Repeatability of a morphoscopic sex estimation technique for the mental eminence on micro-focus X-ray computed tomography models

Objectives Walker's sex estimation method is based on five morphoscopic features of the human skull. This study aimed at testing the repeatability of one of the five traits, the mental eminence, visually on three-dimensional (3D) models, compared to the traditional, tactile scoring approach on bone. Materials and methods The sample comprised 105 mandibles from the Pretoria Bone Collection and their respective virtual 3D models, obtained from micro-focus X-ray computed tomography (micro-XCT) scans. Four observers independently scored the bones first, followed by the virtual 3D modality. Intra- and interobserver errors (interOE and intraOE) were performed with Fleiss’ and Cohen's Kappa, respectively. We calculated the intermodality agreement per observer with Wilcoxon Signed-Rank tests. Results The intraOE was moderate on bone (κ=0.448) and substantial on 3D (κ=0.799), while the Fleiss’ Kappa test for the interOE resulted in slight agreement both on bone (κ=0.163) and 3D (κ=0.169) irrespective of level of experience. All Wilcoxon Signed-Rank test P-values were significant. Discussion and conclusion The application of the morphoscopic sex estimation for the mental eminence to micro-XCTs could be a matter of personal affinity as the level of experience did not play a role in the results. The expression of the mental eminence trait being population-specific, the individual's population affinity should be considered when sex is estimated in South African skeletons. It remains unclear whether the slight agreement between observers is due to the unreliability of the trait for sex estimation or whether the modalities are not easily interchangeable

Distribution quantitative morphological variation and preliminary molecular analysis of different growth forms of wild rooibos (Aspalathus linearis) in the northern Cederberg and on the Bokkeveld Plateau

Aspalathus linearis (Fabaceae) is endemic to the Cape Floristic Region in the Western Cape and Northern Cape Provinces of South Africa. The reddish leaves and stems, primarily of one cultivar, are used to make a commercially important tea which is marketed locally and internationally as ‘rooibos’ or ‘redbush’ tea. In historical times rooibos was collected in the wild. In the twentieth century cultivation of a single cultivar increasingly replaced wild harvest to meet growing demand. Recently, tea from wild forms of the species, which vary significantly in growth form and reproductive strategy, has been marketed by small-scale farmers in Wupperthal and on the Suid Bokkeveld plateau in the northern part of the species' distribution. Little information on the wild forms of this species has been published, although a rich body of knowledge exists amongst local harvesters and other land-users. In this study, we focus on the northern part of the species’ distribution area where wild rooibos is harvested for commercial sale to niche organic and fair-trade markets. We adopt a transdisciplinary approach to (1) document the different growth forms, (2) develop a bioclimatic model of the potential distribution of the species, (3) quantify the morphological variation that exists between growth forms relative to the established cultivar and (4) use molecular techniques to provide a preliminary insight into the infraspecific diversity of different wild A. linearis growth forms. Our results show that local land users in the region identify four main growth forms of wild A. linearis. These are an ‘erect form’ and a ‘prostrate form’ in the Wuppertal area, a ‘shrub form’ in the Suid Bokkeveld, and a ‘tree form’ that has been observed at specific sites at Wupperthal, Biedouw and the Suid Bokkeveld. The PCA analysis of seven morphological traits identified three growth forms, which support the land user descriptions except in the case of the 'tree' and 'erect' forms which co-occurred in coordinate space. Both shrub and prostrate forms are wider than they are taller and possess more stems closer to the ground than erect forms. While the stems of both shrub and prostrate forms lie relatively flat on the ground, stem thickness is significantly greater in shrub forms. The tree type, the erect form and the cultivar studied possess the highest harvestable biomass. Prostrate forms and shrub forms resprout after fire while erect and tree forms regenerate from seed only. Haplotypic variation was assessed using DNA sequences from a single chloroplast region and revealed strong genetic differences between the different growth forms. Although preliminary, there is some evidence that sprouting and nonsprouting forms of the species are genetically isolated. This has important taxonomic implications for the species. Additional chloroplast regions and a nuclear region were also identified as variable and potentially useful markers for a multi-locus molecular approach to studying taxonomic and ecological questions within the species

Evaluation of age, sex, and ancestry-related variation in cortical bone and dentine volumes in modern humans, and a preliminary assessment of cortical bone-dentine covariation in later Homo.

Cortical bone and dentine share similarities in their embryological origin, development, and genetic background. Few analyses have combined the study of cortical bone and dentine to quantify their covariation relative to endogenous and exogenous factors. However, knowing how these tissues relate in individuals is of great importance to decipher the factors acting on their evolution, and ultimately to understand the mechanisms responsible for the different patterns of tissue proportions shown in hominins. The aims of this study are to examine age-, sex-, and ancestry-related variation in cortical bone and dentine volumes, and to preliminary assess the possible covariation between these tissues in modern humans and in five composite Neandertals. The modern analytical sample includes 12 immature individuals from France and 49 adults from France and South Africa. Three-dimensional tissue proportions were assessed from microtomographic records of radii and permanent maxillary canines. Results suggest ontogenic differences and a strong sexual dimorphism in cortical bone and dentine developments. The developmental pattern of dentine also seems to vary according to individual's ancestry. We measure a stronger covariation signal between cortical bone and dentine volumes than with any other dental tissue. A more complex covariation pattern is shown when splitting the modern sample by age, sex, and ancestry, as no signal is found in some subsamples while others show a covariation between cortical bone and either crown or radicular dentine. Finally, no difference in cortical bone volume is noticed between the modern young adults and the five young adult composite Neandertals from Marine Isotopic Stages (MIS) 5 and 3. Greater dentine Cortical bone and dentine (co)variation volumes are measured in the MIS 5 chimeric Neandertals whereas a strong interpopulation variation in dentine thickness is noticed in the MIS 3 chimeric Neandertals. Further research on the cortical bonedentine covariation will increase understanding of the impact of endogenous and exogenous factors on the development of the mineralized tissues

Analysis of the hard-tissue menton shape in adult South Africans using cone-beam computed tomography (CBCT) scans

Background: In forensic anthropology, the biological profile is based on human variation. To increase understanding shape variation of the mental region, this study analyzed the influence of population affinity and sex on the menton in adult black and white South Africans, using geometric morphometric methods (GMM). Methods: We used cone-beam computed tomography (CBCT) scans of 291 adult dental patients from the Oral and Dental Hospital, University of Pretoria. We placed eleven standard craniometric landmarks on the menton, mandible, and maxilla of three-dimensional (3D) reconstructions by automatic landmarking and analyzed them by applying GMM. In addition, a subtle shape matrix of seven landmarks was created for a focused analysis of the menton only. Finally, we tested the reproducibility of the landmarks placement with a dispersion analysis. Results and Discussion: The landmarks used in this study were reproducible, with an overall dispersion of less than 1 mm. Population affinity significantly influenced menton shape, with P-values = 0.001 in the complete sample and within the sex groups. Differences between sexes for these seven landmarks were also statistically significant (P-values 0.001 to 0.003) in the complete sample, but not within population groups in isolation. The accuracy for estimation of population affinity by discriminant function analysis was 86.9%. Conclusion: The automatic landmarking improved landmark reproducibility. Population affinity and sexual dimorphism significantly influenced menton shape. However, shape analysis, including all eleven landmarks, was not significantly influenced by sex. This study supports further research focusing on the facial approximations for forensic identification in South Africa