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Journal of Archaeological Science 40 (2013) 3506e3518

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Journal of Archaeological Science

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First molecular identification of a hafting adhesive in the LateHowiesons 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, Franceb Laboratoire de Biogéochimie Moléculaire, UMR 7177 CNRS, Université de Strasbourg, 67087 Strasbourg Cedex 2, FrancecCNRS, UMR 7041-ArScAn-AnTET, Maison de l’Archéologie et de l’Ethnologie, Université de Paris X, 21, allée de l’université, 92023 Nanterre, Franced Scientific Research Laboratory, Department of Conservation and Scientific Research, British Museum, London WC1B 3DG, United Kingdome LAMPEA, UMR 7269, Université d’Aix-en-Provence, FrancefUNIARQ, Faculty of Humanities, Lisbon, Portugalg Laboratoire de Biogéochimie Moléculaire, 23 rue Saint-Exupéry, 64000 Pau, FrancehDepartment of Archaeology, Beattie Building, 3rd Floor, University Avenue, Upper Campus, University of Cape Town, Rondebosch, South AfricaiCNRS, UMR 5199-PACEA, Université de Bordeaux 1, Talence, France

a r t i c l e i n f o

Article history:Received 15 September 2012Received in revised form21 December 2012Accepted 21 December 2012

Keywords:Southern AfricaMiddle Stone AgeHowiesons PoortLithic technologyHaftingVegetal adhesivePodocarpus elongatusDiterpenoidsGCeMS

* Corresponding author. Laboratoire de Spectrométet des Systèmes e LSMIS, CNRS, UDS, UMR 7140 “Chi1 rue Blaise Pascal, F-67008 Strasbourg, France. Tel.:

E-mail address: acharrie@unistra.fr (A. Charrié-Du1 Tel.: þ33 (0)146692655.

0305-4403/$ e see front matter � 2013 Elsevier Ltd.http://dx.doi.org/10.1016/j.jas.2012.12.026

a b s t r a c t

The hafting of tools using adhesive is one of the innovative features that characterizes the southernAfrican Middle Stone Age. This technology has mainstream implications but remains insufficientlydocumented, largely due to unequal organic preservation and non-adapted analytical procedures. Anotable 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 residuedistributed over their surface. Their stratigraphic distribution reveals a strict association with theHowiesons Poort (HP) and suggests a close relationship between the appearance of hafting adhesiveand the appearance of blades and geometric backed tools. Macroscopic and microscopic observationsattest 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 flakeattributable to the Late phase of the HP. We determine, for the first time in a MSA context, the nature ofthe compound adhesive and reconstruct a picture of the multilevel operations and interactions thatcomprise 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 andpossibly mixed with fragmented bone and quartz grains. Compared to Sibudu where ochre additive isdocumented, the hafting technology at Diepkloof introduces another level of variability within the HPtradition and suggests the existence of regional expressions and adaptations.

� 2013 Elsevier Ltd. All rights reserved.

rie de Masse des Interactionsmie de la Matière Complexe”,þ33 (0)368851629.haut).

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1. Introduction

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

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socio-economic organization. More recently, the multi-taskinginvolved in the manufacture of compound adhesive has beenemphasized as a relevant behavioural proxy for complex cognitivecapacities (Wadley et al., 2009).

Most of the time, the assumption of tool hafting is based onthe observation of specific tool modification (e.g. the tang for theAterian points) or from macro- and micro-scopic damages (e.g.abrasion of ridges on the upper surface of the tool) (Anderson-Gerfaud and Helmer, 1987; Rots, 2010; Conard et al., in press).Such issues are often connected to the question of huntingpractices and to the debate regarding the appearance of lithicprojectiles among hunteregatherer populations (Lombard andPargeter, 2008; Shea and Sisk, 2010). Occasionally, hafting isinferred because of the presence of residues covering the pre-hensile part of the lithic tool. Such evidence remains exceptional.For example, hafting residue has been recorded at the Italianmiddle Pleistocene site of Campitello in the form of birch barktar (Mazza et al., 2006), at the Middle and Upper PaleolithicRomanian site of Gura Cheii-Râsnov in the form of bitumen(Cârciumaru et al., 2012), and at the Mousterian site of Umm-el-Tlel (Syria) in the form of bitumen imprints on Levalloisflakes and points (Boëda et al., 2008, 2009). In these cases, thestudies tend to focus on the process of hafting itself, on itstechnological and functional implications and, ultimately, on itstransformation over time and variability in space.

For the Southern African Middle Stone Age (MSA), a fewexamples 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 firstwith the bifacial Still Bay and then persisting over time, crossingdifferent technological traditions (Howiesons Poort and post-Howiesons Poort) and geographic areas. The appearance of haft-ing in the Southern African MSA would have coincided with aglobal transformation of societies, illustrated by changes in a wide

Fig. 1. List and location of southern African Middle Stone Age sites where hafting residuesCottage Cave (Howiesons Poort: Gibson et al., 2004); Sibudu Cave (Still Bay, Howiesons PoShelter (Howiesons Poort: Lombard, 2007); Peers Cave (?) (Still Bay: Minichillo, 2005); Die

range of activities, such as blank production, rawmaterial economyand symbolic manifestations (Klein, 1995; McBrearty and Brooks,2000).

