Microwear and residue analyses in perspective: the contribution of ethnoarchaeological evidence

Journal of Archaeological Science 31 (2004) 1287–1299

http://www.elsevier.com/locate/jas

Microwear and residue analyses in perspective:the contribution of ethnoarchaeological evidence

V. Rotsa,), B.S. Williamsonb

aLaboratory for Prehistory, Katholieke Universiteit Leuven, Redingenstraat 16, 3000 Leuven, BelgiumbSchool of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa

Received 16 January 2003; received in revised form 24 July 2003

Abstract

This paper presents the results of combined though independent microwear and residue analyses on an ethnoarchaeologicalassemblage from Ethiopia. Although microwear and residue analyses both aim at deriving functional information from stone tools,

we believe that each addresses different issues and that the techniques are largely complementary. Given the ethnoarchaeologicalnature of the assemblage, a thorough examination and comparison of both methodologies was highly informative. It wasdemonstrated that a combined approach compensates potential deficiencies of a particular method and that it allowed more

confident functional interpretations.� 2004 Elsevier Ltd. All rights reserved.

Keywords: Microwear; Residues; Stone scrapers; Ethnoarchaeology

1. Introduction

The Konso of Southern Ethiopia (Fig. 1) are one ofthe few groups in Ethiopia in which stone tool technol-ogy persists, in particular with regard to hide working[1,2,4]. Stone scrapers are fabricated out of different rawmaterials like chert, quartz and quartz crystal. Thescrapers are inserted into a concavity made in a straightwooden haft and fixed with the aid of resin (Fig. 2). Forthe resin, an Acacia (sp.) tree gum is routinely used. It isground up and then melted in the fire to make the masticused to haft the tools. Charcoal generally forms anaccidental addition to the resin during the heating pro-cess. While male hide workers are a dominant feature insouthern Ethiopia, the Konso are unique in that womenmake and use the stone tools for hide working.

Although microwear and residue analyses have beenrecognised as complimentary sciences in the past, theyhave largely functioned independently. Only Hardy et al.(see [6]) have conducted a comparative study using bothtechniques. The application of microwear and residue

) Corresponding author. Tel.:C32-16-326435; fax:C32-16-326400.

E-mail address: [email protected] (V. Rots).

0305-4403/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.

doi:10.1016/j.jas.2004.02.009

techniques to the analysis of ethnoarchaeologicalmaterial has several major advantages, not least ofwhich is a thorough examination of the methodologieswith their benefits and inherent limitations. Unlike apurely experimental situation, the working conditionswere not simulated and tools were used with sufficientcompetence by skilled hide-workers. Experimental re-sults previously obtained [15,21] could be confirmed.In addition, the results were compared with an anal-ysis of archaeological material derived from recentlyabandoned households, which allowed an evaluationof the impact of burial on the preservation of residuesand other microscopic traces. Moreover, it allowed theauthors to assess the potential of applying the methodsto prehistoric assemblages.

2. Materials and methods

For all ethnoarchaeological scrapers included in theanalysis, details concerning its production and use cycle(e.g. use duration, moment of discard, hide speciesscraped, name of the hide worker) were recorded.A unique artefact number was assigned to each scraper

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1288 V. Rots, B.S. Williamson / Journal of Archaeological Science 31 (2004) 1287–1299

(ethnographic and archaeological) in the field. Thescrapers were stored individually in clean plastic bagsand not washed or handled before being analysed forresidues. Microwear analysis was conducted after residueanalysis, as it requires that the surfaces of the tools becleaned.

A selection of ethnographic (20) and archaeological(18) tools was subjected to both a microwear and aresidue analysis. The selection of ethnographic tools wasprimarily based on raw material, as not all materials areequally suitable for a microwear analysis. Secondly, weaimed to include as many different use stages as possible(including unused tools). Apart from these considera-tions, selections were random (cf. Table 1). The archaeo-logical scrapers were excavated at Gotcha Ayenna, anopen-air village site in Konso area with two recentlyabandoned house floors. The last occupation dates fromaround 1998. We included most of the tools from

Lake Abaya

Konso

Kenya

Eritrea

Ethiopia

Om

o

Atbara

Sudan

Red Sea

Gulf of Aden

Addis Ababa

Somalia

Yemen

DjiboutiEthiopian Plateau

R i f t

V

a l

l e y

200 km

Fig. 1. Map of Ethiopia showing research location.

Fig. 2. Chert scrapers hafted in a concavity of a wooden handle and

fixed with the aid of resin.

Level 2, while tools from other levels were randomlyselected (cf. Table 2). The inclusion of at least a fewartefacts from the lower levels was necessary to assessthe longevity of residues (cf. Table 2).

For microwear analysis, the lithics were examinedusing an Olympus BX60M metallurgical microscopewith bright field illumination and magnifications rang-ing from 50 to 500!. Macroscopic features and micro-scopic polish, striations, rounding and damage wereinvestigated. Polish refers to an altered zone on a stonetool that is visible as a shinier or rougher area in com-parison with the surrounding surface. Striations arelinear features that occur on a flint surface [12]. Round-ing refers to the abrasion or dulling of an edge. Generallythe most prominent points are preferentially affected.Damage is used as a synonym of scarring or micro-chipping and refers to the small stone particles that areremoved from the edge due to a given cause (e.g. [13]).The relative importance of these kinds of wear and theirexact location and pattern over a stone tool allow theinterpretation of their cause. Sufficient referential datafor the identification and interpretation of production[15], use (e.g. [8]) and hafting wear [14–16] were avail-able from previous studies. In short, production wear isalways associated with a technological feature (i.e. butt,bulb, retouch). Use-wear is concentrated in a particularpart of the stone tool and generally several kinds oftraces are associated. A use polish has a clear impact onthe edge and a directional aspect. Hafting wear alwaysshows a distinct patterning over the stone tool, generallyin the zone opposing the working edge. A limit betweenthe used and hafted tool portion can be identified basedon, amongst others, the start of a distinctively differentpolish or scarring, or the occurrence of isolated well-developed polish spots (often in association with scars).Polish and scarring form the most significant kinds ofwear for identifying hafting.

