Doctoral Dissertation Research: Morphological Integration in the Hominid Cranial Base

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The research proposed here will evaluate the functional morphology of the hominid cranial base, and its role in reconstructing patterns of early human evolution (i.e., patterns of hominid phylogeny). This research is significant because it will critically examine the functional and phylogenetic relationships of an anatomical region that has been the subject of debate for most of this century. In the process of doing so, it will collect quantitative postural data that will vastly improve our ability to relate primate positional behavior and morphology. Finally, it will propose an approach whereby functional and structural inferences may be used in phylogenetic analysis. Namely, anatomical features that are functionally or stucturally related to each other will be grouped into complexes, and will then be treated as a unit (i.e., weighted as a single feature) in a cladistic analysis (a method of phylogeny reconstruction). This approach is relevant to cladistic analyses in all fields of biology, regardless of the organism or anatomical region that is under investigation. The cranial base is an appropriate anatomical focus for functional and phylogenetic research. From the standpoint of functional morphology, a wide range of factors may influence basicranial form. Such factors include brain size, posture, vocalization, mastication, and facial architecture. Consequently, there are many functional hypotheses available for testing. From a phylogenetic standpoint, basicranial traits play a vital role in the controversey surrounding patterns of early human evolution. Early members of our own genus (e.g., Homo habilis, Homo erectus) share a number of advanced basicranial features with some australopiothecine species. These features either indicate a close evolutionary relationship between these species and the ancestral members of our genus, or that advanced basicranial characters evolved independently in two or more lineages of early humans. Finally, the cranial base is important from an historical perspective. It has long been recognized that the cranial base of humans is distinct from that of other primates. As a result, a basicranial feature was among those used to identify the first recovered australopithecine skull as being a human ancestor.