Macroscopic hafting adhesives are documented on a few MSAsouthern African sites (Fig. 1). Among these sites, the archaeo-logical record of Sibudu deserves to be considered specifically. Forexample, the study of Lombard (2008) has hypothesized changesover time in hafting materials and hafting configurations of thesegments, possibly related to technological change and adapta-tion. In a different perspective, the technological and exper-imental study of Wadley et al. (2009) has documented the way inwhich the Howiesons Poort (HP) inhabitants at Sibudu madecomplex compound adhesives to haft their tools using ochre-based additives. This result demonstrates that people sustainedmultilevel operations and were competent chemists (properties),alchemists (mixture), and pyrotechnologists (transformation)(Wadley et al., 2009).

Characterization of hafting technology is more than justadditional or optional archaeological data: it represents a dis-crete area of investigation in its own right that permits access toa lost technological “savoir-faire”. In this paper, we would like toplace our chemical study within the context of previous haftingstudies conduct on artifacts from the HP. But for the first time,analyses are performed at molecular level and not only micro-scopic level, which allows the identification of molecular mark-ers (biomarkers) leading to the characterization of naturalorganic substances. Our pioneering chemical approach for a MSAcontext is based on the collection from Diepkloof Rock Shelter(DRS), where the organic preservation is remarkable. Our goalsin this study are: (1) to document the technological tradition ofthe HP inhabitants of Diepkloof and to understand their inter-actions with the resources of the environment; (2) to offer newavenues of interpretation and comparisons for the southernAfrican MSA; (3) to investigate the question of the earliest

have been recorded: Apollo 11 (Late MSA: Wendt, 1976; Vogelsang et al., 2010); Roseort, post-Howiesons Poort: Lombard, 2006; Wadley et al., 2009); Umhlatuzana Rockpkloof Rock Shelter (Howiesons Poort).

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hafting technology and contribute to the debate on the techno-logical changes that occurred within African anatomically mod-ern human societies.

2. Black residues and evidence of hafting at Diepkloof RockShelter

The site of Diepkloof is located in the Western Cape Province,about 180 km north of Cape Town and 14 km from the Atlanticcoast. Excavations began in 1998 in the framework of a SouthAfricaneFrench collaboration and expose to date a MSA strati-graphic sequence of ca. 3.1 m deep, which has been subdivided into53 stratigraphic units (SU) (Parkington et al., 2013). The TL and OSLdating of Tribolo et al. (2013) bracket the current MSA sequencefrom the OIS 5 d to the beginning of the OIS 3. Details on theluminescence ages, clarification with other dating results (Jacobs

Fig. 2. Examples of Late Howiesons Poort lithic artifacts with a residual black adhesive onflakes; 9e10: laminar blanks) (drawing by M. Grenet).

et al., 2008) and archaeological implications are further discussedin Tribolo et al. (2013) and Porraz et al. (2013a,b).

2.1. Introduction to the collection

The first macroscopic residues found on MSA lithic artifacts atDiepkloof were reported in 2006 (Rigaud et al., 2006). Since then,the number of lithic pieces with such evidence has increasedconsiderably (see below). All of these pieces present very similarcharacteristics (Fig. 2): the residue is black and homogeneous;the outlines of the residue are clearly delimited on the piece; theresidue covers only a part of the surface of the tool and is alwaysopposite to the sharpened edge (when the blank is non-symmetric, the residue is on the irregular part); the residue canalways be observed on both faces of the tool (even with a dif-ference in preservation) and it is generally bifacially symmetrical.

their side, Diepkloof Rock Shelter (1e5: backed pieces; 6: flake; 7e8: naturally backed

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These observations, as well as the primary use-wear analysis(Igreja and Porraz, 2013), support the hypothesis that thesepieces were hafted and that the black residue corresponds to anold adhesive that was applied to cement the pieces into theirhaft.

In terms of diachronic distribution, evidence of hafting residuesat Diepkloof is restricted to the HP units (Table 1). To date, twopieces 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 (SUKegan), immediately below and in contact with the first HPstratigraphic unit (SU Keeno). Moreover, one of these pieces is abi-truncated tool typical of the Early HP tradition and the other isa bladelet (Porraz et al., 2013a). As a consequence, we considerthese pieces to be associated with the Early HP rather than withthe SB. To date, no hafting adhesive has been observed on the SBbifacial pieces, nor on the post-HP unifacial points. Interestingly,no residue has been found in the technologically distinct MSA-Jack, which is sandwiched between the Early and the Inter-mediate HP (Porraz et al., 2013a). As documented by Miller et al.(2013), no change in depositional or post-depositional processescan explain such a stratigraphic distribution of black residue overthe sequence.

