The interpretation of human evolution depends upon analysis of the behavior and ecology of several extinct hominid species. However, the number of fossil species represented by known specimens remains controversial, as does the assignment of many individual specimens to particular species. A basic unresolved problem concerns the range of diversity of individual species: At what point are the differences between any two or more specimens sufficient to suggest that they are from different species, as opposed to simply representing the differences found among individuals from a single species? Using new computer digitizing technology and three-dimensional analyses, measurements will be taken from the facial bones of virtually all available australopithecine fossils, and measurements of the identical facial structures will be taken on large samples of skeletal material of modern humans, chimpanzees, and gorillas. The range of variation in facial morphology of these three modern species will be used as a basis of comparison for the ranges of variation among australopithecine specimens. These results will provide important insights into population structure and sexual dimorphism of early human ancestors. The extant data will serve to both evaluate the categorization of australpithecine specimens into species groups, as well as to establish whether or not australopithecine species as currently defined are more or less variable than modern analogues.
