First molecular identification of a hafting adhesive in the Late Howiesons Poort at Diepkloof Rock Shelter (Western Cape, South Africa)

Journal of Archaeological Science 40 (2013) 3506e3518

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First molecular identification of a hafting adhesive in the Late Howiesons Poort at Diepkloof Rock Shelter (Western Cape, South Africa) Armelle Charrié-Duhaut a, b, *, Guillaume Porraz c,1, Caroline R. Cartwright d, Marina Igreja e, f, Jacques Connan g, Cedric Poggenpoel h, Pierre-Jean Texier i a

Laboratoire de Dynamique et Structure Moléculaire par Spectrométrie de Masse, UMR 7177 CNRS, Université de Strasbourg, BP 296 R8, 67008 Strasbourg Cedex, France Laboratoire de Biogéochimie Moléculaire, UMR 7177 CNRS, Université de Strasbourg, 67087 Strasbourg Cedex 2, France c CNRS, UMR 7041-ArScAn-AnTET, Maison de l’Archéologie et de l’Ethnologie, Université de Paris X, 21, allée de l’université, 92023 Nanterre, France d Scientific Research Laboratory, Department of Conservation and Scientific Research, British Museum, London WC1B 3DG, United Kingdom e LAMPEA, UMR 7269, Université d’Aix-en-Provence, France f UNIARQ, Faculty of Humanities, Lisbon, Portugal g Laboratoire de Biogéochimie Moléculaire, 23 rue Saint-Exupéry, 64000 Pau, France h Department of Archaeology, Beattie Building, 3rd Floor, University Avenue, Upper Campus, University of Cape Town, Rondebosch, South Africa i CNRS, UMR 5199-PACEA, Université de Bordeaux 1, Talence, France b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 15 September 2012 Received in revised form 21 December 2012 Accepted 21 December 2012

The hafting of tools using adhesive is one of the innovative features that characterizes the southern African Middle Stone Age. This technology has mainstream implications but remains insufficiently documented, largely due to unequal organic preservation and non-adapted analytical procedures. A notable exception is provided by the recent results from the site of Sibudu (Lombard, 2006; Wadley et al., 2009). The excavation at Diepkloof Rock Shelter has revealed several lithic artifacts with a black residue distributed over their surface. Their stratigraphic distribution reveals a strict association with the Howiesons Poort (HP) and suggests a close relationship between the appearance of hafting adhesive and the appearance of blades and geometric backed tools. Macroscopic and microscopic observations attest to a hafting that was exclusively lateralized and preliminary use-wear analysis (Igreja and Porraz, 2013) supports the hypothesis that hafted tools were mostly integrated within daily (domestic) activities. In this study, we focused specifically on a chemical study of a thick black residue found on a quartz flake attributable to the Late phase of the HP. We determine, for the first time in a MSA context, the nature of the compound adhesive and reconstruct a picture of the multilevel operations and interactions that comprise the process of hafting. The molecular analysis attests to the exploitation of Podocarpus elongatus (Yellowwood), collected in the form of a resin that was naturally dried or heated at a low temperature and possibly mixed with fragmented bone and quartz grains. Compared to Sibudu where ochre additive is documented, the hafting technology at Diepkloof introduces another level of variability within the HP tradition and suggests the existence of regional expressions and adaptations. Ó 2013 Elsevier Ltd. All rights reserved.

Keywords: Southern Africa Middle Stone Age Howiesons Poort Lithic technology Hafting Vegetal adhesive Podocarpus elongatus Diterpenoids GCeMS

1. Introduction

* Corresponding author. Laboratoire de Spectrométrie de Masse des Interactions et des Systèmes e LSMIS, CNRS, UDS, UMR 7140 “Chimie de la Matière Complexe”, 1 rue Blaise Pascal, F-67008 Strasbourg, France. Tel.: þ33 (0)368851629. E-mail address: [email protected] (A. Charrié-Duhaut). 1 Tel.: þ33 (0)146692655. 0305-4403/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jas.2012.12.026

Hafting is considered one of the key innovations in the evolutionary process of Paleolithic societies (McBrearty and Brooks, 2000). Indeed, the “savoir-faire” it requires (transmission), the standardization it presupposes (specialization) and the degree of efficiency it presumes (kinetic) imply the existence of complex

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socio-economic organization. More recently, the multi-tasking involved in the manufacture of compound adhesive has been emphasized as a relevant behavioural proxy for complex cognitive capacities (Wadley et al., 2009). Most of the time, the assumption of tool hafting is based on the observation of specific tool modification (e.g. the tang for the Aterian points) or from macro- and micro-scopic damages (e.g. abrasion of ridges on the upper surface of the tool) (AndersonGerfaud and Helmer, 1987; Rots, 2010; Conard et al., in press). Such issues are often connected to the question of hunting practices and to the debate regarding the appearance of lithic projectiles among hunteregatherer populations (Lombard and Pargeter, 2008; Shea and Sisk, 2010). Occasionally, hafting is inferred because of the presence of residues covering the prehensile part of the lithic tool. Such evidence remains exceptional. For example, hafting residue has been recorded at the Italian middle Pleistocene site of Campitello in the form of birch bark tar (Mazza et al., 2006), at the Middle and Upper Paleolithic Romanian site of Gura Cheii-Râs¸nov in the form of bitumen (Cârciumaru et al., 2012), and at the Mousterian site of Ummel-Tlel (Syria) in the form of bitumen imprints on Levallois flakes and points (Boëda et al., 2008, 2009). In these cases, the studies tend to focus on the process of hafting itself, on its technological and functional implications and, ultimately, on its transformation over time and variability in space. For the Southern African Middle Stone Age (MSA), a few examples of tool hafting have been described or hypothesized (e.g. Lombard, 2006; Rigaud et al., 2006; Wadley et al., 2004; Wurz, 1999). These examples document occurrences appearing first with the bifacial Still Bay and then persisting over time, crossing different technological traditions (Howiesons Poort and postHowiesons Poort) and geographic areas. The appearance of hafting in the Southern African MSA would have coincided with a global transformation of societies, illustrated by changes in a wide

