The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Great expec-toe-tions: divergence, convergence, and emergence of the modern hallux

ZACHARY J. THROCKMORTON.

Anthropology, University of Wisconsin-Madison

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The adduction of the first pedal ray in humans, such that the hallux is incapable of functional opposability, is a major feature of the evolution of the hominin foot (e.g. Darwin 1863, Haeckel 1879). Analysis of a large sample (n > 100) of radiographs taken from the dorsal aspect of living human feet elucidates the relationship between osteological measures and the magnitude of hallucal adduction, which is a product of both hard- and soft-tissue anatomy (Lovejoy et al. 2009). I describe the correlation of hallucal convergence with first metatarsal posterior articular facet morphology, which allows inference of hallucal convergence in the absence of the medial cuneiform. I report parameters of modern human hallucal convergence variation and offer insight into the hominin fossil record. I infer that the hallucal convergence of the recently reported specimen from Burtele (BRT-VP-2/73) falls within the range of living human variation, inconsistent with the interpretation that this hominin retained the ability to grasp arboreal substrates with its great toe (Haile-Selassie et al. 2012). Of the fossil hominin first metatarsals surveyed, all fall within the range of living human variation, consistent with previous research on medial cuneiform (McHenry and Jones 2006) and first metatarsal (Berillon 1999) morphology. The small sample size of fossil hominin first metatarsals dooms statistical evaluation, though it appears that reduction of medial obliquity of the first metatarsal’s joint surface with the medial cuneiform followed reduction of medial obliquity of the medial cuneiform’s articular surface with the first metatarsal as argued by Berillon (1999).

This work was funded by the UW-Madison Department of Anthropology and Biocore Curriculum.

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