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Now the transverse arch is stepping into the spotlight, with a proposed central role in the evolution of human foot stiffness.

Venkadesan et al.1 report that another foot arch — the transverse arch, which is in the vicinity of the metatarsal bones — makes a major contribution to foot stiffness.

They estimated the curvature of the transverse arch and determined which species would probably have had sufficient curvature to induce stiffening of this arch to an extent similar to that of modern humans.

Venkadesan et al. report that the transverse arch of A. afarensis was less curved than that of a human foot and thus, according to their model, probably less stiff.

Perhaps those with flat feet have less curvature of their transverse arch and thus potentially reduced stiffness in their feet compared with those whose feet are less flat.