Sexual dimorphism in cranial morphology among modern South Africans

Pattern expressions of morphoscopic cranial traits vary across populations with classification accuracies being highly dependent on the reference collection to which unknown skulls are compared. Despite recent developments in populationspecific standards for South Africans, researchers have not addressed the accuracy of morphological methods. Several studies demonstrate differences in sexual dimorphism between South Africans and North Americans, warranting a need to re-evaluate sex estimation methods in South Africa. The purposes of this study were to test the reliability and accuracy of the Walker (2008) method and to examine patterns of sexual dimorphism among South Africans. A total of 245 modern Black and White South African male and female crania from the Pretoria Bone Collection, University of Pretoria, were scored using theWalker (2008) methodology. Cohen’s kappa was used to evaluate reliability of the method, and percent correct assessed validity of the method. Logistic regression was utilised to create modified population-specific formulae. Inter- and intra-observer agreement was moderate to excellent (0.60–0.90), except for the mental eminence (0.40). The percent correct results for sex were 80%or higher for combinations of glabella,mastoid andmenton and between 68 % and 73 % for menton, mastoid, orbital and nuchal margin using logistic equations of Walker (2008). White males had the highest (94–97 %) and White females had the lowest (31–62 %) percent correct. The low accuracies obtained when using Walker’s (2008) equations emphasised the need for population-specific sex estimation models. Modified formulae for South Africans were created, yielding higher classification rates (84–93 %) than when North American standards were employed.National Research Foundation (NRF)http://link.springer.com/journal/4142016-07-31hb201

Age estimation from the acetabulum in South African black males

Anthropologists are constantly seeking to improve methods for age estimation in the human skeleton. A new method was introduced about a decade ago that assesses the morphological changes that take place in the acetabulum as an individual ages. The pelvis is usually well preserved in forensic cases, which makes this method potentially valuable as an adult age indicator. This method employs seven variables, each with its own set of phases. To test the accuracy and reliability of this method, 100 black South African male acetabula from the Pretoria Bone Collection were assessed based on the criteria described in the original study. Box plots and transition curves were constructed to establish whether progression with age was visible and how it could possibly be modelled. Inter-observer reliability was also assessed by making use of Fleiss’s Kappa statistic. Five specimens were used as out-of-sample examples for which maximum likelihood (point) estimates were calculated. The results demonstrated that middle and older individuals’ age estimates were vastly underestimated. Inter-observer repeatability was poor, which suggested that the classification system most likely needs to be modified. A discussion and recommendation is given for improvement of reliability and repeatability of this method.The National Research Foundation (NRF) of South Africahttp://link.springer.com/journal/4142017-05-30hb201