The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


The chimpanzee is not a valid behavioral model for Ardipithecus ramidus

KEN SAYERS1 and C. OWEN LOVEJOY2.

1Language Research Center, Georgia State University, 2Department of Anthropology and School of Biomedical Sciences, Kent State University

Thursday 8:45-9:00, Grand Ballroom II Add to calendar

Few hominoids have ever differed as greatly as do living chimpanzees and Ardipithecus ramidus. While similar in cranial capacity, the two taxa contrast markedly in almost every major aspect of their dentitions and postcrania. In living forms, these characters are known to directly relate to the niche an animal can or does occupy. We utilize these data and evolutionary ecology to explore divergence in chimpanzee and A. ramidus foraging and reproductive strategies.

Broad research has identified variables critical for predicting diet and social system. For the former, these include food energy, handling time, and encounter rate. A. ramidus is characterized by a more generalized dentition than chimpanzees, lacking both large incisors and increased molar shearing surfaces. These suggest important contrasts in abilities to process and extract energy from particular foods. A. ramidus locomotor characters present an even greater contrast. Associated differences in handling time/costs likely resulted in divergent foraging strategies, particularly regarding putative predatory behavior. In relation to reproduction, the combination of low skeletal dimorphism and lack of a functional canine/premolar complex in A. ramidus indicates a social system unlike any extant great ape.

Our argument is not that chimpanzees are irrelevant to human evolution, or that we should replace this primate with another referential model. We instead propose that broad studies of living primates, including but not limited to chimpanzees, should focus on identifying variables most important to ecology and behavior, and that these variables should be reconstructed specifically for early hominids based on their unique anatomy and habitat.

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