1Department of Anthropology, University of Arkansas, 2Department of Anthropology, Stony Brook University, 3Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, 4Department of Physical Therapy, High Point University
Thursday All day, Clinch Concourse
Australopithecus anamensis and Australopithecus afarensis evince significant change in P3 crown morphology (e.g., anterior crown reduction together with distal crown and metaconid expansion) between 4.2 and 3.0 Ma. Canine crown size also reduces in this lineage, but potential functional changes involving occlusion of the maxillary canine and mesial portion of the P3 have not been addressed. We examined microwear texture along the mesial protoconid crest of P3 in Pan troglodytes (n = 10 males and females each) and A. afarensis (n = 18) using white-light confocal profilometry and scale-sensitive fractal analysis. No significant variation was found between male and female chimpanzees. However, A. afarensis and P. troglodytes differ significantly in two variables (texture fill volume and scale of maximum complexity) that likely correspond to fewer small, shallow microwear features on A. afarensis P3s. No differences between species were found in surface complexity or feature anisotropy. In chimpanzees, the maxillary canine is honed along the mesial crest of the P3, while in A. afarensis, which has a reduced and morphologically derived maxillary canine, no honing occurs along this crest. Microwear texture variation may reflect this functional difference and highlights the potential for such analyses to reveal evolutionary changes in the C-P3 complex in early hominins.
Funded by the LSB Leakey Foundation and the US National Science Foundation