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.     

Discriminant function sexing of the mandible of indigenous South Africans

South Africa currently has a high homicide rate. This results in a large number of unidentified bodies being recovered each year, many of which are referred to the forensic examiner. This situation has resulted in considerable growth of forensic anthropological research devoted to devising standards for specific application in South African medico-legal investigations. The standards suitable for Black South Africans now encompass a wide variety of skeletal elements (e.g. cranium, humerus, pelvis, femur, patella, talus, calcaneus), each with differing degrees of accuracy. Apart from a preliminary investigation of the Zulu local population, however, we note that there appears to be no established metric mandible discriminant function standards for sex determination in this population. The purpose of the present study is to undertake a comprehensive analysis of sexual dimorphism in the mandible of Black South Africans, incorporating individuals from a selection of the larger local population groupings; the primary aim is to produce a series of metrical standards for the determination of sex. The sample analyzed comprises 225 non-pathological mandibles of Black South African individuals drawn from the R.A. Dart Collection. Nine linear measurements, obtained from mathematically transformed three-dimensional landmark data, are analyzed using basic univariate statistics and discriminant function analyses. All of the measurements examined are found to be sexually dimorphic; the dimensions of the ramus and corpus lengths are most dimorphic. The sex classification accuracy of the discriminant functions ranged from 70.7 to 77.3% for the univariate method, 81.8% for the stepwise method, and 63.6 to 84% for the direct method. We conclude that the mandible is a very useful element for sex determination in this population.     

Improving Sex Estimation from Crania Using a Novel Three‐dimensional Quantitative Method,,

This study utilizes an innovative 3D approach to discover metric variables that obtain the highest classification rates for sex estimation from the cranium. Models were constructed from 222 cranial CT scans of U.S. Whites from the Bass Donated Collection. These models were used to create a statistical bone atlas that captures the primary shape variation in the skull and facilitates rapid computer‐automated analyses. The bone atlas showed that important size‐related sex variables are bizygomatic breadth, maximum cranial length, cranial base length, and mastoid height. Shape‐related variables capture sex differences in the projection of the glabellar region, inclination of the frontal, and cranial base flexion. In addition, vault thickness is highly dimorphic, with females having on average thicker vaults in the frontal region, and males having thicker vaults in the occipital region. Cross‐validated linear discriminant analysis obtained >95% accuracy (97.5% with 11 variables and 95.5% with eight variables).     

Sexual dimorphism of the calcaneus of South African blacks

Forensic anthropology is a rapidly growing field in South Africa and skeletal biologists are often called upon by the police to assist in personal identification from skeletal remains, which are recovered in suspected cases of homicide and suicide and in mass disaster. Measurements of the calcaneus have been shown to be sexually dimorphic in South African whites. Since the validity of discriminant function equations in sex determination is population specific, the aim of the present study was to derive similar equations for the calcanei of the South African blacks. The bones that were used in this study were obtained from the Raymond A. Dart Collection of Human Skeletons, School of Anatomical Sciences, University of the Witwatersrand, Johannesburg. One hundred and sixteen (116) intact and non-pathological calcanei, consisting of 58 males and 58 females and belonging to individuals whose age at death ranged between 22 and 75 years, were selected by the simple random sampling technique. The measured variables included the maximum length, the load arm length, the dorsal articular facet length, the body height, the maximum height, the cuboidal facet height, the middle breadth, the dorsal articular facet breadth and the maximum breadth. Discriminant function analyses were done using the Statistical Product and Service Solutions (SPSS) program. All measured parameters of the calcaneus showed significant sexual differences. Length measurements were found to be the most sexually dimorphic. Combinations of variables provided better estimate of sex (79%-86%) than individual variables (64%-79%).     

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.     

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.     

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.     

