this study was to analyze forearm bones obtained from forensic settings in Turkey. The sample consists of 42 males and 38 females with an average age of 40 and 36 years, respectively. Numerous measurements were taken from the radius and ulna including lengths (in millimeters), midshaft diameters, and epiphyseal breadths (0.01 mm). Individuals with any anomaly and pathology were not included in the investigation. A stepwise analysis, when applied to individual bones, selected only length and midshaft transverse dimension in the radius and length only in the ulna. When the length was excluded from the statistic, head diameter and distal breadth of the radius and distal minimum head and midshaft anteroposterior diameters of the ulna provided the best predicting functions. Classification results were 92% for the radius and 91% for the ulna. For the incomplete bones, the accuracy rates were about 92% and 83%, respectively. In conclusion, a sex determination was made, in different rates of accuracy, in the human skeleton. Correct assessment can vary among populations. Dimorphism in our region forearm bones is greater than American whites. This supported the hypothesis that human variation is diverse, and population difference should be taken into account when osteometric standards are applied to others. Further studies are needed to understand why the forearm is more dimorphic in Turks.     

Sex determination from the radius and ulna in a modern South African sample

With a large number of unidentified skeletal remains found in South Africa, the development of population specific osteometric standards is imperative. Forensic anthropologists need to have access to a variety of techniques to establish accurate demographic profiles from complete, fragmentary and/or commingled remains. No research has been done on the forearm of African samples, even though these bones have been shown to exhibit sexual dimorphism. The purpose of this paper is to develop discriminant function formulae to determine sex from the radius and ulna in a South African population. The sample consisted of 200 male and 200 female skeletons from the Pretoria Bone (University of Pretoria) and Raymond A. Dart (Witwatersrand University) collections. Sixteen standard anthropometric measurements were taken from the radius (9) and ulna (7) and subjected to stepwise and direct discriminant function analysis. Distal breadth, minimum mid-shaft diameter and maximum head diameter were the best discriminators of sex for the radius, while minimum mid-shaft diameter and olecranon breadth were selected for the ulna. Classification accuracy for the forearm ranged from 76 to 86%. The radius and ulna can be considered moderate discriminators for determining sex in a South African group. However, it is advised that these formulae are used in conjunction with additional methods to determine sex.     

Sex determination from the head of the femur of South African whites and blacks

The current practice whereby criminals dismember the remains of their victims in an attempt to make their identification difficult requires that simple methods of sex determination from fragmented skeletal remains are available to forensic anthropologists and skeletal biologists. The head of the femur is an example of such bone fragments. Identification and demarking points have been derived from the diameters of the head of the femur and used to determine the sex of individuals. It has been shown, however, that the numerical values of these parameters that permit sex identification vary between races. The objectives of the present study were therefore to establish the standard numerical values of the identification and demarking points for sex determination in South African whites and blacks and to see if these standards are different in the two races. A total of 520 femurs of white (160 males and 100 females) and black (160 males and 100 females) South Africans were obtained from the Raymond Dart Skeletal Collection in the Department of Anatomical Sciences of the University of the Witwatersrand, Johannesburg, South Africa. The vertical and transverse diameters of the heads of the femurs were measured by means of a stainless steel vernier caliper. Identification and demarking points were derived from the values of these diameters. The head diameter identification point and demarking point were found to be sexually dimorphic in both white and black South Africans. The mean head diameter of the male femur was significantly greater than the mean head diameter of the female femur in both population groups (significant at P<0.001). These values were correspondingly greater in the white than the black population. The numerical values of the male identification and demarking points were higher than the corresponding female values in the two population. In both sexes, these values were greater in the whites than the blacks South Africans. It is concluded that the diameters of the head of the femur and the identification and demarking points that are derived from them are sexually dimorphic in South African white and black populations. However, the numerical values of these sex-determining bone parameters defer between the two population groups. Therefore, it is necessary to determine race-specific standards of these parameters.     

