Tooth Wear Related to Marine Foraging, Agro‐Pastoralism and the Formative Transition on the...

* Correspondence to: ArizonBox 210026, Tucson, AZ 857e-mail: [email protected]

Copyright © 2011 Joh

International Journal of OsteoarchaeologyInt. J. Osteoarchaeol. 23: 287–302 (2013)Published online 24 February 2011 in Wiley Online Library(wileyonlinelibrary.com) DOI: 10.1002/oa.1247

Tooth Wear Related to Marine Foraging,Agro‐Pastoralism and the FormativeTransition on the Northern Chilean CoastJ. T. WATSON,a* B. ARRIAZA,b,c V. STANDENc AND I. MUÑOZ OVALLEc

a Arizona State Museum and School of Anthropology, University of Arizona, PO Box 210026, Tucson,AZ 85721, USAb Instituto de Alta Investigación and Centro de Investigaciones del Hombre en el Desierto, Universidadde Tarapacá, Arica, Chilec Departamento de Antropología, Universidad de Tarapacá, Arica, Chile

ABSTRACT Occlusal surface wear scores were
examined in a sample of 200 Formative period (1500 BC–AD 500)skeletons from the lower Azapa Valley in northwest Chile. Wear rate and plane (angle) were additionallyevaluated using a subsample of paired first and second mandibular molars. The Formative period representsthe transition from marine foraging to agro‐pastoral dependence in the region, and differences in oralpathology indicate that diet varied by site location (coast vs valley interior) but not by archaeological phase(early vs late). We predicted that occlusal wear would demonstrate similar patterns, resulting fromdifferences in food consistency, and therefore hypothesised that in coastal groups consuming greaterquantities of foraged foods, occlusal surfaces should wear faster and exhibit flat molar wear, whereas amongvalley interior groups consuming greater quantities of agro‐pastoral products, these should wear slower butexhibit more angled molar wear. Heavier posterior tooth wear was identified among coastal residents, butrate and angle of molar occlusal attrition did not differ significantly by location. Heavier overall wear and asteeper molar wear plane were identified during the early phase indicating that food consistency variedsomewhat over the course of the Formative period. Overall, the results indicate that, although limiteddifferences in tooth wear exist by site location, wear varied more over time likely reflecting a gradual transitionfrom foraging to agro‐pastoral dependence in the lower Azapa Valley. Although oral health indicators point todifferences in dietary investment by location, maintenance of a mixed subsistence economy likely sustaineda comparative consistency of foodstuffs. Copyright © 2011 John Wiley & Sons, Ltd.
Key words: Chile; Formative period; marine foraging; occlusal wear plane; tooth wear

Changes in diet and subsistence patterns associatedwith the ‘Neolithic Revolution’ (Childe, 1925) hadprofound effects on the oral health of past populationson a global scale (Cohen & Armelagos, 1984; Steckel &Rose, 2002; Cohen & Crane‐Kramer, 2007). Theadoption of agriculture often caused a reduction indietary breadth and created a softer, more processed dietthat resulted in increased oral disease, uneven tooth wearand malocclusion (Molnar, 1971; Smith, 1984; Larsen,1997; Hillson, 2002). In addition, the aetiologies of oraldiseases and differential tooth wear frequently interactand co‐contribute to the advancement of each other(Hillson, 2002). However, they can also be quantifiedindividually in skeletal samples and used to aid in the

a State Museum, University of Arizona, PO21-0026, USA.a.edu

n Wiley & Sons, Ltd.

reconstruction of dietary behaviours of past populations,refining our understanding of the health consequences ofthe agricultural transition (Molnar, 1971; Smith, 1984;Sciulli, 1997; Pechenkina et al., 2002; Chattah & Smith,2006; Watson, 2008a, 2008b; Deter, 2009; Fujita &Ogura, 2009; Liu et al., 2010).Wear of the occlusal tooth surface is a multifactorial

process that results from three main interactingmechanisms: attrition, abrasion and erosion (Kaidoniset al., 1988; Miles, 2001; Hillson, 2002). Attrition iscaused by wear of the tooth surface through frictionresulting from tooth‐on‐tooth contact (Larsen, 1981,2002; Milner & Larsen, 1991; Lukacs, 1992; Hillson,2002). Abrasion is the loss of surface detail from frictionwith exogenous material (Kaidonis et al., 1988; Hillson,2002). Erosion is the reduction of dental surfaces due tonon‐bacterial exogenous or endogenous chemicalsubstances (Kieser et al., 2001). Each of these processes

