The influence of artificial cranial deformation on discontinuous morphological traits



Following the elucidation by geneticists of the nature of minor skeletal variants in the mouse, anthropologists have stressed the potential of these traits for tracing the affinities and movements of extinct human populations. Earlier Sullivan observed that discrete traits could be particularly valuable where artificial cranial deformation limits the use of craniometry.

Twenty-eight minor variants were studied in bifronto-occipitally deformed and undeformed skulls of a sample of 78 from a single Hopewell mound. The pattern of frequency differences between deformed and undeformed with respect to traits at the back of the vault and in the frontal region, interpreted in developmental terms, reveals a hypostotic effect in these regions in the deformed skull; while, in contrast, traits of the lateral vault, facial skeleton and cranial base point to a general hyperostotic effect in these regions. Each of three emissaria tends to be more constant in the deformed.

That minor cranial variants manifest a plastic response to this type of environmentally-imposed stress is consistent with the nature of such variants as elucidated by genetics research in mice. The findings suggest that deformed crania should be excluded from population studies in which genetic divergence between groups is estimated in terms of cranial trait frequencies.