Manuscript Click here to access/download;Manuscript;Ma et al. manuscript_R2_clear.docx 1 Technological adaptations of early humans at the Lower Pleistocene 1 2 3 2 Nihewan Basin, North China: the case of the bipolar technique 4 1,2,3 1,2 4 1,2,3 1,2 5 3 Dongdong Ma , Shuwen Pei , Ignacio de la Torre , Zhe Xu , Hao Li 6 7 4 8 9 5 1 Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate 10 11 6 Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 12 13 7 100044, China 14 15 8 2 CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China 16 17 3 18 9 University of Chinese Academy of Sciences, Beijing 100049, China 19 4 20 10 Department of Archaeology, Institute of History, National Research Council-CSIC, 21 22 11 Albasanz, 26-28, 28037 Madrid, Spain 23 24 12 25 26 13 *Corresponding author (E-mail: [email protected]) 27 28 14 29 30 31 15 ABSTRACT 32 33 16 The Nihewan Basin in North China has proved to be a key area for the study of human 34 35 17 evolution outside of Africa due to its continuous record of hominin occupation since 36 37 18 the Early Pleistocene. Lower Palaeolithic lithic assemblages at Nihewan are attributed 38 39 19 to the East Asian Mode 1 techno-complex, which is often defined by the widespread 40 41 20 use of freehand knapping techniques. However, our ongoing investigation of several 42 43 44 21 early Pleistocene archaeological sites at Nihewan has revealed a higher prevalence of 45 46 22 bipolar stone artefacts than previously considered, which may have been 47 48 23 underestimated in the past due to the disparity of analytical techniques applied to Early 49 50 24 Stone Age assemblages and the poor quality of the Nihewan Basin raw materials. This 51 52 25 has constrained the identification of bipolar attributes and their differentiation from 53 54 26 freehand knapping products. This study aims to investigate technological and 55 56 27 economical differences between the two techniques based on experimental results of 57 58 59 28 chert from the Nihewan Basin, creating a referential framework for the study of bipolar 60 1 61 62 63 64 65 29 artefacts that we apply, to the Early Pleistocene assemblages of Xiaochangliang and 1 2 3 30 Cenjiawan. Our results highlight morphological and technological differences between 4 5 31 bipolar and freehand products, but they also demonstrate that both techniques share 6 7 32 significant similarities in terms of dimensions and productivity. Overall, our results help 8 9 33 to contextualize the technological flexibility of East Asian Mode 1 assemblages in the 10 11 34 Nihewan Basin, where early hominins employed alternative flaking techniques, often 12 13 35 in the same assemblage, to overcome constrains imposed by the poor quality of most 14 15 36 of the raw materials available. 16 17 18 37 19 20 38 Keywords: Nihewan Basin, North China, Early Pleistocene, Bipolar technique, 21 22 39 Experimental Palaeolithic archaeology 23 24 40 25 26 41 1. Introduction 27 28 42 The bipolar technique, in which a core is placed on an anvil stone and struck with 29 30 31 43 a stone percussor, is one of the most important lithic techniques from the earliest 32 33 44 archaeological sites to the ethnographic present (Leakey 1967; Bordes 1968; S Bordaz 34 35 45 1970; Schick and Toth 1993). The occurrence of bipolar knapping in Oldowan sites 36 37 46 such as Omo (de la Torre 2004; Boisserie et al. 2008), Fejej FJ-1a (Barsky et al. 2011), 38 39 47 FxJj3 (Ludwig and Harris 1998) and others show it was one of the earliest knapping 40 41 48 techniques used to obtain sharp stone tools (Schick et al., 1999; Wynn et al., 2011). 42 43 44 49 Whilst bipolar knapping has often been considered an expedient knapping technique 45 46 50 used to overcome poor flaking quality of raw materials, new evidence indicates that 47 48 51 this technique can be applied to produce even bladelet-like products or Levallois cores 49 50 52 (Tabrett 2017), and archaeologists have long sought to understand the technological 51 52 53 characteristics and variability of human behaviour associated with bipolar knapping 53 54 54 (Teilhard de Chardin and Pei 1932; Hayden 1979; Shott 1989, 1999; de la Torre, 2004; 55 56 55 de la Peña and Wadley 2014; de la Peña 2015; Byrne et al. 2016; Arroyo and de la Torre, 57 58 59 56 2018). 