Department of Anthropology, University of Texas at Austin
Friday All day, Clinch Concourse
The longitudinal arch of the foot is a crucial adaptation facilitating a modern human-like bipedal gait. Certain osteological features have been argued to reflect the presence of an arch, yet our understanding of their relationship to external arch height is limited. This study uses an ontogenetic skeletal sample to test the hypothesis that these features are related to arch height. Arch height is unknown for skeletonized individuals. However, the arch is absent at birth and develops between the ages of 3-6. Therefore, individuals younger than age 6 are expected to differ from older individuals in metrics thought to be positively correlated with arch height. These metrics include the anterior inclination of the distal tibia (DTIA); the angle between the calcaneal plantar and calcaneocuboid surfaces (CCA); and the base-diaphysis angle of the fourth metatarsal (MT4BA).
Tibiae, calcanei, and fourth metatarsals of 134 individuals from the Sudanese Mis Island skeletal collection (ca. 500-1400AD) were photographed and respective measurements were made using Image J. Consistent with predictions, the CCA and MT4BA were significantly smaller in individuals aged 0-6 years compared to older individuals (p<0.001). While the mean DTIA was lowest for those aged 0-6 years, it was not significantly different from other age categories. This latter result is surprising given that the anterior tilt of the distal tibia has been proposed to develop as a by-product of arch development. A more thorough understanding of how these features relate to arch height is necessary for reconstructing the presence of an arch in fossil hominins.