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range of activities, such as blank production, raw material economy and symbolic manifestations (Klein, 1995; McBrearty and Brooks, 2000). Macroscopic hafting adhesives are documented on a few MSA southern African sites (Fig. 1). Among these sites, the archaeological record of Sibudu deserves to be considered specifically. For example, the study of Lombard (2008) has hypothesized changes over time in hafting materials and hafting configurations of the segments, possibly related to technological change and adaptation. In a different perspective, the technological and experimental study of Wadley et al. (2009) has documented the way in which the Howiesons Poort (HP) inhabitants at Sibudu made complex compound adhesives to haft their tools using ochrebased additives. This result demonstrates that people sustained multilevel operations and were competent chemists (properties), alchemists (mixture), and pyrotechnologists (transformation) (Wadley et al., 2009). Characterization of hafting technology is more than just additional or optional archaeological data: it represents a discrete area of investigation in its own right that permits access to a lost technological “savoir-faire”. In this paper, we would like to place our chemical study within the context of previous hafting studies conduct on artifacts from the HP. But for the first time, analyses are performed at molecular level and not only microscopic level, which allows the identification of molecular markers (biomarkers) leading to the characterization of natural organic substances. Our pioneering chemical approach for a MSA context is based on the collection from Diepkloof Rock Shelter (DRS), where the organic preservation is remarkable. Our goals in this study are: (1) to document the technological tradition of the HP inhabitants of Diepkloof and to understand their interactions with the resources of the environment; (2) to offer new avenues of interpretation and comparisons for the southern African MSA; (3) to investigate the question of the earliest

Fig. 1. List and location of southern African Middle Stone Age sites where hafting residues have been recorded: Apollo 11 (Late MSA: Wendt, 1976; Vogelsang et al., 2010); Rose Cottage Cave (Howiesons Poort: Gibson et al., 2004); Sibudu Cave (Still Bay, Howiesons Poort, post-Howiesons Poort: Lombard, 2006; Wadley et al., 2009); Umhlatuzana Rock Shelter (Howiesons Poort: Lombard, 2007); Peers Cave (?) (Still Bay: Minichillo, 2005); Diepkloof Rock Shelter (Howiesons Poort).

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hafting technology and contribute to the debate on the technological changes that occurred within African anatomically modern human societies.

et al., 2008) and archaeological implications are further discussed in Tribolo et al. (2013) and Porraz et al. (2013a,b). 2.1. Introduction to the collection

2. Black residues and evidence of hafting at Diepkloof Rock Shelter The site of Diepkloof is located in the Western Cape Province, about 180 km north of Cape Town and 14 km from the Atlantic coast. Excavations began in 1998 in the framework of a South AfricaneFrench collaboration and expose to date a MSA stratigraphic sequence of ca. 3.1 m deep, which has been subdivided into 53 stratigraphic units (SU) (Parkington et al., 2013). The TL and OSL dating of Tribolo et al. (2013) bracket the current MSA sequence from the OIS 5 d to the beginning of the OIS 3. Details on the luminescence ages, clarification with other dating results (Jacobs

The first macroscopic residues found on MSA lithic artifacts at Diepkloof were reported in 2006 (Rigaud et al., 2006). Since then, the number of lithic pieces with such evidence has increased considerably (see below). All of these pieces present very similar characteristics (Fig. 2): the residue is black and homogeneous; the outlines of the residue are clearly delimited on the piece; the residue covers only a part of the surface of the tool and is always opposite to the sharpened edge (when the blank is nonsymmetric, the residue is on the irregular part); the residue can always be observed on both faces of the tool (even with a difference in preservation) and it is generally bifacially symmetrical.

Fig. 2. Examples of Late Howiesons Poort lithic artifacts with a residual black adhesive on their side, Diepkloof Rock Shelter (1e5: backed pieces; 6: flake; 7e8: naturally backed flakes; 9e10: laminar blanks) (drawing by M. Grenet).