During the microwear analysis, tools were cleanedwith acetone or alcohol in order to remove remains ofgrit, grease or plasticine (used to fix the tool under themicroscope). When necessary, some chemical cleaning(10%HCl solution) was used in order to remove remainsof organic residues adhering to the tool’s surface. Pic-tures were taken throughout the analysis with an Olym-pus CAM3040 digital camera. The analysis was carriedout in the field and all equipment had to be transported.We were, therefore, not able to include a binocular mi-croscope for low power analysis. The analysis focussedon potential wear from each stage of the life cycle ofa tool, including production, resharpening, use, haftingand de-hafting. Results obtained on an experimentallevel [14,15] were compared with the observations madeon the ethnographic and archaeological material.

For the identification of residues, an Olympus BX40Stereo binocular petrographic microscope with anal-ysing and polarising filters and bright and dark field

1289V. Rots, B.S. Williamson / Journal of Archaeological Science 31 (2004) 1287–1299

Table 1

Relevant recorded data for the selected ethnographic hide scrapers (depleted: no further resharpening is possible due to proximity of haft; discard: the

tool is not considered functional anymore by its user)

Tool ID Raw material Stage of use Hafting Details Fractures Hide

K077 Chalcedony Depleted Hafted Discard Goat

K083 Chalcedony Not depleted Hafted Not depleted Goat

K143 Chalcedony Depleted Hafted Discard Fell out of haft Goat


K145 Chalcedony No details Hafted Discard Goat

K166-31 Chert Unused Hafted – – –

K167 Chalcedony Used briefly Hafted Discard Broke during resharpening Cow


K197 Chalcedony Unused Not hafted Heat treated –

K223 Chalcedony Broken Hafted Discard Broken during use Cow

K229 Chalcedony Depleted Hafted Discard Cow


K232 Chalcedony Depleted Hafted Discard Fractured when de-hafting Cow

K238 Chert Unused Not hafted – –

K239 Chert Partially used Hafted Not depleted Goat





K286 Quartz crystal Depleted Hafted Discard Cow

incident light sources was used. Detailed sketches record-ing the exact positions of the different residues weremade and digital images recorded with an OlympusDP10 digital camera. Magnifications used ranged from50! to 800!. The right eyepiece of the microscopewas fitted with a measuring graticule so that the dimen-sions of residues like starch grains, hairs and bloodcells could be measured. The Hemastix� test [21] wasused to distinguish between blood and resin samples ata basic level and to flag residues of suitable haemoglobin

Table 2

Details of the selected archaeological artefacts

Tool ID Level Raw

material

Preserved

tool portion

Inferred moment

of fracture

475 2 Quartz Lateral Resharpening

485 2 Chert Nearly complete,

small proximal

fracture

Heat

487 2 Chalcedony Complete –

489 2 Chert Hafted part Unknown, probably

resharpening

490 2 Chalcedony Probably

complete

–

493 2 Chert Used part Resharpening

494 2 Chert Hafted part Resharpening


559 2 Chalcedony Hafted part Resharpening

561 2 Chert Complete –









concentration for further investigative DNA analysis [5].The Hemastix� test is a presumptive colorimetric testbased on the pseudoperoxidase reaction of the test stripwith the heme unit trapped in the relatively closedenvironment of the dried blood film [11]. Referencematerial was collected for all substances that the toolscould have come into contact with; samples of thecollagenous scrapings from the hides as well as otherseeds, grains and fibres found in the work areas.

The microwear analysis, performed by V. Rots, andthe residue analysis, performed by B. Williamson, func-tioned independently and results were only compared atthe end of the field season. This guaranteed an objectiveand highly informative comparison of the potential ofeach method and an evaluation of how the methods maycomplement each other.

3. Results

3.1. Ethnographic material

All details concerning the analytical results of theethnographic tools are included in Table 3. Some lifecycle stages are not applicable to certain tools becausethey remained unused, while production wear could notbe observed on two tools due to a fracture (the fracturedpart was too small to analyse properly).

3.1.1. Microwear analysisThe analysis was successful and proved very in-

formative. It allowed an insight into the different stagesof a tool’s life cycle, from production up to discard (cf.


Table 3

Results of the microwear (0 = absent, 1 = limited presence to, 4 = extensive presence, – = not applicable) and residue analyses (0 = absent,

