Site function and lithic technology in the Acheulean technocomplex: a case study from Thiongo Korongo (TK), Bed II, Olduvai Gorge, Tanzania

The most recent excavations carried out at the Thiongo Korongo (TK) site, in the upper part of Olduvai Bed II and dating from about 1.353±0.035 Ma, have made it possible to identify a hitherto unknown Acheulean floor. Between 2010 and 2015, we excavated nearly 175 m2 in several areas immediately adjacent to M. Leakey's trenches. Our findings led us to reinterpret TK's general stratigraphy and to identify a hitherto unpublished floor situated between levels TKLF and TKUF (the ones recognized by M. Leakey), which we have called TKSF. The differences we note between these two floors are very significant and concern production techniques and systems, which were aimed at obtaining different types of tools. These differences are especially marked in bifaces. In TKLF, bifacial tools consist of large, very specialized items characterized by a functional point opposite a thick basal area that makes the tool easy to grasp. In TKSF, handaxes are lighter and their cutting edges extend all around their perimeter, and can thus withstand long and varied uses. Considering the stratigraphical proximity and the accumulation rate of the sedimentary processes involved, the differences we observed cannot be correlated with evolutionary developments, which would require long periods of time. The differences observed in the tools seem to be related to the different activities carried out on each of these floors, and show that TK was a complex site with a heuristic capacity that is particularly significant in the context of Olduvai and of the study of behaviour patterns in the Lower Pleistocene.