Drs. Conroy and Vannier are pioneers in the application of computed tomographic (CT) techniques to paleontological materials. With previous NSF support, they have demonstrated that fossilized specimens still partially embedded in sedimentary matrix may be analyzed. With CT, the adhering material can, in effect, be stripped away to reveal the underlying bone. Also it is possible to examine the internal structure of the bone. These results have permitted paleontologists and paleoanthropologists to address new questions. In this project Dr. Conroy and Vannier will continue their study of fossil hominid (human) cranial remains. They will travel to South Africa, where many important specimens were found and are now housed and conduct CT studies. The results, stored in computerized form, will then be analyzed at Washington University. To provide baseline data, a sample of modern specimens will also be studied. In particular, the team will focus on the teeth and stages of dental eruption. In this way they will attempt to determine the age at which individuals died and to reconstruct the patterns of dental eruption. This research is important for several reasons. First, anthropologists cannot agree on how many different kinds of early humans are represented in the African fossil record. Through comparison of developmental rates in a number of fossils, these groupings may become more clear. Secondly, anthropologists argue about the extent to which different hominid species were, in their developmental rates, more human or more pongid (great ape) like. Until this work, the evidence has been limited to visual inspection which noted the teeth protruding from the mandible or maxilla. Because the CT technique allows one to examine the developmental stages of unerupted teeth, it offers a much more sensitive measure. Finally, this research will provide additional insight into the development of basic human biological characteristics.