Craniometric analysis of the modern Cretan population

Despite the fact that sex assessment using craniofacial characteristics is commonly made worldwide, a lack of such investigation is noted in the Balkan area and in Greece in particular. The aim of this study is to develop a sex determination technique using osteometric data from skeletal remains of a contemporary Cretan cemetery population.A total of 90 males and 88 females are measured according to standard osteometric techniques. Age differences are not significant (mean age for men = 68.94 ± 13.41, N = 66; for women = 73.21 ± 16.77, N = 66). A total of 16 dimensions taken from the craniofacial skeleton are used and data are analyzed using SPSS subroutines. A comparison is made with other contemporary populations, including Americans (Terry collection) and South Africans (Dart and Pretoria collections), as well as an archaeological sample (Middle and Late Helladic) from Crete.Results indicate that males are statistically significantly greater than females in all dimensions. Bizygomatic breadth is the most discriminatory single dimension and can provide an accuracy rate of 82% on average. Using a stepwise method involving five dimensions (bizygomatic breadth, cranial length, nasion–prosthion and mastoid height and nasal breadth), accuracy is raised to 88.2%. Interestingly, cranial length is selected as the first discriminating variable by the stepwise analysis when only the neurocranium is available for measurement.     

Estimation of sex from hand and handprint dimensions in a Western Australian population

A number of recent studies have demonstrated that sex can be estimated with a high degree of expected accuracy through the analysis of anthropometric measurements of the hand. Presently, however, the majority of previous related research has been focused on a limited range of global populations. The aim of the present study, therefore, is to evaluate the accuracy of using anthropometric hand measurements for the estimation of sex in a contemporary adult Western Australian population; we also assess if sex can be accurately estimated from the measurement of handprints. The study sample comprises a total of 91 male and 110 female individuals; documented mean age for the males is 38 years (range 19-68) and for the female sample it is 36 years (range 18-63). A total of six linear measurements are taken from each hand and its corresponding print. Measurement data is analysed using basic univariate statistics and a series of direct and stepwise discriminant function analyses are performed to assess the sex classification potential of the hand and handprint variables. All six hand and handprint measurements are sexually dimorphic and sex explains 28.4-61.7% of the sample variance. The breadth and length of the hand contribute most significantly to sex discrimination; cross-validated sex classification accuracies range between 82.6 and 96.5% with a sex bias of ≤5%. We conclude that anthropometric measurements of the hand and handprint can be used to classify sex with a high degree of expected accuracy in a Western Australian population.     

成人颅骨宽度的性别判别分析

为用颅骨判定性别提供依据。应用判别分析方法对收集东北地区已知性别成年男性和女性颅骨40具的颅骨宽度10个指标的性别差异进行分析。结果发现,10个指标中有7项性别差异显著(P<0.05),应用判别分析方法获得4个判别函数方程式,其判别率为96.3%～97.5%,本研究为可用颅骨判定性别提供新的依据。     

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.     

Application of Fordisc 3.0 to Explore Differences Among Crania of North American and South African Blacks and Whites,

Using discriminant function analysis, classification accuracies for ancestry and sex in white and black South Africans were compared using North American (FDB), African groups in Howells (HDB), and South African (SADB) databases in FORDISC 3.0. (FD3). Twenty‐four standard linear measures were collected from a total of 86 black and 101 white crania obtained from the Pretoria Bone Collection. White and black South Africans classified 73% correctly in FDB, 55% correctly in HDB, and 71% correctly in SADB. The percentage of atypical cases was higher with FDB than SADB. In all three databases, misclassification occurred more with sex than ancestry revealing differences in sexual dimorphism between population groups. Broad ancestral differences may explain low misclassification rates for ancestry. FD3, with a modern South African reference sample, can assist South African anthropologists to standardize methodology and to justify procedures for estimating ancestry.     

西南地区成人面颅骨的性别判定

目的建立适合西南地区成人的颅骨性别判定函数。方法性别明确的颅骨67个,测量颅骨最大长、颅骨最大宽、颅高等16项指标,所得数据进行统计学分析,建立单一变量及多变量性别判定方程,并对5个无名颅骨进行回带检验。结果 16项指标中有13项存在显著的性别差异,男性大于女性,单变量函数推断性别以鼻高(男78.4%,女83.3%)、颅骨最大长(男83.8%,女73.3%)准确率较高。多变量性别判定函数以颅周长、鼻高贡献最大,判定准确率男89.2%,女90.0%。结论单变量推断颅骨性别以鼻高或颅骨最大长较为理想,但以颅周长、鼻高联合推断性别准确率更高。     

