A geometric morphometric approach to the quantification of population variation in sub‐Saharan African crania

Abstract

We report here on new data examining cranial variation in 18 modern human sub-Saharan African populations. Previously, we investigated variation within southern Africa; we now extend our analyses to include a series of Central, East, and West African crania, to further knowledge of the relationships between, and variation and regional morphological patterning in, those populations. The sample comprises 377 male individuals; the three-dimensional coordinates of 96 landmarks are analyzed using Procrustes-based methods. Interpopulation variation is examined by calculating shape distances between groups, which are compared using resampling statistics and parametric tests. Phenotypic variance, as a proxy for genetic variance, is measured and compared across populations. Principal components and cluster analyses are employed to explore relationships between the populations. Shape differences are visualized using three-dimensional rendered models. Observed disparity patterns imply a mix of differences and similarities across populations, with no apparent support for genetic bottlenecks, which is likely a consequence of migrations that may have influenced differences in cranial form; supporting data are found in recent molecular studies. The Pygmy sample had the most distinctive cranial morphology; characteristically small in size with marked prognathism. These features characterized, although less strongly, the neighboring Bateke, and are possibly related to similar selective pressures in conjunction with interbreeding. Small cranial size is also involved in the considerable distinctiveness of the San and Khoikhoi. The statistical procedures applied in this study afford a powerful and robust means of quantifying and visualizing the magnitude and pattern of cranial variation between sub-Saharan African populations.

Intra-species structuring in the common shrew Sorex araneus (Lipotyphla: Soricidae) in European Russia: morphometric variability could give evidence of limitation of interpopulation migration

“…Studied samples of the Serov race (Se_F and Se_H) from altitudes of 300-550 m were significantly larger in comparison to the other samples in centroid size of the skull and mandible. Geometric morphometrics gives a facility to evaluate the expression of allometric effects (O'Higgins & Collard, 2002;Cardini & Tongiorgi, 2003;Franklin et al, 2010). In our study, a negative significant correlation between RW1 and CS related to altitude was found in Serov race.…”

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

“…Cranial morphology corroborates a Khoesan influence among some black subgroups, particularly the Xhosa and Zulu [19,66]. Furthermore, the myriad of laws associated with apartheid (e.g.…”

Size variation facilitates population divergence but does not explain it all: an example study from a widespread African monkey

“…Hit‐ratios from discriminant analyses of vervets were approximately 75–85% but only slightly larger than 50% when cross‐validated. This is only marginally better than the average 30–60% cross‐validated hit‐ratios from a study of cranial variation of sub‐Saharan populations of humans (Franklin, Cardini & Oxnard, 2010) and can be contrasted with much higher classification and cross validation rates within the guenons as a whole (Cardini & Elton, 2008a). Thus, on the basis of cranial morphology at least, the six most commonly recognized vervet taxa are better classed as subspecies rather than species.…”