Program of the Seventy‐Seventh Annual Meeting of the American Association of Physical Anthropologists

In a previous study conducted on humerus,radius, ulna, femur, and tibia,Ruff (2002)found that great apes have larger jointssurface areas relative to diaphyseal crosssectionalsize than monkeys, and thatassociations between these structuralproportions and locomotion can bedemonstrated across hominoids. Here I wantto determine if structural proportions ofmetacarpals and metatarsals are useful todistinguish locomotor modes withinhominoids. To that purpose I compare distaljoint surface areas and mid-diaphyseal crosssectionalproperties (section modulus) ofmetacarpals and metatarsals in a sample of85 hominoids (chimpanzee, gorilla,orangutan, and human). Both joint to shaftand metacarpal to metatarsal of the same rayproportions were calculated and comparedbetween species.Results show that orangutans have thegreatest distal articular surfaces relative tomid-diaphyseal section modulus for bothmetacarpals and metatarsals, followed byAfrican great apes. Humans show the lowestvalues. Differences among species arestatistically significant. This is probably aconsequence of the greater amount of mobilityin the proximal phalanx/distal metacarpal ormetatarsal articulations in great apes ascompared to humans. Interlimb comparisonsshow the relatively greatest metacarpal distaljoint in African great apes. This may be aconsequence of the greater dorsiflexion of thefingers in African great apes during knucklewalkinglocomotion.These results are in agreement with resultsobtained using limb long bones and can beapplicable to fossil material which is oftenfragmentary and requires that inferences onlocomotion of extinct species be obtained froma single bone or a few bones