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These observations, as well as the primary use-wear analysis (Igreja and Porraz, 2013), support the hypothesis that these pieces were hafted and that the black residue corresponds to an old adhesive that was applied to cement the pieces into their haft. In terms of diachronic distribution, evidence of hafting residues at Diepkloof is restricted to the HP units (Table 1). To date, two pieces with a hafting residue have been found within the Still Bay (SB) context, but their chronoecultural association is doubtful. Indeed, these two pieces are located at the top of the SB (SU Kegan), immediately below and in contact with the first HP stratigraphic unit (SU Keeno). Moreover, one of these pieces is a bi-truncated tool typical of the Early HP tradition and the other is a bladelet (Porraz et al., 2013a). As a consequence, we consider these pieces to be associated with the Early HP rather than with the SB. To date, no hafting adhesive has been observed on the SB bifacial pieces, nor on the post-HP unifacial points. Interestingly, no residue has been found in the technologically distinct MSAJack, which is sandwiched between the Early and the Intermediate HP (Porraz et al., 2013a). As documented by Miller et al. (2013), no change in depositional or post-depositional processes can explain such a stratigraphic distribution of black residue over the sequence. Regarding the size of our sample (N ¼ 29 lithic pieces coming from squares M6eN6), further fieldwork could change our current model. However, we have carefully looked for residues (at a

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macroscopic scale) on about 15 000 lithic artifacts (>20 mm) from squares M6eN6. We consider, therefore, that further discoveries will not significantly alter the hypothesis that the presence of hafting adhesive at Diepkloof is closely linked (if not exclusively so) to HP technology. This association strongly suggests that the appearance of blade and backed piece technology, in parallel with the change in raw material selection, is a technological “package” that included (and necessitated) the use of adhesive for hafting. Within the HP, hafting residues are found in association with different types of blanks and different raw materials (Table 1), with the exception of the local quartzite, which preserves no evidence for hafting residues. - In the Early HP, evidence of hafting residues relates to 6 pieces and is associated preferentially with laminar products (n ¼ 5/6) and exclusively with silcrete. Half of this sample contains bitruncated pieces. - In the intermediate HP, evidence of hafting residues relates to 9 pieces. We observe a similar pattern, but geometric backed pieces with a black residue are rare (n ¼ 2/9). Interestingly, no evidence of hafting adhesive has been found on the strangulated-notched pieces, despite the fact that they represent the dominant formal tool category during this phase. A different conception of tool hafting and recycling probably explains the absence of hafting adhesives on these pieces.

Table 1 Catalogue of the lithic pieces with a black residue macroscopically identified (squares M6-N6, Diepkloof Rock Shelter). Stratigraphic unit

Raw material

Blank

Debbie Darryl Eric Eric Eric Eric Ester Ester Edgar Edgar Edgar Edgar Eve Eben

Sub-Local Non-local Non-local Quartz Quartz Quartz Quartz Quartz Flint Quartz Non-local Quartz Quartz Non-local

silcrete silcrete silcrete

Débordant flake Blade Bladelet Blade Bipolar product Flake Blade Débordant flake Blade Blade Flake Débordant flake Blade Blade

Frank Fox Fiona John John Jeff Jeff Joy Joy

Non-local Non-local Non-local Quartz Sub-Local Non-local Non-local Sub-Local Sub-Local

silcrete silcrete silcrete silcrete silcrete silcrete silcrete silcrete

Blade Blade Bladelet Flake Blade Undetermined Blade Blade Bladelet

Non-local Non-local Non-local Non-local Non-local Sub-Local

silcrete silcrete silcrete silcrete silcrete silcrete

Flake Blade Blade Blade Bladelet Blade

Post-HP

None

Late Howiesons Poort

Intermediate Howiesons Poort

MSA-Jack

None

Early Howiesons Poort

Kate Kerry Kenny Kegan Keeno* Keeno*

Still Bay Pre-SB Lynn MSA-Mike

silcrete

silcrete

Typology

Segment Bi-truncated

Truncated Segment

Bi-truncated Bi-truncated Bi-truncated

Location of the residue

Lateral Lateral Undetermined Lateral Undetermined Undetermined Lateral Undetermined Lateral Lateral Lateral Lateral Lateral Undetermined Lateral Lateral Lateral Diagonal Lateral Lateral Lateral Lateral Lateral

Undetermined Lateral Lateral Undetermined Lateral Lateral

None None None

*Considering the characteristics of these 2 pieces and their stratigraphic location just below the Early HP, they have been associated with the Howiesons Poort tradition despite the fact they belong to the last Still Bay stratigraphic unit.

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- During the Late HP, evidence of hafting residues relates to 14 pieces. Flakes become more important in the sample set (n ¼ 5/ 14) as well as quartz (n ¼ 8/14). Together with the presence of hafting residue on “naturally” backed pieces (‘geometric’ lato sensu), this sample furnishes a good illustration and support of the technological changes documented during the last phase of the HP (Fig. 2). Only the low proportion of geometric backed pieces (stricto sensu) (n ¼ 2/14) remains somewhat enigmatic, when we consider their proliferation during this phase (Porraz et al., 2013a). The greater amount of pieces with hafting residue in the Late HP (Table 1, Fig. 2), compared to the other HP phases, might reflect differences regarding the number of SUs (and possibly, by extension, differences in the intensity, number or duration of the occupations), but further investigation is required. Hafting was a common practice during the HP and was not restricted to a unique technological or formal category. Changes over time echo the general transformation of the lithic technology. One interesting and persistent characteristic over the sequence concerns the distribution of the black residue on the surface of the lithic artifacts (Fig. 2). Indeed, the adhesive imprint observed on the HP pieces is always lateralized, suggesting that all the HP tools were hafted longitudinally, parallel to the axis of the tool or, more rarely, on a slight diagonal. The pieces exhibiting hafting residue attest to various states of edge preservation. Examples of macroscopic damage observed on

the edges of Early HP tools have been interpreted as a direct consequence of their usage, supporting the hypothesis that Early HP hafted tools functioned predominantly as cutting/scraping implements (see Igreja and Porraz, 2013). However, a few examples of backed pieces with hafting residues show impact-like fracture. This is notably the case for the Late HP assemblage, which documents the presence of backed pieces with transversal burination (at one or at both extremities: e.g. Fig. 2, n ¼ 1). Similar burinations have been interpreted by Villa et al. (2010) as evidence of impact damage. Their presence at Klasies River at a similar age as at Diepkloof suggests a common pattern of use during this phase.

