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The Oldowan-Acheulian Transition and the Emergence of the Acheulian Industry, Field and laboratory Investigations at the Gona Plio-Pleistocene Archaeological Sites, Ethiopia

Final Report Summary - GONA PROJECT (The Oldowan-Acheulian Transition and the Emergence of the Acheulian Industry, Field and laboratory Investigations at the Gona Plio-Pleistocene Archaeological Sites, Ethiopia)

The Gona sites, in the Afar region of Ethiopia, contain fossiliferous deposits (with numerous fossil hominins) spanning the last 6.0 million years (Ma). The Gona Study Area is well-known for the discovery of the earliest Oldowan stone tools dated to 2.6 Ma. Although recent claims have been made for stone tools that date back to 3.3 Ma, the earliest confirmed and well-dated stone artefacts referred to as the Oldowan date back to 2.6 Ma at Gona, and lasted for about one million years with little technological/behavioural changes, up to the beginning of the Acheulian dated to ~1.75 Ma. Despite the evidence from two sites, Konso in Ethiopia, and Kokiselei in Kenya, which preserve the earliest Acheulian ~ 1.75 Ma, very little is known about the nature of the technological transition from the earlier Oldowan to the Acheulian (2.0-1.75 Ma). The Acheulian is a stone technology characterized mainly by deliberately shaped large cutting tools, which are made with much emphasis laid on large size and weight, i.e. in contrast to the Oldowan which is dominated by cores and sharp-edged cutting flakes primarily used for processing animal carcasses. Remarkably, the Oldowan stone industry still persisted with the Acheulian, actually with Mode I type artefacts remaining ubiquitous throughout the entire Paleolithic. It was at this critical juncture that Homo erectus, a large-brained hominin also emerged in East Africa. The most important question still remaining to be answered is the nature (mode and tempo) of the archaeological transition from the Oldowan to the Acheulian, which is among the least known in paleoanthropology. With funding from the European Union Marie Curie Integration Grant, the Gona Project conducted continuous investigations in 2012-2016 to answer this question, and documented over a dozen new archaeological sites estimated between 2.1-1.6 Ma. Promising results were achieved with our field investigations by excavations carried out at three archaeological sites that yielded possible intermediate stone tools, and fossil fauna bearing clear evidence of hominin induced stone tool cutmarks.
Major results of our investigations

We have documented more than a dozen new archaeological localities within the targeted time interval (2.0-1.7 Ma), and excavated five of those in 2012-2016. The most informative sites with a large number of excavated in situ materials were those documented from the Busidima North (BSN) and Ounda Gona South (OGS) areas. Our overall field observations and preliminary investigations indicate that the Oldowan-Acheulian transition was rather complex, and most likely a rapid one. The archaeological materials show that the toolmakers ~2.0-1.7 Ma sought stone tools with major emphasis laid on their heavy weight and large size, with minimum effort invested towards standardizing their shape. In addition, a number of sites estimated to be older than 2.0 Ma (~2.1 Ma), consisted of archaeological materials with very large flakes struck from large cobbles, which are uncommon in the older deposits (2.3-2.6 Ma). In addition, the surface collected materials from the OGN3 and adjacent sites suggest probable beginnings of the seeking out and use of larger cobbles for producing spheroidal/discoidal as well as unifacially/bifacially worked voluminous cobbles which may be precursors to the “proper Acheulian” documented in East Africa ~1.75 Ma. The archaeology team has documented at BSN70 stone assemblages consisting of large specimens with less invasive flaking which are much larger in size, and definitely different from the Oldowan, but not typical of the Early Acheulian (see Appendix 1, and Appendix 2). A volcanic ash capping the stratigraphy at BSN70 appears to be a possible equivalent of the “sub-waterfall” tuff at Gona estimated to 1.7 Ma. Although not totally clear, our preliminary observations around the OGN sites have shown a more complex picture emerging in the archaeological record with more spheroidal/discoidal shaping documented at some sites, and with large size stone artefacts recovered in deposits dated ~2.1-2.0 Ma, though very few which are essentially different from the traditional Oldowan. We are also awaiting for the radioisotopic dating and results of the paleoenvironmental proxy data to evaluate the extent to which the Acheulian innovation was environmentally mediated.
Survey was undertaken in the focused time interval (2.1-1.6 Ma), examining in more detail the cobble conglomerates (raw material sources) associated with the archaeological sites for the experimental knapping. Preliminary analysis of our Oldowan replication experiments showed that bifacial knapping is always more efficient, regardless of cobble form. We may thus conclude that the clear preference for unifacial flaking at some of the Gona Oldowan sites is not driven by the pragmatic convergence of individual learning. Rather, it provides clear evidence of imitation (perhaps even over-imitation) of the kind that could also support cultural transmission of specific production recipes in the Early Acheulean. We conclude that salient cognitive and social implications of the Early Acheulean instead lie with the greater physical skill required to produce and work on large blanks. Future investigations with "Brain Imaging" would be essential to determine cognitive implications of Oldowan and Acheulian stone toolmaking. Unfortunately, we could not accomplish this goal because of the very expensive costs the research entails. We are planning to apply for a major grant to pursue knapping replications and brain imaging studies for understanding the behavioural/cognitive evolution of ancestral toolmakers.

Faunal studies were conducted on the fossils collected/excavated from the targeted sites, as well as comparisons made with the fauna recovered from the earliest Oldowan sites (2.6 Ma) for assessing possible changes in hominin diet. A large number of well-preserved fossil bones with evidence of stone tool cutmarks were identified. Remarkably, comparative study of the bone surface modifications showed more hominin activity on the fossils recovered from the earlier Oldowan (2.6-2.0 Ma) rather than those associated with the Acheulian (~1.7-1.5 Ma). Although Acheulian handaxes are believed to be large cutting tools (LCTs), the archaeological evidence with cutmarks and chop marks for the earliest Acheulian is meager, and still further research is needed to understand whether or not early Acheulian handaxes actually were used in a similar fashion to those of the Oldowan. Further puzzling is the fact that no large size animals were documented with the Early Acheulian despite the consensus view in our field that the Early Acheulian Large Cutting Tools (LCTs) were supposedly invented for processing animal carcasses of large animals.

The Gona Project is providing opportunity for field training of Spanish, European and international students with access to resources in Africa. Further, the researcher is making efforts to create a working relationship between CENIEH and the Ethiopian Antiquities for facilitating research efforts, and for possible exchange of scientific personnel in the nearest future.