1Center for Bioarchaeological Research, School of Human Evolution and Social Change, Arizona State University, 2Center for the Study of Human Origins, Department of Anthropology, New York University
Friday 8, Park Concourse
The permanent first molar (M1) has received particular attention in anthropological studies because it is thought to most accurately represent the ancestral form of the molar field. Indeed, differences in M1 trait expression have been useful in assessing biological relationships among modern human populations and effective in discriminating among Plio-Pleistocene hominin taxa. The deciduous second molar (dm2) is considered the analogue of the permanent M1 and is thought by some to be more phylogenetically conservative and/or under stronger genetic control due to its early development. This study tests that presumption by comparing morphological and metrical variables of the maxillary dm2 (xdm2) and M1 (XM1) within the same individuals. The sample included 64 individuals representing several archaeologically-derived recent human groups. Traits included absolute and relative intercusp distances, cusp areas, cusp angles, occlusal polygon area, and Carabelli’s trait expression. Results show highly significant correlation between the XM1 and xdm2 in all absolute and most relative dimensions and in Carabelli’s trait expression. In addition, the relative areas of the occlusal polygon, protocone and paracone did not differ significantly between the two teeth. These results suggest that crown shape and cusp proportions are partially conserved in the XM1. In contexts in which no permanent XM1s are available, we propose that select traits in the xdm2 may be used as a proxy for XM1 expression. However, while the XM1 may be the most conservative of the permanent maxillary molar field, our results suggest that the xdm2 may better represent the ancestral molar morphology.
Data collection by SEB was supported by the LSB Leakey Foundation. Data collection by KSP was supported by the National Science Foundation Graduate Research Fellowship No. 2011121784.