2.2. Focus on a Late HP quartz flake The preservation of hafting residues is variable within the Diepkloof assemblage, and probably reflects the influence of several pre- and post-depositional factors. Mostly, the hafting residue takes the form of an imprint with patches of variable thickness located on the irregular surface of the tool (e.g. on the back). In order to carry out the chemical analysis of the adhesive, we selected a sample of pieces with a thicker and broader distribution of residue over each piece. While several pieces are still under investigation, in this paper we focus on a single flake recovered in 2004 in square E6 (Fig. 3). This piece was found in SU George, below SU Gavin. It belongs to the Late HP which has been dated by

Fig. 3. Detail on the stratigraphic provenance of a Late Howiesons Poort quartz flake with a thick black residue that has been chemically analysed (Diepkloof Rock Shelter).

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TL (mean age) to ca. 56  10 ka B.P. (Tribolo et al., 2013) and by OSL (SU George, sample DRS6) to 60.5  1.9 ka B.P. (Jacobs et al., 2008). This piece is a déjeté flake in quartz with a dissymmetric section. In this case, the artisan used the dissymmetry of the tool and its thickness as an irregularity to be hafted. The use-wear analysis of the piece attests to a slight chemical weathering of the surface (Fig. 4). However, these post-depositional effects are minor and have not masked the presence of microscopic use-wear, which suggests a use related to the processing of soft animal material. The working of soft animal material is characterized by the presence of polish associated with edge scarring. The features of the polish and the morphology and distribution of the scars exclude a butchery activity. Butchery tends to create a more reticular and “greasy” polish and also displays a macroscopic denticulation of the edge that is easily recognizable (Plisson, 1985; Gonzales Urquijo and Ibanez Estevez, 1994). The texture of the polish, showing a rounded aspect of the microtopography of the surface, associated with the morphology of the scars (“half moon” according to Tringham et al., 1974) along with the presence of scarring on both sides of the edge, suggest instead the cutting of soft animal materials (e.g. dry hide). However, the degree of development of the microwear traces in particular does not allow a more specific diagnosis of the nature of the worked material (Plisson, 1985; Gonzales Urquijo and Ibanez Estevez, 1994). Furthermore, the microscopic striations parallel to the tool (Fig. 4) are typical of a longitudinal working motion and are coherent with the lateral presence of a haft.

3. Analytical method The chemical approach used in this study employs diagnostic biomarkers derived from naturally-occurring organic substances. Biomarkers are molecules which have a carbon skeleton sufficiently specific to be related to their precursor biological lipid enabling identification of the natural substance used. These compounds are ideally resistant to the various alteration processes experienced by the original material (abiotic oxidation, biodegradation). In the case of degradation, it is sometimes possible to rely on specific degradation byproducts as shown for Dipterocarpaceae resins (Burger et al., 2009). Each natural substance has its own molecular fingerprint more or less altered. Consequently, this approach permits the distinction between different biological origins (animal, plant,

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families, species), to elucidate the composition of mixtures, sometimes complex, to evaluate states of alteration (anthropic or natural). The analytical flow chart applied to study archaeological material is directly adapted from the methodology used in petroleum organic geochemistry to analyse bitumen, source rocks and crude oils. An account of the basic principles of this procedure illustrated by some applications and specially adapted to different archaeological contexts is reported in several publications (e.g. Charrié-Duhaut et al., 2009; Connan, 2002). Molecular characterization is performed on an organic extract, fractionated or not, and analysed by gas-chromatography coupled with mass-spectrometry (GCeMS). 3.1. Extraction, fractionation The black residue from the Late HP piece (Fig. 5) was extracted ultrasonically three times for 5 min each with dichloromethane/ methanol (60:40). The combined solvent extracts, forming the total organic extract, were concentrated by evaporation. The analyses were performed using GCeMS after splitting the total organic extract by gravity flow column chromatography and thin layer chromatography (silica gel support). To avoid any contamination, specific treatment of the chemical products and glassware was carried out in addition to negative control of the whole process. 3.2. Mass spectrometric analysis GCeMS analyses were carried out on a triple quadrupole ThermoFisher TSQ Quantum spectrometer connected to a Trace GC Ultra gas chromatograph (PTV e on-column mode e injector, HP-5 MS column, 30 m  0.32 mm i.d., 0.25 mm film thickness). The following temperature program was used: 40  C (1 min), 40e100  C (10  C/min), 100e300  C (4  C/min), isothermal 300  C. Mass spectra were produced at 70eV, source at 200  C, in full detection mode over 50e700 amu. Helium was used as a carrier gas (1.7 mL min1). 3.3. Carbon isotopic composition The compound specific stable carbon isotope analyses (d13C values) were performed at the Stable Isotopes Laboratory of the

Fig. 4. Photographic details of the use-wear traces typical of a longitudinal motion in relation with the processing of animal soft material. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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Fig. 5. Photomontage of the black deposit on the Late Howiesons Poort quartz flake before and after its sampling.

