Heritage Cases

1st step of the project: Baseline 15N values of herbivorous, carnivorous and omnivorous Sterkfontein Member 4 fauna: Prior to evaluating 15N data in hominin tooth fragments directly, we need to establish baseline nitrogen isotope data of Sterkfontein fauna, if possible including all species that were available to early hominins. After consulting with Prof. Marion Bamford and Dr. Dominic Stratford, we decided to focus on Member 4, because it inhabits, next to Australopithecus (sp. and africanus) an extremely diverse fossil fauna. Herbivores are the most common group with abundant bovids species. Member 4 carnivore fossils are represented by felids, canids, machairodontins and hyaenids. Omnivorous species (e.g. genets and bat-eared foxes) are also present in the fossil assemblage. Hence, the highly divers fossil fauna, which is housed at the collection of the Evolutionary Studies Institutes (ESI) at Wits, serves as a great baseline proxy for the nitrogen isotopic flux in a complex Pleistocene southern African food web. Teeth fragments can be used for this method and no complete teeth have to be destructed for sampling. 2nd step of the project: Trophic level and meat consumption of Australopithecus and other primates: After the baseline 15N values of the diverse fauna is produced in the first step, nitrogen isotope ratios of the hominin teeth itself will be analyzed. We plan to measure seven individual tooth fragments to gain a robust dataset. The new nitrogen isotopic results will be unique and the reconstruction of trophic level and especially meat consumption of hominins this old has never been done before. Again, Australopithecus teeth fragments can be used for this method and no complete teeth have to be destructed for sampling. Moreover, we will analyze 15N of other primates as well (Cercopithecoids, Parapapio and Papio) to compare the diet of these primates to the ones of early hominins. Methodology (short): 15N analyses of Member 4 fossil tooth enamel: We will analyze nitrogen isotope ratios of tooth enamel powder of the diverse fauna from the Sterkfontein Member 4 (herbivores, omnivores and carnivores; n=42) to establish a baseline 15N record for interpreting early hominin meat consumption. We will develop a complex picture of the unprecedented dataset of the food chain with trophic levels for diet, habitat preferences and water balance in animals. Ultimately, seven early hominin teeth fragments will be analyzed and the amount of Australopithecus’ consumption of meat resources (and with it the determination of their trophic level) will be quantified for the very first time. Note that we will only use tooth fragments which we will use for sampling, and only a very small amount of tooth enamel (5 mg) will be taken, the rest of the tooth fragment will remain at the ESI. The organic matter bound within the mineral structure of the fossil liberated after the dissolution of the mineral is oxidized to nitrate (see e.g., Ren et al., 2009, Martinez-Garcia et al., 2014). The resulting nitrate is converted into nitrous oxide using the denitrifier method (Sigman et al., 2001). The 15N of the N2O produced by denitrifying bacteria is measured using an automated extraction system coupled to a Thermo Plus 253 isotope ratio mass spectrometer (Weigand et al., 2016; Sigman, 2016).