Ancestral variation in mid-craniofacial morphology in a South African sample

Ancestry estimation is a critical component of the demographic profile compiled by forensic anthropologists when unknown skeletal remains are discovered. The mid-craniofacial region is most frequently used to estimate ancestry as this region reflects the genetic and morphological ancestry of an individual. The diverse composition of the South African population makes ancestry estimation problematic, and necessitates the development of reliable, population-specific standards. This study sought to characterise variations in mid-craniofacial shape and size between South Africans of European ancestry (EA), African ancestry (AA) and Mixed ancestry (MA). Metric, nonmetric and geometric morphometric assessments were performed on 392 crania from skeletal collections in South Africa. Variations in mid-craniofacial shape and size were assessed in the orbital, nasal, zygomatic and maxillary regions in two-and three-dimensions. Univariate and multivariate statistical analyses were employed to characterise variation and estimate ancestry in AA, MA and EA individuals. Multivariate analyses suggest that tightly integrated ancestral variations in each component of the mid-craniofacial region are associated with functional, regional and developmental proximities of these regions. Specifically, AA individuals exhibited wider and shorter midfacial regions than EA individuals, who exhibited the narrowest orbital, zygomatic and nasal breadths and the longest upper facial, orbital and nasal heights. EA individuals exhibited inferiorly-angled orbits, elongated nasal apertures and anteriorly projecting nasal bridges. Rounder nasal apertures, less anteriorly projecting nasal bridges and more anteriorly projecting maxillary regions were detected in AA individuals. MA individuals exhibited heterogeneity in terms of craniofacial shape and size, and therefore produced the lowest ancestry estimation accuracies. Overall, nasal and maxillary regions were the most ancestrally diverse regions. Antemortem maxillary tooth loss and midfacial trauma were confounding factors in ancestry estimation accuracies. The lowest ancestry estimation accuracies were yielded by two-dimensional metric (27%-60.2%) and nonmetric (57.1%-82.4%) methods. Metric and geometric morphometric assessments yielded the highest repeatability (≥ 95%) indicating that these methods may be more reliable for use in medicolegal contexts. Geometric morphometric shape assessments yielded the highest ancestry estimation accuracies (75-97.9%), suggesting the presence of three dimensional shape variations between ancestry groups. These results suggest that a continuum of ancestral variation, with large areas of overlap, exists across South African populations and emphasises the need to develop multivariate ancestry estimation standards which can estimate ancestry reliably

Socio-ecological risk factors, explanatory models and treatment-seeking behaviours associated with Mseleni joint disease: a biocultural mixed methods study

Mseleni Joint Disease (MJD) is a crippling osteoarthropathy of unknown aetiology endemic to southern African Bantu-language speakers in a remote region of Northern KwaZulu-Natal, South Africa. Effective management of MJD has been hindered by limited insight into risk factors, explanatory models or treatment-seeking behaviours in those affected. Until MJD is better understood, disability, unemployment and dependence on social assistance grants and family income for subsistence will remain a reality for those affected. A mixed methods study was conducted with the aims of examining risk factors, explanatory models and treatment-seeking behaviours associated with MJD. The distribution, differential diagnosis and treatment of MJD were statistically analysed using medical records (n=723), MJD-patient surveys (n=37) and a meta-analysis. Socio-economic and cultural risk factors were assessed from surveys (n=99) and census publications. Interviews with MJD patients (n=6), nurses (n=7) and doctors (n=9) were qualitatively analysed for themes pertaining to perceptions, experiences and treatment-seeking for MJD. A point prevalence of 9% was estimated. Women were nearly twice as likely to have MJD than men (OR= 1.89; p=0.03) and the likelihood of MJD increased almost three-fold in those older than 50 years (OR= 2.83; p<0.01). Age was a confounder of the association between gender and MJD, as the sample was skewed in the representation of elderly women. MJD was only detected in patients older than 35 years, indicative of a later onset age than previously reported. The prevalence of MJD in settlements along tar and concrete roads, with access to public transport but limited piped water was suggestive of environmental risk factors or differential access to hospital-based care. Explanatory models of MJD were supernatural (witchcraft or ancestral displeasure); natural (nutritional deficiencies, 'genetics' and/or environmental); and/or social (gender-based practices and lifestyle). MJD patients described supernatural and natural aetiologies, and conceptualised disability as an inevitable reality. Consequently, patients reported taking few measures to prevent joint immobility, focussing instead on immediate symptomatic relief. Psychosocial and systemic barriers to treatment were suggestive of a disconnect between traditional African healing and Western biomedicine. This work demonstrates the value of the biocultural approach in identifying spatial, ecological, social and cultural processes that shape population patterns of health and disease