1 = present) on a selection of ethnographic scrapers from Konso

Tool ID Microwear analysis Residue analysis

Production Use Hafting Retouch De-hafting

Collagen

Blood

Anim

altissue

Mastic

Plantfibres

Starchgrains

Metalscratches

Incidentfatdeposit

Hair

Polish

Edgedamage

Striation

Polish

Edgerounding

Edgedamage

Striation

Polish

Edgerounding

Edgedamage

Striation

Polish

Edgedamage

Striation

Edgedamage

Striation

K077 0 2 2 4 3 2 1 3 0 2 0 0 1 2 3 4 1 1 0 1 1 1 1 0 0

K083 1 3 2 4 4 2 3 0 0 3 0 0 1 1 0 3 0 0 0 1 1 0 1 0 0

K143 0 3 3 2 1 2 0 0 0 3 0 2 1 1 0 4 0 1 1 1 0 0 0 0 0

K144 0 2 0 3 0 2 0 2 2 3 0 0 0 2 0 2 1 0 0 1 0 0 1 0 0

K145 0 3 2 2 2 2 0 0 0 4 0 0 0 0 2 3 0 0 0 1 0 0 0 0 0

K166-31 1 2 2 – – – – 1 0 3 0 – – – 2 2 0 0 0 1 0 0 0 0 0

K167 0 2 2 2 1 0 0 0 0 1 0 0 2 0 0 0 0 0 0 1 0 0 0 0 0

K185 0 3 0 3 2 2 0 2 0 1 0 0 2 2 0 3 1 0 0 1 0 0 0 0 0

K197 0 2 4 – – – – – – – – – – – – – 0 0 0 0 0 0 1 0 0

K223 – – – 3 2 2 0 0 0 4 1 0 0 0 0 0 1 1 0 1 0 0 0 0 0

K229 0 2 0 3 2 2 0 0 0 4 0 0 3 3 0 0 0 0 0 1 0 0 0 0 0

K231 1 4 1 1 0 0 0 0 0 3 0 0 1 0 3 4 1 1 0 1 0 0 0 0 0

K232 – – – 4 3 2 0 0 0 2 0 0 0 3 0 2 1 0 0 1 0 0 0 0 0

K238 0 1 3 – – – – – – – – – – – – – 0 0 0 0 0 0 0 1 0

K239 0 0 0 4 3 2 0 0 0 3 0 0 0 0 1 0 1 1 0 1 0 0 0 0 0

K246 2 3 2 3 2 1 0 0 0 3 0 0 1 2 0 2 0 1 0 1 1 1 0 0 0

K247 0 0 2 4 0 0 0 1 1 2 0 1 2 2 4 3 0 1 0 1 0 0 1 0 1

K249 0 1 2 4 3 1 0 0 0 0 0 0 0 0 0 2 1 1 0 1 0 1 0 0 0

K255 0 0 0 3 2 1 0 1 0 2 0 0 2 3 2 3 1 1 0 1 0 0 0 0 0

K286 0 1 0 2 2 1 0 0 0 3 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0

Total number of tools

with traces

4 15 12 17 14 14 2 6 2 17 1 2 10 10 7 13 9 9 1 18 3 3 6 1 1

Table 3). Practically each stage resulted in interpretablewear. Production traces consist mainly of edge damageand striations. The latter are very distinctive given thata metal hammer is used to knap and retouch the tools.A metal hammer leaves very obvious and irrefutablescratches (Fig. 3a and b) that are often even macro-scopically visible. Production damage consisted pre-dominantly of crushing. Production wear was absent onK223 and K232 due to a proximal fracture that removed(part of ) the platform. Also anvil contact should beconsidered as part of production wear, given that anvilswere only used during the production and initial shapingstages. Resharpening during use took place with thescrapers in the haft and anvils were not used.

Use-wear was observed on all used tools, in variousstages of development (Fig. 3c and d). The duration ofthe last use session after the last resharpening, asopposed to the total use duration, is obviously the keyfactor in determining the use-wear development. Giventhat these are ethnographic tools, all relevant informa-tion is available in support of this. Polish was found onall used tools, generally in association with poor tomoderate rounding. Use damage was more limited dueto the soft nature of hide [8,13,18]. Two tools showeduse polish only and no other use-wear. For K231, this is

due to the very short last use session (i.e. a few minutes),at which point only a minor polish was formed with norounding or damage. Based on the presence of resharp-ening wear and important hafting damage, we candetermine that the total use duration must have beenlonger than witnessed by the use-wear evidence. Therecorded data only confirm this. On K247, a well-developed use-wear polish could be observed, whileother use-wear is absent. This was due to the removal ofa large flake from the dorsal scraper-head that eradi-cated most of the use-wear evidence. This scar is associ-ated with numerous striations produced by a metal tool.The wear can, without any doubt, be attributed to de-hafting, a process that is generally forcefully carried outby the Konso. The resin is heated and a metal tool ispushed into the resin next to the tool in order to lift thetool out of its haft. In this case, the whole lateral rightside of the scraper-head was accidentally removed.A similar interruption in the use-wear evidence is visibleon K143, where it is caused by a partial resharpening ofthe scraper-head (only on the right side).

While hafting wear has been long neglected in mostmicrowear research, the interpretative possibilities ofthis wear have been recently assessed based on extensiveexperimentation [14,15]. During the analysis presented


Fig. 3. Microwear traces on ethnographic tools. (a) Striation from the impact of a metal hammer during knapping observed on the butt of K238

(100!). (b) Striation from the impact of a metal hammer during retouch observed on one of the ventral edges of K231 (200!). (c) Use polish with

associated rounding on a protrusion of the dorsal distal scraper-head of K136 (200!). (d) Use polish with associated rounding on the dorsal distal

scraper-head of K83 (100!). (e) Striation from the impact of a metal hammer during de-hafting associated with scarring (de-hafting) on the ventral

edge of K231 (200!).

here, we had an opportunity to evaluate this largelyexperimental framework. Hafting wear was formed onall but one hafted tool. The raw material of K249 ismainly responsible for the lack of wear, as observationswere very complicated. Damage is no doubt the mostimportant wear formed. Interestingly, two main loca-tions can be distinguished on the edges, one correspond-ing with the resin limit and a second one correspondingwith the actual start of the wooden haft. The first patchis less prominent than the second. Other damageconcentrations are located near the proximal extremitiesand on the proximal extremity itself. This correspondswith the trace pattern that was determined for scraping

tools based on experiments [15]. Well-defined scalar andtrapezoidal scars are dominant. Initiations are clear andterminations are generally abrupt, most often in a hingeor step. Scars are small (!0.5 mm) to moderate (!1 mm)in size, and moderate in depth. They are predominantlydistributed in an uneven, run-together pattern along theedge. Polish is present on six out of 18 hafted tools. Thisis due to the fact that tools were hafted with resin, whichstrongly hinders any polish formation. The most impor-tant moment of polish production in the case of resin-hafted tools is when the tool is extracted from its haft(or when it falls out of its haft). Friction during use isextremely limited to non-existent, though it may occur


when tools are not well fixed in their hafts. Limitedpolish may also form during resharpening, followingthe pressure exerted on the scraper-head by the metalhammer. The hafting polish observed on each of thesescrapers could be attributed to resin friction, making itquite likely that it was produced during de-hafting.However, given the uncertainty of this interpretation formost polishes, the majority were placed in the moregeneral category of ‘‘hafting’’. Striations (K223) as wellas rounding (K144, K247) were rare, which correspondsdirectly with our experimental results [15].