Received 16 July 2010Revised 31 December 2010Accepted 19 January 2011

288 J. T. Watson et al.

is continuous, unidirectional and age progressive(Miles, 2001; Hillson, 2002). A number of studies havesuccessfully correlated differences in the rates andpatterns of these wear processes to differences in overallsubsistence practices among pre‐industrial populations,where occlusal wear is generally severe (Molnar, 1971;Smith, 1984; Larsen, 1997; Kaifu, 1999; Kieser et al.,2001; Deter, 2009; Fujita & Ogura, 2009; Liu et al.,2010). Food consistency and the presence of foreignabrasives have been shown to significantly influence therate of occlusal tooth wear (Hillson, 2002).The wear plane (or angle) of the occlusal surface has

similarly been shown to differ measurably betweenskeletal samples of diverse subsistence economies(Molnar, 1971; Smith, 1984; Pechenkina et al., 2002;Chattah & Smith, 2006; Watson, 2008b). Erosion hasalso been documented to play an important role in thedifferential destruction of tooth surfaces with variousdiets (Kieser et al., 2001). Additional factors have beenconsidered as potential secondary contributors totooth wear including tooth form and structure, occlusalrelationships, enamel quality, ingestion of grit andcultural activities such as the use of teeth as tools (Milner& Larsen, 1991; Sciulli, 1997). However, it has beenshown that dietary composition and food processingmethods have the greatest effect on patterns of occlusalsurface wear observed in archaeological samples(Molnar, 1971; Smith, 1984; Kieser, 1990; Larsen,1997; Sciulli, 1997; Kaifu, 1999; Hillson, 2002). Theapplication of these concepts has been particularlysuccessful in observing changes related to subsistenceand diet in prehistoric skeletal samples (e.g. Larsen,1981, 2002; Milner & Larsen, 1991; Lukacs, 1992;Kieser et al., 2001; Chattah & Smith, 2006; Deter, 2009;Fujita & Ogura, 2009; Liu et al., 2010).Both wear rate and wear plane of the occlusal sur-

face show dramatic changes when human groups altertheir food behaviours, in overall subsistence, consump-tion or processing techniques (Molnar, 1971; Smith,1972; Scott, 1979a, 1979b; Larsen, 1981; Smith, 1984;Pechenkina et al., 2002; Chattah & Smith, 2006; Watson,2008a). Molnar (1971) documented consistent differ-ences in wear rate between skeletal samples of foodforagers and agriculturalists from North America. Hesuggested that because foraging groups consumed awider variety of less processed foods than agriculturalgroups, tough, fibrous diets caused powerful chewingand extensive lateral movements of the jaw, producingflat occlusal wear at relatively rapid rates. Reinhardt(1983) has shown that dietary consistency producessignificantly enough force on the dental arch that itcan create zero to negative overjet (overbite) in groupsexhibiting heavy attrition.

Copyright © 2011 John Wiley & Sons, Ltd.

Occlusal wear angle in the molar region is shaped bydifferential wear of the buccal and lingual cusps(Reinhardt, 1983; Hillson, 2002). With progressivewear, steeper occlusal planes develop from lingual tobuccal in mandibular molars and buccal to lingual inmaxillary molars, with each molar generating steeperangles or wear planes in order of molar eruptionsequence, eventually resulting in a reversed curve ofMonson (Osborn, 1984). This pattern becomes moreapparent in agricultural groups where the consumptionof a narrower dietary breadth and heavily processingfoodstuffs reduces chewing resistance and lateralmovements, increasing the amount of contact betweencusps and creating steeper occlusal plane angles atfaster rates (Smith, 1984). Smith (1984) documentedthis pattern of flatness of molar wear plane incomparisons of archaeological samples of food foragersto dedicated agriculturalists. These studies provideevidence for the correlation between molar occlusalwear and subsistence, which has allowed researchers todraw inferences about dietary behaviours of pastpopulations (e.g. Molnar, 1971; Smith, 1984; Larsen,1997; Kaifu, 1999; Chattah & Smith, 2006; Deter,2009; Fujita & Ogura, 2009).

