QUANTIFYING ENDSCRAPER REDUCTION IN THE CONTEXTOF OBSIDIAN EXCHANGE AMONG EARLY PASTORALISTS IN

SOUTHWESTERN KENYA

STEVEN T. GOLDSTEIN

Washington University in St. Louis, USA

Mobile strategies are foundational components of nomadic pastoralist socio-economic organization in East Africa.Beginning around , BP, nomadic herders in southwestern Kenya had integrated the regular transport of obsi-dian across a km landscape into these strategies. Pastoral Neolithic groups in the region relied on obsidian forthe production of blade based toolkits. Viewed through an organization approach, the patterns of tool reductionand discard in the archaeological record may be used to infer dimensions of obsidian access, as perceived byearly herding communities. In order to begin assessing the social and economic factors structuring obsidianaccess and use in this region, this study examines the intensity of obsidian endscraper reduction as a correlatefor overall stresses on pastoralist obsidian supply. Several excavations in the s and s produced lithicassemblages from southwestern Kenya that were reexamined and sampled for this analysis. Using methods devel-oped in forager contexts in other regions, there appear to be few differences in the intensity in tool use between sites.This pattern may indicate that communities across a large landscape had regular and consistent access to obsidiansfrom distant sources. The study contributes to renewed interest in the Pastoral Neolithic in East Africa, and is situ-ated within ongoing discussions of technological organization in global contexts.

KEYWORDS: Africa, pastoralism, curation, mobility

INTRODUCTION

In Africa, the earliest form of food productionemerged out of a dependence on animal herds inthe northern Sahara sometime before the eighthmillennium BP. Early African pastoralists werelikely more mobile than their Later Stone Age fora-ging predecessors, representing a trajectory offood production that differs from many othersworldwide (Gifford-Gonzalez a, ; Mar-shall and Hildebrand ). As early pastoralistsdispersed southward into East Africa, they contin-ued to employ lithic toolkits that emphasized theproduction of blades and bladelets, while con-fronting new ecological and social challenges.Exploratory lithic analysis in southern Kenya

has identified numerous stylistic attributes thatdifferentiate pastoralist groups from one another,and from the hunter-gatherers who occupied theregion during the Pastoral Neolithic (PN) period,between approximately , and , yearsago (Ambrose ; Bower and Nelson ;Robertshaw ). At least two culture-historicalentities associated with domesticated faunaco-occupied a large territory for almost ,

years, and yet maintained rigid differences inmaterial culture and burial practices. Geochemicalsourcing analyses have added an additionaldimension to these differences, showing that the“Elmenteitan” and “Savanna Pastoral Neolithic”(SPN) groups obtained obsidian for tool pro-duction from two discrete sources in the GreatRift Valley (Ambrose et al. ; Merrick andBrown ; Merrick et al. ). The closeproximity of these sources to each other, butlong distance from the dense pastoral occupationsto the southwest has fueled much of the discussionon social institutions and exchange networksduring the Pastoral Neolithic (Gifford-Gonzalez; Robertshaw ; Simmons ).These discussions are largely structured around

the assumptions that people acquired obsidian pri-marily through exchange network (Ambrose: ; Robertshaw : ), and thattransport costs increased with distance from thesources, leading to more intensive reduction ofobsidian tools at distant habitation sites (Robert-shaw ). Despite the important role of these

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arguments within broader discussions of socialand economic variability in the Kenyan PN, theyhave not been quantitatively tested. Here, I willaddress Robertshaw’s () argument for moreintensive tool use at more distant sites in order tobegin reassessing the organization of PastoralNeolithic economies. Quantifying the intensity oftool reduction within an organizational approachprovides a means to test existing models, as wellas a means for understanding how differentmobile strategies were operationalized to maintainaccess to distant obsidian resources (Andrefsky; Bamforth , ; Bleed ; Hold-away ; Kuhn , ; Parry and Kelley; Shott ). This analysis aims to evaluatewhether or not a correlation between the intensityof reduction and distance from the raw materialsite can be proven for obsidian endscrapers inthe context of the Pastoral Neolithic from the per-spective of five previously excavated archaeologi-cal sites. This will be achieved through a detailedanalysis of endscraper technology at five PastoralNeolithic sites in southwest Kenya: Lemek North-East, Lemek North-West, Narosura, Ngamuriak,and Olopilukunya (Figure ).

BACKGROUND

AFRICAN PASTORAL STRATEGIES

African pastoral economies are highly variable,and are structured around different ecological,environmental, and social parameters when com-pared to foraging and other agriculturalists.Understanding these forces, and their impact onpastoral strategies, is necessary in order to inter-pret any patterns that may exist within lithicassemblages. African pastoral economies are typi-cally defined as those in which people directly orindirectly rely on cattle, sheep, and goat, or otherlivestock for subsistence (Dyson-Hudson andDyson-Hudson : ; Gifford-Gonzaleza, ). As a result, pastoralists prioritizethe movement of livestock to high qualitygrazing above all other activities (Dyson-Hudsonand Dyson-Hudson : ; Gifford-Gonzalez; McCabe ). Mobile strategies are essen-tial for the survival of African pastoralists andtheir herds, especially in savanna ecosystemswith unpredictable rainfall (Marshall ;Western and Dunne ). Some recent pastoral-ists have also shifted into roles as trade andexchange specialists, an opportunity that hasbeen significantly augmented by the domesticationof the donkey (Marshall and Weissbrod ).