‘‘Retouch stage’’ refers to potential resharpeningsessions. In theory, an initial shaping may appear hardto distinguish from resharpening. On ethnographic toolsthis is not the case. In other circumstances a distinctionis generally possible based on use-wear data. After all,resharpening should result in a differential developmentof the use-wear evidence between the resharpened andnon-resharpened parts, or between the concavity of theresharpening flake scar and its protrusions. Only whenthe resharpening is so intense that all previous use-wearis removed, distinctions may be difficult. Subsequent usedoes not necessarily remove all evidence, as resharpen-ing also results in striations that are formed in the centreof the concavity of the negative scar of a resharpeningflake, with a perpendicular or oblique orientation to theedge (Fig. 3b). Given that metal hammers were used,these striations are likely to be preserved (i.e. importantimpact on the tool’s surface, high visibility). These kindsof striations were found on 10 of the 17 used tools.Polish was rarely found (only on K143 and K247), whilethe damage intensity varied. Retouch damage was moreimportant here than in an average experimental con-dition given that the hammer was metal. In severalcases, the scrapers fractured during resharpening; K167is an example. This resulted in an uneven distribution ofthe use-wear traces on the scraper-head. In this case,use-wear traces were not well developed given that thetool fractured early in its use cycle and the total useduration remained short.

The last stage that can be identified in the life cycle ofthese tools is the extraction of the tool from its haft.Given that this extraction was not gentle, many tracesdin particular damage and striationsdwere formed. Thesetraces were generally located on one of the tool’s edgesaround the haft limit, a position that corresponds to theplacement of the metal tool used for extraction. Asmentioned earlier, the resin is heated and a metal tool ispressed into the resin next to the tool in order to lift itout of the haft. The formation of traces can be heardduring the extraction itself (scratching and fracturingsound). Not surprisingly, tool fractures may occur atthis stage of the tool’s life cycle (e.g. K232). Damageformed during de-hafting generally consists of a fewsmall or a few larger scars with intense crushing at theirinitiation. Numerous metal scratches are generally as-

sociated with the fractures. Often, both kinds of wearare located on opposite faces due to the pressure exerted(striations form on the face where the pressure isexerted, while damage forms on the opposite face). Inthis regard, it is also important to note that determiningtool use is not necessary for determining whether or nota tool was hafted, even though the amount of wear isincreased and an interpretation of its life cycle can bemore certain. K166-31 is a very good example of this.The tool was hafted but not used, and distinct haftingand de-hafting wear was formed. Similar observationswere made on an experimental level [15]. Not surpris-ingly, the most important wear consists of damage. Inthe case of de-hafting, it is associated with manystriations (metal) (Fig. 3e).

It is clear from this overview that detailed microwearanalysis is able to distinguish traces resulting fromdifferent stages of the tool’s life cycle. While one couldperhaps contest its reliability on an archaeological level,the evidence is incontestable on an ethnographic level.Consequently, the ethnographic case provides well-founded arguments on which one can base archaeolog-ical interpretations. Backed with sufficient experimentaldata, reliable and far-reaching inferences can be made.An illustration of this is presented below for scrapersexcavated at Gotcha Ayenna (Konso).

3.1.2. Residue analysisAn examination of unused ethnographic tools has

a particular advantage for residue analysis. It allows oneto look for background, non-use related residues thatmay occur on the tools. Their importance is evaluatedand ways to distinguish them from use related residuesare proposed. Consequently, this kind of analysis con-tributes significantly to the reliability and accuracy offuture interpretations.

In addition to the data presented in Table 3 for theused ethnographic tools, we discuss some of the residuesfound on the ethnographic tools in detail. On K77 themass of plant fibres with associated starch grains wasfound on the ventral side near the tip of the tool, awayfrom the mastic/hafting margin. This is possibly anincidental residue and not use-related as it was notmacerated onto the tool and did not form the char-acteristic matrix one would expect from a use-residue. Athin, brown-coloured blood film was found nearby andcollagen scrapings were jammed into the edge of themastic. K83 had a mass of cotton fibres that weretrapped in the mastic ( possibly during hafting), metalscratches were found on the dorsal side. K167 had nouse residues, but did have mastic deposited on thesurface. This tool was used only briefly because it wasbroken during retouch and discarded. The scraper K197also had no use residues but numerous metal scratches.On K238 no use residues were found because this was anunused control sample. The incidental fat deposits are


attributed to the fact that the scraper was placed ona hide after manufacture. The fat residues did notresemble a use residue and no fat residues were found onany of the used scrapers. On K239, the presence of ablood residue found within the haft margin can tenta-tively be explained in terms of capillary action where themastic did not adhere to the surface of the stone toolentirely and some of the hydrated blood from the hidewas drawn up and deposited between the mastic andstone. A blood film was found over most of the exposedsurface of K246. A plant tissue residue appeared macer-ated onto the tool surface at the haft margin. This mayhave been deposited on the surface during de-hafting,and is not likely to be due to contact with the haft as thestone insert is usually completely encapsulated withinthe mass of mastic used to hold it in the haft. A thickblood residue was found on the ventral side of K249near the working edge. Other residues included collagenscraping on top of the mastic on the dorsal side andthree patches of possibly cooked starch on the butt ofthe tool (ventral side) that can be attributed to incidentalcontact after de-hafting.

The analysis confirmed expectations for some of theresidues found on the ethnographic hide scrapers, andelucidated some less intuitive residues. Not surprisingly,most of the ethnographic scrapers had residues of masticgiven that the resin was not entirely scraped off after de-hafting. The mastic residues were sometimes brittle andappeared to already be breaking off the surface of thetool. Thus the extent of the mastic residue did notalways exactly reflect the haft margin. The constituentsof the mastic (tree gum and charcoal) could be identifiedunder even low magnification (Fig. 4a). The mastic wasusually reheated to facilitate de-hafting of exhaustedscrapers and one could see how it had been heated andpulled before solidifying again.

