Forearm bone curvature has been invoked in interpretation of fossil hominin behavior. Apes have curved radii, reflecting hypertrophied forearm musculature needed for below-branch arboreal locomotion and increased leverage for pronation and flexion of the hand. As bipeds, humans have straighter radii adapted to manipulatory rather than locomotor activities. When this evolutionary transition took place, however, is poorly understood. Several radii are known from fossil hominins but they are all incomplete. If curvature could be estimated from fragmentary fossils, it would be possible to evaluate the evolution of forearm curvature in hominins. This study tests the hypothesis that bone curvature could be estimated from proximal radii fragments
