Department of Anthropology, University of Iowa, Evolutionary Studies Institute, University of the Witwatersrand
March 27, 2015 3:15, Grand Ballroom E/F/G
The chin, or mentum osseum, is considered a Homo sapiens autapomorphy and has long played a prominent role in the determination of systematic relationships in genus Homo. Despite extensive literature describing the anatomical traits comprising the anterior mandibular symphysis, the timing of their appearance throughout genus Homo evolution is still not fully understood, particularly given the incipient chins seen on some Neandertals (e.g., Zafarraya). This project assesses the taxonomic validity of the topographic traits comprising H. sapiens anterior mandibular morphology, testing whether five key features of the chin statistically significantly differentiate H. sapiens from two other taxa (Homo heidelbergensis and Homo neanderthalensis) in static adult comparisons. Surface scans were collected from a large sample of Homo heidelbergensis, Homo neanderthalensis, and Homo sapiens, and 3D coordinate (semi)landmark data were subjected to principal components analysis of Procrustes shape variables. Tukey's HSD test confirms that H. sapiens separate from both H. neanderthalensis and H. heidelbergensis along PC1; however, along PC2, H. sapiens and H. neanderthalensis group together, but separately from H. heidelbergensis. While warp grids for PC1 emphasize the topography of the chin itself, PC2 emphasizes the incurvatio mandibulae, highlighting differences that have been noted regarding the relative lack of topography on the H. heidelbergensis symphysis compared to both H. sapiens and some Neandertals. Given the importance of the chin in defining H. sapiens, this research, demonstrating overlap in overall anterior symphyseal shape between H. sapiens and Neandertals, raises questions about the distinctiveness of the human chin.
This study was supported by the following organizations at the University of Iowa: T. Anne Cleary Fellowship, Stanley Graduate Award, CAPS, CGRER, ECGPS, GSS, and the Department of Anthropology.