Tarsal and tarsometatarsal coalitions from Mound C (Ocmulgee Macon Plateau site, Georgia): implications for understanding the patterns, origins, and antiquity of pedal coalitions in Native American populations.

Tarsal and tarsometatarsal coalitions are malsegmentation errors that result in incomplete division between two or more normally separate bones of the foot. Coalitions may be osseous, characterized by bony union, or non-osseous, in which the affected elements are united by fibrous tissue, cartilage, or some combination of both. Evidence indicates that non-osseous coalitions are frequently overlooked or misinterpreted in skeletal samples. The purpose of this study is to (1) report two non-osseous coalition cases (naviculocuneiform I, CF3-MT3) from the Ocmulgee Mound Site in Georgia, and (2) examine the occurrence of coalitions throughout the foot in Native American samples relative to other major populations. Evidence suggests that Native Americans exhibit a pattern of coalitions in the foot that differs from that recently documented for European and African samples. Native Americans display a relatively high rate of midfoot and forefoot coalitions, and known cases are both geographically and temporally diverse. This distribution, along with evidence of similar patterns in East Asian samples, suggests that the pattern of coalition seen in Native Americans has origins in Asiatic parent populations during the late Pleistocene. Individuals migrating to the New World with proximal midfoot coalitions are likely to have endured biomechanical stress during prolonged physical activity and walking, as frequently seen in modern clinical cases.