Starting Off on the Wrong Foot

Maladies of the foot and ankle are quite common in Homo sapiens, making foot orthopaedics a global, multi-billion dollar industry. Given that the modern human foot functions primarily as a stable platform and a propulsive lever, it is far from ideal that the anatomical precursor was a mobile, grasping appendage. But, because we are primates, and natural selection tinkers with pre-existing structures, the transformation of a flexible, grasping foot to a stiff propulsive lever is precisely the evolutionary legacy of our foot and ankle. The evolution of a stable structure from a grasping one has left us particularly susceptible to a variety of foot and ankle injuries. Of considerable importance is the fine balance between excessive pronation and supination, and the various injuries that can result from excessive motion at the subtalar joint. This talk will discuss sprains and tears of the anterior talofibular ligament (ankle sprains), flat-footedness, compression fractures, plantar fasciitis, bunions, Achilles tendonitis and bursitis, as by-products of our evolutionary history. Prior to this decade, hominin foot evolution has been understood through isolated pedal fossils from East and South Africa, the relatively complete OH 8 foot, and the Laetoli footprints. Fortunately, this decade has witnessed the discovery and publication of a flurry of new associated pedal fossils from Ardipithecus ramidus, “Little Foot” (StW 573), a juvenile Australopithecus afarensis from Dikika, and feet from both Au. sediba and Homo floresiensis. These fossils help us reconstruct the mosaic pattern of foot evolution, and track the timing of anatomies that would have rendered these early hominins susceptible to many of the same foot and ankle maladies experienced by humans today.