University of Lausanne (Institute of Mineralogy and Geochemistry). They were obtained by the use of an Agilent 6890 GC coupled to a Thermoquest/Finnigan MAT Delta S isotope ratio mass spectrometer by a combustion (C) interface III (GCeirmMS) under a continuous helium flow. The irmMS ion source pressure is lower than 6  106 bar. The GC was operated with the same type of column and temperature program used for GCeMS analyses. The repeatability and intermediate precision of the GCeirmMS procedure, and the performance of the GC and combustion interface were evaluated every 5 analyses by injection of an in-house mixture of n-alkanoic acids (UNIL-FAME MIX) of known isotopic composition and at least three replicate analyses of the samples. The standard deviations for repeatability ranged between 0.05 and 0.4& for the main FAME and for intermediate precision between 0.3 and 1.1&.

4. Results of the chemical analysis of the hafting residue The presence of an organic extract of the fine black powder scraped off on the tool’s surface confirms the existence of natural organic substances adhering to the HP quartz flake. This extract represents 39% of the hafting residue. However, we cannot redissolve the totality of the organic extract. This is also sometimes the case for bitumen and probably indicates a high degree of degradation of the organic substances. Consequently, the fractionation was only carried out on approximately 8% of the hafting residue. As there was only a small quantity of material available to sample (few tens of milligrams), the amount of each fraction was quite small (<1 mg). On the other hand, analysis of the residue by scanning electron microscopy (SEM) showed the presence of quartz crystals and fragments of bone (cf. Discussion).

4.1. GCeMS analysis after silylation The GCeMS total ion current traces of the silylated total extract consist mainly of linear and diterpenoid structures (Fig. 6a). The presence of diterpenic structures provides evidence for a Gymnosperm contribution, essentially conifer precursors which are divided into several families including Pinaceae, Araucariaceae, Cupressaceae, Podocarpaeae, Taxodiaceae (Langenheim, 2003). The specific distribution of biomarkers with an abietane skeleton allows the differentiation of each family. According to Otto and Wilde (2001), the reports of abietane derivatives reveal two groups: the “regular” abietanes and the “phenolic” abietanes. Several parameters are presented in the literature for distinguishing southern hemisphere resins (e.g. Bendall and Cambie, 1995; references therein; Mangoni and Caputo, 1967; Cox et al., 2007). “Phenolic” abietanes are divided into three groups: those of totarol, ferruginol and sempervirol. They are absent in Pinaceae. Totarol and ferruginol derivates are biomarkers for Cupressaceae and Podocarpaceae. The distinction between these two families is made on the presence of sempervirol, which is restricted to Cupressaceae, and the predominance of ferruginol derivatives in this family. Therefore, identification of phenol diterpenic derivatives should allow the determination of the family of Gymnosperm used. The presence of a compound from the totarol family as a major component, totarol-7-one, suggests the use of a product derived from the Podocarpaceae family. Isolated specimens of these trees are still present in the area of Diepkloof at the present day. To better understand the molecular fingerprint of the archaeological sample, bark of Podocarpus elongatus, identified in the charcoal collection of Diepkloof (see Cartwright, 2013), was analysed by the same chemical approach. The GCeMS total ion current trace of the silylated total extract of the present bark (Fig. 6b) also consists mainly

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Fig. 6. GCeMS total ion current traces of the silylated extract from (a) archaeological residue from DRS (b) bark from P. elongatus.

of phenolic diterpenic structures related to totarol and corresponds to those presented by Cox et al. (2007). The major components of the present bark are totarol, 3-hydroxytotarol, 4-carboxynortotarol, 3-hydroxy-4-carboxynortotarol and 3-hydroxyferruginol. These phenolic structures were not identified in the archaeological sample. On the other hand, structures based on totarol skeleton with more oxygen functionalities, namely totarol-7-one and sugiol were detected in the ketone fraction. From a chemical point of view, phenolic structures are very sensitive to oxidation, especially in benzylic position. Consequently, degradation byproducts are easily formed both by natural ageing (biodegradation, oxidation) and by anthropogenic (intentional or accidental) transformations (burning). These alteration processes strongly influence the chemical signature. Little information on the oxidized products of such components is available in the literature. Moreover, the distinction of each phenol family (totarol, ferruginol, sempervirol) is sometimes difficult to achieve in analysis (Enzell and Wahlberg, 1970). The archaeological residue is so degraded that direct correlation with the current natural product is no longer possible. As mentioned earlier, linear structures are present in the silylated extract of the archaeological sample. The fingerprint of the linear structures identified in the archaeological sample of hafting residue is dominated by linear monocarboxylic acids (even predominance, ranging from C14 to C18) and by linear diacids (also called linear a,u-dicarboxylic acids), ranging from C7 to C14, with the term C9 (azelaic acid) predominant (Fig. 6a). According to Villa

et al. (2012), the detection of such components suggests the presence of a bio-polyester, derived from suberin. The similarity of the two chromatographic profiles is indeed striking. These linear structures are also described as being formed after oxidation (autoxidation or by heating) of unsaturated fatty acids (Passi et al., 1993). For example, C9 diacids come from oleic acid (C18 fatty acid with one double bond in position 9). In an archaeological context, presence of diacids is indicative of animal fat or plant oil (Bastien, 2011; Newman, 1998). 9,10-dihydroxyoctadecanoic acid, compound usually present with the diacids, was not detected in this sample.

