| This dissertation seeks to provide greater insight into the phylogenetic relationships among African and Eurasian Middle Pleistocene humans by placing their facial morphology in a broad evolutionary and developmental context. More specifically, the research goals are to gain a clearer understanding of the developmental variation of facial features and their covariation with size and to identify temporal trends in facial morphology that could potentially clarify the polarity (i.e., primitive or derived) of facial features during Pleistocene human evolution. To do so, I apply a recently developed method, semilandmark geometric morphometrics, to quantify the developmental and adult variability of facial features from childhood to adulthood in archaic and modern humans.;Additionally, this dissertation evaluates the morphology and phylogenetic relationships of specific Middle to Late Pleistocene fossils that are often not included in morphometric analyses because of their fragmentary condition. These fossils include the early Middle Pleistocene fossil ATD6-69 from Atapuerca, Spain, the mid-Middle Pleistocene fossil Zuttiyeh from Israel, and the Late Pleistocene fossil Saint-Cesaire from Southwestern France.;Surface and computed tomography scans of modern and Pleistocene fossil humans were acquired and landmarks and semilandmarks were digitized on three-dimensional models created from the scans. Procrustes shape coordinates in shape-space and form-space (i.e., shape and size) were analyzed.;The general results of this dissertation are that some population and species-specific features are already established at the time of birth and that postnatal facial growth further contributes to shape differences among adults. Additionally, this research shows that allometric scaling played an important role in the facial differences between Middle Pleistocene humans and Neanderthals, while modern human facial morphology is the derived condition. The distinctly modern human pattern of facial morphology is already present in Jebel Irhoud 1, dated to around 170 ka. ATD6-69 expresses a mosaic pattern of facial morphology, and several features are certainly modern human-like (e.g., infraorbital depression). Zuttiyeh exhibits a generalized morphology possibly indicative of the population that gave rise to modern humans and Neanderthals. Lastly, the results of the Saint-Cesaire study do not provide morphological evidence of admixture between Neandethals and modern humans in this particular specimen. |
