Late Prehistory in the lakes region (Ziway, Shala, Langano, Abijata), Main Ethiopian Rift, Ethiopia

The lakes region (Ziway, Shala, Langano, Abijata) is located in the central part of the Main Ethiopian Rift. Thirty years ago geological and hydrological investigations in this area highlighted a cycle of rises and falls in lak level related to general changes in rainfall during the late Quaternary. Joint archaeological researches had shown the interest of this area for the knowledge of the late Prehistory of Ethiopia (mainly Middle and Late Stone Age). The correlation between the palaeo-environmental restitutions and the history of human settlement justified our mission in this area. Among the various geomorphological contexts explored since 2007, the richest information came from the banks of the Bulbula, the river connecting lake Ziway to Abijata. Geological data and pedo-sedimentary conditions from this area permit to find sites with lithics and organic assemblages and make possible to ascribe these archaeological remains within the general history of the landscape. Multidisciplinary approach allows us to obtain a more complete and precise sequence of the evolution of human behaviour, placed within their palaeo-environmental framework. We identified a Late Quaternary sequence including lakes fluctuations and volcanic events. Three main archaeological phases are recognised: the first (1) yield lithic industries belonging to the end of the Pleistocene and contribute to the debate on the final MSA and the transition to the early LSA. The second phase (2), dated around 11.500 BP (i.e. just before the last great phase of increase of the lakes level), is particularly well documented in a rock shelter (B1s1), where a rich stratified lithic industry is found associated with abundant well preserved faunal remains. These contexts allow us to approach the question of economy, in particular the interaction between lacustrine environment and subsistence behaviour. The third phase (3) postdates the last main regression of the lakes levels, which took place approximately 5000 years ago. It yield a totally different lithic industry dominated by flake production associated with ceramics. However the first evidence of domestic animals (cattle) appears during this phase.

Keywords: Ethiopia, Late Stone Age, evolution of the landscape, Bulbula River