Homo sapiens--in which facial projection is highly reduced, with the facial skeleton located primarily inferior (rather than anterior) to the braincase--is derived vis-à-vis other primates species, including others in the genus Homo. Previous research suggested that variation in facial projection is explained by: (1) cranial base angulation; (2) upper
facial length; (3) anterior cranial base length; (4) anterior sphenoid length; and/or (5) anterior middle cranial fossa length. However, previous research was based on taxonomically narrow samples and relatively small sample sizes, and comparative data on facial projection in anthropoid primates, with which these observations could be
contextualized, do not currently exist.
This dissertation fills this gap in knowledge. Specifically, data corresponding to the hypotheses listed above were collected from radiographs from a sample of anthropoid primates (N = 37 species; 756 specimens) . These data were subjected to phylogenetically-controlled multiple regression analyses. In addition, multivariate and univariate models were statistically compared, and the position of Homo sapiens relative to univariate and multivariate regression models was evaluated.
The results suggest that upper facial length, anterior cranial base length, and, to a lesser extent, cranial base angle are the most important predictors of facial projection. Homo sapiens conforms to the patterns found in anthropoid primates, suggesting that these same factors explain the condition in this species. However, a consideration of the
evidence from the fossil record in the context of these findings suggests that upper facial length is the most likely cause of the extremely low degree of facial projection in Homo sapiens. These results downplay the role of the brain in shaping the form of the human cranium. Instead, these results suggest that reduction in facial skeleton size--which may
be due to changes in diet--may be more important than previously suggested.
Multidecade-long debates over the agents responsible for individual BSM indicate systemic flaws in historical approaches to identification. These debates are in part due to the extreme morphological overlap between BSM produced by certain agents of modification. The primary goal of this dissertation project therefore, is to construct probability models of BSM capable of identifying individual marks with an associated probability of assignment. Using a multivariate Bayesian approach to analyze experimentally-generated BSM data, this dissertation uses two different models, one incorporating both two and three-dimensional (3D) metric and attribute data associated with individual BSM and a second model comparing 3D geometric morphometric (GM) shape data associated with BSM.
The 2D/3D attribute model of BSM is used evaluate an assemblage of fossil BSM recovered from the Ledi-Geraru research area, Ethiopia (2.82 Ma) in spatiotemporal association with early Homo. The results of the analysis reveal compelling evidence for early butchery activities, suggesting hominins may have been using both modified and unmodified stone implements to process carcasses.
The second model, based upon 3D GM data, was used to evaluate the earliest purported evidence for stone-mediated butchery at Dikika, Ethiopia (3.39 Ma). The Dikika marks have been argued to be the result of crocodile feeding, trampling, and butchery by three different research groups. The 3D GM model evaluates the likelihood of each of these actors in the production of the controversial Dikika marks.
The role that climate and environmental history may have played in influencing human evolution has been the focus of considerable interest and controversy among paleoanthropologists for decades. Prior attempts to understand the environmental history side of this equation have centered around the study of outcrop sediments and fossils adjacent to where fossil hominins (ancestors or close relatives of modern humans) are found, or from the study of deep sea drill cores. However, outcrop sediments are often highly weathered and thus are unsuitable for some types of paleoclimatic records, and deep sea core records come from long distances away from the actual fossil and stone tool remains. The Hominin Sites and Paleolakes Drilling Project (HSPDP) was developed to address these issues. The project has focused its efforts on the eastern African Rift Valley, where much of the evidence for early hominins has been recovered. We have collected about 2 km of sediment drill core from six basins in Kenya and Ethiopia, in lake deposits immediately adjacent to important fossil hominin and archaeological sites. Collectively these cores cover in time many of the key transitions and critical intervals in human evolutionary history over the last 4 Ma, such as the earliest stone tools, the origin of our own genus Homo, and the earliest anatomically modern Homo sapiens. Here we document the initial field, physical property, and core description results of the 2012–2014 HSPDP coring campaign.