Preservation assessments and carbon and oxygen isotopes analysis of tooth enamel of Gigantopithecus blacki and contemporary animals from Sanhe Cave, Chongzuo, South China during the Early Pleistocene

As one of the largest primates that ever lived, the finding of Gigantopithecus blacki mainly occurs in southern China during the Early and Middle Pleistocene. Previous stable carbon isotope analysis of G. blacki teeth showed that it relied on C3–based foods in the Early Pleistocene. However, the deficiency of preservation assessment, other ape samples, and oxygen isotope data may hinder the dietary interpretation and understanding the dietary preference of G. blacki compared to human relative apes. In this study, XRD and FTIR were used to assess the crystallinity variation of apatite in fossil enamel of G. blacki and animals during the Early Pleistocene from Sanhe Cave, Chongzuo, Guangxi, South China. The results indicated that the carbonate group in enamel apatite still retained its biogenic signature although the crystallinity was enhanced during fossilization. The carbon isotope values of all fossil animals suggest that they consumed C3–based foods. Most importantly, the oxygen isotope values of all animal fossils show that G. blacki as well as Pongo was engaged in mixed–feeding strategy, perhaps relying on grasses, plant leaves, stems or possible roots that are depleted in 18O. Moreover, lower oxygen isotope values of G. blacki than those from Pongo are observed, suggesting that G. blacki preferred plant roots or stems with lower δ18O values.