Race and global patterns of phenotypic variation

Highlights• Population data for facial soft tissue thickness (STT) of Black and Coloured South African children are provided for facial reconstruction / approximation of juvenile remains.• STT data should be pooled as two age groups subdivided at age 10 with ancestry taken into account.• Sex should not be considered as it seems not to impact STT with more than 2 mm at any landmark.• STTs in Coloured children are generally larger than in Black children. AbstractIn children, craniofacial changes due to facial growth complicate facial approximations and require specific knowledge of soft tissue thicknesses (STT). The lack of South African juvenile STT standards of particular age groups, sex and ancestry is problematic. According to forensic artists in the South African Police Service the use of African-American values to reconstruct faces of Black South African children yields poor results. In order to perform a facial approximation that presents a true reflection of the child in question, information regarding 2 differences in facial soft tissue at different ages, sexes and ancestry groups is needed. The aims of this study were to provide data on STT of South African Black and Coloured children and to to assess differences in STT with respect to age, sex and ancestry. STT was measured using cephalograms of South African children (n = 388), aged 6 -13 years. After digitizing the images, STT measurements were taken at ten mid-facial landmarks from each image using the iTEM measuring program. STT comparisons between groups per age, sex and ancestry were statistically analyzed. The results showed that STT differences at lower face landmarks are more pronounced in age groups per ancestry as opposed to differences per age and sex. Generally, an increase in STT was seen between 6 -10 year old groups and 11 -13 year old groups, regardless of ancestry and sex, at the midphiltrum, labiale inferius, pogonion, and beneath chin landmarks.This research created a reference dataset for STT of South African children of Black and Coloured ancestry per age and sex that will be useful for facial reconstruction / approximation of juvenile remains.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Soft tissue thickness values for black and coloured South African children aged 6–13 years

Briers¹,

Briers²,

Becker³

et al. 2015

“…South Africa provides a testament to how geographical and social factors can influence population variation. The wide range of morphological variation among groups in South Africa is the cumulative result of varying geographic origins, unique population histories and structure, positive assortative mating and social and/or political barriers [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

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

Liebenberg

L'Abbé

Stull

2015

Highlights AbstractThe 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 2 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.

“…Social race is a concept of identification based on cultural, historical or familial affiliation and has no biological reality [1][2][3][4]. However, morphological differences are recognized among groups because positive assortative mating, geographical distances, and social forces act as barriers for gene flow, thus limiting group interaction and increasing the variation between groups [5][6][7]. In turn, forensic anthropologists quantify morphology to estimate ancestry, or social race, which provides practical information that is useful in a medico-legal setting [2,5].…”

Section: Introductionmentioning

confidence: 99%

Ancestry estimation in South Africa using craniometrics and geometric morphometrics

Stull

Kenyhercz

L'Abbé

2014

Population history and positive assortative mating directs gene flow in such a way that biological differences are recognized among groups. In turn, forensic anthropologists quantify biological differences to estimate ancestry. Some anthropologists argue that highly admixed population groups, such as South African coloureds, cannot achieve acceptable accuracies because within group variance is too large. Whereas ancestry estimation in South Africa has been limited to craniometric data from South African 2 blacks and whites, the current study integrates craniometric and geometric morphometric data from the three largest South African groups.Crania from 377 South African individuals (black = 158, white =112, and coloured = 107) comprised the sample. Standard measurements were collected and the coordinate data were subjected to Generalized Procrustes Analysis (GPA), which resulted in size-free shape variables (ProCoords). A principal component analysis was used to combine the shape variation captured in the ProCoords (ProCoords PC). Linear discriminant analysis (LDA), using equal priors, stepwise variable selection and leaveone-out cross-validation, was conducted on the ProCoords, the ProCoords PCs, and the traditional craniometric data.The LDA using 18 stepwise selected ProCoords resulted in the highest crossvalidated accuracy (89%). Utilization of geometric morphometric data emphasized that the relative location of cranial landmarks was more discriminating than simple linear distances. Regardless of high levels of genetic admixture, South African coloureds are a homogeneous group and morphologically distinct from other contemporaneous South African populations. Furthermore, the present study demonstrated a correspondence between peer-reported race and morphological differences in the crania of black, white, and coloured South Africans.