Almost half of the ethnographic scrapers had collagenor ‘‘scrapings’’ trapped under the edge of the mastic and

pushed back from the working edge (Fig. 4b). This is tobe expected considering the action of scraping a hide. Atleast half of the ethnographic scrapers had collagenresidues that were directly attributable to hide-scrapingadhering to them. The hides that were scraped wereusually completely desiccated. It was not expected thatblood residues would therefore be found on the tools.Observing the hide scrapers at work, however, it wasnoticed that many of them added water to the hide tomake it more pliable. This hydrated the blood trappedin the subcutaneous layer of the hide. Blood films werefound on just less than half of the ethnographic scrapersanalysed. Hair was found on only one of the ethno-graphic scrapers.

Other residues not expected on the ethnographicscrapers are plant tissue and starch residues because itis known that the scrapers were never used to processplant foods. The cooked starch residue can be explainedas being due to incidental contact with cooked starchfoods lying around the hearth during hafting or de-hafting when the mastic was soft. The same argumentapplies to cotton fibres trapped in the mastic. The ethno-graphic scrapers were clearly not used to process cottonin any way but cotton is a ubiquitous crop in the Konsoregion and is processed anywhere in the living andworking area of the household. However, these obser-vations highlight potential problems that residue anal-ysis may encounter and it is important to suggest waysto prevent the misinterpretation of this kind of residue.

In our opinion, and based on the previous analysis[21], confident distinctions can be made between use-related and incidental residues. Use related residues,whether of plant or animal origin, usually have a moremacerated or smeared appearance on the surface of thetool. They may also be trapped or jammed into cracks,crevices and under semi-detached flakes. Residues ofthis nature often form a matrix of fibres and exudate(plant) or collagen and blood (animal) to mention only

Fig. 4. Residues on ethnographic tools. (a) A typical mastic residue found on many of the ethnographic scrapers (in this case K249) comprisingAcacia

tree gum and charcoal fragments (50! magnification). (b) A fragment of collagen (on K77) scraped from the subcutaneous layer of a dry hide

(100!).


two possibilities. Sand or clay grains may also be incor-porated into the residue if the tool is discarded immedi-ately after use. Non-use related residues (or ‘‘incidental’’residues) usually appear in isolated spots on a tool.Most importantly though, residue analysis is a recursiveprocess and deciding whether a residue is use-relatedor not depends on the context of the residues, i.e., inrelation to other residues and their positions on the toolsurface, residues found on the rest of the assemblage andsite and soil conditions.

3.2. Archaeological material

The majority of the analysed archaeological artefactswere derived from Level 2. Only three artefacts fromlower levels (15 and 16) were added to this selection.Some use stages are not represented for some tools dueto a fracture (cf. Table 4: coded as –).

3.2.1. Microwear analysisAs with the ethnographic tools, different stages in the

life cycle of each archaeological tool could be identified.The microwear traces proved to accommodate to thesame characteristics and patterns as the ethnographicexamples. Production wear is present on the majority ofscrapers, mainly as scarring and striations. Striations areconcentrated on the butt, where the contact with the

metal hammer took place. The attribution of these shinymetallic scratches to the metal hammer is certain.Damage is mainly found on the dorsal and ventraledges of the butt. Minor scars are removed on the edgesadjacent to the platform (butt) due to the high pressureexerted by the hammer on the platform. When polishis present, it is located on the edges of the butt or theventral bulb. In all cases it can be attributed to thefriction that occurs when it is detached from the core.Other wear is rare.

Use-wear traces are formed on all tools of which theused portion was preserved. For two artefacts (GA489and GA494) we could determine that only the haftedportion of the tool remained. Interestingly, no residueswere found on GA494, while GA489 showed plant resi-due that appeared to be use-related (cf. infra) (Fig. 6).This cannot be confirmed with microwear analysis, butwe can establish that the tool was hafted. The inter-pretation of this plant residue is discussed in the residueanalysis section below. The use-wear on the other toolscomprises associated polish, rounding and scarring inpractically all cases. Striations were not observed. Incomparison to the ethnographic examples, roundingis significantly more important on the archaeologicalexamples, although it remains poorly developed overall.

For the hafting data, a very similar pattern to theethnographic examples was observed. Scarring is again

Table 4

Results of the microwear (0 = absent, 1 = limited presence to, 4 = extensive presence, – = not applicable) and residue analyses (0 = absent,

