Maryna Steyn

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.

Sex determination from the femur and tibia in South African whites

With the current high incidence of violent crimes in South Africa, it has become very important to be able to determine the sex of individuals from their skeletal remains. The aim of this study is to provide standards usable for this purpose, to be used on the contemporary South African white population. Very little skeletal data is available for this group. Osteometric information was obtained from 56 male and 50 female individuals from cadaver collections. Six femoral and seven tibial measurements were taken, and subjected to SPSS discriminant function analysis. The distal breadths from both the femur and tibia provided the best discrimination. Formulae were developed for a number of combinations of measurements, which can be used to determine the sex on fragmentary remains. Average accuracies ranged from 86% to 91%, with female accuracies slightly higher than those of the males. The results of this study compares well with others, e.g., those from American whites.

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.

Sexually dimorphic pelvic morphology in South African whites and blacks

It is well known that there is metric and morphologic variation in the expression of sexual dimorphism between racial phenotypes and populations. Therefore, the purpose of this research is to assess morphologic sex differences in the pelves of South African whites and blacks. Results will be used to improve the identification of human skeletal remains by producing group specific standards. Morphologic features of both left and right os coxae were studied in a sample of 400 known sex/race individuals from the Pretoria and Dart collections. Bones that were clearly pathologic or visibly deformed were excluded from the study. Data were subjected to SPSS analysis. Results indicated that overall, public bone shape was the easiest to assess and was the most consistently reliable morphological indicator of sex in both sexes and population groups. At 88% average accuracy, the most discriminating traits in whites were pubic bone shape and subpubic concavity form. In blacks, greater sciatic notch form allowed the highest separation, averaging 87.5%, followed by pubic shape at 84.5%. Important findings included the fact that there were significant differences in the accuracy of sex determination from pelvic morphology between both males and females and whites and blacks. In conclusion, this study provides quantification of individual morphological traits in the os coxae of white and black South Africans that will be of value in forensic and archaeological analyses, especially when dealing with fragmentary remains. It also demonstrates that population differences affect the expression of sexual dimorphism and must be accounted for to develop the most effective methods of analysis.

Metric sex determination from the pelvis in modern Greeks.

The ability to determine sex from unknown skeletal remains is vital, and methods to do this on the various bones of the human skeleton have been researched extensively. Many researchers have emphasized the need for population specific data for methods which are based on measurements, as there are vast differences in body size in various populations. The pelvis is known to be the most sexually dimorphic part of the human body, and no discriminant function formulae for this bone are available for Greek or other Mediterranean groups. The purpose of this study was therefore to develop discriminant functions which can be used for sex determination on measurements of the pelvis of modern Greeks. A sample of 97 male and 95 female pelves in a skeletal collection housed in Heraklion, Crete, was used. Measurements were taken from the articulated pelvis, single os coxae and the sacrum. Discriminant function formulae for all measurements and various combinations were used in order to assess the degree of sexual dimorphism in various parts of the pelvis, and to make the formulae usable on fragmented remains. For the single os coxae, average accuracies of 79.7-95.4% (79.1-93.5% on cross-validation) were found. However, it was found that measurements of the sciatic notch were unreliable and yielded poor results, and it is advisable that this characteristic must only be used as a last resort. Dimensions of the sacrum were not very dimorphic (average accuracy 60.9%), while measurements from the articulated pelvis yielded poorer results than that from single innominate bones. The diameter of the acetabulum was the single most dimorphic characteristic, providing on average 83.9% accuracy when used in isolation.

Craniometric determination of population affinity in South Africans.

Abstract A vital aspect of skeletal analysis is the determination of population affinity of an unknown individual. The aim of this paper is to develop discriminant function formulae to determine race from craniometric dimensions of South African blacks and whites. Skeletons used in this study came from the Universities of the Witwatersrand and Pretoria. The sample is composed of 53 white males and 53 white females and 45 black males and 45 black females. Using 13 standard cranial and 4 mandibular dimensions, average accuracies of 98% were obtained from the crania, which were much more discriminatory than the mandibles (74% males, 87% females). When a “leave-one-out classification” technique was applied to the sample to measure accuracy of multivariate classification, this accuracy was about the same as obtained from the multivariate function. A posterior probability of 0.80 or more was found in as much as 96% of the sample. Stepwise discriminant function formulae for incomplete remains (vault and face) were also derived. Prediction accuracy was considerably lower when North American based formulae were tested on the South Africans, indicating significant craniometric differences between these populations.

Age Estimation from Sternal Ends of Ribs by Phase Analysis in South African Blacks

The sternal ends of ribs are used in age determination of unknown adult remains. Standards for American populations have been described and tested. The method described by Işcan et al. is reviewed and compared with other age markers of the human skeleton. Three hundred and thirty-nine (265 male, 74 female) sternal ends of right fourth ribs, belonging to black individuals deceased in the Gauteng Province of South Africa, were collected during 1994, 1995, and 1996. Three South African investigators applied the existing method and found the repeatability among them acceptable, although the method was less accurate to predict age in this population. New phases with adjusted criteria and age ranges were developed specifically for the South African black population. A tendency toward delayed maturation was found, as well as a diversion of the appearance of female ribs perimenopausally. Future studies involving more individuals in the older age ranges, and females of all ages, could broaden the representativeness of these phases.

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.

Geometric morphometric analysis of the greater sciatic notch in South Africans.

The width of the greater sciatic notch of the pelvis is a characteristic commonly used to determine sex in unknown individuals. Recent research on South African skeletal material indicated that this feature may not be so reliable, especially in South African white males. In this study the greater sciatic notches of 115 known skeletons of South African origin were analysed using geometric morphometrics. Geometric morphometrics is a relatively new method that helps to quantify shape. Using this method, it was observed that South African black males have the typical narrow shape, while both the black and white females have typical wide notches. The white males, however, showed a very wide variation and their shapes scattered across the range. The shape of the greater sciatic notch is therefore not reliable to use in sex determination in this population group. Geometric morphometric analysis proved to be a valuable and reliable method to verify morphological characteristics observed with more traditional methods.

Facial reconstruction : soft tissue thickness values for South African black females

In forensic science, investigators frequently have to deal with unidentified skeletonised remains. When conventional methods of identification are unsuccessful, forensic facial reconstruction (FFR) may be used, often as a last resort, to assist the process. FFR relies on the relationships between the facial features, subcutaneous soft tissues and underlying bony structure of the skull. The aim of this study was to develop soft tissue thickness (STT) values for South African black females for application to FFR, to compare these values to existing literature or databases and to add these values to existing population data. Computerised tomography scanning was used to determine average population-specific STT values at 28 facial landmarks of 154 black females. Descriptive statistics are provided for these STT values, which were also compared to those reported in three other comparable databases. Many of these STT values are significantly different from those reported for comparable groups, suggesting that individuals from different geographical areas have unique facial features thus requiring population-specific STT values. Repeatability tests indicated that most measurements could be recorded with a high degree of reliability.