Assessing the sexual dimorphism of the upper limb in a Free State skeletal population using univariate measurements
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Date
2020-11
Authors
Smal, Sunette Amanda
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Publisher
University of the Free State
Abstract
Increasing numbers of incomplete unidentified skeletal remains requiring anthropological analysis have created the need for studies of bones other than the pelvis and cranium for sex estimation purposes. This study evaluated the use of 20 measurements of the radius, ulna, humerus, scapula and clavicle of 30 males and 30 females from a Free State skeletal collection. Measurements were assessed for side differences and sexual dimorphism. Sectioning points were calculated for each measurement and used to classify the sex of each individual with the accuracies of classifications also being calculated and compared to those obtained using existing classification standards. All measurements showed a significant positive correlation to each other, ranging from moderate (R=0.6) to very strong (R=0.99), reflecting the proportional biological relationship between body dimensions. Males were larger than females for all measurements (p<0.001), despite large overlaps in the ranges, reflecting the genetic and adaptive differences between the sexes. The largest proportional difference between the means of the males and females was found in the sagittal diameter at the midshaft and the acromial epiphyseal width of the clavicle, as well as in the anterior-posterior diameter at the midshaft of the radius, while the smallest was found in the maximum lengths of the radius, ulna, humerus and clavicle. Classification of sex based on the Free State derived sectioning points of each measurement was most accurate for measurements taken at joints or muscle attachment sites, such as the vertical head diameter of the humerus and the sagittal diameter at the midshaft of the clavicle with accuracies of more than 90%. The least accurate measurement for classification of sex was the acromial epiphyseal width (71.67%), which may have been as a result of the different type and rates of ossification of the clavicle affecting the variability of its morphology beyond sexual differences. For most measurements, the Free State-derived sectioning points performed better than those of the existing sectioning points and the existing classification standards, suggesting that regionally specific standards for classification may be useful. These results indicate that there is sufficient dimorphism in the upper limb bones to allow for accurate classification of sex in this Free State skeletal sample, but that differences in expression of dimorphism may exist between regional South African populations and may need to be considered when deciding which measurements to use for sex estimation. Further studies on the need for such regionally specific standards would be useful in the South African context.
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Keywords
Dissertation (M.Med.Sc. (Anatomy and Cell Morphology))--University of the Free State, 2020, Skeletal, Sex estimation, Sexual dimorphism, Univariate measurements, Upper limb, Bones, Free State, South Africa