Lepolosi is located on the Sambu Escarpment, 500 m on top of Lake Natron and 5 km South-West from the Type Section area. The site, originally named MHS and Bayasi, was discovered and excavated in 1964. Between 1996 and 2002, the Spanish team unearthed remarkable clusters of Acheulean large cutting tools and published the preservation of Acacia phytoliths adhered on the artifact cutting edges. Starting in 2008, our team continues the archaeological research at Lepolosi with the main goals of: enlarging the excavated area (43 m2 exposed since 2008), undertaking additional stratigraphic and contextual studies (including micromorphological, pollen and phytolith sampling), and defining the Early Acheulean technological behaviors carried out by early humans at the spot. Lepolosi is located 3 m on top of the T4 tephra layer, in the Upper Sands and Clays Unit of the Humbu Formation. The archaeological horizon is composed by greenish muddy sandstone interbedded with rootmarked sandstone lenses. Current paleoenvironmental interpretation suggests that the archaeological occupation occurred in a low energy flood plain related to a fluvial system in a deltaic context.
At Lepolosi, the Acheulean toolmakers were knapping good quality basalts available in the middle section of the Peninj River watercourse. The main trait that defines the technological behaviors undertaken at Lepolosi is the production of Large Cutting Tools. Very large and thick flakes were being detached in the vicinity of the site and transported in-site fully or partially shaped. We have found that the Lepolosi toolmakers had the precise knowledge to produce rather symmetrical bifaces. However, the bulk of the LCT sample is defined by more casual shaping processes. Toolmakers were interested in superficial transformation of large flake blanks in order to produce points and/or broad cutting edges that added an extra functional meaning to these massive and heavy tools.