Pastoralists have a number of options in tailoringeconomic and mobility strategies to the needs ofthe herd. These can be seen in terms of calibrationsof a suite of logistical movements of individuals orsmall groups to accomplish specific tasks on thelandscape that are integrated within the residentialmovements of whole family units. The frequencyand magnitude of these forms of mobility variessubstantially across East Africa. A single residen-tial settlement may be occupied for a singleseason or for several years, depending largely onrainfall patterns, ecological conditions, and thesize of the family group (McCabe ; Spencer). Residential sites serve as home-bases forlivestock, which are herded between grazinglands and these sites on daily, weekly, or seasonalcircuits. The organization of mobility is tradition-ally considered to be a product of topography,soils, rainfall, grazing conditions, and the localavailability of potable water (Galvin ).Because these factors have remained largely con-sistent since the Pastoral Neolithic period,modern pastoral strategies are relevant (sensuWylie ) for thinking about ancient patterns.When grazing land is abundant during wetseasons in well-watered southwestern Kenya thedistances livestock are herded in a day are small,usually from to km (Marshall b). Withan average of around mm of rain fall peryear, single basecamps in southwestern Kenyamay persist for up to a decade, and relocationsare typically within km (Western and Dunne). The movement of livestock in these situ-ations is not necessarily related to the movementof households.

THE “PASTORAL NEOLITHIC” IN KENYA

The earliest pastoralists entered southern Kenyathrough the Great Rift Valley by , BP,having migrated southward from the LakeTurkana region where they had arrived some years prior (Hildebrand and Grillo ).These early migrants relied on herds that includeAfrican cattle, goats, sheep introduced throughthe Nile corridor, and donkeys. There is no evi-dence of plant cultivation or agriculture beingpracticed in southern Kenya until , BP inthe Lake Victoria region (Robertshaw ;Robertshaw and Wetterstrom ).There are many ceramic styles associated with the

earliest herders, along with specific burial practicesand preferential use of highland savanna ecologies.For this reason, sites fitting this pattern are

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compiled under the broad cultural-historicalumbrella of “Savanna Pastoral Neolithic” (SPN),which likely encompasses a wide range of socio-economic variability (Ambrose ; Bower). Despite their potential differences, SPNgroups were linked together through their relianceon a small cluster of grey obsidian sources in theLake Naivasha basin (Brown et al. ; Merrickand Brown ). Around , BP, a new set ofpastoral material and burial traditions began toappear in the Central Rift and the southern high-land plains, and these sites were situated across abroader range of ecologies, and even in the highmountains of the Mau Escarpment. This entitywas named the “Elmenteitan” after the type of sitealong Lake Elmenteita, and was classified by theexclusive presence of undecorated lugged andspouted ceramic style with mica temper thatdiffers from any SPN styles (Ambrose ;Bower ). Over percent of obsidian artifactsat Elmenteitan sites are sourced to a discreteoutcrop of green obsidian on the northeast slopeof Mt. Eburru, only km north of the SPNsource (Merrick and Brown : ; Merricket al. ). These sources do not appear to havebeen exploited by foraging groups before, orduring, the PN, and the patterns of SPN and Elmen-teitan source preference are maintained within a km radius from the Rift Valley sources.

For both SPN and Elmenteitan producinggroups, obsidian was the dominant source oflithic raw material for tool production, althoughthere was occasional use of lower quality alterna-tives. Chert from the shores of Lake Magadi insouthern Kenya is represented in small quantitiesat many PN sites, and most of the cobblesexploited in antiquity appear to have been toosmall for the production of blades or large flakes(Robertshaw ). Course basalts and quartzesare locally available throughout much of south-western Kenya; however, when PN groups didtake advantage of these materials, it was largelyrestricted to bipolar reduction or expedient flakeproduction. Obsidian makes up between –percent of the total lithic assemblage by count atPN sites, nearly all of which corresponds toeither the Mt. Eburru or Lake Naivasha source,depending on the particular affiliation of a site.Qualitative differences in lithic typology and

technology exist, and provide a means of dis-tinguishing between Elmenteitan and SPN assem-blages. Elmenteitan blades are longer and lesscurved than those of the SPN, and are morelikely to be notched and retain evidence of inten-sive use (Ambrose ; Robertshaw ).Elmenteitan blade production also seems to haveinvolved grinding and dorsal-proximal facetingas a means of platform preparation (Ambrose

FIGURE . Southwestern Kenya, with sites included in this study and obsidian sources.

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). This is more variable at SPN sites, butmicro-faceted platform preparation is far morecommon in the SPN than in Elmenteitan assem-blages (Ambrose ). Combined with the preva-lence of bi-directional scars on blades, these linesof evidence suggest significant differences in coredesign between these two assemblage groups. Iffuture research is able to quantitatively validatethese patterns, it may suggest more substantialstrategic divides among pastoralists than are cur-rently hypothesized for southern Kenya.There are also differences in the style of formal

tools that pastoral groups produced and used.Both Elmenteitan and SPN assemblages contain ahigh frequency of microlithic elements, encom-passing a wide array of segmented and blackedbladelets. Crescent shaped microliths are themost common variety at most PN sites; however,Elmenteitan crescents are always much smallerwith less metric variance in comparison to theirSPN counterparts (Ambrose ). Blades werealso used as blanks for manufacturing endscrapersin both groups, which are one of the few retouchedtool types present in these assemblages. Pastoralistsin southwestern Kenya also frequently used bladesegments as bipolar cores, and although theseheavily battered cores are common, there is a dis-proportionately low representation of bipolar deb-itage at habitation sites (Robertshaw ). Burinsand informal tools of various morphologies are alsocommon; however, previous inter-site analyseshave focused primarily on comparing counts ofbipolar pieces, microliths, and scrapers.Robertshaw (: ) concluded that most of

