1Center for the Advanced Study of Hominid Paleobiology, Department of Anthropology, The George Washington University, 2Hominid Paleobiology Doctoral Program, The George Washington University, 3Department of Biology, James Madison University, 4Human Origins Program, National Museum of Natural History, Smithsonian Institution
Friday 10:00-10:15, Grand Ballroom II
Fossil footprints, though rare in the fossil record, provide the only direct evidence of bipedal gait in extinct hominins. The recent discovery of 1.5 million-year-old hominin footprints from multiple horizons in Ileret, Kenya improve this sparse record, but a limited understanding of the relationship between pedal anatomy, gait, speed, and footprint morphology inhibits our ability to interpret hominin print assemblages. In this project, controlled experiments with habitually unshod and minimally shod Daasanach men (n=19) and women (n=19) from Ileret were conducted to clarify and quantify these relationships.
Biometric data were collected on each subject. Subjects were then filmed while traveling at a range of qualitatively defined speeds across an open-ended trackway that contained a patch of rehydrated sediment from the hominin print layer. 2D kinematic data were collected using Peak Motus and ImageJ. Regression analyses show significant relationships between dimensionless stride length and speed across the full range of speeds (r2=0.91, p<0.001), as well as across the walking speeds (r2=0.82, p<0.001) and running speeds (r2=0.77, p<0.001) when analyzed separately. Using the experimentally derived regression equation, we provide estimates of the travel speeds inferred from the fossil print trails, which range from 0.23 m/s to 2.2 m/s. If the 1.5 million-year-old hominins had foot length:stature proportions equivalent to those of the modern Daasanach, the fossil footprints of multiple individuals show evidence of large stature (>150 cm), suggesting that these prints were created by H. erectus or male P. boisei individuals.
This study was funded by NSF grants BCS-0924476 and DGE-0801634, as well as the GW Undergraduate Research Fellowship and the GW Cotlow Research Fund. This research was approved by the GW Institutional Review Board, #031030.