Abstract

Fossil record indicates that the emergence of arches in human ancestral feet coincided with a transition from an arboreal to a terrestrial lifestyle. Propulsive forces exerted during walking and running load the foot under bending, which is distinct from those experienced during arboreal locomotion. I will present mathematical models with varying levels of detail, accompanied by data from human subject experiments and fossilized human ancestral feet, to illustrate a simple function of the transverse arch. Just as we curve a dollar bill in the transverse direction to stiffen it while inserting it in a vending machine, the transverse arch of the human foot stiffens it for bending
deformations. A fundamental interplay of geometry and mechanics underlies this stiffening—curvature couples the soft out-of-plane bending mode to the stiff in-plane stretching deformation.