4.2. GCeMS analysis after fractionation For a better identification of the biomarkers present in the archaeological sample, the organic extract was split into five fractions of increasing polarity: less polar components (alkanes, alkenes, aromatic hydrocarbons, esters) in very tiny amount (<0.5 mg), ketones, alcohols, acids and polyfunctionalised compounds. Organic extract from the bark of P. elongatus was also split for comparison. Fractionation enables the concentration of compounds, some of which are present in minute amounts and therefore are not detected by the procedure described above. Such minor compounds can help characterize the origin of a sample or its degree of alteration. Moreover, fractionation simplifies GCeMS traces (Charrié-Duhaut et al., 2009).

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Fig. 7. GCeMS total ion current traces of the ketone fraction from (a) archaeological residue from DRS and (b) bark from P. elongatus.

The distribution of n-alkanes (C20 to C35) is dominated by long chain molecules with a strong odd/even carbon number predominance after C27. Such a distribution is generally observed in higher land plants. No polyaromatic structure like phenanthrene, anthracene, chrysene e typical of pyrolytic signature e has been detected in the hafting residue. All polar fractions (esters, ketones, alcohols, acids) consist mainly of phenolic diterpenoid structures. Traces of component indicators of degraded fat (plant or animal origin) were detected: g-lactones (C16 major), carboxylactones (with a distribution similar to that of diacids, C9 major) (Bastien, 2011). To illustrate the distribution of diterpenic components, Fig. 7 shows the GCeMS traces of the fraction with the polarity of ketones in the archaeological sample and in modern bark from P. elongatus. The distributions are very different. In the bark, the three phenols, sempervirol, totarol and ferruginol are present in association with some oxidized forms such as totarol-7-one or dihydroxytotarol. By contrast, in the archaeological residue, the phenols are absent and the fraction is dominated by oxidized forms, a few which are different from those in the bark. The distinction of the derivatives of all three families of phenols based only on mass spectrum analysis is problematic because of the similarity of mass spectra (Enzell and Wahlberg, 1970). However, the diterpenoids, identified by their mass spectra, belong to the series of totarol and ferruginol. Sempervirol derivatives seem to be absent. Moreover, no diagnostic molecules of the well-known Pinaceae resins were identified (Langenheim, 2003). In conclusion, the use of a product derived from Podocarpaceae is likely.

Although it is possible to characterize archaeological materials by their molecular composition alone, gas chromatographycombustion-isotope ratio mass spectrometry (GCeCeIRMS) is often useful for providing more accurate information on the biological sources of organic matter. The ratio 13C/12C called d13C (in &/ PDB) is measured by this technique. Stable carbon isotopic data were recorded on several components from the Diepkloof sample (totaro-7-one: 30.0&/PDB; palmitic acid: 28.5&/PDB; stearic acid: 28.2&/PDB). To the best of our knowledge, few d13C values from Podocarpaceae have been published in the literature (Cernusak et al., 2008). In the specific case of Podocarpaceae, many phenolic structures need to be elucidated to study the degradation processes. For example, podototarin, a bisditerpenoid frequently described in the chemistry of Podocarpaceae (Cambie et al., 1963), identified in the extract of barks is not detected in the archaeological sample. Phenolic diterpenic units are likely to form bis-diterpenoids by the condensation of two units (Le Métayer et al., 2008). Such components were detected in the two studies but with different structures. To summarize, our chemical analysis strongly supports the hypothesis of the use of P. elongatus (Yellowwood) to furnish the adhesive substance found on the HP quartz flake of Diepkloof. Considering the fact that charcoals of this wood taxon have been identified in the Diepkloof archaeological record (Cartwright, 2013), it is thus possible that Podocarpaceae tar was collected and used, in the same way as the well known pitch (tar deriving from Pinaceae) and birch bark tar. Heating modifies the molecular composition but, as in the case of pitch, aromatic structures should

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be detected in tar, which is not the case in the Diepkloof sample. Villa et al. (2012) explain that the presence of linear monocarboxylic acids and a,u-dicarboxylic acids is diagnostic of a suberin-containing pitch. In the case of DRS sample, as specific component indicators of degraded fat (g-lactones, carboxylactones) were detected and as no long chain hydroxyl-fatty acids seem to be present, the origin of these acids is rather a fat than a tar. We conclude that the hafting adhesive used by the LHP inhabitants of Diepkloof derives from P. elongatus and most probably corresponds to an oxidized resin. 5. Discussion 5.1. The adhesive manufacture at Diepkloof Rock Shelter In the context of the South African MSA, several authors mention or infer the presence of other ingredients in the hafting adhesive, such as acacia gum, mastic, beeswax and ochre (Lombard, 2006; Wadley et al., 2009). Their biomarkers (long chain fatty esters for beeswax, typical triterpenoid for mastic, hopanes and steranes for bitumen or polysaccharides for acacia gum) were not identified on the analysed quartz flake of Diepkloof. Freely-added ochre, for example, allows the adhesive to become insoluble in water without being hydroscopic. SEM was used to try to detect the presence of this natural iron oxide in the residue but none was found. So, none of the classic additives has been identified in the adhesive analysed. Like the resin of the Dipterocarpaceae family which, for instance, is used without processing (Burger et al., 2009), it is then possible that the resin of Podocarpaceae family has been used as a pure material. However, the detection of degraded fat in the hafting residue of Diepkloof raises questions about its origin. The presence of fat may reflect contamination, or might indicate its use as additive. For example, the presence of fat as part of the adhesive recipe has been observed at the site of Sibudu (Lombard, 2006). In addition, the SEM identification of bone fragments and quartz grains, within the hafting residue of Diepkloof, might also indicate that these components were used for additive mixture. But caution is urged because of the nature of the sediment that surrounded the piece (see Miller et al., 2013), which is composed of numerous detrital anthropical remains and quartz grains originating from the disaggregation of the rock shelter. A similar question concerns the presence of botanical fragments initially observed on the adhesive, but which we currently interpret as contamination from the surrounding sediment. Further chemical analysis of hafted residues from Diepkloof and other sites will assuredly provide additional data for this discussion. The modification of the hafting residue documented at Diepkloof could either imply a process of natural drying or a heat treatment. Based on chemical or macroscopic data, it is difficult to evaluate whether or not heating has been used to transform the adhesive. However even if heating has been used, the temperature reached was likely to have been moderate and restricted to the softening of the resin, as no pyrolitic byproducts were recorded in the sample. Further research is now required to replicate the hafting and to assess the technological expertise required for the use of a resin from P. elongatus. 5.2. Towards a reconstruction of the hafting process at Diepkloof Rock Shelter Hafting technology has been recently analysed in terms of multilevel tasks and interpreted as the expression of complex