Sexual dimorphism in the crania and mandibles of South African whites

Numerous studies have clearly demonstrated that skeletal characteristics vary by population. To date, there are no metric cranial criteria for South African whites. Therefore, the purpose of this study is to establish population specific standards for sex determination from the skull. A total of 12 standard cranial and five mandibular measurements were taken from 44 male and 47 female skeletons of known sex and race from the Pretoria and Dart collections. These were subjected to SPSS discriminant function analysis. Bizygomatic breadth was the most dimorphic dimension. Five functions were developed from the complete cranium, vault, face, mandible and bizygomatic breadth. Dimensions from the complete cranium provided the best accuracy. In the mandible, bigonial breadth was the most dimorphic of the measurements taken. Average accuracies ranged from 80% (bizygomatic breadth alone) to 86% (cranium). These accuracies are similar to those obtained by researchers on other groups (e.g., 84% in Japanese crania and about 86% in American whites and blacks). Diagnostic accuracy, however, is lower than that obtained from the South African femur and tibia.     

Sexual dimorphism in the humerus: a comparative analysis of Chinese, Japanese and Thais

Determination of sex from the skeleton is vital to medicolegal investigations. There is no longer any question that populations differ in size and proportions and these differences affect the metric assessment of sex. The extent of variation in sexual dimorphism among Asian Mongoloids within and between regions has not been quantified by discriminant function analysis, nor have standards for most groups been introduced for the humerus. Therefore, the purpose of this research is to establish metric standards for sex determination from the humerus of Chinese, Japanese and Thais, as well as to compare size and sexual dimorphism in these Asian Mongoloid populations. The database for this study consisted of documented skeletal samples from China (N = 87), Japan (N = 90), and Thailand (N = 104). Six standard dimensions, including maximum length, vertical head diameter, minimum midshaft diameter, maximum midshaft diameter, midshaft circumference, and epicondylar breadth were taken and subjected to stepwise and direct discriminant function analysis. Of dimensions selected by the stepwise function, vertical head diameter and epicondylar breadth were the only elements common to all three groups. Overall, mean accuracies were highest using formulae produced by the stepwise procedure and ranged from 86.8% in the Chinese to 92.4% in the Japanese to 97.1% in the Thais. Group comparisons also revealed that while the Chinese had the largest measurements, they were the least dimorphic. The reverse was true for the Thais and the Japanese were intermediate on both counts. In cross validation tests, classification accuracy decreased in all cases where a formula from one group was applied to another. It was therefore concluded even though all individuals were Asian Mongoloids, these regionally diverse populations exhibited significant metric differences that affect sex determination from the skeleton. These findings confirm those of previous studies that there is a need for group specific metric standards of assessment.     

Discriminant function sexing of the calcaneus of the South African whites

The skull and some postcranial elements, such as the humerus, femur, and tibia, have been used in their intact states for sex determination in forensic and archaeological cases. But, in practice, these bones are often recovered in fragmented states, which render them unsuitable for use in sex determination. The calcaneus is a compact bone that is able to withstand high tensile forces. Some of its parameters have been used for sex determination in American whites and blacks (1) and Italians (2). This bone has not been used for sex determination in the South African white population. Therefore, the aim of this study was to assess the degree of sexual dimorphism of the calcaneus of the South African white population sample, derive discriminant function score equations for use in sex determination, and determine the level of accuracy of its sex-determining ability. Nine parameters were measured on each pair of 53 male and 60 female calcanei of known South African white skeletons, obtained by a random sampling technique from the Raymond A. Dart Collection of Human Skeletons, School of Anatomical Sciences, University of the Witwatersrand, Johannesburg. Basic statistic and discriminant function analysis was performed on the acquired data. The basic statistics showed that all measured parameters were sexually dimorphic. Discriminant function score equations were generated for use in sex determination. The average accuracy of sex classification ranged from 73 to 86% for the univariate method, 81 to 91% for the stepwise method, and 82 to 92% for the direct method. It is concluded that the calcaneus is useful for sex determination in the South African white population.     

