Using 3-D Geometric Morphometric Techniques to Further Understand the Relationship Between Neanderthals and Homo sapiens
The relationship between hominids in the middle and late Pleistocene has been a heated subject of debate since Neanderthals were first recognized. Neanderthals are either a distinctly separate species from Homo sapiens that were replaced by Homo sapiens without any genetic interaction, which supports the taxonomical title for Neanderthals as Homo neanderthalensis, or there was at least a minimal genetic interaction between contemporaneous Neanderthals and early humans, designating Neanderthals as a subspecies with a taxonomic title of Homo sapiens neanderthalensis. The purpose of this research was to further explore this issue by conducting a quantitative analysis on several aspects of morphological variation evident in crania of Neanderthals and Homo sapiens. Cranial landmarks were digitized on the cranial vault (cranial vault analysis) and midfacial area (alpha triangulation analysis) of the specimens. Digitizing cranial landmarks preserves the information inherent in those landmarks relative to other landmarks in three dimensions. The data was fitted using generalized procrustes analysis, a geometric morphometric technique that is a statistically powerful mathematical superimposition method that essentially eliminates size as a variable, while preserving the variables present in shapes. This method breaks down complexities inherent in three dimensional data and allows the landmark data collected by the digitizer to be compatible with statistical analyses. The fitted data was then analyzed using multivariate statistical methods that included principal component analysis and canonical variates analysis. The results of the cranial vault analysis distinguished Neanderthals from both modern humans as well as early modern humans. The alpha triangulation analysis produced relatively ambiguous results. In the discriminant analysis of the cranial vault data set, several individual specimens were misclassified into the Neanderthal group through resubstitution and cross-validation using linear discriminant functions. It is clear that these individual specimens have a unique morphology compared to their associated groups, and that they are closer in morphology to Neanderthals than their associated group means. The morphological degree of variation cannot conclusively define the taxonomic position of Neanderthals because morphologically based research is limited to explaining the differences and similarities inherent in forms, but cannot accurately define a species.
Advisor:Dr. Ashley McKeown; Dr. Randall Skelton; David Dyer
School:The University of Montana
School Location:USA - Montana
Source Type:Master's Thesis
Date of Publication:05/13/2008