Regarding the size of our sample (N ¼ 29 lithic pieces comingfrom squares M6eN6), further fieldwork could change our currentmodel. However, we have carefully looked for residues (at a

Table 1Catalogue of the lithic pieces with a black residue macroscopically identified (squares M

Stratigraphic unit Raw material

Post-HP None

Late Howiesons Poort Debbie Sub-Local silcreteDarryl Non-local silcreteEric Non-local silcreteEric QuartzEric QuartzEric QuartzEster QuartzEster QuartzEdgar FlintEdgar QuartzEdgar Non-local silcreteEdgar QuartzEve QuartzEben Non-local silcrete

Intermediate Howiesons Poort Frank Non-local silcreteFox Non-local silcreteFiona Non-local silcreteJohn QuartzJohn Sub-Local silcreteJeff Non-local silcreteJeff Non-local silcreteJoy Sub-Local silcreteJoy Sub-Local silcrete

MSA-Jack None

Early Howiesons Poort Kate Non-local silcreteKerry Non-local silcreteKenny Non-local silcreteKegan Non-local silcreteKeeno* Non-local silcreteKeeno* Sub-Local silcrete

Still Bay NonePre-SB Lynn NoneMSA-Mike None

*Considering the characteristics of these 2 pieces and their stratigraphic location just belowthe fact they belong to the last Still Bay stratigraphic unit.

macroscopic scale) on about 15 000 lithic artifacts (>20 mm) fromsquares M6eN6. We consider, therefore, that further discoverieswill not significantly alter the hypothesis that the presence ofhafting adhesive at Diepkloof is closely linked (if not exclusively so)to HP technology. This association strongly suggests that theappearance of blade and backed piece technology, in parallel withthe 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 withdifferent types of blanks and different raw materials (Table 1), withthe exception of the local quartzite, which preserves no evidencefor hafting residues.

- In the Early HP, evidence of hafting residues relates to 6 piecesand is associated preferentially with laminar products (n¼ 5/6)and exclusively with silcrete. Half of this sample contains bi-truncated pieces.

- In the intermediate HP, evidence of hafting residues relatesto 9 pieces. We observe a similar pattern, but geometricbacked pieces with a black residue are rare (n ¼ 2/9). Inter-estingly, no evidence of hafting adhesive has been found onthe strangulated-notched pieces, despite the fact that theyrepresent the dominant formal tool category during thisphase. A different conception of tool hafting and recyclingprobably explains the absence of hafting adhesives on thesepieces.

6-N6, Diepkloof Rock Shelter).

Blank Typology Location of the residue

Débordant flake LateralBlade LateralBladelet UndeterminedBlade LateralBipolar product UndeterminedFlake UndeterminedBlade LateralDébordant flake UndeterminedBlade LateralBlade LateralFlake Segment LateralDébordant flake LateralBlade Bi-truncated LateralBlade Undetermined

Blade LateralBlade LateralBladelet Truncated LateralFlake Segment DiagonalBlade LateralUndetermined LateralBlade LateralBlade LateralBladelet Lateral

Flake UndeterminedBlade Bi-truncated LateralBlade Bi-truncated LateralBlade UndeterminedBladelet Bi-truncated LateralBlade Lateral

the Early HP, they have been associatedwith the Howiesons Poort tradition despite

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- During the Late HP, evidence of hafting residues relates to 14pieces. Flakes becomemore important in the sample set (n¼ 5/14) as well as quartz (n ¼ 8/14). Together with the presence ofhafting residue on “naturally” backed pieces (‘geometric’ latosensu), this sample furnishes a good illustration and support ofthe technological changes documented during the last phase ofthe HP (Fig. 2). Only the low proportion of geometric backedpieces (stricto sensu) (n ¼ 2/14) remains somewhat enigmatic,whenwe consider their proliferation during this phase (Porrazet 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 reflectdifferences regarding the number of SUs (and possibly, by exten-sion, differences in the intensity, number or duration of the occu-pations), but further investigation is required. Hafting was acommon practice during the HP and was not restricted to a uniquetechnological or formal category. Changes over time echo thegeneral transformation of the lithic technology. One interesting andpersistent characteristic over the sequence concerns the dis-tribution of the black residue on the surface of the lithic artifacts(Fig. 2). Indeed, the adhesive imprint observed on the HP pieces isalways lateralized, suggesting that all the HP tools were haftedlongitudinally, parallel to the axis of the tool or, more rarely, on aslight diagonal.

