Doctoral Dissertation Research: Postcranial Proportional Variation in Australopithecus

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The specific objective of the proposed research is to evaluate species boundaries in the hominid genus Australopithecus using a novel method. This will be achieved by evaluating variation in postcranial skeletal proportions of unassociated individuals from the fossil assemblages recovered at Hadar, Sterkfontein, and Makapansgat, and comparing it to that seen in all extant large hominoid taxa. Because the species is the most fundamental unit in biological and phylogenetic studies, determining species boundaries in the early hominid fossil record is imperative to all other analyses involving hominid biology, evolution, and behavior. Recent discoveries and analyses have increased the perceived amount of variation in hominids, some of which has been interpreted as indicating divergent locomotor behaviors among species. Accurate assessment of species boundaries is more important than ever in order to critically evaluate these claims, to trace the trajectory of morphological and behavioral change among early hominids, and to accurately estimate the variability upon which selection acted to produce our genus, Homo. Previous attempts to determine species boundaries have relied primarily on the assessment of craniodental remains and have often produced conflicting results. Recently, however, it has been demonstrated that postcranial data validly reflect the molecular phylogeny of extant primates. Unfortunately, the early hominid fossil record is composed primarily of isolated skeletal elements from numerous individuals. By combining pairs of these elements from presumably different individuals, variation in body proportions can be assessed using nonparametric density estimation. This method is well established in other fields, but has never been applied to paleoanthropological problems. It will allow the thorough exploitation of the postcranial fossil assemblages and will shed significant light on questions of taxonomy and phylogeny in Australopithecus. Additionally, not only is this research expected to help clarify species boundaries in these early hominids, it will also significantly contribute to the understanding of both human and ape postcranial proportional skeletal variation.This research will have several broad impacts. First, it will advance the graduate training of the student. It will also develop a novel approach to studying variability. Third, it will establish a method that holds great promise for other areas of anthropology in which the recognition of individual skeletons from commingled skeletal assemblages is desired, such as in forensics and bioarchaeology.