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cognition (Wadley et al., 2009; Wadley, 2010). Our multidisciplinary approach gives an illustration of these operations and of the type of behaviour and knowledge that was required. The hafting of a tool is a convergence of three main sous-chaînes opératoires: 1) the manufacture of the lithic piece, 2) the manufacture of the haft, 3) the manufacture of the adhesive. It implies that the activities were carried out in different places (the acquisition of the resource and, eventually, its transformation), but the existence of a central place where these technological operations converge. The hafting technology implies, therefore, a good knowledge, management and control of natural resources, as well as an efficient territorial and socioeconomical organization. The cost of the technical operation is directly linked to the nature of the activities. Focusing on the artifact that has been chemically analysed, we can observe that the lithic piece actually shows a low technological investment. Indeed, the raw material of the flake is likely to originate from the slope of the shelter (quartz pebble) while its characteristics suggest a reduction sequence oriented towards the production of blanks that were not highly standardized. The criterion of selection was then based on the presence of a sharp and regular edge as well as a dissymmetric section (to be hafted). The case is different when we consider the question of the adhesive. Indeed, our data suggest an investment focused on the acquisition of a specific wood species (P. elongatus), with the possible occurrence of a specific trip to collect its resin, implying a good phytogeographic knowledge of the area. The resin would have then been naturally dried or heated at a low temperature, and possibly mixed with fragmented bone and quartz grains. We do not know the nature and the morphology of the wood that was selected to be transformed into a haft (if any), but this activity was most certainly timeconsuming (depending on the nature of the haft), starting with the selection of the wood, the acquisition of the suitably-sized branch, its transformation (pruning, planing, etc.) and its final adaptation to the type of handle desired (including the mode of insert into the haft). If we try to schematize this process of hafting, we observe differences between the technological operations, regarding the cost of the raw material acquisition and its process of transformation. These multi-level operations suggest the existence of different technological skills, as well as different levels of planning and curation. The microwear analyses show that the hafted quartz flake was used as a knife to cut soft animal materials. It is thus worth saying that hafting was not restricted to the manufacture of hunting tools, but embraced a wide range of activities (see Igreja and Porraz, 2013), as documented in other Middle or Upper Palaeolithic contexts (Anderson-Gerfaud and Helmer, 1987; Boëda et al., 2009). Hafting appears then as a common practice in the daily life of the population. It suggests a complex level of communication at a horizontal (communication) and vertical (transmission) scale, and implies cognitive abilities that were as complex as any other modern hunter-gatherer societies. 5.3. Hafting adhesives in the South African context The exploitation of P. elongatus as a resource of adhesive has been documented for the first time in 2011 (Charrié-Duhaut et al., 2011), and has since been identified at Border Cave (Villa et al., 2012). The current set of available data indicates that P. elongatus has been used, at least, in 2 distinct techno-cultural contexts: at ca. 60e55 ka B.P. during the HP at Diepkloof, and at ca. 43e42.5 ka B.P. during the Early Later Stone Age of Border Cave.

