Endless Forms Most Beau-toe-ful: Evolution of the Human Hallux

Zachary Throckmorton Lincoln Memorial University-DeBusk College of Osteopathic Medicine Department of Anatomy Abstract Background. The adduction of the first pedal ray in humans, such that the hallux is incapable of functional opposability, is a major feature of the evolution of the hominin foot (e.g. Darwin 1872, Haeckel 1879, Latimer and Lovejoy 1990). While hallucal adduction facilitates obligate bipedalism, it inhibits but does not eliminate arboreal grasping ability. The angle of the hallux (as determined by the longitudinal axis of the first metatarsal) relative to the rest of the foot (as determined by the longitudinal axis of the second metatarsal) is a product of both hardand softtissues. Given the failure of soft tissue to fossilize, direct evidence for hallucal angle evolution is scanty, and consensus has not emerged as to when and how the modern human condition of hallucal non-opposability evolved.