Anthropology, University of Texas at Austin
Friday 10:00-10:15, Galleria North
Hallucal propulsion at toe-off is a distinct feature of mature human bipedalism. As a means of creating a stable metatarsophalangeal joint (MTPJ) for toe-off, collateral ligaments surrounding the 1st MTPJ tighten, producing high compressive joint forces. By comparison, toddlers have weak plantarflexors and lack a propulsive toe-off. This study tested the hypothesis that epigenetically-sensitive trabeculae in first metatarsal heads of juveniles differs from that of adults. High resolution X-ray computed tomography was used to analyze trabecular bone structural parameters within dorsal, central, and plantar volumes of interest (VOI) in juvenile human (1-4 years, n=6) and African ape (0-5 years; Pan troglodytes n=10, Pan paniscus n=2, Gorilla sp. n=7) first metatarsals. Juvenile data were compared to those of adults (Griffin et al., 2010).
Results support the hypothesis that trabecular bone structural parameters within the first metatarsal head differ between juveniles and adults. Among all juveniles, humans had the highest DA in both dorsal and plantar VOI. In African apes and humans, compared to juveniles, conspecific adults had a higher DA and a higher BV/TV. Relatively low DA in juvenile African apes is consistent with a more varied locomotor repertoire and foot function. A high DA in adult humans suggests that the close-packing of the MTPJ is associated with highly organized first metatarsal head trabeculae while the lack of a mature toe-off in juvenile humans and African apes of all ages is associated with more isotropic trabeculae. Results support the use of ontogenetic studies of pedal trabecular architecture when identifying bipedal correlates.
This study was funded by the Leakey Foundation and NSF (BCS 1028958).