The formative transition in the lowerAzapa Valley

The Andes is one of the global centres ofindependent domestication (Smith, 1998; Pearsall,2008), but the suite of domesticates that formed thefoundation of Formative cultures in the area includeboth local species such as quinoa (Chenopodium quinoa),potatoes (Solanum tuberosum, Tropaeolum tuberosum, Oxalistuberosa andUllucus tuberosus), manioc (Manihot esculentum),llama (Lama glama), alpaca (Lama pacos) and guinea pig(Cavia porcellus and other species), and foreign speciesfrom North America such as corn (Zea mays), beans(Phaseolus vulgaris) and squash (Cucurbita pepo and otherspecies) (Smith, 1998). This is important to thecultural development in South America because manyscholars have argued that foreign domesticates suchas maize played a major role in stimulating thedevelopment of early Andean civilization, such as atChavin de Huantar (Mangelsdorf & Reeves, 1939;Kidder, 1962; Kidder et al., 1963; Finucane, 2009). Agreat deal of the evidence for domestication of localplant species and the arrival of foreign speciesappears just prior to about 2000 BC throughout theAndean region but would likely have been used invarious capacities well beforehand (Smith, 1998;Pearsall, 2008).

Int. J. Osteoarchaeol. 23: 287–302 (2013)

289Tooth Wear in Northwest Chile

Alongmuchof theAndean coast, there is evidence thatthe first attempts by coastal residents to produce food areaccompanied by intensification in the exploitation ofmarine resources (Rivera et al., 1974; Focacci, 1980;Rivera, 1984, 1991; Stanish, 2001;Muñoz, 2004; Arriaza& Standen, 2008; Pearsall, 2008; Finucane, 2009;Watson et al., 2010). This new economic contributionalso perhaps produced intensification in meat andwool for the manufacture of textiles (Kidder, 1962;Focacci, 1980; Santoro, 1980a, 1980b; Muñoz, 1981,1983; Pearsall, 2008; Finucane, 2009). The incorpor-ation of camelids into the economies of these groups isreflected in several cultural expressions, such as intextile motifs and in rock art of the region (Focacci,1980; Muñoz, 1989, 2004; Finucane, 2009). Theperiod just prior to the formation of agriculturalvillages and larger socio‐ceremonial centres along thecentral Andean coast demonstrates that the processwas not a violent interruption of existing foragingadaptations in the region but instead fitted into alarger gradual process of cultural development andincreasing complexity whereby the actors integrated

Figure 1. Location of sites in the lower Azapa Valley.


new resources and technologies into the primaryeconomic system.The Formative period (1500 BC–AD 500) in the lower

Azapa Valley (Figure 1) is principally demarcated fromthe preceding Archaic period (8000–1500 BC) by thecessation of artificial mummification as a typical burialpractice, the appearance of sand‐tempered ceramics,incipient agricultural production and pastoralism, andthe establishment of villages in the valley interior(Focacci, 1974; Santoro, 1980a, 1980b, 1980c; Muñoz,1981, 1983, 1989, 2004). Previous settlements in thearea, known as the Chinchorro culture, comprisedapproximately 6000 years of stable marine and somelimited terrestrial foraging (Allison et al., 1984; Arriaza,1994, 1995). Although there is evidence for continuouscontact between the coast and altiplano throughoutprehistory (Rivera, 1984), the Chinchorro maintained asedentary lifestyle heavily reliant on the rich marineresources that are available along the Pacific coast(Arriaza, 1994, 1995; Arriaza et al., 2005; Arriaza &Standen, 2008). During the early part of the secondmillennium BC, groups along the coast began to



cultivate domesticated crops including quinoa, potato,manioc, corn, beans, squash and chillies (Muñoz, 2004).Some of the populace relocated in the interior of the SanJosé River valley and began practising animal husbandrywith domesticated camelids, such as llama and alpaca(Muñoz, 2004). The beginning of the Formative periodtherefore represents a major shift in subsistence strategyfrom that practised by the area’s previous inhabitants.Formative period sites in the lower Azapa Valley can

be separated into two groups based on location: coastaland valley interior sites. Coastal sites (Playa Miller‐7and Quiani‐7—Figure 1; Camarones‐15—Figure 2) arelocated directly adjacent to the shoreline and close tothe marshy mouths of the San José and Camaronesrivers (Focacci, 1974, 1980). Although evidence forcultigens and low level agro‐pastoral investment isplentiful, the dietary base focused on exploitation ofreadily accessible marine resources (Muñoz et al., 1991;Watson et al., 2010). Valley interior sites (Azapa‐14,70, 71 and 75—Figure 1) are located adjacent to theSan José River floodplain approximately 12 km from