Discriminant function sexing of fragmentary femur of South African blacks

When fragmentary and incomplete bones are all that are available to the forensic anthropologist for use in sex determination, non-metric and metric sex discriminating parameters that have been derived from complete bones may be of little use. In such circumstances, sex discriminating metric methods that are of specific application to fragmentary bones will be more useful. Since such studies have not been systematically carried out in bones of South African blacks, the aim of this study was to begin to provide such data. Two hundred and twenty left femurs of black South Africans were obtained from the Raymond A. Dart Collection of African Skeleton, School of Anatomical Sciences, University of the Witwatersrand, South Africa. Five variables from the upper end of the femur and three variables from the lower end of the femur were measured and subjected to univariate and multivariate discriminant function analyses. The vertical head diameter and the medial condylar length were most successful in sex identification from the upper and lower ends of the femur respectively. The combined variables were more useful than the use of variables individually. Discriminant function score equations were derived for individual and combined variables from the upper and lower ends of the femur of the South African blacks.     

Sexual Dimorphism of the Humerus in Contemporary Cretans—A Population‐Specific Study and a Review of the Literature*

Abstract: Sex determination is the first essential step for positive identification when a decomposed body is recovered. Taking into consideration the population aspect of sexual dimorphism of the skeleton, the present study aimed to create a sex identification technique using osteometric standards, derived from a contemporary Cretan population. A total of 168 left humeri were measured according to standard osteometric techniques. The differences between the means in males and females were significant (p < 0.0005). About 92.3% of cases were correctly classified when all measurements were applied jointly. Stepwise procedure produced an accuracy rate of 92.9%. The most effective single dimension was vertical head diameter (89.9%). The current study provides standards for a population that has not been represented so far in the existing databases. It demonstrates that the humerus is an effective bone for the estimation of sex because even in a fragmentary state it can give high classification accuracy.     

Sex determination from the distal part of the femur in a French contemporary population

Until now, determining the sex of a recently deceased individual using the measurement of the bicondylar breadth of the femur (also known as condylar width, epicondylar breadth and distal epiphyseal breadth) raised some concerns as to accuracy because no sample of contemporary French subjects was available. In this study, a sample of 88 female and male femurs taken from recently deceased elderly French people was studied. The bones were collected from subjects who had donated their bodies to the Medical School of Nice. The mean value of the male bicondylar breadth was found to be greater than that of females (84.3mm versus 74.8mm), confirming the sexual dimorphism of this parameter. Furthermore, the results showed a 95.4% accuracy rate for sexing individuals. To date, in the French population, as in some other samples, epicondylar breadth is the single most accurate measurement of sex determination, ahead even of head diameter. A discriminant function is presented to allow sex determination from remains of the distal femur. With regard to the data available in the literature, sexual dimorphism is probably the result of both genetic and environmental factors. The comparison of our results with those of other populations shows that there are inter-population variations of the bicondylar breadth, and also intra-population variations that account for the differences in the accuracy rate of this variable for the purposes of sex determination. These findings underscore the need to re-evaluate bone measurements within various contemporary populations.     

Discriminating sex in South African blacks using patella dimensions

For many years, sex determination has been carried out on skeletal remains to identify individuals in forensic cases and to assess populations in archaeological cases. Since it has been shown that not all bones are found in a forensic case, discriminant function equations should be derived for all bones of the body to assist in sex determination. Numerous studies have shown the usefulness of bones of the lower extremity (e.g. femur, tibia) in sex determination using discriminant function analysis, but the use of patella measurements has not been extensively investigated for this purpose. It is therefore the aim of this study to derive discriminant function equations for sex determination from measurements of the patella of South African blacks as represented in the Raymond A. Dart Collection of Human Skeletons. A total sample of 120 (60 male, 60 female) patellae were measured using six measurements. The Statistical Product and Service Solutions (SPSS) program was used to derive the equations. Stepwise and direct analyses were performed with the highest rate of classification of 85% thereby making the patella useful for sex determination. Thus, the proposed equations derived from this study should be used with caution and only on the South African black population group.     

Anterior femoral curvature revisited: race assessment from the femur.

