Doctoral Dissertation Research: Modeling hominin variability in Australopithecus africanus

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

One of the fundamental goals of anthropological research is to understand humanity's biological origins and evolution, for which the hominin fossil record is a primary source of data. However, it is difficult to determine, for a given time period and location, whether the relatively limited and fragmentary hominin fossils represent one or multiple species. Such is the case for South African fossils attributed to the species Australopithecus africanus. The variability in this assemblage of fossils has been proposed to represent more than one species, but there is little agreement about how to sort the various fossils. Determining species designations for this assemblage is important because it affects interpretations of A. africanus as a direct ancestor of our own genus Homo and therefore our understanding of how and where the genus Homo evolved. By incorporating methods from systematic biology and developing new statistical methods, this research will provide a necessary framework to define hominin fossil species and address diversity in hominin evolution. This project will also support training and mentoring of students, including from groups underrepresented in STEM fields, science outreach to high school students, and scan data that will be made available through Morphosource. The recognition of species in the fossil record is of critical importance to understanding hominin evolution and diversity. A vast literature exists on species concepts, but process-based definitions cannot be easily applied to fossil species. Accordingly, levels of variation within purported hypodigms have typically been used to delineate hominin species, but such approaches rest on the problematic assumption that these parameters are comparable in extinct and extant species. Elsewhere in biology, methods have been developed that use the structure of variance within a sample to detect the presence of discrete species. Despite continued controversy over hominin species delineation, these methods have yet to be employed in anthropology. Australopithecus africanus exemplifies this problem. Resolving its alpha taxonomy is critically important to interpreting human evolution, but it remains a contentious issue. The possibility that A. africanus subsumes two or more species has significant implications for the interpretation of the hominin phylogeny and the evolution of the genus Homo. The goal of this research is to quantitatively model species variation in extant primates and fossil hominins in order to re-evaluate the taxonomic heterogeneity of the A. africanus assemblage. This will be accomplished by using phylogenetic comparative methods to estimate an appropriate null hypothesis model of hominin variability. Data will be collected from 3D surfaces of extant primate and fossil hominin teeth using landmarks, semi-landmarks, and GIS-based approaches. The data from this study will provide a detailed model of hominin variability using both mixture models and matrix correlation analyses.