The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

3D geometric morphometrics of the LB1 mandible support the new species diagnosis (Homo floresiensis)


1Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, 2Department of Anatomical Sciences, Stony Brook University Medical Center, 3ARKENAS, Jakarta, Indonesia, 4School of Earth and Environmental Sciences, University of Wollongong, Australia

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Debate continues over the systematics of the Late Pleistocene fossils from Liang Bua (Flores, Indonesia). The designation of the holotype (LB1) as a new species, Homo floresiensis, has been contested by some who believe that the morphology of this fossil falls within the range of variation seen in pathological humans. Here we present a three-dimensional, landmark-based morphometric study of the LB1 mandible in order to assess if its shape is ever observed within a large sample of modern humans that includes pathological individuals diagnosed with microcephaly and cretinism.

Data were collected from mandibles of 250 non-pathological modern humans, 8 microcephalics, 6 cretins and 9 fossil hominins. Principal components (PC) of shape were extracted, and a canonical discriminant analysis (CDA) based on the first five PCs was performed after dividing the comparative samples into 3 groups: non-pathological, pathological, and fossil hominin. LB1 was treated as an unknown.

The CDA classified LB1 as a member of the fossil hominins with a 99% probability of group membership. LB1 had a 1% probability of being classified as a normal modern human, but a 0% probability of being classified as pathological. Morphology of the LB1 mandible is therefore most similar to that observed in other hominin fossils, whereas microcephalic and cretin mandibles extend the modern human shape space away from the fossils. These results allow one to firmly reject the pathological modern human hypothesis, lend strong support to the recent conclusions of Brown and Maeda (2009), and corroborate the new species diagnosis for LB1.

This project was funded by a National Science Foundation Graduate Research Fellowship and the Australian Research Council.

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