Stable isotope ecology of Cape dune mole-rats (Bathyergus suillus) from Elandsfontein, South Africa: Implications for C4 vegetation and hominin paleobiology in the Cape Floral Region

Abstract

The archaeological and paleontological records from the west coast of South Africa have potential to provide insights into ecosystem dynamics in the region during the mid-Pleistocene. Although the fossil record suggests an ecosystem quite different than that of the region today, we understand little about the ecological factors that contributed to this disparity. The site of Elandsfontein (EFT) dates to between 1.0 and 0.6 million years ago (Ma), preserves in situ lithic and faunal materials found in direct association with each other, and provides the rare opportunity to examine the relationship between hominin behavioral variability and landscape heterogeneity in a winter rainfall ecosystem. In this study, we examine the stable carbon isotopic composition of a large sample (n=81) of Cape dune mole-rats (Bathyergus suillus) and contemporaneous large mammals (>6kg; n=194) from EFT. We find that δ13C values of B. suillus are significantly different to those of contemporaneous large mammals from EFT indicating a significant presence of plants utilizing the C4 photosynthetic pathway during the mid-Pleistocene, in contrast to present C3 dominated ecosystems along the west coast of South Africa. Additionally, we find that artifact density at EFT localities is positively correlated with δ13C values in B. suillus enamel suggesting that evidence of more intense hominin occupation may be associated with the presence of more C4 vegetation. Lastly, we hypothesize that this unique distribution of vegetation 1) provided abundant resources for both hominin and non-hominin taxa and 2) may have concentrated hominin and animal behavior in certain places on the ancient landscape.