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

BACKGROUND/OBJECTIVE : In forensic anthropology, the biological profile is based on human variation and can help in the process of personal identification. In order to better understand 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). MATERIALS AND METHODS : We used cone-beam computed tomography (CBCT) scans of 291 adult dental patients with dentition patterns up to Eichner Index B3, retrospectively collected from the Oral and Dental Hospital, University of Pretoria. We placed eleven standard craniometric landmarks on the menton, mandible, and maxilla of threedimensional (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 : 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 (Pvalues between 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 use of 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.UP Postgraduate Bursary and the Bakeng se Afrika funding.https://www.sciencedirect.com/journal/forensic-imagingam2024AnatomySDG-03:Good heatlh and well-bein

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

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

Human evolution in the South African school curriculum

A decade after the introduction of the topic into the South African public school curriculum, the theory of evolution by natural selection is poorly understood among those who teach it, and that flawed understanding is transferred to those attempting to learn it. The curricula, support material and textbooks designed to underpin teaching and learning of evolution are often inaccurate. Deeply held religious views in the country, especially Christianity, remain a stumbling block towards understanding and accepting evolution. The lack of scientific literacy allows for the continuation of Social Darwinism and racial stereotypes and deprives the victims of those ills of the knowledge and mechanisms of thought to counter these ideas. This review explores the relatively sparse but nevertheless well-conducted research into evolution education in South Africa. We conclude that an understanding of human evolution is essential to the country’s growing democracy because it provides a framework within which South Africans can understand and appreciate the diversity and heterogeneous nature of our society. Significance: Various obstacles in the teaching and learning of evolution are identified, and generalisable recommendations are provided to improve evolution education on a practical level. Evolution education is important for the South African public: to take pride in our rich fossil resources; to understand and appreciate human diversity; to dispel the racist myths of Social Darwinism; and to ensure the success of our education system by teaching the consilience of induction and logical reasoning. This synthesis of the research provides a starting point for anyone wanting to conduct evolution education research in South Africa in the future, specifically those in the fields of curriculum reform, life sciences or biological anthropology

Human evolution in the South African school curriculum

A decade after the introduction of the topic into the South African public school curriculum, the theory of evolution by natural selection is poorly understood among those who teach it, and that flawed understanding is transferred to those attempting to learn it. The curricula, support material and textbooks designed to underpin teaching and learning of evolution are often inaccurate. Deeply held religious views in the country, especially Christianity, remain a stumbling block towards understanding and accepting evolution. The lack of scientific literacy allows for the continuation of Social Darwinism and racial stereotypes and deprives the victims of those ills of the knowledge and mechanisms of thought to counter these ideas. This review explores the relatively sparse but nevertheless well-conducted research into evolution education in South Africa. We conclude that an understanding of human evolution is essential to the country’s growing democracy because it provides a framework within which South Africans can understand and appreciate the diversity and heterogeneous nature of our society. Significance: Various obstacles in the teaching and learning of evolution are identified, and generalisable recommendations are provided to improve evolution education on a practical level. Evolution education is important for the South African public: to take pride in our rich fossil resources; to understand and appreciate human diversity; to dispel the racist myths of Social Darwinism; and to ensure the success of our education system by teaching the consilience of induction and logical reasoning. This synthesis of the research provides a starting point for anyone wanting to conduct evolution education research in South Africa in the future, specifically those in the fields of curriculum reform, life sciences or biological anthropology

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