Lawrence Barham Backed tools in Middle Pleistocene central Department of Archaeology, Africa and their evolutionary significance University of Bristol, 43 Woodland Road, Bristol The fashioning of stone inserts for composite tools by blunting flakes BS8 1UU, U.K. e-mail: and blades is a technique usually associated with Late Pleistocene [email protected] modern humans. Recent reports from two sites in south central Africa (Twin Rivers and Kalambo Falls) suggest that this backed tool Received 5 December 2001 technology originated in the later Middle Pleistocene with early or Revision received ‘‘archaic’’ Homo sapiens. This paper investigates these claims critically 23 March 2002 and from the perspective of the potential mixing of Middle and Later accepted 8 July 2002 Stone Age deposits at the two sites and the possible creation of Keywords: central Africa, misleading assemblages. The review shows that backed tools form a Middle Stone Age, statistically minor, but technologically significant feature of the early Lupemban industry, backed Middle Stone Age of south central Africa. They first appear in the tools. Lupemban industry at approximately 300 ka and remain an element of the Middle Stone Age technological repertoire of the region. Comparisons are made with early backed tool assemblages of east Africa and with the much younger Howiesons Poort industry of southern Africa. The paper concludes that Lupemban tools lack the standardization of the Howiesons Poort backed pieces, but form part of a regionally distinctive and diverse assemblage of heavy and light duty tools. Some modern-like behaviours appear to have emerged by the later Middle Pleistocene in south central Africa. 2002 Elsevier Science Ltd. All rights reserved. Journal of Human Evolution (2002) 43, 585–603 doi:10.1006/jhev.2002.0597 Available online at http://www.idealibrary.com on Introduction in the Lupemban predates the appearance of this technology in east Africa at 130 ka It has recently been claimed that backed (Mehlman, 1989) and in southern Africa stone tool technology is present in the at 75 ka with the Howiesons Poort Middle Pleistocene archaeological record of industry (Gru¨n & Beaumont, 2001). The south-central Africa (Barham, 2000, 2001; backed tools of the Howiesons Poort have Clark, 2001; Clark & Brown, 2001). been interpreted as evidence of behavioural Blunted, truncated and snapped flakes modernity having been developed by OIS4 and blades have been reported from the based on their similarity to Later Stone Age Zambian sites of Twin Rivers and Kalambo backed artefacts of the mid-Holocene (H. J. Falls, and are attributed to the later Deacon, 1992). The similarities include the Lupemban industry of the Middle Stone standardization of size and shape for hafting, Age. At Twin Rivers they account for up to the use of nonlocal raw materials and the 15% of the retouched tool assemblage relatively brief duration of the backed com- (Barham, 2000:206), and are bracketed by ponent of each industry. The arbitrary TIMS U-series dates of between >400 and change in tool design represented by 140 ka with a probable median age of the appearance and disappearance of the 260 ka. The Lupemban at Kalambo Falls is Howiesons Poort is considered by some to presumed to be of a similar age range represent not just technological adjustments (Clark, 2001). The presence of backed tools to changing resources, but also evidence of 0047–2484/02/110585+19$35.00/0 2002 Elsevier Science Ltd. All rights reserved. 586 . Figure 1. (a). material culture embedded in social dis- the mixing of deposits and the creation of a course. Backed tools are culturally deter- spurious association of old dates with mined conventions or mental templates younger artefacts. As the most recent exca- indicative of modern symbol-based behav- vator at Twin Rivers, I want to draw atten- iours (Wurz, 1999). If such an interpret- tion to the formation of the site and its ation can be extended to the backed tools of contents so that the reader can make an the Lupemban, then the co-evolution of informed opinion about the above claims. behavioural and anatomical modernity is The recent publication of the results from challenged (e.g., Stringer, 2001). The the original excavation at Twin Rivers in the apparent emergence of symbol based 1950s (Clark & Brown, 2001) can now be technological complexity in the Middle considered alongside those from the 1999 Pleistocene long precedes the evolution of excavations (Barham, 2000). The dating anatomically modern humans (as defined by and stratigraphic context of the artefacts are Lieberman et al., 2002). reviewed and the extent of possible mixing is Given the potential behavioural signifi- assessed. The evidence for backed tools at cance of early backed tool