Diagnosing Bone Fracture to Assess Early Hominin Behaviour, Meat-Eating, and Socioecology at FLK-Zinjanthropus, Olduvai Gorge, Tanzania
This study develops a fractographic method to diagnose hammerstone- and carnivore induced fracture. This is important because interpretations of hominin entry into the carnivore guild and evolution of meat-eating are based on rare tool and tooth marks in Oldowan (2.5-1.8mya) fossil assemblages. Consequently, estimating hominin and carnivore involvement is difficult, and questions remain about Oldowan hominin’s position in the carnivore guild and socioecology. One aspect of bone damage, fracture surfaces, is ubiquitous, but largely unstudied. The fractographic (study of fracture surfaces) method is based on fracture principals, particularly how differences in static- and impact-loading affect material response and fracture features resulting from loading extremes. The method is applied to analysis of fracture features in a) the Amboseli Hyaena Den assemblage, b) an experimental hammerstone-broken assemblage, c) a Plio-Pleistocene assemblage previously interpreted as a carnivore accumulation, FLK-NN2 (Olduvai Gorge), and d) the zooarchaeological assemblage from FLK-Zinj, (Olduvai Gorge). This is the first zooarchaeological/taphonomic study to demonstrate that a) static and impact fracture differ fundamentally in applied load size and material responses to loading extremes, b) impact-forces are significantly greater than the maximum carnivore bite-force, c) cones, incipient flakes, radiating cracks, and lateral stress features are characteristic of impact fracture, and e) Oldowan hominins at FLK-Zinj were responsible for breakage of 54% of the limb assemblage (a 37% – 40% increase over estimates based on percussion marks). The socioecological implications of the habitual transport of food from death and/or kill sites to secondary locations are explored by examining reasons why social carnivores transport food. Aspects of modern carnivore behaviour suggest general mammalian constraints that may have predicated food transport by early Homo. Early Homo food transport behaviour was structured by anti-predator defense strategies associated with a) foraging in an open habitat rich with competing predators, b) the lack of masticatory and digestive apparatus to quickly consume animal tissue, and c) the presence of altricial young in the hominin group.
QH Natural history, QH301 Biology, QL Zoology
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