Exploring northeast African metric craniofacial variation at the individual level: A comparative study using principal components analysis

Abstract

A principal components analysis was carried out on male crania from the northeast quadrant of Africa and selected European and other African series. Individuals, not predefined groups, were the units of study, while nevertheless keeping group membership in evidence. The first principal component seems to largely capture "size" variation in crania from all of the regions. The same general morphometric trends were found to exist within the African and European crania, although there was some broad separation along a cline. Anatomically, the second principal component captures predominant trends denoting a broader to narrower nasal aperture combined with a similar shape change in the maxilla, an inverse relation between face-base lengths ("projection") and base breadths, and a decrease in anterior base length relative to base breadth. The third principal component broadly describes trends within Africa and Europe: specifically, a change from a combination of a relatively narrower face and longer vault, to one of a wider face and shorter vault; it shows the northeast quadrant Africans along a cline with the other Africans. Stated in relative terms, the northeastern Africans tend to exhibit narrower bases in relationship to more projecting faces, and broader nasal areas than Europeans, although there is range of variation. Relative to the other African groups, they have narrower nasal areas and narrower faces in relationship to vault length. The crania from the northeast quadrant of Africa collectively demonstrate the greatest pattern of overlap with both Europeans and other Africans. Variation was found to be high in all series but greatest in the African material as a whole. Individuals from different geographical regions frequently plotted near each other, revealing aspects of variation at the level of individuals that is obscured by concentrating on the most distinctive facial traits once used to construct "types." The high level of African interindividual variation in craniometric pattern is reminiscent of the great level of molecular diversity found in Africa. These results, coupled with those of Y chromosome studies, may help generate hypotheses concerning the length of time over which recent craniometric variation emerged in Africa.

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