1 = present) of the archaeological scrapers of Gotcha Ayenna

Tool ID Microwear analysis Residue analysis

Production Use Hafting Retouch De-hafting

Blood

Mastic

Plantfibres

Starchgrains

Ochre

Metalscratches

Fatdeposit

Polish

Edgerounding

Edgedamage

Striation

Polish

Edgerounding

Edgedamage

Polish

Edgedamage

Striation

Edgedamage

Striation

Polish

Edgedamage

Striation

475 0 0 0 0 3 2 2 2 3 0 0 0 0 0 0 0 0 0 0 0 0 0

485 0 0 0 0 3 1 2 2 0 0 0 2 0 3 3 0 0 0 0 0 1 0

487 0 0 2 1 4 1 0 1 4 0 3 0 0 0 1 0 0 0 0 0 0 1

489 0 0 0 0 – – – 2 4 0 0 0 0 0 0 0 0 1 0 0 0 0

490 0 0 0 0 2 0 3 2 3 0 0 0 – – – 0 0 0 0 0 0 0

493 0 0 0 0 3 1 3 – – – 0 0 – – – 0 1 0 0 0 0 0

494 0 0 0 0 – – – 2 4 0 4 0 0 0 0 0 0 0 0 0 0 0

544 2 0 2 1 4 3 2 0 4 0 0 1 0 0 0 0 1 0 0 0 0 0

559 0 0 0 0 3 1 2 0 3 0 0 2 – – – 0 0 0 0 0 0 0

561 – – – – – – – – – – – – – – – 0 1 0 0 1 0 0

579 1 0 2 0 3 1 2 0 4 0 0 0 2 3 4 0 0 0 0 0 0 0

601 1 1 2 2 3 1 2 2 3 0 0 2 0 0 3 0 0 0 1 0 0 0

603 2 0 3 2 3 2 2 2 4 0 0 2 0 0 3 0 0 0 0 0 0 0

624 0 0 2 0 3 1 2 1 3 0 0 0 0 2 4 0 0 0 0 0 0 0

640 2 0 0 2 3 1 1 3 4 0 0 0 0 3 3 1 0 0 0 0 0 0

1067 0 0 2 2 3 2 2 3 3 1 1 0 0 0 0 0 1 0 0 0 0 0

1081 0 0 2 0 2 1 2 2 4 0 0 2 0 2 4 0 1 0 0 0 1 0

1082 0 0 3 3 2 1 0 0 2 0 3 2 0 4 3 0 0 0 0 0 0 0

Total number of tools

with traces

5 1 9 7 15 14 13 12 15 1 4 7 1 6 9 1 5 1 1 1 2 1


Fig. 5. Microwear traces on archaeological tools. (a) Typical hafting scars on the ventral left proximal edge of GA579 (200!). (b) Typical hafting

scar on the ventral left edge, around the haft limit, of GA579 (200!).

the most dominant trace to be observed (Fig. 5a and b),while rounding and striations are rare. The only differ-ence concerns the frequency of hafting polish, which isdistinctively higher on the archaeological tools than onthe ethnographic ones. All polish observed on the haftedtool portions was generally poorly developed and mostoften occurred in spots. It resulted from friction withsmall, detached flakes or from friction with resin par-ticles, probably during de-hafting. As with the ethno-graphic tools, the latter kind of polish has been classifiedunder the more general category ‘‘hafting’’. A possibleexplanation for the higher frequency of these polishspots is increased friction due to more limited heating ofthe resin, or the addition of other abrasive particles (e.g.charcoal, sand or ochre) to the resin either intentionallyor accidentally. The latter interpretation is not unlikelybecause an examination of the mastic residues revealedthat they contained charcoal fragments. The putativemastic residues on the archaeological samples appearedto be very similar to the residues on the ethnographicscrapers. We can conclude that the hafting method usedfor these scrapers is similar as for the ethnographic ones:a tool fixed in a concavity with the aid of resin. The haftmaterial could not be directly derived, since no corres-ponding polish was observed. It is, however, doubtfulthat the haft would have been manufactured from any-thing other than wood.

Explicit retouch evidence was less frequent than onthe ethnographic tools, especially as it pertains to dam-age. For striations, the difference in frequency is small.This implies that retouch wear was formed, but thatedge damage was not so apparent for some reason. Oneexplanation could be that modern day knappers causemore damage when retouching than those in the past.However, in three out of four cases, the retouch damagewas not associated with striations. Examples were alsoobserved ethnographically, though rare. It may thus bethat some knappers produce striations, while others tendto produce damage. Whatever case, we can be certainthat resharpening leads to the same kinds of traces now

as it did in the past. Microwear analysis is clearly capableof identifying resharpening wear in both instances.

An important point that needs to be included con-cerns the observation of prehension damage on one ofthe scrapers (GA494). The scarring consists of slicedscars (i.e. half-moon shaped removals that cut throughboth surfaces about equally) with bent initiation. Theyare located on the left lateral edge, near the scraper-head(outside the hafted tool portion), and can be attributedto retouch. They correspond to the placement of thefinger under the scraper-head to support the scraper andprevent it from fracturing during retouch. Scrapers areretouched while in the haft, which makes them suscep-tible to fractures when not sufficiently supported. Thesame observation was made on one of the ethnographicscrapers (K236), but given that no residue analysis wasundertaken on this particular scraper, it was not dis-cussed further. In addition, we have experimental sup-port for the interpretation of this type of scarring [15].

The method of extraction for the archaeological toolsappears to be similar to that used currently. There isa significant similarity between the trace patterns and inparticular the presence and frequency of striationscaused by metal tools used for tool extraction. As withthe ethnographic examples, scarring is not frequent, butit is always associated with striations. Again both typesof traces are generally located on opposite faces of thesame edge.

No difference can be observed between the tracepattern on the three tools from the lower levels (1067,1081 and 1082) and the ones from Level 2. There is thusno true influence on the preservation of these kinds oftraces throughout the sequence. Consequently, there isno reason why interpretations based on these traces andtheir pattern should lose confidence with increasingburial time.

3.2.2. Residue analysisAll data from the residue analysis of the archaeolog-

ical scrapers are included in Table 3, but a more detailed


Fig. 6. Residues on archaeological tools. (a) The macerated plant tissue found on tool GA489 (100!magnification). The residue is birefringent under

cross-polarised light, a characteristic of plant material. (b) A smeared ochre residue found on some of the archaeological scrapers (e.g., GA561)

(100! magnification). (c) A decomposing mastic residue. The tree gum component is crumbling and the charcoal inclusions can still be seen (100!

magnification).

description for some of the tools is included here. OnGA601, a white starchy residue with starch grains (2 mmin diameter) was found at the mastic margin on thedorsal side. A very concentrated blood film was foundon the dorsal side at the working edge of GA640.

The scraper GA489 (Fig. 6a) that had no use-weartraces but a potentially problematic plant tissue residueneeds further discussion. A small deposit of maceratedplant tissue was found on the non-working edge of thistool within the portion that would most likely have beenhafted. It appeared to be use-related. Some plant tissuecould have been incorporated into the mastic duringhafting but this is unlikely, as it would have beenremoved from the tool surface with the mastic. Thehafted surface of the tool was perhaps not entirelyencased in mastic, leaving part of an edge exposed thatcould have come into contact with the wood of the haft.The pressure exerted during scraping would have macer-ated the wood/plant tissue onto the tool. Hardy et al. [6]report woody residues on a hafted scraper, although notrace of the hafting medium was found. If this tool(GA489) had been found in a regular archaeologicalcontext where site information was not available, as isthe case with Gotcha Ayenna, this kind of residue wouldstill have been interpreted as a hafting residue as it doesnot occur on the working edge of the tool.

