The longitudinal arch is a unique characteristic of the human foot, yet the timing and pattern of its evolution remain controversial, in part due to the disagreement among researchers over which skeletal traits are the best indicators of its presence or absence.
The small size of the human navicular tuberosity has previously been linked to the presence of a longitudinal arch, implying that the large tuberosity of early hominins such asÂ
Australopithecus afarensis reflects a flat foot. However, this hypothesis is at odds with other evidence of pedal form and function, such as metatarsal, tarsal, and footprint morphology, which show that a longitudinal arch was probably present inÂ
´¡.Ìý²¹´Ú²¹°ù±ð²Ô²õ¾±²õ. This study reevaluates the morphometric affinities of theÂ
´¡.Ìý²¹´Ú²¹°ù±ð²Ô²õ¾±²õ naviculars among other Plio-Pleistocene fossil hominins and anthropoid primates (
NÂ =Â 170). Multivariate cluster analyses show that all fossil hominin naviculars, including those attributed to
´¡.Ìý²¹´Ú²¹°ù±ð²Ô²õ¾±²õ, are most similar to modern humans. A measure of navicular tuberosity size quantified as the ratio of the tuberosity volume to the surface area of the talar facet shows thatÂ
Ateles has the largest navicular tuberosity among the anthropoid sample and that there is no difference between highly arboreal and terrestrial taxa in this metric (e.g.,Â
HylobatesÌý²¹²Ô»åÌý
Gorilla beringei). Instead, a relatively large navicular tuberosity may reflect the development of leg musculature associated with ankle plantarflexion. The functional inferences derived from the morphology of theÂ
´¡.Ìý²¹´Ú²¹°ù±ð²Ô²õ¾±²õ naviculars are consistent with the morphology of the Laetoli footprints.
Reevaluating the functional implications of Australopithecus afarensis
navicular morphology
Thomas C. Prang
DOI:
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