The purpose of this project is to document and explain evolutionary changes in two critical features of the early hominid cranio-facial complex: 1) the angulation (flexion) of the cranial base and 2) the position of the face relative to the cranial base. Although it is often assumed that these features evolved together, previous studies have not adequately quantified them. New measurements of facial positioning and cranial base flexion will be collected from original fossils housed in Kenya and South Africa. Such measurements will improve our understanding of the pattern of change in these key cranial features. Previous authors have suggested that evolutionary changes in flexion and facial positioning are secondary to changes in the shape and relative size of skull components such as the brain and masticatory apparatus. Using comparative samples of modern human and African ape crania, hypotheses relating the overall and relative size of these cranial components to variation in flexion and facial positioning will be tested. The results of this project will aid interpretation of variation among fossil crania and will be especially useful in explaining evolutionary changes among closely related species in our own genus.
