Comparative and Experimental Investigations of Cranial Robusticity in Pleistocene Hominins.

Comparative and Experimental Investigations of Cranial Robusticity in Pleistocene Hominins. Comparative and Experimental Investigations of Cranial Robusticity in Pleistocene Hominins. This dissertation project investigates behavioral, biochemical, and biomechanical influences on the thickness of cranial vault bones in order to better understand Homo erectus' behavioral patterns. Elucidating the etiology of cranial vault thickness (CVT) will (1) maximize the amount of paleobiological information available from skull vault fragments of any hominin species, (2) distinguish the value of CVT as a trait for classification purposes and behavioral reconstruction, and (3) provide new information about H. erectus specifically, a species occupying a critical period in human evolution. The function of the cranial vault is to protect the brain and to serve as an attachment site for many muscles, but molecular influences on the development of its three layers of bone are not well understood. For example, the effect of exercise on hormone levels, which may in turn influence cranial bone development, is uncertain. This study will use both comparative and experimental methods to explore influences on increased CVT. Previous studies have limited their measurement of CVT to total thickness; this study measures all three layers of the bone. These measures will be correlated (in a sample of 70 non-human primate and 10 hominin species) with several characters preserved in the cranium such as the size of chewing muscles and brain case shape. In addition, attempts will be made to increase CVT in mice by manipulating chewing strain and growth hormone. This study of CVT is the first to include an experimental component. It will expand knowledge of physiological processes in bone development, provide a better understanding of hormonal influences on cranial vault growth, and test hypotheses for increased and decreased skeletal robusticity throughout human evolution.