the variation in tool ratios and the intensity oftool utilization among Pastoral Neolithic siteswas a factor of the distance from the Central Riftobsidian sources. It is argued that sites furtherfrom the obsidian sources had less access to lithicraw material, and thus more intensely retouchedtools (Robertshaw : ). In light of the par-ticular sourcing patterns of the PN in this region,the argument made by Robertshaw () formore intensified obsidian tool curation with dis-tance from the source becomes highly relevantfor dialogues on Pastoral Neolithic organization.

BACKGROUND TO THE SAMPLED SITES

I chose to limit the scope of this preliminary studyto habitation sites in the southern highlands ofKenya. While there are very few large scale exca-vations of sites outside the Central Rift, regionalsurveys suggest that pastoralist occupation was

far denser in the southern highlands, and sostudies of the highlands may provide a more repre-sentative image of ancient pastoralist lifeways(Robertshaw : ). The sample includes twoof the largest Elmenteitan sites outside of theGreat Rift Valley; Ngamuriak and Olopilukunya,and the three SPN sites of Narosura, Lemek NE,and Lemek NW. Ngamuriak and the Lemek sitesare located in the high-rainfall Lemek Valley,whereas Narosura and Olopilukunya are situatedwithin the ecologically variable Loita Hills. Thereis no evidence of previous forager occupation atany of these sites, and while they may be palimp-sests of multiple occupations within the PN, strati-graphic and spatial datasets reinforce the likelihoodthat these sites reflect single occupations of indeter-minate lengths (Odner ; Robertshaw et al.). The expansion of large scale agricultureand road construction in southwestern Kenyaover the last years makes it very difficult to relo-cate and resample these sites. The archaeologicalassemblages from the sample sites were analyzedwith permission of the Kenya National Museumin Nairobi (Figures and , Table ).

NGAMURIAK

Ngamuriak was the largest Pastoral Neolithicoccupation excavated outside of the Rift Valley,offering one of the most detailed windows intopastoral strategies within the Lemek Valley. Thesite was located near rich grasslands, between anAcacia xanthophloea woodland and a Tarcho-nanthus camphoratus bushland (Robertshaw andMarshall : ). Excavations conducted byPeter Robertshaw and Fiona Marshall from to , covered over sq. m. Ngamuriak revealed a single Pastoral Neo-lithic occupational horizon, with no apparenthorizontal or vertical differences in the compo-sition of material culture (Robertshaw and Mar-shall a: ). The site is only coarsely dated,but the radiocarbon dates available support thehypothesis for a single component habitation,formed around , BP.The material culture at Ngamuriak is character-

istically Elmenteitan, with typical mica temperedceramic vessels and a high frequency of notchedand strangulated blades. A total of whole end-scrapers were recovered from across the site. Mostof these endscrapers were manufactured on longthin blades, although a few were made on widerand thicker flakes. Over , faunal specimenswere recovered, and percent were identified as

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domesticated cattle, sheep and goat, suggesting ahighly specialized form of pastoralism (Marshall). Despite the size of the site there are mark-edly few features, including a single possible hutfloor, one large midden, and several deposits ofun-burnt animal dung.

LEMEK NORTH-EAST AND NORTH-WEST

Both Lemek NE and NW were excavated as a partof the archaeological project in the Lemek Valleyundertaken by Peter Robertshaw and Fiona Mar-shall in . These sites are located within a km extent of the Lemek River in a thick sectionof bush dominated by Tarchonanthus camphoratus(leleshwa), Acacia sp. and Euphorbia candelabrum(Robertshaw and Marshall b: ). The dense

FIGURE . Scrapers from SPN sites; Narosura and Lemek NE.

FIGURE . Scrapers from Ngamuriak (Elmenteitan).

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bush restricted excavation to a single by m.trench, and the entire deposit extended less than cm below the surface. The ceramics weretypical of the SPN tradition, and the lithics weremade on the grey variety of obsidian typical ofSPN assemblages (Robertshaw and Marshallb: ; Wandibba , ). Excavationsat Lemek NW totaled three by m. trenches, tothe same depth as Lemek NE. Once again thestyle of all pottery was identifiable as SPN, with apredominance of grey obsidian (Robertshaw andMarshall b: ). The lithic assemblage atLemek NW contained only scrapers, ofwhich were whole endscrapers, and at Lemek NEthe scraper assemblage contained whole end-scrapers. Endscrapers at both sites were manufac-tured on blades of varying lengths. These aresmall assemblages, but should be representative ofthe general patterns at each site.

NAROSURA

The site of Narosura, named after the nearby Nar-osura River, was discovered the northeastern LoitaHills, only about km from the western edge ofthe Rift Valley. In the late s, Knut Odnerexcavated a total of sq. m. of the site, to adepth of cm (Odner : ). Ceramicsand lithics are stylistically and typologicallysimilar throughout the sequence, and the entire

site has been interpreted as a single horizonformed by a single pastoral occupation (Odner). Obsidian artifacts are almost entirely man-ufactured on grey obsidian from the Lake Naiva-sha basin. Lithic and ceramic styles appearlargely similar to SPN sites in other regions. Naro-sura is the only site with preserved evidence forpostholes. Although depths of the post holesvary, all of them begin contiguously at – cmbelow the surface, further supporting the prob-ability of a single occupation. Despite being a rela-tively large site for the Loita region, the lithicassemblage yielded only whole endscrapers.

