Afr Archaeol Rev (2018) 35:107–131 https://doi.org/10.1007/s10437-018-9287-1 ORIGINAL ARTICLE Biface Knapping Skill in the East African Acheulean: Progressive Trends and Random Walks C. Shipton Published online: 8 March 2018 # The Author(s) 2018. This article is an open access publication Abstract Over the 1.5-million-year duration of the Acheulean at Olduvai Gorge, a temporal trend was indeed Acheulean, there is considerable variation in biface fi- apparent. Possible factors influencing this trend include nesse. It is not clear, however, if there is an improvement the invention of new knapping techniques, the addition of in biface knapping ability over time, or if variation be- adolescence as a life history stage, and evolving hominin tween sites is largely unrelated to their age. The diversity cognition. and duration of the East African Acheulean presents an opportunity to examine this issue. Variables that reflect Résumé Au cours de la durée de 1.5 million d’années difficult aspects of biface knapping, and which were de l’Acheuléen, il existe une variation considérable de la likely important goals for Acheulean hominins, were finesse biface. Cependant, il n’est pas clair s’il existe measured in order to assess skill. These variables—re- une amélioration de la capacité de taille en biface dans le finement (thinness), edge straightness, and symmetry— temps, ou si la variation entre les sites est en grande were compared across four East African Acheulean sites: partie sans lien avec leur âge. La diversité et la durée de Olduvai Gorge, Olorgesailie, Kariandusi, and Isinya. The l’Acheuléen de l’Afrique de l’Est sont l’occasion influence of rock type, blank type, reduction intensity, d’examiner cette question. Des variables qui reflètent aberrant scar terminations, and invasive flaking on these des aspects difficiles du taille biface, susceptibles d’être variables was assessed. Over relatively short timescales, importants pour les hominins Acheuléen, ont été confounding factors, including ones not possible to con- mesurées afin d’évaluer les compétences. Ces variables trol for, tend to obscure any temporal signature in biface étaient le raffinement (minceur), la rectitude du bord, et knapping skill. However, over the vast timespan of the la symétrie, et ont été comparées dans quatre sites Acheuléen de l’Afrique de l’Est: gorges d’Olduvai, Electronic supplementary material The online version of this Olorgesailie, Kariandusi, et Isinya. L’influence du type article (https://doi.org/10.1007/s10437-018-9287-1) contains de roche, du type support, de l’intensité de réduction, supplementary material, which is available to authorized users. des terminaisons de éclat aberrantes et des écailles inva- sives sur ces variables a été évaluée. Sur des échelles de C. Shipton (*) McDonald Institute for Archaeological Research, University of temps relativement courtes, les nombreux facteurs qui Cambridge, Cambridge, UK affectent les formes de bifaces tendent à masquer toute e-mail: [email protected] signature temporelle dans la compétence de biface knap- ping. Cependant, sur le vaste laps de temps de C. Shipton ’ British Institute in Eastern Africa, Nairobi, Kenya l Acheuléen sur des sites comme Olduvai Gorge, une tendance temporelle est en effet évidente. Parmi les C. Shipton facteurs qui peuvent influencer cette tendance, on peut Centre of Excellence for Australian Biodiversity and Heritage, citer l’invention de nouvelles techniques de taille, l’ajout Australian National University, Canberra, Australia 108 Afr Archaeol Rev (2018) 35:107–131 de l’adolescence comme stade de l’histoire de la vie et made examples occur in later assemblages. With the l’évolution de la cognition de l’hominine. revision of Louis Leakey’s fine progression, Glynn Isaac’s (1971) random walk model came to the fore, in which Keywords Olduvai Gorge . Handaxe . Cleaver. progressive signatures in bifaces are largely obscured by Refinement . Symmetry. Edge straightness the range of variation between sites of similar age: BWhat do numbered stage divisions such as those formerly employed in the Somme, Morocco or Olduvai mean if a Introduction penecontemporaneous set shows almost as much diversi- ty as a markedly diachronic series?