New evidence of bipolar technique use in the eastern Africa Middle Stone Age (MSA)

The bipolar technique has been employed throughout the Palaeolithic and across the entire globe. Regular cores were made placing the stone object on an anvil, to be hit from above by a hammer (Hiscock, 2015) held with bare hand, causing blanks to detach from the top and the edge in direct contact with the anvil (de la Peña, 2015). In Africa, the bipolar reduction has long been recognised as a key feature in many lithic industries and techno-complexes (de la Peña, 2015). Despite this knapping technique has been seen first as a typological and then as a technological marker for the appearance of the Later Stone Age (LSA), probably linked to the miniaturisation of the lithic objects (de la Peña, 2015), evidence of bipolar knapping is present since the early Stone Age. While bipolar reduction was an integral component of late Pleistocene lithic miniaturisation strategies across the continent (Hiscock, 2015), in early Pleistocene contexts bipolar knapping is usually interpreted as a strategy to produce large flakes or to open cobbles (de la Peña 2015). The bipolar technique is, in fact, well-attested at a very early stage of lithic technology development - probably for butchering purposes - preceding chopper-like core reduction, providing a link between primate nut-cracking technologies and the emergence of other and sophisticated lithic technologies (Hayden 2015). Bipolar knapping has been recognised mainly from bipolar cores and specific flake products, e.g. splintered pieces / scaled pieces. Nevertheless, the understanding of the typological morphotypes such as splintered pieces (pièce esquillées) has been highly controversial in prehistory: whether they are tools or cores has not been solved unambiguously; however, there is no reason why this has to be framed in oppositional and not continuous terms (Shott, 1999). Bipolar technique is linked to the use of small raw materials in order to i) initialise small lithic cores, ii) extend the core life, and iii) manufacture specific products (e.g. backed pieces) (Hiscock 2015). This paper presents new evidence from two sites in Ethiopia: Garba III, Melka Kunture; and GOT10 site, Gotera area. Garba III, in the upper Awash Valley, is one of the many sub-sites of Melka Kunture (FIG.1A; B) and has an archaeological sequence spanning from Acheulean to MSA, associated with three cranial fragments of Homo sapiens (Mussi et al. 2014). The sequence has no absolute dating, however, an age of Early MSA has been proposed. New research highlights flake and bladelet production from small obsidian pebbles, available locally in the alluvium deposits, and here the bipolar percussion is mainly used to increase the use life of small cores. The Gotera area is located 500 km south of Addis Ababa (FIG. 2A). In 2018 a new site was discovered that presents a dense concentration of surface material (lithic implements and bone fragments, with few ostrich eggshell fragments) and displays an in-situ stratigraphy (FIG. 2B; C). The site is dated to the MIS3, a chronological period where LSA technological features appeared in some East African contexts. The raw materials exploited are quartz and basalt. The preliminary analysis of lithic assemblage shows high utilisation of the bipolar technique for quartz artefacts, here employed together with other MSA reduction strategies such as Levallois and discoid method and volumetric exploitation. The bipolar technique may be linked to the small size of quartz cobbles, while it has not been used to flake larger basalt cobbles. Moreover, the miniaturisation of the lithic assemblage and the extension of core-life, as testified by the use of other knapping methods in association with the bipolar technology on the same pieces, may have played an essential role in the economy of the chaîne opératoire.