Neandertal pedal proximal phalanges: diaphyseal loading patterns

Neandertal proximal pedal phalanges have been described as short relative to foot length with relatively wide diaphyses, the latter purportedly to resist elevated levels of mediolateral loading during locomotion. Analysis of proximal pedal phalanges from samples of Neandertals, early modern humans, and recent small-scale and industrial society humans demonstrates that the Neandertals have moderately shorter proximal pedal phalanges with the middle (digits 2–4) phalanges having significantly wider diaphyses relative to the recent humans. The early modern humans have relatively abbreviated phalanges, similar to the Neandertals, and occupy an intermediate position with respect to relative phalangeal shaft breadth. These data suggest: (1) a higher frequency and/or level of mediolateral loading of the anterior foot among Upper Pleistocene humans related to contrasting behavioral patterns, and (2) a generally higher level of robusticity of the anterior foot with the elevated dorsoplantar stress on the phalanges being resisted more by extensor and flexor tendon tension and the mediolateral and torsional stresses being resisted by increased diaphyseal breadth. This study, in conjunction with other lower-limb morphological comparisons between Neandertals, early modern humans and recent humans, suggests gradual decreases in locomotor anatomy robusticity (and hence locomotor activity levels) through the later Upper Pleistocene and Holocene with a possible change in lower-limb loading patterns with the emergence of early modern humans.