Cortical Structure of Hallucal Metatarsals and Locomotor Adaptations in Hominoids

dc.contributor.authorJashashvili, T.
dc.contributor.authorDowdeswell, M.R.
dc.contributor.authorLebrun, R.
dc.contributor.authorCarlson, K.J.
dc.description.abstractDiaphyseal morphology of long bones, in part, reflects in vivo loads experienced during the lifetime of an individual. The first metatarsal, as a cornerstone structure of the foot, presumably expresses diaphyseal morphology that reflects loading history of the foot during stance phase of gait. Human feet differ substantially from those of other apes in terms of loading histories when comparing the path of the center of pressure during stance phase, which reflects different weight transfer mechanisms. Here we use a novel approach for quantifying continuous thickness and cross-sectional geometric properties of long bones in order to test explicit hypotheses about loading histories and diaphyseal structure of adult chimpanzee, gorilla, and human first metatarsals. For each hallucal metatarsal, 17 cross sections were extracted at regularly-spaced intervals (2.5% length) between 25% and 65% length. Cortical thickness in cross sections was measured in one degree radially-arranged increments, while second moments of area were measured about neutral axes also in one degree radially-arranged increments. Standardized thicknesses and second moments of area were visualized using false color maps, while penalized discriminant analyses were used to evaluate quantitative species differences. Humans systematically exhibit the thinnest diaphyseal cortices, yet the greatest diaphyseal rigidities, particularly in dorsoplantar regions. Shifts in orientation of maximum second moments of area along the diaphysis also distinguish human hallucal metatarsals from those of chimpanzees and gorillas. Diaphyseal structure reflects different loading regimes, often in predictable ways, with human versus non-human differences probably resulting both from the use of arboreal substrates by non-human apes and by differing spatial relationships between hallux position and orientation of the substrate reaction resultant during stance. The novel morphological approach employed in this study offers the potential for transformative insights into form-function relationships in additional long bones, including those of extinct organisms (e.g., fossils).en_ZA
dc.description.sponsorshipTJ was funded by a post-doctoral fellowship from the Claude Leon Foundation and the Strategic Planning and Allocation of Resources Committee at the University of the Witwatersrand. The South African Department of Science and Technology and the National Research Foundation,as well as the Centre of Excellence in Palaeosciences and the Evolutionary Studies Institute at the University of the Witwatersrand provided funding in support of the Virtual Imaging in Palaeosciences laboratory.en_ZA
dc.identifier.citationJashashvili, T. et al. 2015. Cortical Structure of Hallucal Metatarsals and Locomotor Adaptations in Hominoids. PloS ONE 10(1): 10.1371/ journal.pone.0117905en_ZA
dc.journal.titlePLoS ONEen_ZA
dc.publisherPublic Library of Scienceen_ZA
dc.rightsCopyright: © 2015 Jashashvili et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.en_ZA
dc.subjectAdaptation (Biology)en_ZA
dc.subjectGait in animalsen_ZA
dc.subjectCerebral cortex -- Anatomyen_ZA
dc.subjectComparative studiesen_ZA
dc.titleCortical Structure of Hallucal Metatarsals and Locomotor Adaptations in Hominoidsen_ZA
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