OLOPILUKUNYA

Located some km southwest of Narosura, and ata high altitude rather than at the base of the hill, wasthe Elmenteitan site of Olopilukunya, excavated byCharles Cable in . The site itself is situated neara seasonal stream within open grassland, whereasthe vegetation surrounding the site is mostlyAcacia drepanolobium and Commiphora sp.(Robertshaw : ). Excavations covered atotal of . sq. m. sampling the entire extent ofthe site. Excavators noted that archaeologicalmaterials were restricted to a cm layer, leadingto the assertion that it too represents a single occu-pation (Robertshaw : ). Ceramics andlithics are in all respects clearly discernible as

TABLE . RADIOCARBON DATES AND DISTANCE FROM RIFT VALLEY OBSIDIAN SOURCES FOR THE SAMPLE SITES

Site C Date Lab # Distance to Source (km) Citation

Ngamuriake . ± BP GX- Robertshaw ()Olopilukunyae ± BP GX- Siiriäinen ()Lemek NEs ± BP GX- Robertshaw ()Lemek NWs N/A N/A Robertshaw ()Narosuras ± BP N- Odner ()e = Elmenteitan, s = SPN.

TABLE . SUMMARY ARTIFACT COUNTS FROM THE SAMPLED SITES

Site Microliths Burins SplinteredPieces

Scrapers(Endscrapers)

Unshapedtools

UnmodifiedFlakes

Cores Total

Ngamuriak ()

Olopilukunya ()

Lemek NE ()

Lemek NW ()

Narosura () n/a

*Statistically significant difference.

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Elmenteitan, and the faunawasalmost entirelydom-esticates. The entire technological package hasnumerous similarities to those noted for the Elmen-teitan of the Lemek valley (Table ).

THEORETICAL AND METHODOLOGICAL

FRAMEWORK

Stone artifacts are one of the most durable formsof material culture produced in prehistory; theydo not decay, and are far more resistant to chemi-cal and physical weathering, and trampling thanmost other materials. Most importantly, theforms of stone tools in the archaeological recordare the result of intentional and meaningfulhuman activities. Lithic analysis has produced asignificant body of middle range theories relatingaspects of stone tools to specific patterns of mobi-lity, as well as the practical methods with which toapply theoretical approaches.Archaeologists have developed robust models

for situating the remains of prehistoric stone tooluse within broader socio-economic contexts,drawing initially from the curation frameworkproposed by Binford (, ). Curated tech-nologies were set up as those in which tool pro-duction, use, and maintenance were temporallyand strategically organized around predictionsfor future needs. Researchers have since reinter-preted, expanded, and restructured the conceptof curation in many different ways, but typicallycontinue to emphasize the role of cost-benefit stra-tegizing in shaping the archaeological record(Andrefsky , ; Bamforth ; Kelly; Kuhn ; MacDonald ; Nelson; Parry and Kelley ; Shott , ;Torrence ). These formulations fall underthe umbrella of the technological organizationapproach, which may take into account a rangeof economic factors like raw material access,mobility, and subsistence, at different spatialscales. If human groups intentionally design andmodify lithic toolkits for economic needs on thelandscape, then the technological organizationapproach may aid in reconstructing the prehistoricconditions that produced archaeologicalassemblages.Operationalizing this framework is more pro-

blematic; however, many archaeologists havedeveloped methods for quantifying dimensions oflithic reduction at the tool and assemblage levels,and have used this data to generate inferencesabout the economic parameters of prehistoric

societies (Blades ; Clarkson ; Erin et al.; Kuhn ; Morrow ; Wallace andShea ; Weedman a, b, see alsoMcCall ). Quantifications can come in theform of classifying the intensity of retouch, calcu-lating the material removed from a tool during itsuse-life, or can be derived from quotients of basicmeasurements. Relating the data producedthrough metrological approaches back to curationis not straightforward, and depends on contextua-lization within the particular behavioral patternsthat structured prehistoric tool use (McCall). While many circumstances of prehistorictool use will never be known, analyses have pro-ceeded under the assumption that larger scaleeconomic forces can be reconstructed from lithicdata. Specifically, archeological investigationsfocus largely on the interrelated dimensions ofgroup mobility and raw material access(Andrefsky , ; Bamforth ; Gouldand Saggers ; Parry and Kelly ; Shott; Wallace and Shea ). Following thisbody of research, and considering the patterns ofobsidian use within PN contexts, I argue thatraw material access was the most substantialfactor affecting the intensity of tool retouch forearly pastoral groups in southern Kenya. There-fore, quantifying the retouch of potentiallycurated tools can be used to address the assump-tions that raw material constraints at moredistant sites resulted in more intensive use of obsi-dian tools.