technology, the Kalambo Falls is considered separately. The Zambian database warrants close scrutiny. two datasets are then combined and com- The site of Twin Rivers in particular is pared to the Howiesons Poort industry. The problematical because of the potential for backed pieces of the Lower Lupemban lack Figure 1. (b). Figure 1. (a) Location map of Twin Rivers and section through the length of A Block (1999 excavation) showing the relationship between breccia, red sandy sediment and U-series dates on speleothem (numbered). Samples 2 and 3 are >400 ka and sample 1 is 265 ka (see Barham et al., 2000: Table 10.1 for analytical details). (b) Photograph of A Block section, north wall, at start of excavation in 1999. The excavator is sitting on breccia and pointing to area of red sediment fill between the breccia and remnant cave passage at back and above. 587 588 . the standardization of the Howiesons Poort (ibid:181–3) and falls within the final age tools and there is no evidence of preferential range for the two caves. The maximum age selection of raw materials for backing. These for F Block appears to be about 200 ka differences aside, the Zambian tools do based on U-series dating of a speleothem demonstrably reflect a degree of planning that capped the breccia in the centre of the and problem solving comparable to that cave passage2 (Barham & Smart, 1996; exhibited by Late Pleistocene modern Barham, 1998). humans in southern Africa. Human occupation continued on the hill- top from the Late Pleistocene to the historic present (ibid:183). This later use of the Twin Rivers site is a potential source of contamination of the collapsed cave deposits, especially of The hilltop site of Twin Rivers (1531S; the unconsolidated sediments. It could be 2811E) is an extension of the Lusaka argued that the backed tools found in the limestone plateau which is composed of cave fills were simply intrusive from the dolomitic marble in which vadose fissures more recent surface deposits. To assess and phreatic caves are common. The the likelihood of contamination, the top- Lupemban inhabitants of Twin Rivers lived ography of the site will be examined in on the surface of the hilltop where two relation to the loose sediments found in the phreatic cave entrances once existed. The passages. Excavation methods have a role to mouths of the caves may have been used as play too and are discussed as a source of shelters, but the caves themselves were taphonomic bias. The backed tools from A unlikely living sites because of the narrow and F Block will also be compared to those (<2 m wide) and dipping passages. The found during recent excavations of the former caves were excavated in 1954 and surface deposits on the central platform 1956 and labelled A and F Block respec- (G Block). tively (Clark, 1971).1 The remaining deposits in both passages were excavated in 1999 (Barham, 2000). Stone artefacts and A Block bone accumulated in the passages as gentle A plan of Twin Rivers (Figure 2) shows the debris flows on which lenses of flowstone location of A and F Blocks in relation to were deposited (ibid:169). The oldest and each other and the extent of the platform stratigraphically lowest flowstone occurs in available to more recent occupants. The A A Block and is U-series dated to >400 ka Block passage is located downslope of the (ibid:178–9) (Figure 1). In A Block, the hilltop and once the roof collapsed, younger sediments were largely consolidated into sediments could have entered the deposits breccia by the time of the collapse of the by erosion from above. The surface of A cave roofs, a process which was completed Block was an unlikely living area given its late in the Middle Pleistocene. The youngest narrow width of <2 m and the pronounced U-series date on speleothem from F Block is dip of the slope. F Block is entirely within 138 ka BP (corrected age) and 160 ka BP the hilltop platform and the surface created (corrected age) from A Block (ibid: Table 2The U-series dates for F Block are not conformable 10.1). A thermoluminescence date on cal- with the younger speleothem (168/140 ka corrected) cite of 13527 ka also comes from A Block underlying the capping speleothem dated to 195 15 ka. The younger speleothem is shown in Clark 1The labelling of A Block was changed to C Block in (1971) as a dipping lens of flowstone that originated at Clark & Brown (2001), but the original attribution of the same surface level as the capping flowstone, but Clark (1971 and his fieldnotes) has been retained here presumably flowed downwards and settled around and in Barham (2000). existing blocks of breccia. 589 Figure 2. Plan of Twin Rivers hilltop showing the location of A, F and G Blocks and areas excavated in the 1950s and in 1999 (after Barham et al., 2000).