Some Ruminations on Australopith Diets

Abstract

There are few data regarding hominin diets prior to 3.6 Ma, and thus we have only vague notions about the role of diet in early human evolution. We do know that the australopith masticatory package (e.g., robust mandibles, thick enamel, megadont molars) is evident in an incipient state over 4 Ma, and that these features are consistent with a diet of hard and/or abrasive foods. Nonetheless, recent studies found great similarities in the dental microwear of Australopithecus afarensis and extant African apes, especially the gorilla, and no evidence for the consumption of hard foods. This may indicate that these hominins consumed diets qualitatively similar to those of gorillas and chimpanzees during much of the year, but then utilized harder and/or more abrasive fallback foods when preferred resources (probably fleshy fruits) were scarce (the “fallback hypothesis”). We might speculate by analogy that the earliest East African hominins had large home ranges when in savanna woodlands much like extant chimpanzees, as such environments make it necessary to range widely to obtain sufficient preferred “forest” resources. South African australopiths, in contrast, more regularly consumed significant quantities of hard foods and C4 resources which would have enabled them to utilize savanna woodlands more efficiently. This might have led to reduced home ranges and increased population densities, which might have redounded to their locomotor adaptations. However, the idea that australopith diets largely differed from those of extant African apes in their fallback foods has significant weaknesses, and recent studies suggest the possibility that extant ape and East African australopith diets differed profoundly. Thus, formulation of competitors to the fallback hypothesis is warranted.