Evaluating the Accuracy of Cranial Indices in Ancestry Estimation Among South African Groups

Abstract

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.

Morphometric Analysis of the Neurocranium in an Adult South African Cadaveric Sample,

“…White individuals in the present study presented with significantly larger mean centroid sizes than both Black and Colored individuals. This agrees with previous metric studies of other skeletal elements that indicate that White South Africans have larger body sizes than Black South Africans (26,53). An individual's growth potential is primarily determined by genetic factors, but the extent to which such potential can be reached is greatly influenced by external factors such as nutritional quality and availability, physical activity patterns, and general socio-economic living conditions (54)(55)(56).…”

A morphometric analysis of prognathism and evaluation of the gnathic index in modern humans

“…This includes a lack of reliable assessments of whether the gnathic index successfully describes these shape variations and therefore provides an appropriate measurement of prognathism. Further, indices and ratios present well-known statistical and geometric problems, including violations of the assumption of isometry, the loss of relevant geometric information, and the potential to mislead due to the reduction of complex biological variation to a one-dimensional form (Green and Chapman, 2011;Franks and Cabo, 2014;Liebenberg et al, 2015). Thus, the first goal of this study is to quantify changes in prognathic variation from a set of three-dimensional (3D) craniofacial landmarks and compare the resulting morphometric characterization of this character to that provided by the gnathic index.…”

“…The gnathic index is calculated as a ratio of basion-prosthion length to basion-nasion length ( Fig. 1) and has continued to be used among bioarchaeologists, skeletal biomechanists, forensic anthropologists, and paleoanthropologists to document and analyze subnasal prognathism (Brooks et al, 1990;Brown, 2012;Brown and Maeda, 2004;Hershkovitz and Galili, 1991;Hershkovitz et al, 1995;Kennedy and Possehl, 2012;Liebenberg et al, 2015;Orish and Ibeachu, 2016;Patriquin, 2013;van Rensburg et al, 2012). For example, Brown (2012) recently used the gnathic index to assert that the level of prognathism seen in the LB1 hominin specimen from Flores does not overlap with the range of indices seen in modern human myxoedematous endemic cretins.…”

Assessing the physical and pathological traits of human skeletal remains from cemetery localities at the Rakhigarhi site of the Harappan Civilization

“…Preserved conditions of skull (7.2 A2 BR 19) and both humeri (7.2 A2 BR 17A): all skeletal surfaces were heavily plastered with hard material. and brachycranic (80-84.9) (Liebenberg et al, 2015). We estimated the stature of the Rakhigarhi people from the maximum length of the long bones, following the Trotter-Gleser formula (Trotter and Gleser, 1958).…”