The pieces exhibiting hafting residue attest to various states ofedge preservation. Examples of macroscopic damage observed on

Fig. 3. Detail on the stratigraphic provenance of a Late Howiesons Poort quartz flake wi

the edges of Early HP tools have been interpreted as a directconsequence of their usage, supporting the hypothesis that EarlyHP hafted tools functioned predominantly as cutting/scrapingimplements (see Igreja and Porraz, 2013). However, a few exam-ples of backed pieces with hafting residues show impact-likefracture. This is notably the case for the Late HP assemblage,which documents the presence of backed pieces with transversalburination (at one or at both extremities: e.g. Fig. 2, n ¼�1). Similarburinations have been interpreted by Villa et al. (2010) as evidenceof impact damage. Their presence at Klasies River at a similar ageas at Diepkloof suggests a common pattern of use during thisphase.

2.2. Focus on a Late HP quartz flake

The preservation of hafting residues is variable within theDiepkloof assemblage, and probably reflects the influence of sev-eral pre- and post-depositional factors. Mostly, the hafting residuetakes the form of an imprint with patches of variable thicknesslocated on the irregular surface of the tool (e.g. on the back). Inorder to carry out the chemical analysis of the adhesive, weselected a sample of pieces with a thicker and broader distributionof residue over each piece. While several pieces are still underinvestigation, in this paper we focus on a single flake recovered in2004 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

th 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 sec-tion. In this case, the artisan used the dissymmetry of the tool andits thickness as an irregularity to be hafted. The use-wear analysisof the piece attests to a slight chemical weathering of the surface(Fig. 4). However, these post-depositional effects are minor andhave not masked the presence of microscopic use-wear, whichsuggests a use related to the processing of soft animal material.The working of soft animal material is characterized by the pres-ence of polish associated with edge scarring. The features of thepolish and the morphology and distribution of the scars exclude abutchery activity. Butchery tends to create a more reticular and“greasy” polish and also displays a macroscopic denticulation ofthe edge that is easily recognizable (Plisson, 1985; GonzalesUrquijo 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 ofscarring on both sides of the edge, suggest instead the cutting ofsoft animal materials (e.g. dry hide). However, the degree ofdevelopment of the microwear traces in particular does not allowa more specific diagnosis of the nature of the worked material(Plisson, 1985; Gonzales Urquijo and Ibanez Estevez, 1994). Fur-thermore, the microscopic striations parallel to the tool (Fig. 4) aretypical of a longitudinal working motion and are coherent withthe lateral presence of a haft.

3. Analytical method

The chemical approach used in this study employs diagnosticbiomarkers derived from naturally-occurring organic substances.Biomarkers aremolecules which have a carbon skeleton sufficientlyspecific to be related to their precursor biological lipid enablingidentification of the natural substance used. These compounds areideally resistant to the various alteration processes experienced bythe original material (abiotic oxidation, biodegradation). In the caseof degradation, it is sometimes possible to rely on specific degra-dation byproducts as shown for Dipterocarpaceae resins (Burgeret al., 2009). Each natural substance has its own molecular finger-print more or less altered. Consequently, this approach permits thedistinction between different biological origins (animal, plant,

Fig. 4. Photographic details of the use-wear traces typical of a longitudinal motion in relaticolour in this figure legend, the reader is referred to the web version of this article.)

families, species), to elucidate the composition of mixtures, some-times complex, to evaluate states of alteration (anthropic ornatural).

The analytical flow chart applied to study archaeologicalmaterial is directly adapted from the methodology used inpetroleum organic geochemistry to analyse bitumen, sourcerocks and crude oils. An account of the basic principles of thisprocedure illustrated by some applications and specially adaptedto different archaeological contexts is reported in several pub-lications (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 cou-pled with mass-spectrometry (GCeMS).

3.1. Extraction, fractionation

The black residue from the Late HP piece (Fig. 5) was extractedultrasonically three times for 5 min each with dichloromethane/methanol (60:40). The combined solvent extracts, forming the totalorganic extract, were concentrated by evaporation. The analyseswere performed using GCeMS after splitting the total organicextract by gravity flow column chromatography and thin layerchromatography (silica gel support). To avoid any contamination,specific treatment of the chemical products and glassware wascarried out in addition to negative control of the whole process.

3.2. Mass spectrometric analysis

GCeMS analyses were carried out on a triple quadrupole Ther-moFisher TSQ Quantum spectrometer connected to a Trace GC Ultragas chromatograph (PTV e on-column mode e injector, HP-5 MScolumn, 30 m � 0.32 mm i.d., 0.25 mm film thickness). The fol-lowing temperature program was used: 40 �C (1 min), 40e100 �C(10 �C/min), 100e300 �C (4 �C/min), isothermal 300 �C. Massspectra were produced at 70eV, source at 200 �C, in full detectionmode over 50e700 amu. Helium was used as a carrier gas(1.7 mL min�1).

