Acheulean technological behaviour in the Middle Pleistocene landscape of Mieso (East-Central Ethiopia) Ignacio de la Torre a, * , Rafael Mora b , Adrian Arroyo a , Alfonso Benito-Calvo c a Institute of Archaeology, University College London, 31-34, Gordon Square, WC1H 0PY London, United Kingdom b Centre d'Estudis del Patrimoni Arqueologic de la Prehistoria, Facultat de Lletres, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain c Centro Nacional de Investigaci on sobre Evoluci on Humana (CENIEH), Paseo Sierra de Atapuerca S/N, 09002 Burgos, Spain article info Article history: Received 10 February 2014 Accepted 23 June 2014 Available online 22 July 2014 Keywords: Early Stone Age Acheulean East Africa Large cutting tools Mieso valley abstract The Mieso valley is a new paleoanthropological sequence located in East-Central Ethiopia. It contains Middle and Upper Pleistocene deposits with fossil and lithic assemblages in stratified deposits. This paper introduces the Middle Pleistocene archaeological sequence, attributed to the late Acheulean. Low density clusters of artefacts suggest short-term use of the landscape by Acheulean hominins. In Mieso 31, one of the excavated assemblages, refit sets indicate fragmentation of the reduction sequences and enable study of the initial stages of biface manufacture. Mieso 7, also a stratified site, is primarily characterized by a small concentration of standardized cleavers, and portrays another dimension of Acheulean technology, that related to final stages of use and discard of large cutting tools. Available radiometric dates place the Mieso Acheulean around 212 ka (thousands of years) ago, which would make this sequence among the latest evidence of the Acheulean in East Africa, in a time span when the Middle Stone Age is already documented in the region. © 2014 Elsevier Ltd. All rights reserved. Introduction Our knowledge of the Early Stone Age in East Africa has increased substantially over the last few decades. Intensive field- work in Kenya, Ethiopia and Tanzania has enabled the establish- ment of a solid radiometric and archaeological framework for Oldowan and Acheulean contexts. This is particularly true of the Ethiopian Rift Valley, where systematic surveys (e.g., Asfaw et al., 1990) led to the discovery of key sites, unknown to paleoanthro- pology prior to the 1990s (WoldeGabriel et al., 2000). Over the last few years, however, the pace of discovery of new sequences has slowed down, and a substantial part of archaeological fieldwork is conducted in areas already known. Here we introduce the archaeological sequence of Mieso, discovered during our surveys in 2008, and systematically inves- tigated in consecutive field seasons between 2009 and 2012. The Mieso valley is named after the town of Mieso (c. 300 km east of Addis Ababa), on the road from Awash town to Asebe Tefari and Dire Dawa (Fig. 1). The Mieso valley is located approximately 60 km south-east of Chorora, well-known for the discovery of Miocene great ape fossils (Suwa et al., 2007). Mieso also lies between two sites discovered by Desmond Clark during his surveys across the Main Ethiopian Rift in the 1970s (Clark and Williams, 1978), namely Aladi Springs (a stratified Middle Stone Age site 26 km to the north- east), and Arba (an Acheulean surface site 30e40 km to the south- west). Despite its proximity to known archaeological sites, the Mieso deposits nonetheless remained unreported until the begin- ning of our field project. During our surveys across the Mieso valley, Middle and Upper Pleistocene deposits were documented including fossils and arte- facts attributable to the Acheulean, Later Stone Age and putatively also to the Middle Stone Age. The geology and chronology of the Mieso Middle Pleistocene deposits are presented elsewhere (Benito-Calvo et al., submitted for publication), while emphasis will be given here to the archaeological contexts. Thus, this paper will introduce the archaeological sequence of the Mieso valley, focusing on the archaeo-stratigraphy of the Acheulean sites and, particularly, on the lithic assemblages. Our aim is to present a detailed account of the Acheulean technology in this previously unreported Middle Pleistocene sequence, and discuss the significance of well- preserved low density assemblages for the reconstruction of Acheulean hominin behaviour. In this context, our technological analysis will discuss methods of handaxe production and data derived from refit studies, the implications of assemblage structure * Corresponding author. E-mail address: i.torre@ucl.ac.uk (I. de la Torre). Contents lists available at ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol http://dx.doi.org/10.1016/j.jhevol.2014.06.008 0047-2484/© 2014 Elsevier Ltd. All rights reserved. Journal of Human Evolution 76 (2014) 1e25