Anthropological Institute and Museum, University of Zurich
Saturday 3:30-3:45, Ballroom C
The femur is a key locomotor element, and femoral morphology is of special relevance to understand the evolution of human and great ape locomotor adaptations. Inferring locomotor function from long bone form, however, is a complex task, since long bone morphology reflects processes of taxon-specific evolutionary adaptation, development, and in-vivo modification. Here, we analyze the femoral diaphyseal morphology in fetuses and neonates of Homo sapiens, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus to explore morphological variation before the onset of taxon-specific locomotor behaviors. CT-based morphometric mapping shows that taxon-specific features of the femoral diaphysis are present already at birth. Our results indicate that humans and chimpanzees show various shared-derived features despite substantially different locomotor behaviors, while chimpanzees and gorillas have clearly distinct femoral diaphyseal morphologies despite similar terrestrial locomotor behaviors. These results indicate that patterns of femoral diaphyseal variation of hominoids contain a strong phyletic signal, which may reflect retained adaptive traits of ancestral taxa, or alternatively, phyletic divergence not related to locomotor adaptations. Our data are consistent with the hypothesis that chimpanzee and gorilla modes of knuckle-walking are a consequence of convergent evolution, and that evolution of human bipedality is unrelated to extant great ape locomotor specializations.