3.3. Carbon isotopic composition

The compound specific stable carbon isotope analyses (d13Cvalues) were performed at the Stable Isotopes Laboratory of the

on with the processing of animal soft material. (For interpretation of the references to

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

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University of Lausanne (Institute of Mineralogy and Geochemistry).They were obtained by the use of an Agilent 6890 GC coupled to aThermoquest/Finnigan MAT Delta S isotope ratio mass spec-trometer by a combustion (C) interface III (GCeirmMS) under acontinuous helium flow. The irmMS ion source pressure is lowerthan 6 � 10�6 bar. The GC was operated with the same type ofcolumn and temperature program used for GCeMS analyses. Therepeatability and intermediate precision of the GCeirmMS proce-dure, and the performance of the GC and combustion interfacewere evaluated every 5 analyses by injection of an in-house mix-ture of n-alkanoic acids (UNIL-FAME MIX) of known isotopiccomposition and at least three replicate analyses of the samples.The standard deviations for repeatability ranged between 0.05 and0.4& for the main FAME and for intermediate precision between0.3 and 1.1&.

4. Results of the chemical analysis of the hafting residue

The presence of an organic extract of the fine black powderscraped off on the tool’s surface confirms the existence of naturalorganic substances adhering to the HP quartz flake. This extractrepresents 39% of the hafting residue. However, we cannot re-dissolve the totality of the organic extract. This is also some-times the case for bitumen and probably indicates a high degreeof degradation of the organic substances. Consequently, thefractionation was only carried out on approximately 8% of thehafting residue. As there was only a small quantity of materialavailable to sample (few tens of milligrams), the amount of eachfraction was quite small (<1 mg). On the other hand, analysisof the residue by scanning electron microscopy (SEM) showedthe 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 extractconsist mainly of linear and diterpenoid structures (Fig. 6a). Thepresence of diterpenic structures provides evidence for a Gymno-sperm contribution, essentially conifer precursors which are divi-ded into several families including Pinaceae, Araucariaceae,Cupressaceae, Podocarpaeae, Taxodiaceae (Langenheim, 2003).The specific distribution of biomarkers with an abietane skeletonallows the differentiation of each family. According to Otto andWilde (2001), the reports of abietane derivatives reveal twogroups: the “regular” abietanes and the “phenolic” abietanes.Several parameters are presented in the literature for dis-tinguishing 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: thoseof totarol, ferruginol and sempervirol. They are absent in Pinaceae.Totarol and ferruginol derivates are biomarkers for Cupressaceaeand Podocarpaceae. The distinction between these two families ismade on the presence of sempervirol, which is restricted toCupressaceae, and the predominance of ferruginol derivatives inthis family.

Therefore, identification of phenol diterpenic derivatives shouldallow the determination of the family of Gymnosperm used. Thepresence of a compound from the totarol family as a major com-ponent, totarol-7-one, suggests the use of a product derived fromthe Podocarpaceae family. Isolated specimens of these trees are stillpresent in the area of Diepkloof at the present day. To betterunderstand the molecular fingerprint of the archaeological sample,bark of Podocarpus elongatus, identified in the charcoal collection ofDiepkloof (see Cartwright, 2013), was analysed by the samechemical approach. The GCeMS total ion current trace of the sily-lated total extract of the present bark (Fig. 6b) also consists mainly

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

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of phenolic diterpenic structures related to totarol and correspondsto those presented by Cox et al. (2007). The major components ofthe present bark are totarol, 3-hydroxytotarol, 4-carboxynortotarol,3-hydroxy-4-carboxynortotarol and 3-hydroxyferruginol. Thesephenolic structures were not identified in the archaeological sam-ple. On the other hand, structures based on totarol skeleton withmore oxygen functionalities, namely totarol-7-one and sugiol weredetected in the ketone fraction. From a chemical point of view,phenolic structures are very sensitive to oxidation, especially inbenzylic position. Consequently, degradation byproducts are easilyformed both by natural ageing (biodegradation, oxidation) and byanthropogenic (intentional or accidental) transformations (burn-ing). These alteration processes strongly influence the chemicalsignature.

Little information on the oxidized products of such componentsis available in the literature. Moreover, the distinction of eachphenol family (totarol, ferruginol, sempervirol) is sometimes diffi-cult to achieve in analysis (Enzell and Wahlberg, 1970). Thearchaeological residue is so degraded that direct correlation withthe current natural product is no longer possible.

As mentioned earlier, linear structures are present in the sily-lated extract of the archaeological sample. The fingerprint of thelinear structures identified in the archaeological sample of haftingresidue is dominated by linear monocarboxylic acids (even pre-dominance, ranging from C14 to C18) and by linear diacids (alsocalled linear a,u-dicarboxylic acids), ranging from C7 to C14, withthe term C9 (azelaic acid) predominant (Fig. 6a). According to Villa

et al. (2012), the detection of such components suggests the pres-ence of a bio-polyester, derived from suberin. The similarity of thetwo chromatographic profiles is indeed striking. These linearstructures 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 acidwith 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, com-pound usually present with the diacids, was not detected in thissample.

