Assessing endocranial variations in great apes and humans using 3D data from virtual endocasts

Authors

  • Thibaut Bienvenu,

    Corresponding author
    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements (iPHEP), CNRS/Université de Poitiers, 86022 Poitiers, France
    2. Collège de France, Chaire de Paléontologie humaine, 75231 Paris Cedex 05, France
    • iPHEP, 40 Avenue du Recteur Pineau, F-86022 Poitiers Cedex, France
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  • Franck Guy,

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements (iPHEP), CNRS/Université de Poitiers, 86022 Poitiers, France
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  • Walter Coudyzer,

    1. Department of Radiology, University Hospitals Leuven, B-3000 Leuven, Belgium
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  • Emmanuel Gilissen,

    1. Department of African Zoology, Royal Museum for Central Africa, B-3080 Tervuren, Belgium
    2. Université Libre de Bruxelles, Laboratory of Histology and Neuropathology, B-1070 Brussels, Belgium
    3. Department of Anthropology, University of Arkansas, Fayetteville, AR 72701
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  • Georges Roualdès,

    1. CHU La Milétrie, Service de Neurochirurgie, 86021 Poitiers, France
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  • Patrick Vignaud,

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements (iPHEP), CNRS/Université de Poitiers, 86022 Poitiers, France
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  • Michel Brunet

    1. Institut International de Paléoprimatologie, Paléontologie Humaine: Evolution et Paléoenvironnements (iPHEP), CNRS/Université de Poitiers, 86022 Poitiers, France
    2. Collège de France, Chaire de Paléontologie humaine, 75231 Paris Cedex 05, France
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Abstract

Modern humans are characterized by their large, complex, and specialized brain. Human brain evolution can be addressed through direct evidence provided by fossil hominid endocasts (i.e. paleoneurology), or through indirect evidence of extant species comparative neurology. Here we use the second approach, providing an extant comparative framework for hominid paleoneurological studies. We explore endocranial size and shape differences among great apes and humans, as well as between sexes. We virtually extracted 72 endocasts, sampling all extant great ape species and modern humans, and digitized 37 landmarks on each for 3D generalized Procrustes analysis. All species can be differentiated by their endocranial shape. Among great apes, endocranial shapes vary from short (orangutans) to long (gorillas), perhaps in relation to different facial orientations. Endocranial shape differences among African apes are partly allometric. Major endocranial traits distinguishing humans from great apes are endocranial globularity, reflecting neurological reorganization, and features linked to structural responses to posture and bipedal locomotion. Human endocasts are also characterized by posterior location of foramina rotunda relative to optic canals, which could be correlated to lesser subnasal prognathism compared to living great apes. Species with larger brains (gorillas and humans) display greater sexual dimorphism in endocranial size, while sexual dimorphism in endocranial shape is restricted to gorillas, differences between males and females being at least partly due to allometry. Our study of endocranial variations in extant great apes and humans provides a new comparative dataset for studies of fossil hominid endocasts. Am J Phys Anthropol, 2011. © 2011 Wiley-Liss, Inc.

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