In contrast to the ethnographic tools, no collagen wasfound on any of the archaeological scrapers. A bloodfilm, on the other hand, was preserved on one archaeo-logical tool. Blood residues, whether originally a driedfilm [7] or as rehydrated blood, seem to be more persis-tent than collagen residues from a dried hide. The factthat blood residues still survive and that they are stillbiochemically active after 50–100 years (as evidenced bythe Hemastix� test; [22]) is due to the fact that bloodforms hydrophobic and persistent residues [11]. Anotherresidue found on the archaeological scrapers thatresembled those on the ethnographic scrapers wasdecomposing mastic.

AlthoughGA561 was not analysed for microwear, it isnevertheless interesting to shortly include it here. A smallochre deposit was found on a ridge on the dorsal side(Fig. 6b) and decomposing mastic was found on thecorners on the ventral side near the butt of the tool(Fig. 6c). No ochre was found on the other archaeologicaltools or on the ethnographic samples. A suitable ex-planation for the presence of ochre is still being sought[19]. The ochre residue did not appear to be the result ofincidental contact with ochre that was lying around andsuggests possibly a practice that has since been dis-continued in the area. However, the scraping of hidessubsequent to the application of ochre is at least a bit


strange given that ochre is before all a colouring agent. Atthe present time, ochre and ground up castor oil beans aresometimes added to scraped hides to colour and softenthem, but the hides are not scraped after this application.

4. Discussion: comparison of results

Given the high number of data involved, and theirvaried origins, we were able to compare our analyticaldata at several levels:

- Ethnographic versus archaeological data for bothmethods.

- Microwear versus residue analysis for all data.

4.1. Ethnographic versus archaeological data

While the observations made for ethnographic andarchaeological material during the microwear analysiswere not significantly different, the opposite is true forthe residue analysis. Marked differences can be observed(cf. Table 5).

Far more archaeological artefacts than ethnographicscrapers had no use residues on them. In addition, onlytraces of mastic were preserved on tools from the lowerlevels. Gotcha Ayenna, being an open-air site, was subjectto the elements and periods of fairly high rainfall. Re-sidue analysis of artefacts from cave sites in SouthAfrica [20] has shown that the dry, enclosed environ-ment of a cave leads to better preservation of organicresidues on stone tool surfaces. However, the fact that atleast some residues are preserved means that artefactsfrom open-air sites can be investigated for residues.

4.2. Microwear versus residue analysis

The problems caused by the kind of material anal-ysed (i.e. ethnographic or archaeological) were largelydiscussed above. Here, we want to focus on the problems(analytical and interpretative) that each method has inrelation to the other, and examine whether a combina-tion of both methods could potentially resolve these

Table 5

Summary of residues found on the ethnographic and archaeological

samples for comparison (% do not add up to 100 because more than

one residue type found on a tool)

Ethnographic tools Archaeological tools

N ¼ 20 % N ¼ 18 %

Use residues absent 1 5 8 44

Mastic 18 90 5 28

Blood films 9 45 1 6

Collagen 9 45 0 0

Metal scratches 6 30 2 11

Plant residues 3 15 1 6

Starch 3 15 1 6

problems. Also the contribution of this particular anal-ysis to methodological improvements is evaluated.

Microwear analysis aims to resolve slightly differentissues in comparison to a residue analysis. While exactdata concerning the preserved organic materials are notobtained, a microwear analysis allows an insight intoa tool’s whole life cycle instead of only into its last usesession. Although use-wear has been the main focus formany years, changes have occurred recently. The pre-sented analysis confirms the ability to interpret far moretrace causes based on a microwear analysis than pre-viously believed (e.g. [9]). Examples are the following: thematerial used to produce and shape the tool, the workedmaterial, the action undertaken, the material used to haftthe tool, the hafting method and the method used toextract the tool from its haft. The latter is particularlyimportant for resin-hafted tools, most other haftingmethods do not really require specific extraction tools(e.g. hafting with bindings). Given the care that isgenerally taken during experiments to extract tools fromtheir hafts, this analysis is the first of its kind to identifytraces resulting from this process. Even though the impactof metal tools is far more notable and distinct, thisknowledge can still be used to improve experiments andanalyses of other archaeological samples. Other rawmaterials can be expected to reveal similar trace patterns.

In comparison with residue analysis, a few con-straints of microwear analysis can be noted. In the firstplace, microwear analysis tends to make more use ofanalogies. The interpretation of a microwear trace isbased on its resemblance with an experimental example.However, residue analysis also makes use of analogies.Certainly during the primary analysis, many residueinterpretations are based on morphological similaritiesbetween observed and known residues. Later on, chem-ical tests can be used to examine certain interpretations(e.g. blood), but certainly not all. This implies thatmicrowear and residue analyses are partially confrontedwith the same problem. Both techniques need to berecursive and use multiple lines of evidence to reacha reasonable interpretation of tool function.

Secondly, a detailed microwear analysis is often moretime-consuming (i.e. about one hour per tool versus15 min for residue analysis dependant on the nature andabundance of the residues). Each part of the tool needsto be thoroughly examined. Nevertheless, this constraintis largely compensated by the amount of data that canbe derived and by the level of confidence of interpreta-tion that can be obtained. Under time constraints, onecan limit oneself to a low power analysis (with abinocular microscope only), which is a lot quicker. Thedetail that is lost, such as exact material identifications,is compensated by the residue analysis as it can po-tentially provide exact material identifications.

A last issue concerns tool raw material. In contrastto residue analysis, the raw material is of greater


importance for microwear analysis. Coarse-grained toolsare more difficult to examine, and tools made fromquartz crystal show wear that is more similar to obsidianthan to flint or chert. For coarse-grained tools, an anal-ysis with a binocular microscope is often more revea-ling than with a metallurgical microscope. A binocularmicroscope was not available in the field, so thisstatement cannot be substantiated. However, it is usefulto combine either of these methods with residue analysisfor coarse-grained materials. For quartz crystal, one isforced to rely on scarring, rounding and striations, be-cause polish observations are difficult. Thus for coarserraw material, residue analysis is no doubt appropriate.Material identifications by microwear cannot be asdetailed without the information provided by polishes(i.e., only relative hardness can be determined).

