An Early Stone Age in Western Africa? Spheroids and polyhedrons at Ounjougou, Mali

Abstract

Ounjougou stratigraphic sequence (Bandiagara, Dogon Country, Mali) is the most complete record in Western Africa for the Middle Pleistocene. This paper focuses on the lithic industry unearthed in the lowest levels of the sequence. Despite the impossibility to fix the dating of those layers, the assemblage clearly presents Oldowan features. A strong erosive process, combined to the absence of Acheulean industry, strengthens the idea of a probable ancient age for the lithic industry. Morphometric, Technological and techno-functional approaches were performed to study sandstone polyhedrons, spheroids and bolas, abundant in the collection, along with a flake production on quartz and quartzite pebbles.
 This study demonstrates that polyhedrons, spheroids and bolas were shaped from independent chaînes opératoires to realize specific tasks. The hypothesis of opportunistic knapping does not fit with these materials at Ounjougou. The evidence of shaping is highlighted by diacritic schemes showing that the flakes detached are not controlled for their usability, but for shaping the morphology of the spheroid. Apart from those polyhedrons and spheroids, flake production is also identified. While the shaping process is made on sandstone cobbles, sharp flakes are produced from quartz pebbles. This clear choice of different raw materials to produce shaped heavy tools in one hand and light flake tools in another hand strengthens the idea of a deliberate shaping of spheroid tools.
 The discussion compares this assemblage with other known assemblages like Ain Hanech and Olducai Gorge. Our point focus on the methodology used to study these specific artefacts, very different from one author to another. We stress out the fact that using the term ‘polyhedron’ is not accurate to define artefacts that can refer to shape tools or multifacial cores. We suggest to avoid using it and to focus on a technical identification to name the artefacts as cores or tools. The technological and techno-functional approaches are relevant to make this distinction.
 Then we propose some hypothesis about the use of spheroid and bolas and suggest experiments and traceological analyses in the future to confirm their functionality.
 Ounjougou lithic tool kit, composed of flake débitage, retouched flakes and shaped tools on pebbles, along with the spheroids and bolas component, gives an evidence of a diversified tool kit corresponding to the Oldowan Industrial Complex, and then represents the first Early Stone Age site in stratigraphy in Western Africa.

Palaeolithic polyhedrons, spheroids and bolas over time and space

“…Generally, as for most Palaeolithic sites, assemblages with PSBs yielded big mammal remains. The absence of such remains is generally due to taphonomic processes, for instance high soil acidity that dissolved organic materials, as is the case at Ounjougou, Mali [ 11 ], or in the majority of sites from Rajasthan, India. When large faunal remains are present in the corpus, they are mainly intentionally anthropically broken bones, except in the Levant, possibly to extract marrow ( Table 5 ).…”

“…This is also the case in Beds I and II of Olduvai, where polyhedrons are made of lavas whereas spheroids and bolas are almost all in quartz [ 18 ]. Based on diacritic schemes, De Weyer [ 11 ] also argues that at the site of Ounjougou (Mali, Oldowan cultural facies attribution), polyhedrons, spheroids and bolas stem from different operative chains.…”

“…For instance, Titton et al [ 13 ] carried out a study of the five PSBs from the Oldowan site of Barranco León (Spain), combining diacritical and 3D geometric morphometric analysis with an evaluation of the raw material (limestone) and of percussive use-wear (types and localisation). De Weyer [ 11 , 32 ] proposed an analysis of the PSBs from Ounjougou with technological, techno-functional and morphometric approaches, comparing these pieces with PSBs from other sites such as Olduvai Gorge and Ain Hanech. The most extensive and significant works on PSBs may be attributed to Willoughby (e.g., [ 6 , 17 ]) for her techno-functional analysis, to Sahnouni, Schick and Toth for their experimental and morpho-technical studies (e.g., [ 9 , 33 , 46 ]), and to Texier and Roche for their experimental and technological approaches [ 8 , 36 , 47 ].…”

“…These rounded morphologies lasted for nearly two million years as they are found until the Neolithic (e.g., [2]) and even historical periods (e.g., [3]). Different hypotheses have been put forward as to their possible functions (e.g., exhausted cores, hammerstones or projectiles) [4][5][6][7][8][9][10][11][12][13]. Interestingly, PSBs seem quite common in African and Asian assemblages whereas they are less documented in European sites.…”

Following the evolution of Homo sapiens across Africa using a uniparental genetic guide

“…Regrettably, although its archaeological record is still scarce, western Africa seems to be a region of delayed and stagnant hominin evolution. Putative Oldowan, Acheulean, Sangoan and other Middle Stone Age incipient industries are sensibly more recent in West Africa [76][77][78] than their counterparts in eastern and central-southern Africa [7,79]. Likewise, the scarce hominin fossils remains unearthed show primitive features even at recent Pleistocene to Holocene boundaries as is the case of the Nigerian Iwo Eleru remains, reflecting either admixture with archaic humans or long-term survival of primitive anatomical features at recent (11.7 -16.3 Ka) times [80,81].…”