Isotopic insights into mammalian diets and local vegetation cover during the Oldowan-Acheulean transition at Garba IV and Gombore I (Melka Kunture, Upper Awash Valley, Ethiopia)

The archaeological assemblage of Melka Kunture (MK) demonstrates that the Ethiopian Highlands in eastern Africa, along with its high-elevation paleoenvironment, is pivotal for understanding early hominins’ behavior and technological advances. Two localities within the MK site-complex, namely Garba IV and Gombore I, yielded Oldowan lithic tools at ∼2 million years ago (Ma) and the earliest known Acheulian artifacts at 1.95 Ma, associated with Homo erectus remains, as well as evidence of paleofauna and paleoflora. Previous palynological studies suggest that, when H. erectus first produced Oldowan and later Acheulean artifacts, the vegetation consisted of the Dry evergreen Afromontane Forest and Grassland Complex (DAF) type, with changes in the proportions of open and wooded environments over time. However, previous isotopic analysis indicated that the changes in vegetation composition did not influence animal feeding behavior, with C₄-dominated and mixed C₃-C₄ diets and their habitat partitioning. In order to further refine the ecological reconstruction of the Oldowan and Acheulean contexts in the Ethiopian Highlands, this paper presents an intra-site isotopic analysis of the archaeological levels at Garba IV and Gombore I. Isotopic data indicate no statistically significant differences between the Oldowan and Acheulean contexts; overall, the combination of pollen, faunal and isotopic evidence suggests local ecological stability associated with a mosaic montane vegetation containing both C₃ and C₄ grasses. This study demonstrates that the information collected so far does not support any purported link between technological and major ecological changes, at least in the case of MK in the Ethiopian Highlands.