60 2 61 62 63 64 65 57 Bipolar knapping involves three elements, i.e. a hammer, a core and an anvil 1 2 3 58 (Patterson and Sollberger 1976). Flaking experiments have shown that striking force 4 5 59 rebound causes damage to the distal end of the core that is characteristically different 6 7 60 from freehand knapping (Patterson and Sollberger 1976; de Lombera-Hermida et al. 8 9 61 2016), but it is unlikely that all strikes produce cores with identifiable bipolar features 10 11 62 on both proximal and distal ends. Vergès and Ollé (2011) argued that the spatial relation 12 13 63 between the impact point and the counterstrike can vary in the bipolar knapping process, 14 15 64 and typical bipolar fracture depends on the core morphology and delineation of the 16 17 18 65 resting surface of the anvil. Since not every bipolar flake will be initiated with 19 20 66 equivalent forces in the proximal and distal ends, a significant proportion of bipolar 21 22 67 products may possess attributes similar to those obtained during freehand knapping 23 24 68 (Bordes 1968; Barham 1987; Bradbury 2010; Byrne et al. 2016), which will largely 25 26 69 depend on the type and quality of raw materials (Jeske and Lurie 1993). Thus, assessing 27 28 70 the extent of bipolar flaking in archaeological assemblages faces the challenges of both 29 30 31 71 correctly identifying the characteristic attributes of this technology, and accounting for 32 33 72 the invisibility of this technique among the ‘non-textbook’ products that lack distal 34 35 73 damage. Various experiments (de la Peña and Wadley 2014; de la Peña 2015; Byrne et 36 37 74 al. 2016) have been applied to explore the constrains of bipolar identification in lithic 38 39 75 assemblages. However, theses are often site-specific and therefore fail to establish 40 41 76 universal criteria that can be applied to Palaeolithic sites in other regions such as Asia, 42 43 44 77 or more specifically, the Nihewan Basin, the case study discussed here. 45 46 78 In this paper, we present the results of a series of bipolar and freehand knapping 47 48 79 experiments with local chert collected in Nihewan Basin, compare such experimental 49 50 80 results with the Early Pleistocene assemblages of Xiaochangliang and Cenjiawan, and 51 52 81 we discuss the technological and economical differences between the two knapping 53 54 82 techniques in the context of the Palaeolithic in China. Our primary goal is to develop 55 56 83 analytical protocols for the identification of bipolar artifacts in the Early Palaeolithic of 57 58 59 84 the Nihewan Basin, and to establish the proportion of bipolar pieces that can be 60 3 61 62 63 64 65 85 expected in Early Stone Age assemblages in this area. Additionally, we aim to compare 1 2 3 86 the productivity of freehand and bipolar techniques using Nihewan chert, and thus 4 5 87 contribute new insights into the benefits and constraints involved in the choice of each 6 7 88 technique during the East Asian Early Palaeolithic. 8 9 89 10 11 90 2. Materials and methods 12 13 91 2.1 Geographic and archaeological context 14 15 92 The Nihewan Basin, located in the transition zone between the North China Plain 16 17 18 93 and the Inner Mongolian Plateau (Zhou et al. 1991; Zhu et al. 2001, 2004; Deng et al. 19 20 94 2008), is a key area for the study of human behavioural evolution worldwide. Most of 21 22 95 the Early Pleistocene archaeological sites from East Asia have been excavated in this 23 24 96 basin (Wei and Xie 1989; Zhu et al. 2001, 2003, 2004; Wang et al. 2005; Deng et al. 25 26 97 2006, 2007; Xie et al. 2006; Ao et al. 2010, 2013a,b; Liu et al. 2010; Pei et al. 2019; 27 28 98 Yang et al. 2019)(Fig. 1), yielding important materials for the study of human origins 29 30 31 99 and dispersal during “Out of Africa I” (Schick et al. 1991; Zhu et al. 2001, 2004; Gao 32 33 100 et al. 2005; Deng et al. 2008; Braun et al. 2010; Dennell 2010, 2013; Pei et al. 2017). 34 35 101 It is widely accepted that the technological characteristics of the Nihewan Basin 36 37 102 sites fall within the East Asian Mode 1 techno-complex, characterized by core and flake 38 39 103 assemblages (Pei et al., 2017, 2019). Most studies have emphasized the predominance 40 41 104 of freehand knapping of poor- quality chert local outcrops (Schick et al. 1991; Keates 42 43 44 105 2000; Shen and Wei 2004; Gao et al. 2005; Dennell 2008; Liu et al. 2013; Guan et al. 45 46 106 2016; Yang et al. 2016; Pei et al. 2017) (see Table 1). In recent years, however, re- 47 48 107 analyses of previously excavated assemblages from Xiaochangliang and Donggutuo 49 50 108 have identified higher frequencies of bipolar artifacts than originally reported (Yang et 51 52 109 al.