ENDSCRAPER USE IN THE PASTORAL NEOLITHIC

In conducting this analysis, I chose to focus onobsidian endscrapers as having the potential tohave been curated tools that had been extensivelyretouched during their use-lives. Microliths andbacked blades are the most common tool type inmost African LSA assemblages, but are proble-matic for curation studies because they servereplaceable parts in multi-component tools.Microlithic elements are not subjected to curationpressures, since they are often a means of repairrather than being directly retouched themselves.Obsidian endscrapers are among the tools tohave both a formal and intentionally imposeddesign, and to have had a single working edgethat was systematically repaired.Pastoralists in southern Kenya appear to have

employed scrapers in much the same way as pre-historic groups elsewhere; processing animalhides for leather production (Beyries and Rots

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; Weedman b). The spread of iron tech-nology around , BP, and the historicalmigrations of Nilotic pastoralists in the region,have removed direct ethnographic links to prehis-toric hide-working in southern Kenya. Some eth-noarchaeological work with recent populationsin the area (Mutundu ), and considerationof archaeological data permits some speculationon how scraper use was integrated within socio-economic systems.Individuals likely engaged in hide working pri-

marily to supply the immediate family groupwithin a habitation site, with some of the pro-ducts moving within, and between, kin groupsacross the landscape. It is through these exchangenetworks that obsidians for tool productionmoved from the Rift sources to communities upto km away (Ambrose ; Robertshaw). This diverges considerably from thepattern of sedentary specialized scraper pro-duction among the Gamo and Konso groups ofEthiopia (Shott and Weedman ; Weedmana, b). At the same time, raw materialaccess was not embedded within residential mobi-lity, which were usually intra-regional andoriented around finding fresh grazing lands. Intraveling from the southwestern highlands ofKenya toward the Rift, pastoralists would haveto leave behind higher annual rainfall andsubject cattle to soils that lack essential nutrients(Marshall a). Pastoral Neolithic groups hadto plan stone tool use around their degree of inte-gration within exchange networks, rather thanthe perceived physical or temporal distance tothe next stone source.Specific methods of hide preparation, frequency

of hidescraping events, the availability ofmaterials involved in the scraping and tanningprocesses and a slew of other technical factorsundoubtedly impose additional constraints onthe tool retouch and curation strategies of thesegroups (McCall : ). Actually reconstruct-ing these factors is difficult given present evi-dence, and so I will proceed under theassumption that variability is low enough withinthe contexts of the PN as to permit inter-assemblage comparisons. Raw material avail-ability will thus be considered as the most sub-stantive force impacting rates of tool use andrepair. Because raw material access appears tobe linked with regional exchange, the intensityof scraper retouch may be viewed in terms oftool “curation” between obsidian imports. Thatis to say, groups who perceive long time gaps

between obsidian accesses will exhibit more inten-sive scraper retouch, while those who plan onconsistent access through networks will beunder less pressure to maximize tool use-lives.These different patterns will affect the proportionof heavily retouched artifacts that are depositedinto the archaeological record. This is only onedimension of a much larger set of problems, butprovides a starting point for building assemblagescale analyses.

METHODS

SAMPLING

I selected blades and scrapers from thelithic assemblages of the sample sites for the cura-tion study. Only whole (unbroken) scrapers withunifacial reduction at the end of an obsidianblade could be used. It was essential that the scra-pers were initially produced on a whole blade (i.e.,there was clear evidence of a platform or bulb ofpercussion present). Only scrapers out of theinitial sampling fit these criteria.

CALCULATING WORKING EDGE AREA LOST (WEAL)

Specific methods for quantifying endscraper cura-tion as a measure of mobility have not been devel-oped in situ for African pastoral material, butresearchers working with scrapers producedwithin analogous blade technologies in otherregions have produced an array of methods todraw from (Blades , ; Carr ;Morrow ; Rolland and Dibble ; Shott; Shott and Weedman ). The methodsused here are developed out of previous studies,and despite the social and economic differencesbetween mobile foragers and African pastoralists,this study is situated within these ongoing discus-sions of blade technologies.Unifacial scraper reduction has been explored in

a number of contexts, providing the largest bodyof literature on measuring the intensity ofretouch to draw upon (Blades ; Clarkson; Dibble ; Erin et al. ; Kuhn ;Morrow ). The best known method for quan-tifying uniface reduction is Kuhn’s () index ofreduction, which uses the angle and height ofretouch, compared to maximum flake thickness,to estimate the volume lost from the initial flakeblank or cobble. Index of reduction values (IRvalues) are calculated as decimal values between, or no retouch, and , representing themaximum retouch on a unifacial tool.

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The principle problem with applying the Indexof Reduction on endscrapers is the assumption ofa single point of maximum thickness on ascraper. Formal endscrapers made on bladeshave a fairly consistent thickness across theentire tool. The maintenance of a convex scraperedge ensures that most flakes will “curve” aroundthe dorsal edge, and will intersect the maximumthickness of the working edge. This problem hasbeen described elsewhere as the “flat flakeproblem” (Dibble : ). Simply put, blankswith a flat cross section (like endscrapers) willhave a maximum IR value almost immediately,with little to no change to that value through thereduction process. Using the trigonometricassumptions at the foundation of the IR modelmight then not accurately represent intensity ofretouch. Even though the flat flake problem haselsewhere been found to be less problematic(Hiscock and Clarkson ), and the index ofreduction has been significantly elaborated, themethod is difficult to apply to blade-based end-scrapers (Erin et al. : )I therefore use an alternative method for quanti-

