Doctor of Philosophy
Dr. Andrew Nelson
This study explores locomotion and locomotor variability in Plio-Pleistocene hominins by examining cross-sectional properties and mechanical loading patterns in the proximal and midshaft femur of Paranthropus, fossil Homo sp. and H. erectus. Modern human and Pan models are used for comparative purposes. Cross-sectional properties in the proximal and midshaft femur of fossil hominins are examined to test the hypothesis that members of the same genus should exhibit similar locomotor behavior. In the proximal femur, fossil Homo sp. cluster with modern humans to the exclusion of Paranthropus, and East and South African Paranthropus cluster together. Group differences are primarily due to differences in average bending and torsional strength. KNM-ER 738, which has been allocated to both Paranthropus and Homo, is more similar to paranthropine samples than to modern and fossil Homo. In the midshaft femur, fossil Homo sp. and H. erectus cluster with modern humans. OH 62 (H. habilis), however, forms a cluster by itself. It is unclear if this indicates a non-Homo status or if locomotor behavior was highly variable in early Homo. KNM-ER 1592, which is generally attributed to Paranthropus, clusters with modern and fossil Homo. This either suggests that mechanical loading is comparable between Paranthropus and Homo or that KNM-ER 1592 is misclassified as Paranthropus. KNM-ER 736 and KNM-ER 1807, which have been allocated to both Paranthropus and Homo, cluster with modern and fossil Homo, and therefore cannot be excluded from this genus. Group differences in the midshaft femur are largely due to differences in average bending and torsional strength. Relationships between cross-sectional properties in the proximal and midshaft femur are examined to investigate if mechanical loading patterns in fossil hominin femora suggest human-like locomotion, Pan-like locomotion or intermediate locomotor behavior. The relative amount of cortical bone is elevated in modern humans compared to Pan, and in fossil hominins compared to modern humans. Axial strength is greater relative to average bending and torsional strength in modern humans compared to Pan. Fossil Homo sp. and H. erectus are most similar to modern humans in this regard. OH 62, however, displays the Pan-like pattern. Mechanical loading patterns in Paranthropus are more similar to patterns in modern humans than to patterns in Pan. The relationship between bending strength in the medio-lateral plane relative to bending strength in the antero-posterior plane of the proximal and midshaft femur is not significantly different between modern humans and Pan. Thus, different mechanical demands could potentially yield similarities in diaphyseal shape.
Bleuze, Michele M. Ms., "Cross-sectional Morphology and Mechanical Loading in Plio-Pleistocene Hominins: Implications for Locomotion and Taxonomy" (2010). Electronic Thesis and Dissertation Repository. 64.