Dietary strategies of Pleistocene Pongo sp. and Homo erectus on Java (Indonesia)

During the early Pleistocene, Java was inhabited by a high variety of hominid and hominin taxa with hitherto unclear seasonal dietary demands. We undertook the first geochemical analyses of Pongo sp., Homo erectus and mammalian Pleistocene teeth from Sangiran. We reconstructed past dietary strategies at daily resolution and inferred sub-seasonal ecological patterns. Histologically-controlled spatially-resolved elemental analyses by LA-ICPMS, confirmed the preservation of authentic biogenic signals despite very weak diagenetic overprint. The Sr/Ca record of mammals is in line with expected trophic positions, contextualizing fossil hominid diet. Herbivorous Pongo sp. displays marked seasonal cycles with ~3-month-long strongly elevated Sr/Ca peaks, reflecting highly nutritional plant food during monsoon seasons. Lower Sr/Ca signals suggest different food availability during the dry season. In contrast, omnivorous Homo erectus shows low and less accentuated intra-annual Sr/Ca variability. We infer that Homo erectus maintained its nutritional demands independent of seasonal fluctuations by exploiting the regional diversity of high-quality food resources.