^ (Isaac 1971, p. 173). For nearly 150 years, scholars of the Acheulean have Isaac (1971) observed that in variables such as biface speculated that there may be chronological patterns length, elongation, and thinness, the variation between within the period (de Mortillet 1873), but the issue individual localities at Olorgesailie, Isimila, and Kalambo remains controversial (McNabb and Cole 2015). East Falls exceeded the variation between these broad sites of Africa is the original homeland of the Acheulean with different ages. His random walk model proposed that due the earliest sites documented c. 1.75 million years ago to the influence and interaction of traditions, functional (mya) at Konso in the southern Ethiopian Highlands, requirements, and raw materials, any time trends in Kokiselei on the west side of Lake Turkana, and at Acheulean biface skill would be extremely weak. This Olduvai Gorge to the southeast of Lake Victoria characterisation of intra-assemblage variability exceeding (Beyene et al. 2013; Diez-Martín et al. 2014; Lepre much inter-assemblage variability also holds up in multi- et al. 2011). The Acheulean in East Africa persists until variate analyses of several linear dimensions on bifaces at least c. 0.2 mya (Benito-Calvo et al. 2014;McKinney (Gowlett 2015). Isaac (1971, p. 184) did see weak trends 2001; Tryon and McBrearty 2006)whenitissucceeded for increasing refinement at Olorgesailie, but he noted by the Middle Stone Age. East Africa thus presents an that Bthere is room for a great deal of random oscillation excellent opportunity to examine temporal trends in the within a general drift of change that lasted almost a period. The longue dureé perspective on the Acheulean million years.^ In his more recent study of the Olduvai is epitomised by Olduvai Gorge where successive layers Gorge bifaces, Roe (1994) saw that there were general of Acheulean occupation can be found spanning 1.75 to trends from the vast timespan covered between Bed II and 0.4 mya (McHenry 2005; McHenry et al. 2008; Tamrat post-Bed IV, but emphasised that these were local trends et al. 1995). In fact, in Louis Leakey’s(1951) original and there was substantial variation within each bed. study of the Olduvai Gorge bifaces, he divided them into The perception that there is progression through no less than 11 progressive stages (Fig. 1): BThe culture time in the Acheulean more generally is widespread sequence – from the base of the deposits of Bed I to the (Clark 1994; Gaillard et al. 1986; Hodgson 2015; top of Bed IV – reveals a slow and gradual evolution Misra 1978; Paddayya 2007; Sahnouni et al. 2013; from the simple pebble tools of the Oldowan to the most Schick and Clark 2003), though not often formally beautifully made small hand-axes and cleavers of the tested. Earlier Acheulean bifaces are characterised as Late Acheulean type^ (Leakey 1951,p.158). being relatively asymmetrical, with thick cross-sec- Each of Leakey’s original stages had distinctive tech- tions, and wavy sinusoidal profiles, while late Acheu- nological features, such as Stage 2 with its large handaxes lean forms are described as thinner, more symmetrical, with thick butt-ends and plano-convex profiles, or Stage 7 and with straighter edges (Fig. 1) (Clark 1999, 2001; with its frequent use of a soft hammer, the presence of Roe 1994; Wynn 2002). cleavers, and large well-made bifaces (Leakey 1951). Experimental knappers note the high skill levels re- Stratigraphic revisions were made to the Olduvai se- quired to replicate the finer examples of Acheulean quence following Leakey’s preliminary publication. The bifaces (Bradley and Sampson 1986;Edwards2001; relative ages of assemblages within beds were altered Newcomer 1971; Winton 2005). Geribàs et al. (2010) from their original positioning, leading Louis and Mary identify the type of percussion support, the position of Leakey to reject the fine progression schema (L. Leakey the blank, and the angle of the blow as three gestures et al. 1965; M. Leakey 1967, 1971). Individual examples that must be mastered for handaxe knappers to become of well-made bifaces occur in early assemblages at experts. Other studies highlight the need for hierarchical Olduvai Gorge (Diez-Martín et al. 2014), and poorly organisation, in which knapping proceeds in stages Afr Archaeol Rev (2018) 35:107–131 109 Fig. 1 Four Acheulean handaxes from Olduvai Gorge used in this study and also selected by Leakey to represent his evolutionary stages (after Leakey 1951). The top left specimen is from the bot- tom of Bed II, the top right from the middle of Bed II, the bottom left from Bed III and the bottom right from Bed IV. Note that the lower two handaxes are relatively thinner, they have straighter edges, and are more symmetrical. Note that the lower pieces have been both invasively flaked to re- move any cortex and were fin- ished with small marginal trim- ming flakes requiring different strategies; from roughing out a cob- shape, and more symmetrical in plan form between ~ ble or preparing a giant core, to thinning and shaping the 1.4 and 0.5 mya (Gilead 1970, 1977; Grosman et al. blank (Newcomer 1971; Winton 2005). 2011a; Saragusti et al. 2005; Saragusti et al. 1998). At Some studies have reported time trends in Acheulean the late Acheulean site of Mieso 7 in Ethiopia, the final bifaces, such as increasing mean thinness (Shipton stage in cleaver production after the pieces had been 2013). In the Eastern Rift Valley, the early Acheulean thinned, was typically marginal trimming to regularise bifaces from Peninj are relatively thicker and have fewer the planform shape (de la Torre et al.