Evolution of the human foot

Evolution of the human foot
Madhusudhan Venkadesan, Yale University
Date and time: Wed, Apr 06, 2016 - 4:00pm
Refreshments at 3:45pm
Location: ILC S131 - Refreshments in Hasbrouck lobby
Category: Departmental Colloquium
Abstract:
Human feet are unique among primates. Our arched feet provide a stiff propulsive lever for locomotion. Non-human primates, and those humans suffering from flatfootedness, have a flat and flexible midfoot that severely deforms when pushing on the ground. Although human feet have two distinct arches, the longitudinal and the transverse, the transverse arch has generally not been studied in the context of foot stiffness. Common experience however shows otherwise; a drooping dollar bill stiffens significantly upon curling it in the transverse direction. Using mathematical and physical models of the foot as a shallow thin shell, I will show that the curvature of the transverse arch is the primary determinant of foot stiffness. The dependence of stiffness on curvature of the shell has two asymptotic regimes, one that resembles a soft flat plate, and the other that shows a power-law dependence with an exponent of 3/2. Human feet belong to the 3/2 power-law regime, but other primate feet including chimpanzees and gorillas belong to the flat plate regime. Using this framework, I present a functional interpretation for fossil feet from human ancestors. I will intersperse my talk with the necessary background on anatomy, human evolution, and biomechanics.