An assessment of the accuracy of discriminant function equations for sex determination of the femur and tibia from a South African population

The purpose of this study is to test the accuracy of seven discriminant function equations that have been derived by Steyn and Is?an for sex determination using measurements of the femur and tibia of South Africans of European descent (SAED). While the validity of some of the discriminant functions has been assessed by the authors who derived them, no previous independent study has been carried out to assess the accuracy of these equations. These equations have not been tested on skeletons located outside of the Gauteng province. A suite of measurements were taken on 272 femora and 256 tibiae obtained from four South African skeletal collections. The validity of each of the previously published equations for the femur was confirmed. However, two functions of the tibia showed low accuracy rates, most likely due to difficulties in recording the distal epiphyseal breadth measurement, and thus were found to be poor assessors 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 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.     

Testing the validity of population-specific sex estimation equations: An evaluation based on talus and patella measurements

Sex estimation is essential for forensic scientists to identify human skeletal remains. However, the most sexually dimorphic elements like pelvis or skull are not always assessable. Osteometric analyses have proven useful in sex estimation, but also to be population specific. The main purpose of this study was to test the validity of contemporary Greek and Spanish discriminant functions for the talus and the patella, respectively, on a Swiss skeletal sample and to quantify the utility of the measurements as a novel approach in osteometric sex assessment.Four talus and three patella measurements on dry bone were obtained from 234 individuals of the modern cemetery SIMON Identified Skeletal Collection. The previously derived discriminant functions were applied, accuracies determined, the utility of the different measurements was assessed and new multivariable equations constructed.Accuracies varied between 67% and 86% for talus and 63% and 84% for patella, similar to those reported by the original studies. Multivariable equations should be preferred over equations based on single measurements and combining the most significant measurements rather than using several variables obtained the best possible accuracy. The new discriminant functions did not provide a substantial improvement to the original ones. The overall utility of talus and patella is limited, allowing sex estimation with sufficient certainty only in a small proportion of individuals.Discriminant functions developed in contemporary Greek or Spanish populations are in principle applicable also to Swiss contemporary populations. We recommend that at present existent studies of this type should be validated and tested rather than developing new formulas.     

Osteometric variation in the humerus: sexual dimorphism in South Africans

There has been a surge of research on forensic anthropology in South Africa. Differences between the populations of this country and others are demonstrated in many studies. Yet, many forensic osteometric techniques based on other populations are still in use. The purpose of the present study is to develop an osteometric sex determination technique using the humerus. The sample is composed of skeletons of 104 whites and 88 blacks from the Dart and Pretoria collections. Six humeral dimensions were initially analyzed using stepwise discriminant function statistics. Humeral head diameter, deltoid tuberosity circumference and epicondylar breadth were individually calculated in order to make the technique usable for fragmented remains. The results indicated that the head and epicondylar diameters are the best in whites to differentiate sexes from each other, while head diameter and maximum length are best in blacks. Accuracy of correct classification was as high as 96% in whites and 95% in blacks. Crossvalidation provided the same accuracy as the original classification. These accuracy percentages are as high as those expected from the femur and tibia. Posterior probability, which measures the percent affiliation of the sample with its original sex group, was also mostly 80% or better. South African collections are ideal for osteometric analysis, because they are still growing in numbers with cross-sectional representatives from the country.     

Morphometric Analysis of the Neurocranium in an Adult South African Cadaveric Sample,

Craniometric studies of South Africans yield high accuracies of sex and ancestry classification, but most assess only inter‐group variation of Black and White individuals, excluding the highly heterogeneous Colored group, which constitute a significant proportion of the population. This study applied a geometric morphometric approach to the neurocrania of 774 Black, Colored, and White individuals to assess sex and ancestry estimation accuracy based on the detected morphological variation. Accuracies of 70% and 83% were achieved for sex and ancestry, respectively, with ancestry‐related variation contributing the largest proportion of overall observed variation. Even when comparing the closely related Black and Colored groups, relatively high accuracies were obtained. It is thus recommended that a similar approach be used to develop a contemporary three‐dimensional database, which can be used to objectively, reliably, and accurately classify unknown remains in the South African forensic context.