4.2. GCeMS analysis after fractionation

For a better identification of the biomarkers present in thearchaeological sample, the organic extract was split into five frac-tions of increasing polarity: less polar components (alkanes,alkenes, aromatic hydrocarbons, esters) in very tiny amount(<0.5 mg), ketones, alcohols, acids and polyfunctionalised com-pounds. Organic extract from the bark of P. elongatus was also splitfor comparison. Fractionation enables the concentration of com-pounds, some of which are present in minute amounts and there-fore are not detected by the procedure described above. Suchminorcompounds can help characterize the origin of a sample or itsdegree of alteration. Moreover, fractionation simplifies GCeMStraces (Charrié-Duhaut et al., 2009).

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

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The distribution of n-alkanes (C20 to C35) is dominated by longchain molecules with a strong odd/even carbon number predom-inance after C27. Such a distribution is generally observed in higherland plants. No polyaromatic structure like phenanthrene, anthra-cene, chrysene e typical of pyrolytic signature e has been detectedin the hafting residue.

All polar fractions (esters, ketones, alcohols, acids) consistmainly of phenolic diterpenoid structures. Traces of componentindicators of degraded fat (plant or animal origin) were detected:g-lactones (C16 major), carboxylactones (with a distribution similarto that of diacids, C9 major) (Bastien, 2011).

To illustrate the distribution of diterpenic components, Fig. 7shows the GCeMS traces of the fraction with the polarity ofketones in the archaeological sample and in modern bark fromP. elongatus. The distributions are very different. In the bark, thethree phenols, sempervirol, totarol and ferruginol are present inassociation with some oxidized forms such as totarol-7-one ordihydroxytotarol. By contrast, in the archaeological residue, thephenols are absent and the fraction is dominated by oxidizedforms, a few which are different from those in the bark. Thedistinction of the derivatives of all three families of phenolsbased only on mass spectrum analysis is problematic because ofthe similarity of mass spectra (Enzell and Wahlberg, 1970).However, the diterpenoids, identified by their mass spectra,belong to the series of totarol and ferruginol. Sempervirolderivatives seem to be absent. Moreover, no diagnostic moleculesof the well-known Pinaceae resins were identified (Langenheim,2003). In conclusion, the use of a product derived from Podo-carpaceae is likely.

Although it is possible to characterize archaeological materialsby their molecular composition alone, gas chromatography-combustion-isotope ratio mass spectrometry (GCeCeIRMS) isoften useful for providing more accurate information on the bio-logical sources of organicmatter. The ratio 13C/12C called d13C (in&/PDB) is measured by this technique. Stable carbon isotopic datawere recorded on several components from the Diepkloof sample(totaro-7-one: �30.0&/PDB; palmitic acid: �28.5&/PDB; stearicacid: �28.2&/PDB). To the best of our knowledge, few d13C valuesfrom Podocarpaceae have been published in the literature(Cernusak et al., 2008).

In the specific case of Podocarpaceae, many phenolic structuresneed to be elucidated to study the degradation processes. Forexample, podototarin, a bisditerpenoid frequently described in thechemistry of Podocarpaceae (Cambie et al., 1963), identified in theextract of barks is not detected in the archaeological sample.Phenolic diterpenic units are likely to form bis-diterpenoids by thecondensation of two units (Le Métayer et al., 2008). Such com-ponents were detected in the two studies but with differentstructures.

To summarize, our chemical analysis strongly supports thehypothesis of the use of P. elongatus (Yellowwood) to furnish theadhesive substance found on the HP quartz flake of Diepkloof.Considering the fact that charcoals of this wood taxon have beenidentified in the Diepkloof archaeological record (Cartwright,2013), it is thus possible that Podocarpaceae tar was collectedand used, in the same way as the well known pitch (tar derivingfrom Pinaceae) and birch bark tar. Heating modifies the molecularcomposition 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 mono-carboxylic acids and a,u-dicarboxylic acids is diagnostic of asuberin-containing pitch. In the case of DRS sample, as specificcomponent indicators of degraded fat (g-lactones, carboxylactones)were detected and as no long chain hydroxyl-fatty acids seem to bepresent, the origin of these acids is rather a fat than a tar. Weconclude that the hafting adhesive used by the LHP inhabitants ofDiepkloof derives from P. elongatus and most probably correspondsto an oxidized resin.

5. Discussion

5.1. The adhesive manufacture at Diepkloof Rock Shelter

In the context of the South African MSA, several authorsmention or infer the presence of other ingredients in the haftingadhesive, such as acacia gum, mastic, beeswax and ochre(Lombard, 2006; Wadley et al., 2009). Their biomarkers (longchain fatty esters for beeswax, typical triterpenoid for mastic,hopanes and steranes for bitumen or polysaccharides for acaciagum) were not identified on the analysed quartz flake of Diepkloof.Freely-added ochre, for example, allows the adhesive to becomeinsoluble in water without being hydroscopic. SEMwas used to tryto detect the presence of this natural iron oxide in the residue butnone was found. So, none of the classic additives has been iden-tified in the adhesive analysed. Like the resin of the Dipter-ocarpaceae family which, for instance, is used without processing(Burger et al., 2009), it is then possible that the resin of Podo-carpaceae family has been used as a pure material.

