The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Morpho-functional signals in the wrist of extant hominoids derived from 3D geometric morphometrics: the hamate as a test case

SERGIO ALMÉCIJA1,2,3, CALEY M. ORR4, MATTHEW W. TOCHERI5, BIREN A. PATEL6 and WILLIAM L. JUNGERS1.

1Department of Anatomical Sciences, Stony Brook University, 2Department of Vertebrate Paleontology and NYCEP, American Museum of Natural History, 3Paleoprimatology and Human Paleontology, Institut Català de Paleontologia Miquel Crusafont, 4Department of Anatomy, Midwestern University, 5Human Origins Program, Department of Anthropology, National Museum of Natural History, 6Cell and Neurobiology, University of Southern California

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Accurately assessing the relationship between bone shape and function in extant species is an indispensable first step before making functional inferences for extinct taxa. Here we analyze hamate functional morphology among extant hominoids using 3D geometric morphometrics (3DGM). The sample includes 114 hominoid specimens of known sex, comprising all extant great ape genera, hylobatids and modern humans. Thirty-one 3D coordinates were collected from surface models using Landmark Editor. These coordinate data were analyzed using generalized Procrustes methods, principal components analysis (PCA) and multivariate regression of shape on locomotor substrate preference categories (based on published data) using MorphoJ. The shape changes associated with each PC axis were visualized by exporting the coordinates of the shape-change vector into Landmark Editor, so that each 3D model could be morphed into any desired axis position. Overall the first three PC axes accurately segregate each of the hominoid taxa, and the regression of shape onto substrate preference categories explained a significant portion of the total shape variance in our sample (p<0.0001). These results show that 3DGM can capture the subtle and complex shape differences among the hamates of living hominoids and can help decompose the portion of the shape variability explained by locomotion and other factors (e.g., size and sex). Thus, the potential to infer manual adaptations to suspensory, terrestrial, and possibly manipulative behaviors on the basis of hamate morphology in extinct hominoid taxa is promising.

Spanish Ministerio de Economía y Competitividad (CGL2011-27343), the Fulbright Commission (2009 BFUL 00049) and the Generalitat de Catalunya (2009 BP-A 00226) to S.A.; the Smithsonian Scholarly Studies Program to M.W.T.; Wenner-Gren funding to C.M.O.; and Leakey Foundation grant to B.A.P.

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