fying the material lost during reduction specificallyfor endscrapers based on the hypotheses ofMorrow () and Shott (), that shorterlengths in endscrapers are a sign of increased dis-tance (magnitude) and frequency of Paleoindianmoves. A similar relationship between endscrapersize and mobility has also been observed in FrenchAurignacian assemblages (Blades ; Brooks, ). Having one endscraper that isshorter than another is only meaningful if theywere originally the same length and one has beenmore intensively reduced. To this end it is alsoimportant to determine, and account for, any dis-crepancy in the length of the working edge. If oneis able to estimate the original length of the bladeblank used for the manufacture of an endscraper,it is possible to subtract the length of that endscra-per as it existed at disposal, and calculate thelength that was lost as a result of retouch andrepair. If this value is multiplied by the width ofthe endscraper (which is consistent for blades),the product is a value that represents theworking edge area lost during reduction. Theinclusion of width has not been suggested before,but I argue that it is essential in order to correctfor the differing rates with which a narrowworking edge will wear compared to a widerone. Wider working edges may require less fre-quent repair than more narrow edges duringsimilar lengths and intensities of work, because

that work is being distributed across a larger toolsurface.First, it is necessary to predict the original size of

a blade blank from some aspect of the endscraper.This requires a measurement of some aspect of thetool that had not changed during manufacture orreduction. A variation of the surface-area/maximum thickness ratio for flake size prediction(Dibble , Holdaway ) was employed tofacilitate this estimation. Experimental workwith a variety of reduction strategies has shownthat there is a predictable relationship betweenflake width, thickness, and length. Hypothetically,if one or two of these variables are known, theother can be calculated mathematically (Dibble). The relationship between any of thesemetrics will vary considerably depending on rawmaterial and method of reduction; however,Quinn et al. () successfully demonstratedthat correlations between length and thicknessfor chert blades from Near-Eastern contextscould be used to estimate the original length ofretouched blade tools.If the goal is to determine length lost from end-

scrapers, it can be achieved by looking for such arelationship in the blade blank debitage from thesample sites. Maximum thickness will almostnever be altered from the original blade blankduring production, use, or repair of endscrapers,making it the best (and only) predictive value fororiginal length available. Striking platform areamay also be a good predictor of surface area(Dibble and Whittaker ), but complete strik-ing platforms are rare on PN endscrapers.Blades () proposed the ratio between

maximum thickness (T) and maximum length(L), which proved to be a useful correlate for end-scraper curation. The presence of a similarrelationship was investigated by measuring atotal of whole blades from Narosura, Nga-muriak, Olopilukunya, and Lemek NE. Thissample consisted of specimens that were at leasttwice as long as they were wide and appeared tobe the product of systematic prepared corereduction. Of this sample, specimens wereremoved from consideration before analysis.They fit the technical definition for blades, but Iconsidered them to be platform removals, or reju-venations, that would not have been producedunder the same conditions as blade blanksremoved for tool manufacture.Lengths and thicknesses for all blades were

recorded and these data were assessed for any cor-relation between the measurements that would

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allow length to be predicted from thickness. If thatcorrelation was found and if it was strong enough,it would be possible to use a regression (whateverits nature may be) to calculate the original length(L) for each endscraper based on its thicknesswhich remains constant throughout use andreduction. L for each endscraper was calculatedusing the linear regression generated for bladeblanks, and the measured length of scrapers at dis-posal (LD) were subtracted from the originallength estimates, providing an estimated lengthlost (LLS) for each specimen (i.e. L −LD = LLS).LLS for each scraper was then multiplied by thewidth of that scraper to transform the value intoan estimate of the working edge area removedduring reduction. It can best be viewed as a quo-tient relating the material lost to the total esti-mated size of the original flake. This value willbe calculated as “WEAL” (See Figure ).

EDGE ANGLE

Edge angles have been proposed as a second indi-cator of curation, wherein higher curationpressure is signaled by steeper working edgeangles (Blades ; Brooks , ;Morrow ; Shott ). The angle of theworking edge will necessarily increase with useand repair for all scraper types, including blade-based endscrapers (Blades ; Kuhn ).While it is true that edge angles between to degrees are “optimal” for scraping tasks, theethnographic reality is that endscrapers can haveedge angles as shallow as degrees at first use(Shott and Weedman ). In all observedcases, edge angle increases through the artifacts

use life. For this study, edge angle was not usedto discriminate what was or was not a scraper,but as an indicator for relative curation. Anglewill be assessed first as an independent value,and then the relationship between edge angle andthe previous measure, Area Lost, will be explored.Individualsmake conscious decisions on the angle

with which they strike the working edge of an end-scraper in order to retouch it. Shallow strikingangles will largely maintain the working edgeangle while reducing length, whereas more obliqueretouch will increase that angle, with less changeto overall length. Edge angles cannot be retouchedbeyond degrees. If curation pressure is high,shallow retouch will be applied as long as possibleto maximize the use-life potential of the endscraper.Otherwise the scraper will reach a disposalthreshold before meeting its maximum use-life asmeasured by length. Although not wholly indepen-dent, there is no reason that edge angle and ALwill necessarily correlate. Testing for this correlationwill show how many scrapers were expedientlyrepaired rather than curated as long as possible.