Residue analysis has the distinct advantage of pro-viding direct traces of the last material that the toolcame into contact with. Should sufficient organic mate-rial remain as a residue from the last use-event, then thepossibility of biomolecular investigation to obtain thespecies of origin can be explored [6,10]. For example,the processing of wild species, as opposed to domesti-cated species in the distant past can be elucidated.However, residue analysis is also limited by a number ofnon-negligible problems that were highlighted in thiscomparative study.

Firstly, the residues alone could not identify theworking edge with certainty. Residues are generallylocated away from the working edge (e.g. against themastic) and their location did not always prove toprovide confident data regarding the working edgelocation. This problem can be overcome by integratinglimited wear data, like edge scarring, polish, rounding.By contrast, with microwear analysis the identificationof the working edge is not a problem (e.g. in blind tests).Given that the same microscopic equipment is used,residue analysts are advised to integrate basic wear datato support their interpretations. If a residue analysis iscombined with a microwear analysis, working edgelocation should not be problematic.

Secondly, the occurrence of incidental contact resi-dues can confuse interpretations. Plant residues, in par-ticular often adhered to the tool’s surfaces but had norelation to the tool’s use. They were deposited on thetool accidentally, as for instance when the hot andsoftened resin was placed on the ground where it couldpick up anything that was lying around. Replicationexperiments for tool use and hafting practices can helpto identify characteristics of use-related vs. incidental re-sidues. Residue data should ideally be compared andcontrasted with microwear data to obtain the bestinterpretation possible. Microwear analysis is not con-fronted with this kind of problem. Accidental traces canoccasionally be formed by some (hard) materials (e.g.metal), but interpretative problems are not to arise from

them. More specifically, use-wear traces do not resembleaccidental wear: they show a clear impact on the tool’sedge and they are clearly concentrated in a particularzone of the tool [15]. Furthermore, traces resulting fromother causes (e.g. production, hafting) display markedlydifferent characteristics [14,15].

A third problem for residue analysis, of course,concerns the preservation of organic residues. While thisproblem is most apparent in archaeological settings(particularly open-air settings), the presented analysisdemonstrated that this problem also arises for ethno-archaeological samples. Consequently, it needs to bestressed that the absence of residues certainly does notimply that the tools were unused. The residues may havebeen removed after use. Residue analysis, therefore, isnot adequate to correctly assess the percentage of usedtools in an assemblage. The only way to accurately makethis kind of statements is to combine the residue analysiswith at least a minimal microwear analysis.

Lastly, it is thought that residues primarily provideevidence of the last use session of a tool. Given that theanalysed scrapers were only used for one task, this issuewas irrelevant. For archaeological assemblages, how-ever, multiple tool use may be more problematic but isnot insurmountable. Multiple tool use has been identi-fied in the residues of tools from the Crimea [6] andsouthern Africa [20]. Different residue types can overlyeach other on the tool surface or have different distribu-tion patterns, especially if the residue laid down in thefirst use-event is particularly persistent. Striations orscratches in the surface of a persistent residue such asresin sometimes indicate a second use event.

The contribution of residue analysis to microwearanalysis is mainly in terms of detail. While one canestablish that a tool is used to work hides, it is im-possible based on microwear data alone to determine thekind of animal from which the hides were procured.DNA analyses are able to make these kinds of dis-tinctions [3]. In addition, the observation of collagen,blood or animal tissue can strengthen the interpretationbased on wear. Also, confirmation can be obtainedregarding hafting methods. While each hafting methodresults in a different wear pattern, the observation ofmastic on a tool is obviously a very strong and incon-testable argument to interpret the hafting method. Thus,when residue and wear data are used in combination,more confident interpretations can be obtained.

The above data no doubt stress the fruitful nature ofa combination of approaches. While both methodsprovide quite different data, they are able to strengthenthe confidence of each other’s interpretations. On occa-sion, one method also provides data that are difficult orimpossible to obtain with the other, though relevant oreven necessary. The location of the working edge or theidentification of exact worked (used) materials are justtwo examples.


5. Conclusions

The analysis above shows that microwear and residueanalyses are largely complementary. Two of the majorproblems with residue analysis are the identification ofthe working edge and the association of residues withthe actual use of the tool but these issues can be resolvedby including microwear in the analysis. On the otherhand, residue analysis can provide more concrete dataconcerning tool use than can be obtained based ona wear analysis alone. We feel, therefore, that a tandemstudy, employing both techniques, provides archaeolo-gists with a uniquely powerful method for examining thelife cycle of lithic artefacts.

No doubt the microwear analysis presented here hasdemonstrated the important progress that has beenmade for these kinds of studies since the recognition ofits significance in Western Europe ([17], English trans-lation). Microwear analysis is not just a way to deter-mine tool use; it has become a valid research approachin itself that can be used to examine archaeologicalassemblages. Inferences, impossible to reach with othermeans, are now attainable. Residue analysis is stillyoung, but important achievements have already beenmade [3]. While a combined analysis such as this onehighlights the problems of each method in a markedway, we believe that it also stimulates methodologicalimprovements. In particular residue analysis needs to beimproved at several levels. For the moment, the com-bination of a microwear and residue analyses can over-come practically all problems, but we strongly believethat residue analysis will come up with solutions of itsown, some of which were suggested in this paper.

Acknowledgements

We are indebted to Steven Brandt and KathrynWeedman from the University of Florida for theinvitation to participate in this project and for allowingaccess to the material. The project was funded by theNational Science Foundation, for which we are grateful.We thank the field team for the care taken whenrecording and collecting the samples discussed here. Wethank the two anonymous reviewers for their usefulcomments. Veerle Rots is indebted to the Onderzoeks-fonds from the Katholieke Universiteit Leuven for theirfinancial support of her research. Equipment used byBonny Williamson was provided by the University ofthe Witwatersrand.

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Documents

Microwear and residue analyses in perspective: the contribution of ethnoarchaeological evidence