After the emergence of the Acheulean at Melka Kunture (Upper Awash, Ethiopia): From Gombore IB (1.6 Ma) to Gombore Iγ (1.4 Ma), Gombore Iδ (1.3 Ma) and Gombore II OAM Test Pit C (1.2 Ma)

While the emergence of the Acheulean is well documented in East Africa at similar to 1.7 Ma, subsequent developments are less well understood and to some extent controversial. Here, we provide robust evidence regarding the time period between 1.6 Ma and 1.2 Ma, based on an interdisciplinary approach to the stratigraphic sequences exposed in the Gombore gully of Melka Kunture, in the upper Awash Valley of Ethiopia. Throughout the Pleistocene, the environment differed significantly from elsewhere in Africa because of the elevation at 2000 m asl, the cooler and rainy climate, the Afromontane vegetation, the development of endemic animal species, and the recurrent impact of volcanic activity. At Gombore IB, dated similar to 1.6 Ma, remains of Homo erectus/ergaster have been discovered, associated with a rich early Acheulean assemblage. The techno-typological analysis of the lithic record from Gombore I gamma (similar to 1.4 Ma) and Gombore I delta (similar to 1.3 Ma), where substantial areas have been excavated, and the contrasting evidence from Gombore OAM Test Pit C (similar to 1.2 Ma), suggest that the scarcity or lack of large flakes and large cutting tools at the two earlier sites is possibly not just the outcome of sampling bias, but rather of the adaptation of H. erectus/ergaster to the local resources, in a relatively isolated environment. The sites of Gombore gully provide new evidence on the complex pattern of human evolution and adaptation in East Africa during the Lower Pleistocene.