The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Life history transitions and the origin of genus Homo

SUSAN C. ANTÓN1 and J. JOSH. SNODGRASS2.

1Center for the Study of Human Origins, Department of Anthropology, New York University, 2Department of Anthropology, University of Oregon

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We use an integrated dataset of fossil, archaeological and human biological data to consider the origin and early evolution of genus Homo. These data provide new perspectives on three important shifts in human evolutionary history: 1) the emergence of Homo; 2) the transition between non-erectus early Homo and H. erectus; and 3) the appearance of regional variation in H. erectus. Using new fossils we compare size and dimorphism in Australopithecus and early Homo, and among their species and we estimate their total daily energy expenditures (TDEEs). Although our understanding of body size and intra-/interspecific variation has been changed by recent fossil finds, the data still suggest that body and brain size increase in early Homo. An increase in TDEE appears to signal a marked dietary shift. These differences became more pronounced in H. erectus but the transformation was almost certainly not as extreme as previously envisioned. Regional variation is similar to that in modern humans and likely reflects the importance of local adaptive pressures and perhaps developmental plasticity. Many aspects of the human life history package, including reduced dimorphism, likely occurred later in evolution than previously envisioned. These analyses suggest that regional variation in H. erectus reflects the combined influences of shifts in extrinsic mortality rates and differences in resource sufficiency and quality. We describe a positive feedback model for the origin and evolution of Homo that incorporates cooperative breeding, diet, cognitive abilities, body composition, and extrinsic mortality risk as central elements.

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