Viewpoints: Diet and Dietary Adaptations in Early Hominins: The Hard Food Perspective

Recent biomechanical analyses examin- ing the feeding adaptations of early hominins have yielded results consistent with the hypothesis that hard foods exerted a selection pressure that influenced the evolution of australopith morphology. However, this hy- pothesis appears inconsistent with recent reconstructions of early hominin diet based on dental microwear and sta- ble isotopes. Thus, it is likely that either the diets of some australopiths included a high proportion of foods these taxa were poorly adapted to consume (i.e., foods that they would not have processed efficiently), or that aspects of what we thought we knew about the functional morphology of teeth must be wrong. Evaluation of these possibilities requires a recognition that analyses based on microwear, isotopes, finite element modeling, and enamel chips and cracks each test different types of hypotheses and allow different types of inferences. Microwear and isotopic analyses are best suited to recon- structing broad dietary patterns, but are limited in their ability to falsify specific hypotheses about morphological adaptation. Conversely, finite element analysis is a tool for evaluating the mechanical basis of form-function rela- tionships, but says little about the frequency with which specific behaviors were performed or the particular types of food that were consumed. Enamel chip and crack anal- yses are means of both reconstructing diet and examin- ing biomechanics. We suggest that current evidence is consistent with the hypothesis that certain derived aus- tralopith traits are adaptations for consuming hard foods, but that australopiths had generalized diets that could include high proportions of foods that were both compliant and tough. Am J Phys Anthropol 151:339-355,