Geometric morphometric analysis of mid-sagittal cranial profiles in Neandertals, modern humans and their ancestors

The recent development of geometric morphometrics – and, particularly, the procedures based on the interpolating function thin-plate-spline (TPS) – combine multivariate statistics with deformation grids in the D’Arcy Thompson’s style, allowing to distinguish deformation components as well as to explore the variation of the morphological change taken as a whole. Cranial mid-sagittal profiles of fossil specimens referable to the genus Homo, spanning in time from Early to Late Pleistocene have been investigated with this method, with particular reference to the comparison between Neandertals and modern humans. The results show a clear clustering of two main groups, respectively represented by a generalised “archaic” shape and a well characterised “modern” architectural pattern. These results are discussed in the light of a working hypothesis where different archaic Homo lineages represent regional clades of the same anagenetic process of evolution. In contrast, it is suggested that the appearance of modern H. sapiens was a relatively rapid and localised cladogenetic event.