Figure 2. Location of the Camarones‐15 site in lower Camarones Val


the coast (Focacci & Erices, 1972–1973; Focacci, 1980).These sites also present considerable evidence forexploitation of marine resources, especially shellfish;but archaeological evidence indicates that the dietarybase focused equally on agro‐pastoral production andthe exploitation of marsh resources along the river(Santoro, 1980a, 1980b, 1980c; Muñoz, 1981, 1983,1989, 2004; Watson et al., 2010).The Formative period can additionally be divided

into concurrent archaeological phases at both loca-tions in the lower Azapa Valley. The early phase(1500–500 BC) is termed Faldas de Morro in coastalsites (Dauelsberg, 1963) and Azapa in valley sites(Santoro, 1980b). The late phase (500 BC–AD 500) istermed El Laucho in coastal sites (Focacci, 1974) andAlto Ramirez in valley sites (Santoro, 1980b). Subtledifferences in artefact assemblages define the arch-aeological phases, but they are basically analyticaltools used to highlight variability observed in thearchaeological record (Arriaza & Standen, 2008).Material culture recovered from these sites is similar

ley.



in the broader sense that cultigens and itemsrepresenting agricultural technology are present inboth areas (Rivera, 1984, 1991). Although differ-ences are present, they are minor compared withthe unmistakable impact the arrival of domesti-cated cultigens had on subsistence strategy, as ob-served in the archaeobotanical record of these sites(Muñoz, 2004).Several scholars suggest that the Formative transi-

tion in the lower Azapa Valley is the result of demicdiffusion of highland agriculturalists into the area(Santoro, 1980b; Rothhammer et al., 1982, 2002;Muñoz, 1983, 1989). They often cite the appearanceof altiplano ceramics and textile motifs during theFormative period to support the conclusion that theagro‐pastoralist subsistence strategy was brought in bymigrants from the cordillera (Rivera, 1984, 1991;Varela & Cocilovo, 2002). If this were the case, onewould expect to find greater archaeological differencesbetween contemporaneous coastal and valley interiorsites, and the evidence for mixed subsistence practicesfrom both locations would be somewhat counter-intuitive. Other researchers document continuouscultural and biological continuity in the lower AzapaValley (Sutter, 1997, 1999, 2000, 2005a, 2005b, 2006;Rothhammer & Santoro, 2001). Most of Sutter’s workwith the Azapa Valley samples has involved defininglocal, regional and temporal genetic distances usingdiscrete dental traits (Sutter, 1997, 1999, 2000, 2005a,2005b, 2006; Sutter & Mertz, 2004). In every case, hisresults demonstrate genetic continuity within groups ofthe lower valley, a pattern that generally persiststhrough time (Sutter, 1997).In a recent related study, we identified that markers

of oral health varied significantly by site location butnot by archaeological phase during the Formativeperiod in the lower Azapa Valley (Watson et al., 2010).Fewer caries (3.8%) and lost teeth (9.6%) wereobserved in skeletal samples from the coast, whereasnumerous caries (19.7%) and more lost teeth (13.4%)were observed in skeletal samples from the valley

Table 1. Skeletal sample from lower Azapa Valley

Site N

AZ‐14 30AZ‐70 25AZ‐71 5AZ‐71 18AZ‐75 27CAM‐15 11PLM‐7 80QUIANI‐7 4


interior (p < 0.05). These percentages reflect thefrequency or ‘observed rate’ [caries rates were correctedusing Lukacs' (1995) formula to account for toothloss], which describe the percentage of teeth oralveolar segments affected and are calculated bydividing the number of carious or missing teeth bythe total number of locations observed.Although the archaeological evidence indicates that

both groups practised a shared mixed subsistenceeconomy, residents along the coast placed greaterinvestment in foraging marine resources whereasresidents in the valley placed greater investment inagro‐pastoral production. We concluded that thesepatterns reflect niche construction and differences indietary base between the coast and valley interior(Watson et al., 2010). This pattern of differentialinvestment could also produce measurable variabilityin tooth wear and further affect patterns of oraldisease observed in the samples. Here, we examineocclusal surface wear in the same skeletal samples ofincipient agriculturalists from the lower Azapa Valleyto test the hypothesis that, concomitant withdifferences observed in oral pathology, in coastalgroups consuming a greater percentage of foragedfoods, occlusal surfaces should wear faster and exhibitflat molar wear plane angles, whereas among valleyinterior groups consuming a greater percentage ofagro‐pastoral products, these should wear slower butexhibit more angled molar wear.

