Meeting Abstract
26.4 Saturday, Jan. 4 14:15 Three-Dimensional Head Kinematics During Terrestrial Locomotion in Humans and Chimpanzees THOMPSON, N.E.*; O’NEILL, M.C.; DEMES, B.; Stony Brook University Medicine; Stony Brook University Medicine; Stony Brook University Medicine nathan.thompson@stonybrook.edu
Osseous semicircular canal morphology has been used to reconstruct aspects of locomotor behavior in living and fossil primates. Relative to chimpanzees and other apes, humans exhibit significantly larger anterior and posterior canal radii of curvature. As such, humans and chimpanzees should differ significantly in their head motion across speed and gait. However, the three-dimensional (3D) head motion of apes during terrestrial locomotion is currently unknown. To address this issue, head kinematics during terrestrial locomotion were collected from three male chimpanzees (Pan troglodytes; 29.6±6.7 kg) and five male humans (78.3±7.9 kg). A 3D head marker set was used to determine roll, pitch and yaw angular velocity parameters (i.e. maximum, root-mean-square and average resultant velocity) about anatomical axes of the skull over a full stride. Angular velocities during human walking and running are lower than for any chimpanzee gait (i.e. bipedal walking, quadrupedal walking and galloping). Our data expands the body mass range of primate species for which 3D kinematic data exist by 18-fold. Over this range, angular head velocities are negatively correlated with body mass (pGLS, r2 = 0.63). Relative to mass, humans exhibit negative residuals during walking and running, indicating uniquely stable heads. Based on this, we propose that the adoption of habitual bipedal locomotion in the hominin lineage was characterized by an overall decrease in 3D head motion. Therefore, the enlargement of human semicircular canal radii is likely an adaptation for greater head stability during locomotion. Supported by NSF BCS 0935321.
