Extended Data Fig. 2: Origins of kinematic hypotheses.

(a) Maya visualization of the foot at midstance directly above the track that this foot produced during a walking trial. (b) An ‘animation snapshot’ positioned at the same height as the foot in A, directly above the 3-D model of the track that this foot and its motion produced. The foot at midstance is relatively flat compared with the longitudinally arched track. However, the animation snapshot and the track are similarly arched. A sequence of similar observations led us to hypothesize that track arch morphology was a product of foot kinematics and not foot anatomy.