The increasing need for accurate race assessment from postcranial skeletal remains has emphasized the lack of simple, replicable methods by which to accomplish the task. Several techniques have been proposed, but without adequate results. Anterior femoral curvature was first suggested and researched by T. Dale Stewart in 1962 (6). The technique used in that study was subjective at best. He provided no substantial discrimination between whites or blacks. Two later studies only reused Stewart's technique and/or data. This study was assumed to address these issues and provide an improved technique. Skeletal collections at the Smithsonian, as well as the forensic collections at the University of Florida and the University of Tennessee, provided the specimens for this study. The historical collection of the First African Baptist Church of Philadelphia, PA, and the modern forensic collection at Louisiana State University provided the test samples. Only black and white individuals were used, and those were selected based on previous soft tissue or positive identification. Thirteen measurements were taken, including six newly developed measures. Age, race, and sex were also documented. Discriminant analysis was used to develop functions for race assessment. After analyzing the data through SPSSx using Discriminant, the variables selected provided an accuracy of 88.15% using the right femur and 86.10% with the left femur. Age was divided into two groups: under 30 and over 30. Most skeletons can be easily aged into these categories.     

Sex determination of Chinese femur by discriminant function

The objective of this study was to provide a method of sex determination for Chinese femur, especially for fragmentary remains. Statistical analysis of 17 measurements based on 141 northeastern Chinese femora shows that all measurements have significant sex differences. Sex determination by the midpoint method of a single measurement can obtain an average accuracy of 76.8%. The results indicate that of all dimensions the maximum head diameter is the best discriminator of sex. It alone can determine the sex of a femur with 85.1% accuracy. The results also show that maximum head diameter, transverse head diameter, epicondylar breadth, upper breadth, and medial condylar length have higher sexual dimorphisms than the dimensions of length. According to the result to stepwise discriminant analysis and the need for sexing fragmentary remains, 22 discriminant functions composed of various combinations of variables were calculated which can determine the sex of the femur correctly 82.3 to 87.2%. The methods of sex determination provided by this paper can be used to sex poorly preserved femora.     

A study of sexual variation in Indian femur

Assessment of sex from femoral dimensions have been tried before in several populations. Studies conducted so far have demonstrated that populations differ from one another in size and proportion. Therefore, the discriminant formulae developed for determining sex for one population group cannot be applied on another. As to date no detailed study of femur on the subject has been reported from India, an attempt has been made in the present study to examine the sexual dimorphism in femur of Indian origin using 124 femora from central India. Eleven standard dimensions were measured on the bones. The data were analysed using discriminant function procedures and the results of different measurements are reported independently and in various combinations. Maximum head diameter alone could correctly assign sex to 92.5% of males and 95.5% of females. Evaluation of the discriminating ability of the variables selected in stepwise analysis are then conducted using cross validation procedure. To understand the population variation, the discriminant formula derived from Thai, Chinese, South African white, American black and white were applied on the present sample. The comparison indicated that Indians have very different dimension from South African whites and American whites. Their dimensions are more closer to Thais and Chinese but in no way identical to them.     

Further evidence to show population specificity of discriminant function equations for sex determination using the talus of South African blacks

Several studies have shown that osteometric differences exist between different population groups. Thus, discriminant function equations derived for the determination of sex from skeletal elements are population specific. In a previous study, the authors derived such equations from nine measurements of the talus of South African whites with high levels of average accuracies. The validity of some of the equations was tested on data collected from a South African black sample that consisted of 120 tali, equally distributed by sex, derived from the Raymond A. Dart Collection of Human Skeletons. The average accuracies dropped significantly. This necessitated the derivation of new equations for the South African black population and the average accuracies obtained ranged between 80% and 89%. The validity of the equations derived from the present study was tested using the leave-one-out classification and two independent samples (1 and 2). The applicability of the equations with very high classification rate from the present study was tested on Independent sample 1 of 10 white tali with poor results. The result of the validity of these equations on an Independent sample 2 of 10 black tali revealed acceptably high average accuracies in correct classification thereby supporting earlier observations on population specificity of discriminant function equations.