However, the detection of degraded fat in the hafting residueof Diepkloof raises questions about its origin. The presence of fatmay reflect contamination, or might indicate its use as additive.For example, the presence of fat as part of the adhesive recipehas been observed at the site of Sibudu (Lombard, 2006). Inaddition, the SEM identification of bone fragments and quartzgrains, within the hafting residue of Diepkloof, might alsoindicate that these components were used for additive mixture.But caution is urged because of the nature of the sediment thatsurrounded the piece (see Miller et al., 2013), which is com-posed of numerous detrital anthropical remains and quartzgrains originating from the disaggregation of the rock shelter. Asimilar question concerns the presence of botanical fragmentsinitially observed on the adhesive, but which we currentlyinterpret as contamination from the surrounding sediment.Further chemical analysis of hafted residues from Diepkloof andother sites will assuredly provide additional data for thisdiscussion.

The modification of the hafting residue documented at Die-pkloof could either imply a process of natural drying or a heattreatment. Based on chemical or macroscopic data, it is difficult toevaluate whether or not heating has been used to transform theadhesive. However even if heating has been used, the temperaturereached was likely to have been moderate and restricted to thesoftening of the resin, as no pyrolitic byproducts were recorded inthe sample. Further research is now required to replicate thehafting and to assess the technological expertise required for theuse of a resin from P. elongatus.

5.2. Towards a reconstruction of the hafting process at DiepkloofRock Shelter

Hafting technology has been recently analysed in terms ofmultilevel tasks and interpreted as the expression of complex

cognition (Wadley et al., 2009; Wadley, 2010). Our multi-disciplinary approach gives an illustration of these operationsand of the type of behaviour and knowledge that was required.The hafting of a tool is a convergence of three main sous-chaînesopératoires: 1) the manufacture of the lithic piece, 2) the man-ufacture of the haft, 3) the manufacture of the adhesive. Itimplies that the activities were carried out in different places(the acquisition of the resource and, eventually, its trans-formation), but the existence of a central place where thesetechnological operations converge. The hafting technologyimplies, therefore, a good knowledge, management and controlof natural resources, as well as an efficient territorial and socio-economical organization.

The cost of the technical operation is directly linked to thenature of the activities. Focusing on the artifact that has beenchemically analysed, we can observe that the lithic piece actuallyshows a low technological investment. Indeed, the raw materialof the flake is likely to originate from the slope of the shelter(quartz pebble) while its characteristics suggest a reductionsequence oriented towards the production of blanks that werenot highly standardized. The criterion of selection was then basedon the presence of a sharp and regular edge as well as a dis-symmetric section (to be hafted). The case is different when weconsider the question of the adhesive. Indeed, our data suggest aninvestment focused on the acquisition of a specific wood species(P. elongatus), with the possible occurrence of a specific trip tocollect its resin, implying a good phytogeographic knowledge ofthe area. The resin would have then been naturally dried orheated at a low temperature, and possibly mixed with frag-mented bone and quartz grains. We do not know the nature andthe morphology of the wood that was selected to be transformedinto a haft (if any), but this activity was most certainly time-consuming (depending on the nature of the haft), starting withthe selection of the wood, the acquisition of the suitably-sizedbranch, its transformation (pruning, planing, etc.) and its finaladaptation to the type of handle desired (including the mode ofinsert into the haft). If we try to schematize this process ofhafting, we observe differences between the technological oper-ations, regarding the cost of the raw material acquisition and itsprocess of transformation. These multi-level operations suggestthe existence of different technological skills, as well as differentlevels of planning and curation.

The microwear analyses show that the hafted quartz flakewas used as a knife to cut soft animal materials. It is thus worthsaying that hafting was not restricted to the manufacture ofhunting tools, but embraced a wide range of activities (seeIgreja and Porraz, 2013), as documented in other Middle orUpper Palaeolithic contexts (Anderson-Gerfaud and Helmer,1987; Boëda et al., 2009). Hafting appears then as a commonpractice in the daily life of the population. It suggests a complexlevel of communication at a horizontal (communication) andvertical (transmission) scale, and implies cognitive abilitiesthat were as complex as any other modern hunter-gatherersocieties.

5.3. Hafting adhesives in the South African context

The exploitation of P. elongatus as a resource of adhesive hasbeen 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. elongatushas 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 ofSibudu but only Podocarpus sp. has been identified. One taxon,formerly a Podocarpus genus, has now been taxonomicallyreclassified as Afrocarpus, i.e. A. falcatus. It is relevant to note thatP. elongatus is endemic to southern Africa and is currently con-fined to the winter-rainfall Western Cape. Within the archaeo-logical record of Diepkloof, P. elongatus is documentedthroughout 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 thewetter areas of different types of fynbos. The fact that this par-ticular taxon can adapt to different types of habitat, when nec-essary, is significant with regard to the sequence at Diepkloof, asit may mean that P. elongatus would have been available, perhapsin stunted form, even if climatic or soil moisture conditions hadchanged over time. Independently of environmental changes ortechnological traditions, the charcoal record at Diepkloof showsthat P. elongatus has been a resource that was continuously col-lected by the Diepkloof inhabitants (Cartwright, 2013). This woodcould have been collected for different purposes, such as fuellingfires, supporting perishable structures or providing wooden haftsfor artifacts. To date, the earliest use of its resin as an adhesive isdocumented for the later phase of the HP at Diepkloof. On-goingchemical analysis will give further precision on the diversity ofvegetal species used to make adhesive, at both a synchronic anddiachronic scale.

