Isotopic insights into the Early Acheulean (1.95 Ma–1.66 Ma) high-elevation paleoenvironments at Melka Kunture (Upper Awash Valley, Ethiopia)

Abstract

In this paper, we present stable carbon and oxygen isotope analyses of fauna tooth enamel from Garba IVD (1.95 Ma) and Gombore IB (1.66 Ma), two Early Acheulean sites of Melka Kunture (Upper Awash, Ethiopia), and discuss faunal taxonomy and fossil pollen. Our aim is to infer the diet and habitat of the fossil fauna, as well as the environment of both sites, in order to provide a broader paleoecological reconstruction. During the Pleistocene, the vegetation of the highlands of Ethiopia belonged to the Dry evergreen Afromontane Forest and grassland complex, which is distinct from the savanna of lower elevations in eastern Africa. Our carbon isotopic results indicate that all the analyzed faunal taxa were grazers consuming C4 plants, whereas oxygen isotopic results discriminate the taxa according to their semiaquatic or terrestrial habitats. These results are consistent with the taxonomic composition of the faunal assemblages and the palynological results, suggesting extended mountain grasslands in the landscape at Garba IVD. In contrast, the carbon isotopic results do not totally agree with the pollen paleoenvironmental reconstruction at Gombore IB, where the open vegetation was interrupted by forests and bushy vegetation. Stable isotope and pollen data provide different outcomes (feeding strategies vs. nearby plants) and have different temporal and spatial resolutions. This is relevant when reconstructing past environments by using independent proxies. Furthermore, isotopic comparisons with other Early Pleistocene paleontological and archaeological sites from eastern Africa indicate that all the analyzed taxa in common fed on C4 plants and that their dietary strategies were not affected by variations linked to the difference in elevations.