Population differences in the postcrania of modern South Africans and the implications for ancestry estimation

The cranium is widely recognized as the most important skeletal element to use when evaluating population differences and estimating ancestry. However, the cranium is not always intact or available for analysis, which emphasizes the need for postcranial alternatives. The purpose of this study was to quantify postcraniometric differences among South Africans that can be used to estimate ancestry. Thirty-nine standard measurements from 11 postcranial bones were collected from 360 modern black, white and coloured South Africans; the sex and ancestry distribution were equal. Group differences were explored with analysis of variance (ANOVA) and Tukey’s honestly significant difference (HSD) test. Linear and flexible discriminant analysis (LDA and FDA, respectively) were conducted with bone models as well as numerous multivariate subsets to identify the model and method that yielded the highest correct classifications. Leave-one-out (LDA) and k-fold (k = 10; FDA) cross-validation with equal priors were used for all models. ANOVA and Tukey’s HSD results reveal statistically significant differences between at least two of the three groups for the majority of the variables, with varying degrees of group overlap. Bone models, which consisted of all measurements per bone, resulted in low accuracies that ranged from 46% to 63% (LDA) and 41% to 66% (FDA). In contrast, the multivariate subsets, which consisted of different variable combinations from all elements, achieved accuracies as high as 85% (LDA) and 87% (FDA). Thus, when using a multivariate approach, the postcranial skeleton can distinguish among three modern South African groups with high accuracy.National Research Foundation of South Africa (NRF)http://www.elsevier.com/locate/forsciint2016-12-31hb201

Evaluating the accuracy of cranial indices in ancestry estimation among South African groups

Historically, population differences were quantified using cranial indices. Even though the application of indices is associated with numerous statistical and methodological problems, the use of cranial indices to estimate ancestry persists as demonstrated by its inclusion in several recent papers and conference presentations. The purpose of this study was to classify 207 South African crania and compare the results of five standard cranial indices to linear discriminant analysis (LDA). New sectioning points were created to contend with low classification accuracies (40% - 79%) and possible secular trends. Although the accuracies of the new sectioning points increased (66% - 87%), the accuracies associated with the stepwise LDA were higher (84%) and could classify the crania into one of the three South African groups. The results of the study demonstrate that indices cannot compete with multivariate techniques and should not be used in forensic anthropological analyses for ancestry estimation.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1556-40292016-09-30hb201

Hominin cranial fragments from Milner Hall, Sterkfontein, South Africa

The Sterkfontein Caves site is one of the richest early hominin localities in Africa. In addition to significant fossil assemblages from Members 2 and 4 of the Sterkfontein Formation, recent excavations have revealed hominin-bearing sedimentary deposits in the lesser-known Milner Hall. We describe two hominin cranial fragments excavated from the Milner Hall in 2015 and present the results of a high-resolution microtomographic-based approach to diagnosing the anatomical and taxonomical origin of these specimens. Based on external morphology, StW 671 and StW 672 are tentatively identified as frontal and occipital fragments, respectively. Our non-invasive bi-dimensional quantitative investigation of the two cranial fragments reveals a mean cranial thickness of 8.8 mm and 5.6 mm for StW 671 and StW 672 respectively and a contribution of the diploic layer to the cumulative cranial thickness that is less than 50%. While the mean cranial thickness of StW 671 falls within the range of Homo, the relative proportion of the diploë in both StW 671 and StW 672 is lower than in Australopithecus (>60%) and extant humans (>50%). Accordingly, in terms of both cranial thickness and inner structural organization, the Milner Hall hominins combine derived and unique traits, consistent with the condition of other postcranial and dental material already described from the deposit. Moreover, our study opens interesting perspectives in terms of analysis of isolated cranial fragments, which are abundant in the hominin fossil record. Significance: The Sterkfontein Caves have widely contributed to our understanding of human evolution. Besides the well-known Members 4 and 2, where the iconic ‘Mrs Ples’ and ‘Little Foot’ have been found, in this study we suggest that the Milner Hall locality represents an additional, stratigraphically associated source of not only fossil hominins, but also Oldowan stone tools. In particular, we describe for the first time two cranial fragments, StW 671 and StW 672, identified as frontal and occipital bones, respectively. Our microtomographic-based analysis of these materials reveals some affinities with Homo combined with unique characters. In this context, our study suggests an intriguing mosaicism consistent with the description of the two fossil hominins found in the Milner Hall

The Pretoria Bone Collection: A 21st Century Skeletal Collection in South Africa

The Pretoria Bone Collection (PBC) began in 1942 with the opening of a medical school at the University of Pretoria (UP) in Pretoria, South Africa, where this skeletal collection is housed in the Department of Anatomy. The purpose of this paper is to provide information on the national legislation associated with obtaining, curating and researching skeletal remains in South Africa, the demographic composition of the PBC, and the inclusion of a portion of these remains into a digital repository known as Bakeng se Afrika (BsA). The PBC comprises 873 complete skeletons, 344 complete postcrania without crania, and 308 complete crania without postcrania. Skeletal contents are reflective of the population statistics of South Africa, with a smaller proportion of White (32%) than Black (65%) South Africans. Unlike the population profile, males in the PBC are greater in number (75.5%) than females (24.5%), which may be explained by the number of migrant labourers traveling into a large city such as Pretoria. From this sample, crania (206), maxillae (141), mandibulae (408), femora (137), and radii (134), as well as several other skeletal elements were micro-XCT scanned and are available on the BsA server. A researcher needs to submit an online application to the Human Research Ethics Committee (HREC) of the Faculty of Health Sciences at the University of Pretoria for access to these collections