Patterns of resource use in early Homo and Paranthropus

Abstract

Conventional wisdom concerning the extinction of Paranthropus suggests that these species developed highly derived morphologies as a consequence of specializing on a diet consisting of hard and/or low-quality food items. It goes on to suggest that these species were so specialized or stenotopic that they were unable to adapt to changing environments in the period following 1.5 Ma. The same conventional wisdom proposes that early Homo species responded very differently to the same environmental challenges. Instead of narrowing their niche it was the dietary and behavioral flexibility (eurytopy) exhibited by early Homo that enabled that lineage to persist. We investigate whether evidence taken across eleven criteria supports a null hypothesis in which Paranthropus is more stenotopic than early Homo. In six instances (most categories of direct evidence of dietary breadth, species diversity, species duration, susceptibility to dispersal, dispersal direction, and non-dietary adaptations) the evidence is inconsistent with the hypothesis. Only one line of indirect evidence for dietary breadth—occlusal morphology—is unambiguously consistent with the null hypothesis that Paranthropus' ability to process tough, fibrous food items (e.g., leaves) was reduced relative to early Homo. Other criteria (habitat preference, population density, direct and indirect evidence of dietary breadth related to incisor use) are only consistent with the hypothesis under certain conditions. If those conditions are not met, then the evidence is either inconsistent with the hypothesis, or ambiguous. On balance, Paranthropus and early Homo were both likely to have been ecological generalists. These data are inconsistent with the conventional wisdom that stenotopy was a major contributing factor in the extinction of the Paranthropus clade. Researchers will need to explore other avenues of research in order to generate testable hypotheses about the demise of Paranthropus. Ecological models that may explain the evolution of eurytopy in early hominins are discussed.