RESULTS

WORKING EDGE AREA LOST (WEAL)

There is a statistically significant correlationbetween the thickness and length of obsidianblades from the sampled sites, with thicknessexplaining approximately percent of the totalvariation in length (Spearman ρ: r = ., p <.). These are close to the values found byQuinn et al. () in their comparison of chertblade thickness and length. While thickness isnot a perfect predictor, it is the best estimator fororiginal length currently available. The relation-ship is consistent across all sites suggesting that itis a mechanical characteristic of obsidian bladeproduction. (Figure ) With a strong correlationestablished, a linear regression was calculated toprovide a predictive equation for estimating theoriginal length of a blade blank (L) from thethickness of a reduced endscraper. This linearmodel was calculated as:

L1 ¼ 25:024þ 5:826t

where t =maximum thickness of the endscraper.Few data points are more than mm off fromthe upper or lower bounds of the confidence inter-val for the equations predictive model. This meansthat a predicted original length would most likelybe within cm from the actual value. The L:Trelationship suggested by Blades () was

FIGURE . Schematic representation of variables used to cal-culate Working Edge Area Lost (WEAL) index.

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therefore proven valid for the PN obsidian assem-blages of southwestern Kenya, and subsequentlyapplied to the blade-based endscrapers from thestudy sites.The original length for each endscraper is calcu-

lated using the linear regression generated forblade blanks, and the measured length of scrapersat disposal were subtracted from the originallength estimates, providing an estimated lengthlost for each specimen. The Kruskal–Wallis testsuggests that there is no statistically significantdifference between any of these sites (p = .,r = .). Larger samples tend to have greater var-iances, but it is likely that increasing the samplefrom the smaller sites would bring their rangesand variances even closer to the larger samples (evi-denced by the apparent outliers for Lemek NE).The results of a Kruskal–Wallace test with ,

bootstrap resamples do not generate any statisti-cally significant results (p = ., r = ., χ =

.) (Table ). Figure shows the relationshipbetween the mean WEAL quotients at each site,and the distances of those sites from their respect-ive obsidian sources. A strong correlation betweendistance from obsidian source is not apparent(Spearman ρ = ., Linear regression: r = .,p = .); however, considering the size and distri-bution of the sample, this should be consideredwith some skepticism.

EDGE ANGLE

Edge angles distributions at several sites werefound to have statistically significant differencesfrom one another using a Kruskal–Wallis test,and the probability of the samples being drawnfrom the same population (i.e., generated by thesame conditions) was significantly low (p = .,r < ., χ = .) (Table ). Some of the pat-terning appears to be based on techno-cultural

FIGURE . Blade blank metrics from all sampled sites.

TABLE . KRUSKAL–WALLIS PAIRWISE RESULTS FOR WEAL VALUES FOR ALL SITES

Site OLI NAR NGA LMK NE LMK NW

OLI .* . . .*NAR .* . .NGA . .LMK NE .LMK NW

*Statistically significant difference.

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affinity, wherein endscrapers at Elmenteitan sitestend to enter the archaeological record withlower angled working edges than is the case forSPN sites. Statistically significant differences onlyappear between sites of opposite assemblagegroups. Where sample size is large enough todiscern an overall pattern, it is clear that mostedge angle distributions have a strong left skew.High edge angles are thus more common thanlow edge angles. Differences between sites donot, however, pattern according to distance fromraw material source, cultural affiliation, or eco-logical zone.There is no correlation between edge angle and

WEAL values for any site (Spearman ρ = .,r = .). No site has a discrete enough distri-bution to place it within any one of the four infer-ential categories proposed in the previous section.Three sites, however, have characteristics of onlytwo signatures. Scrapers at Narosura tend tohave high edge angles while scrapers at LemekNE tend to have lower edge angles, whereas bothhave a wide range of WEAL values. These

differences are unrelated to distance from obsidiansources.

DISCUSSION

SUMMARY OF THE FINDINGS

The primary aim of this study was to test thehypothesis that tools (specifically endscrapers)were deposited after more intensive retouch atsites further from the obsidian sources, due toincreasing costs associated with acquiring obsi-dian through exchange networks. Additionally,the focus on endscrapers serves as a pilot studyfor future work exploring the technological organ-ization of early pastoralists in southwestern Kenyaby adapting methods for analyzing blade technol-ogies from hunter-gatherer contexts. As is the casein other regions, quantifying and interpreting toolreduction in terms of curation is problematic;however, these preliminary results support thecontinued application of lithic technological ana-lyses on Pastoral Neolithic materials.None of the measures used were able to show

significant differences in the scale of endscraperretouch in the sampled assemblages. In no case isthere any correlation between the amount scrapershave been reduced and repaired at a site, and thedistance between that site and the obsidiansource in the Mt. Eburru-Naivasha Basin area.One explanation for the patterns observed in thepastoral assemblages in Kenya is that longer occu-pation spans at pastoral sites created a palimpsestof signatures, combining scrapers that were inten-sively used when rawmaterial stockpiles were low,and scrapers that were more readily abandonedwhen stockpiles were replenished. When a singlesite is occupied for a longer time, a greater rangeof possible short-term scenarios will be time-averaged into a single signature, appearinghighly variable.The lack of an effect of raw material transport

contrasts with known Clovis and Aurignacianexamples, where there are strong correlations

FIGURE . Average WEAL index value by distance of sitefrom obsidian source.