Considering the hafting tradition described above, Diepkloofdiffers notably from Sibudu, where ochre appears to be anelement commonly (but not necessarily) present on the back ofthe backed pieces (Wadley and Mohapi, 2008). At Diepkloof, allthe pieces with a black imprint have been carefully looked atmagnifications of �10e�40, but none of them showed thepresence of red pigments. We conclude, therefore, that ochrehas never been used as a loading agent at Diepkloof. Thesedifferences cannot be explained at a diachronic scale insofaras the Late HP at Diepkloof and the HP at Sibudu are dated tothe same age (Wadley and Jacobs, 2006; Tribolo et al., 2013).Nevertheless, the technological differences of the Late HP atDiepkloof compared to the HP at Sibudu, including a flake-based component (Porraz et al., 2013a), could also testify to adivergent technological trajectory including that of adhesivefabrication. The differences between the two sites, located indifferent environments and at a distance of about 1200 kmfrom one another, likely reflects the expression of the sametechnological phenomenon (comprising blades, backed pieces,lateral hafting, and use of adhesive) but locally adapted anddifferently manipulated (following regional traditions). Alsorelevant are the sites of Rose Cottage Cave and UmhlatuzanaRock Shelter, where ochre has also been identified as anadhesive component (Gibson et al., 2004; Lombard, 2007), thusextending the framework of reference of the hafting traditionas recorded at Sibudu. At Apollo 11 (south of Namibia), where apiece with adhesive has been discovered, ochre as an ingre-dient of the adhesive has not been described (Vogelsang et al.,2010).

6. Conclusions

The MSA of Southern Africa surprises us by the antiquity of itsbehavioural innovations as well as by the exceptional preservationof its archaeological record. Some of these innovations e thehafting of tools and the use of affixing adhesive e illustrate another

level of technological skill and of socio-economic organization. Inthe Diepkloof sequence, the use of adhesive is closely linked to theHP. Adhesive imprints are documented from the Early HP phase,dated by TL at 105 � 10 ka (SUs Kerry-Kate) and by OSL at109 � 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 ofDiepkloof has enabled, for the first time in a MSA context, theidentification of the nature of the organic resource used to preparethe adhesive. The HP inhabitants of Diepkloof collected the resin ofP. elongatus, dried or heated the resin at a low temperature, andpossibly mixed it with additives such as bone fragments and quartzgrains.

The results of the study highlight the wide range of exploita-tion of the organic and mineral resources by the inhabitants ofDiepkloof. Our results show that hunteregatherer populationswere perfectly integrated into their environments and fully awareof the potential of the resources. The results also demonstratethat Diepkloof was a central place in the territorial system ofthese populations. All the archaeological finds (e.g. ostrich egg-shells 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 thesite individualize Diepkloof as a place where a large range ofactivities 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 socio-economic transformation, but also represents a factor of tech-nological change. It is worth saying that the use of adhesive atSibudu was likely to have persisted through the time of thesequence, crossing distinct technological and hafting traditions(Lombard, 2006; Wadley et al., 2009). Though not all adhesivefrom Sibudu contains ochre, ochre as additive is documented invarious contexts, notably during the HP. This persistence and thisdifference with Diepkloof fuel the question of the technologicalshifts versus the regional survivals. Bearing in mind that thesample remains restricted, the differences between Diepkloofand Sibudu are likely to reflect local adaptations to resources andexpress different regional traditions. These distinct hafting tra-ditions echo previous differences observed in the lithic technol-ogy as well as in the symbolic patterns, and throws into sharpfocus the role of regional organization and networks in theevolutionary process of the innovative Howiesons Poort (Porrazet al., 2013b).

Acknowledgements

The scientific project and excavation at Diepkloof have beenfunded by the French Ministry of Foreign Affairs (MAE), theAquitaine region, the Provence-Alpes-Côte-d’Azur region, theCentre National de la Recherche Scientifique (CNRS), the Paleon-tological Scientific Trust (PAST) and the National Research Foun-dation (NRF) of South Africa. One of us (GP) has been supported bythe Fyssen and the Alexander von Humboldt Foundations, and hasbenefited from collaborations with the University of Cape Townand 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 tothank the ANR for the support of the program “Archeomolecule”and the Kirstenbosch National Botanical Garden for providing barkof Podocarpus.

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

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