Australopithecus at Sterkfontein did not consume substantial mammalian meat

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Editor’s summary

Diet has long been hypothesized as a driver of change among hominins, especially with regard to the increase in brain size. However, identifying diet in early hominins has been difficult because of the diagenic loss of organic matter in collagens older than 200,000 years. Lüdecke et al. looked at carbon and nitrogen isotopes bound to tooth enamel in fauna from an approximately 3.5-million-year-old site that includes several Australopithecus fossils. Dietary niches reconstructed based on these fossils showed that the Australopithecus individuals had diets very similar to both contemporaneous and modern herbivores but different from carnivores. Thus, consumption of meat in these early hominins did not pave the way to humanizing traits such as larger brains. —Sacha Vignieri

Abstract

Incorporation of animal-based foods into early hominin diets has been hypothesized to be a major catalyst of many important evolutionary events, including brain expansion. However, direct evidence of the onset and evolution of animal resource consumption in hominins remains elusive. The nitrogen-15 to nitrogen-14 ratio of collagen provides trophic information about individuals in modern and geologically recent ecosystems (<200,000 years ago), but diagenetic loss of this organic matter precludes studies of greater age. By contrast, nitrogen in tooth enamel is preserved for millions of years. We report enamel-bound organic nitrogen and carbonate carbon isotope measurements of Sterkfontein Member 4 mammalian fauna, including seven Australopithecus specimens. Our results suggest a variable but plant-based diet (largely C3) for these hominins. Therefore, we argue that Australopithecus at Sterkfontein did not engage in regular mammalian meat consumption.

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