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


Three-dimensional head kinematics in chimpanzees and humans: implications for the study of semicircular canal morphology

NATHAN E. THOMPSON, MATTHEW C. O'NEILL, BRIGITTE DEMES and SUSAN G. LARSON.

Department of Anatomical Sciences, Stony Brook University School of Medicine

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Semicircular canal morphology is thought to be indicative of locomotor capabilities in primates. Among hominids, humans are unique in possessing relatively larger radii of curvature of the anterior and posterior canals. This morphology has been associated with habitual bipedal behavior, which is predicted to entail greater angular head motions during locomotion. In this study, we test the hypothesis that humans have larger head angular velocities than chimpanzees during overground locomotion.

Head movements of humans and chimpanzees (Pan troglodytes) were collected using a four-camera motion capture system (Xcitex Inc., Boston, MA). A three-dimensional head marker set was used to calculate pitch, yaw, and roll angular velocities (maximum and root mean square) in space about anatomical axes of the skull over a full stride cycle. Data were collected from human normal and bent-hip, bent-knee (BHBK) walking, and from chimpanzee quadrupedal and bipedal walking.

Initial results indicate that humans experience significantly smaller head angular velocities than chimpanzees engaged in either quadrupedal or bipedal walking (P < 0.05). In addition, while the angular velocities for normal and BHBK walking in humans are similar, chimpanzee bipedal walking produces higher angular pitch velocities than quadrupedal walking. Additional kinematic data from other locomotor modes will lead to a clearer picture of how habitual head movements are linked to semicircular canal morphology, and will ultimately allow for more accurate interpretations of canal morphology in extinct hominins.

Supported by NSF BCS 0935321.

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