TABLE . KRUSKAL–WALLACE PAIRWISE RESULTS FOR ENDSCRAPER EDGE ANGLES

Site OLI NAR NGA LMK NE LMK NW

OLI . . . .NAR . . .NGA . .LMK NE .LMK NW

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between distance from source and endscraperreduction over comparable distances (Blades; Morrow ). The lack of a fall-offpattern related to distance supports the likelihoodthat obsidian was acquired through networks,rather than through other embedded strategies.Furthermore, obsidian distribution, at leastwithin the km zone assessed here, may bemore complicated than simple exchange. Theapparent regularity in which both SPN andElmenteitan producing groups acquired obsidianfrom very specific sources suggests that socialcontracts within these community networksensured regular access to obsidian, permittingstockpiling. With pastoral families regularlymoving around the landscape, staying connectedto these networks and redirecting obsidians mayhave interesting implications for social insti-tutions and organization in the PN. Continuedanalysis of obsidian acquisition, transport, anduse within southwestern Kenya will help elabor-ate these phenomena.A few statements can be made based on the

overall composition of assemblages includedhere. Cortex is present on large debitage so fre-quently that it indicates that rock was not arrivingat sites in the form of completely prepared cores,but possibly in the form of raw cobbles. Had infor-mal down-the-line exchange brought cores to thesite, increasing reduction would be expected ascores were used and passed on. Very little cortexshould remain on cores that have been reducedby numerous individuals as they were slowlytransported over km. One possible expla-nation for high frequencies of cortical material atdistant sites is the common practice of passingon low quality materials, while keeping the highquality stone (Andrefsky ). If people didthis, I would expect higher proportions of theopaque, crystallized obsidians relative to the trans-parent, high quality obsidian, at sites far fromobsidian sources. This is not the case however,and low quality obsidian is always a smallpercent of the total material.Understanding the exact nature of the obsidian

procurement system is important beyond its econ-omic and technological implications; it could havebeen an extremely important structuring elementin pastoralist socio-politics. This possibility hasbeen recognized by Robertshaw (: ), whoargued that the nearly exclusive use of specific obsi-dian source groups by the Elmenteitan and SPNentities over long distances required some level ofpolitical or hierarchical structure. Robertshaw

(, ) proposed a system of lineage-basedmonopolies on obsidian, with a “big man” systemof organized distribution. The model has been cri-tiqued for the implicit assumption of male domi-nated exchange systems (Gifford-Gonzalez b:–). Moving obsidians may actually havebeen quite simple, if pastoralists employed domesti-cated donkeys to carry large quantities of materialacross the landscape (Close ). Few donkeyremains are known from archaeological contextsin Kenya, obscuring their importance in prehistoriceconomies (Weissbrod and Marshall ).Obsidian was unquestionably being moved

from the Rift Valley across southwestern Kenya,and the mechanism for this must be explained inorder to understand the lithic technology that pas-toralists used, and the possible socio-politicalimpacts of this across the ancient landscape. Inunraveling these networks, we might better under-stand the complex variability of ceramic styles(Bower ), the distribution of ground stoneand beads, and the role of food producer andforager interactions.

CONCLUSIONS

Ancient pastoralists were not intensively reducingobsidian endscrapers, relative to their totalretouch potential, at sites in southwestern Kenya.In light of the evidence provided by this endscraperanalysis, I conclude that an impact from rawmaterial constraints cannot be currently validatedfor either Savannah Pastoral Neolithic or Elmen-teitan sites within the study area. Pastoralists ofall affiliations appear to have had consistent andpredictable access to specific, culturally preferred,obsidian sources in the Great Rift Valley.Regional exchange systems may have had animportant role in providing regular access, whichproduced the pattern presented here. Theseresults verify the applicability of the methodsdeveloped here, and show the potential forsimilar curation studies on a broader range oflithic material, especially debitage. Contextualizedwithin a technological organization framework,these findings suggest systems of obsidian acqui-sition and transport may have been in place thatwould have significant social ramifications. Eluci-dating these important aspects of prehistoric pas-toralist economy is not possible without asignificant restructuring of the current, very limit-ing, typological framework, and the applicationof innovative studies that focus on curation and

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technological organization as a landscapephenomenon.A substantial problem with this kind of analysis

is the relatively small sample sizes of formal toolsavailable from many pastoral sites. While insome cases this may be a product of limited exca-vations, it is more often due to the ephemeralnature of pastoral sites in southwestern Kenya.The sites analyzed here may even be exceptionallylarge in comparison with the vast majority of pas-toralist habitations, which would yield evensmaller lithic assemblages. An important futuredirection is the expansion of the scope of techno-logical studies beyond formal tools. This includesstudies of debitage patterns, toolkit and coredesign, quarrying activities, and other lines of evi-dence that help reconstruct the entire lithicreduction sequence of the Pastoral Neolithic insouthwestern Kenya.

ACKNOWLEDGEMENTS

This research was supported financially by the I-CARESorganization, and Washington University in St. Louis. Facili-ties and support were provided by the Kenya NationalMuseum. This research would not have been possiblewithout the archaeological projects of Ari Siirianin, PeterRobertshaw, and Knut Odner. I am indebted to Fiona Mar-shall and Stanley Ambrose for their comments, and to theanonymous reviewers whose input greatly improved thismanuscript. The author is solely responsible for any errors.

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NOTE ON CONTRIBUTOR

Steven Goldstein is a Ph.D. candidate in the department of Anthropology at Washington University in St. Louis. He has a B.A. inAnthropology from Stony Brook University, and an A.M. from Washington University in St. Louis.

Correspondence to: Steven T. Goldstein, Department of Anthropology, Washington University in St. Louis, CB , Brook-ings Drive, St. Louis, MO , USA. Email: stgoldstein@wustl.edu

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