Geometric morphometric quantification of Sub-Saharan cranial variation

[Lulletje Rozewater]

April 23, 2009

Geometric morphometric quantification of Sub-Saharan cranial variation

American Journal of Human Biology doi:10.1002/ajhb.20908

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

Daniel Franklin et al.

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.

Link




http://dienekes.blogspot.com/2009/04...ification.html

[Lulletje Rozewater]

X-linked haplotype of Neandertal origin in non-Africans

This seems like a very good case for the presence of something (B006 haplotype) clearly non-African and Neandertal-related in non-Africans.

What I find most interesting, however, is the presence of African-specific haplotypes that seem quite divergent from the most common human haplotypes.


For example (Table 1), haplotype B006 differs from the modal Eurasian haplotype B001 (which is common to Eurasians and Africans) at 13 sites, and B007 (which is African-specific) differs from B001 at 11 sites. It seems to me that B007 might represent archaic African admixture.


It is also not clear why the common haplotype in Neandertals and Eurasians cannot be due to modern human admixture in Neandertals.

An X-linked haplotype of Neandertal origin is present among all non-African populations