Abstract
Although dissimilarities in cranial and post-cranial morphology among African pygmies groups have been recognized, comparative studies on skull morphology usually pull all pygmies together assuming that morphological characters are similar among them and different with respect to other populations. The main aim of this study is to compare cranial morphology between African pygmies and non-pygmies populations from Equatorial Africa derived from both the Eastern and the Western regions in order to test if the greatest morphological difference is obtained in the comparison between pygmies and non-pygmies. Thirty three-dimensional (3D) landmarks registered with Microscribe in four cranial samples (Western and Eastern pygmies and non-pygmies) were obtained. Multivariate analysis (generalized Procrustes analysis, Mahalanobis distances, multivariate regression) and complementary dimensions of size were evaluated with ANOVA and post hoc LSD. Results suggest that important cranial shape differentiation does occur between pygmies and non-pygmies but also between Eastern and Western populations and that size changes and allometries do not affect similarly Eastern and Western pygmies. Therefore, our findings raise serious doubt about the fact to consider African pygmies as a homogenous group in studies on skull morphology. Differences in cranial morphology among pygmies would suggest differentiation after divergence. Although not directly related to skull differentiation, the diversity among pygmies would probably suggest that the process responsible for reduced stature occurred after the split of the ancestors of modern Eastern and Western pygmies.
Highlights
The term ‘pygmy’ regroups all human populations with average adult size lower than 155 cm [1]
Significant differences between groups in the first five principal components (PCs) are present in table 1
Since African pygmies share a most recent common ancestor [13,14,15,16] and are living in similar environmental conditions, it is expected that cranial shape and size between pygmies are closer between them than to any other nonpygmy population
Summary
The term ‘pygmy’ regroups all human populations with average adult size lower than 155 cm [1]. Many African human populations show a short adult size with an average stature ranking between 155 and 160 cm. These populations sometimes called ‘pygmoid’ show a large geographical distribution and inhabit diverse and contrasted environments. African pygmies live in the equatorial rainforest and their phenotype has been explained by an adaptation to the rainforest habitat [1–5, see 6 for a recent review]. They share a semi-nomadic way of life with a forager strategy and are associated with farming societies [7]. Many works have researched the genetic and/or endocrinological basis of the small size in Pygmies; the reason of the reduced size remains at moment elusive (see below)
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