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Podocarpaceae are documented within the MSA units of Sibudu but only Podocarpus sp. has been identified. One taxon, formerly a Podocarpus genus, has now been taxonomically reclassified as Afrocarpus, i.e. A. falcatus. It is relevant to note that P. elongatus is endemic to southern Africa and is currently confined to the winter-rainfall Western Cape. Within the archaeological record of Diepkloof, P. elongatus is documented throughout the sequence (Cartwright, 2013). At the present day, this woody taxon is often found in pockets of Afromontane/ Afrotemperate forests in kloofs (mountainous or rocky gorges), along rivers and adjacent to wetlands, and it can also occur in the wetter areas of different types of fynbos. The fact that this particular taxon can adapt to different types of habitat, when necessary, is significant with regard to the sequence at Diepkloof, as it may mean that P. elongatus would have been available, perhaps in stunted form, even if climatic or soil moisture conditions had changed over time. Independently of environmental changes or technological traditions, the charcoal record at Diepkloof shows that P. elongatus has been a resource that was continuously collected by the Diepkloof inhabitants (Cartwright, 2013). This wood could have been collected for different purposes, such as fuelling fires, supporting perishable structures or providing wooden hafts for artifacts. To date, the earliest use of its resin as an adhesive is documented for the later phase of the HP at Diepkloof. On-going chemical analysis will give further precision on the diversity of vegetal species used to make adhesive, at both a synchronic and diachronic scale. Considering the hafting tradition described above, Diepkloof differs notably from Sibudu, where ochre appears to be an element commonly (but not necessarily) present on the back of the backed pieces (Wadley and Mohapi, 2008). At Diepkloof, all the pieces with a black imprint have been carefully looked at magnifications of 10e40, but none of them showed the presence of red pigments. We conclude, therefore, that ochre has never been used as a loading agent at Diepkloof. These differences cannot be explained at a diachronic scale insofar as the Late HP at Diepkloof and the HP at Sibudu are dated to the same age (Wadley and Jacobs, 2006; Tribolo et al., 2013). Nevertheless, the technological differences of the Late HP at Diepkloof compared to the HP at Sibudu, including a flakebased component (Porraz et al., 2013a), could also testify to a divergent technological trajectory including that of adhesive fabrication. The differences between the two sites, located in different environments and at a distance of about 1200 km from one another, likely reflects the expression of the same technological phenomenon (comprising blades, backed pieces, lateral hafting, and use of adhesive) but locally adapted and differently manipulated (following regional traditions). Also relevant are the sites of Rose Cottage Cave and Umhlatuzana Rock Shelter, where ochre has also been identified as an adhesive component (Gibson et al., 2004; Lombard, 2007), thus extending the framework of reference of the hafting tradition as recorded at Sibudu. At Apollo 11 (south of Namibia), where a piece with adhesive has been discovered, ochre as an ingredient of the adhesive has not been described (Vogelsang et al., 2010).

6. Conclusions The MSA of Southern Africa surprises us by the antiquity of its behavioural innovations as well as by the exceptional preservation of its archaeological record. Some of these innovations e the hafting of tools and the use of affixing adhesive e illustrate another

level of technological skill and of socio-economic organization. In the Diepkloof sequence, the use of adhesive is closely linked to the HP. Adhesive imprints are documented from the Early HP phase, dated by TL at 105  10 ka (SUs Kerry-Kate) and by OSL at 109  10 ka (SU Jess), and last until the Late HP phase, dated by TL (mean age) at 56  10 ka (Tribolo et al., 2013). The molecular analysis of a hafting residue from the HP of Diepkloof has enabled, for the first time in a MSA context, the identification of the nature of the organic resource used to prepare the adhesive. The HP inhabitants of Diepkloof collected the resin of P. elongatus, dried or heated the resin at a low temperature, and possibly mixed it with additives such as bone fragments and quartz grains. The results of the study highlight the wide range of exploitation of the organic and mineral resources by the inhabitants of Diepkloof. Our results show that hunteregatherer populations were perfectly integrated into their environments and fully aware of the potential of the resources. The results also demonstrate that Diepkloof was a central place in the territorial system of these populations. All the archaeological finds (e.g. ostrich eggshells flasks, lithic tools, fauna, ochre) and technical operations (e.g. various stages of production, various types of tool use, maintenance of fire, making of ochre powder) documented on the site individualize Diepkloof as a place where a large range of activities were performed (Dayet et al., 2013; Igreja and Porraz, 2013; Steele and Klein, 2013; Miller et al., 2013; Porraz et al., 2013a, Texier et al., 2013). Hafting technology appears as an important proxy of socioeconomic transformation, but also represents a factor of technological change. It is worth saying that the use of adhesive at Sibudu was likely to have persisted through the time of the sequence, crossing distinct technological and hafting traditions (Lombard, 2006; Wadley et al., 2009). Though not all adhesive from Sibudu contains ochre, ochre as additive is documented in various contexts, notably during the HP. This persistence and this difference with Diepkloof fuel the question of the technological shifts versus the regional survivals. Bearing in mind that the sample remains restricted, the differences between Diepkloof and Sibudu are likely to reflect local adaptations to resources and express different regional traditions. These distinct hafting traditions echo previous differences observed in the lithic technology as well as in the symbolic patterns, and throws into sharp focus the role of regional organization and networks in the evolutionary process of the innovative Howiesons Poort (Porraz et al., 2013b).

Acknowledgements The scientific project and excavation at Diepkloof have been funded by the French Ministry of Foreign Affairs (MAE), the Aquitaine region, the Provence-Alpes-Côte-d’Azur region, the Centre National de la Recherche Scientifique (CNRS), the Paleontological Scientific Trust (PAST) and the National Research Foundation (NRF) of South Africa. One of us (GP) has been supported by the Fyssen and the Alexander von Humboldt Foundations, and has benefited from collaborations with the University of Cape Town and the University of Tuebingen. We are indebted to J. Faerber (IPCMS-GSI, Strasbourg) for SEM analysis, to J. Spangenberg (Institute of Mineralogy and Geochemistry, University of Lausanne, Switzerland) for GCeCeirmMS analysis. Finally, we would like to thank the ANR for the support of the program “Archeomolecule” and the Kirstenbosch National Botanical Garden for providing bark of Podocarpus.

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Appendix A. Structures of natural products mentioned in this study.

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