Two Acheuleans, two humankinds: From 1.5 to 0.85 Ma at Melka Kunture (Upper Awash, Ethiopian highlands).

The Acheulean is the longest-lasting human cultural record, spanning approximately 1.5 Ma and three continents. The most comprehensive sequences are found in East Africa, where, in largescale syntheses, the Lower Pleistocene Acheulean (LPA) has often been considered a uniform cultural entity. Furthermore, the emergence and development of Acheulean technology are seen as linked to the emergence and evolution of Homo ergaster/erectus. The criterion for grouping together different lithic assemblages scattered over space and time is the presence of large cutting tools (LCTs), more than of any other component. Their degree of refinement has been used, in turn, as a parameter for evaluating Acheulean development and variability. But was the East African LPA really uniform as regards all components involved in lithic productions? The aim of this paper is to evaluate the techno-economic similarities and differences among LPA productions in a specific micro-regional and environmental context, i.e. at Melka Kunture, in the Ethiopian highlands, and in a specific period of time: between ≈1.5 Ma, when some of the earliest Acheulean complexes appeared, and 1.0-0.85 Ma, when LCTs productions became intensive and widespread. Our detailed comparative analyses investigate all aspects and phases of the chaînes opératoires. Since hominin fossil remains were discovered at some of the analyzed sites, we also discuss differences among lithic productions in relation to the changing paleoanthropological record. Our studies show that at Melka Kunture the LPA techno-complexes cannot be grouped into a single uniform entity. The assembled evidence points instead to "two Acheuleans" well-defined by a strong discontinuity in various aspects of techno-economic behaviors. This discontinuity is related to a major step in human evolution: the transition from Homo ergaster/ erectus to Homo heidelbergensis.