Materials

The skeletal samples analysed for this study are part ofthe osteological collection held in repository at theUniversidad de Tarapaca Museo Arqueológico de SanMiguel de Azapa, Arica, Chile. We examined maxillaryand mandibular dentition from crania of 200 adultindividuals (age≥ 15 years) from seven Formativeperiod sites (Table 1) in the lower Azapa Valley(Figure 1) and one contemporaneous site from the

Location Phase (culture)

Valley Late (Alto Ramirez)Valley Late (Alto Ramirez)Valley Early (Azapa)Valley Late (Alto Ramirez)Valley Late (Alto Ramirez)Coast Early (Faldas de MorroCoast Late (El Laucho)Coast Early (Faldas de Morro


)

)


Camarones Valley coast (Figure 2) in northern Chile.Eleven individuals from the Camarones‐15 site wereadded to the coastal sample to bolster the limitednumber of individuals dating to the early phase.Biological and archaeological variables all suggested ashared history and connection between the Azapa andCamarones Valley residents prior to, and during, theFormative period (Muñoz, 1989, 2004; Muñoz et al.,1991; Arriaza & Standen, 2008). The dental sampleconsists of a total of 1268 teeth. Preservation of thedentition is generally excellent; however, a number ofindividuals were missing teeth because of postmortemloss. Pearson chi‐square cross‐tabulations identify thatthe distribution of teeth does not differ significantlybetween coast and valley interior locations(χ2 = 13.252, df= 15, p= 0.583) or between the earlyand late archaeological phase (χ2 = 6.050, df= 15,p= 0.979).Sex was estimated for individuals in the sample by

examining standard macroscopic aspects of the pelvisand/or cranium (Buikstra &Ubelaker, 1994). The sampleis comprised of relatively even numbers of men (n= 101)and women (n= 99). Age was estimated for the sampleusing dental eruption (after Ubelaker, 1978), epiphysealfusion, cranial suture closure and macroscopic degen-erative changes in the pubic symphysis followingstandards described by Buikstra & Ubelaker (1994).The sample was classified into four ordinal 9‐year agecohorts (15–24, 25–34, 35–44, 45–54 years). Individualsassigned to the oldest age group generally had themost severe attrition, were more often affected bytooth loss or damage resulting in uneven wear andtherefore were eliminated from the sample. Miles(2001) identified that age estimation using attritionscores tends to underestimate older individuals inskeletal samples and coincides with greater tooth loss.Most relevant to this study is the fact that extremewear that compromises the integrity of the crown andcrosses the cemento‐enamel junction results in faster,more unpredictable wear than in earlier stages oryounger individuals (Miles, 2001; Hillson, 2002).Teeth exhibiting severe dental pathology or extremewear (incisor, canine, premolar: wear scores >8; molar:wear scores >32), resulting in loss of crown integrity,and teeth with opposing occlusal teeth missingantemortem were therefore eliminated from analysis.This additionally functioned to eliminate numerousteeth representing the oldest individuals in thesample and resulted in an equal distribution of thesample between the remaining three adult agegroups (χ2 = 2.583, df = 2, p = 0.275). However,two‐tailed Mann–Whitney U‐tests showed that thedifferences in the estimated age compositions of the


adult subsamples between the coast and valleyinterior locations, and between early and latearchaeological phases, were significant at the 5%level. Given that attrition is principally associatedwith age and the duration a given tooth is inocclusion, it is therefore important that we controlfor age in the analyses that follow.

Methods

Three analyses were conducted on the dental samplefrom the lower Azapa Valley comparing attrition bylocation and archaeological phase in order to test thecentral hypothesis that in coastal groups consuminggreater quantities of foraged foods, occlusal surfacesshould wear faster and exhibit flat molar wear,whereas among valley interior groups consuminggreater quantities of agro‐pastoral products, theseshould wear slower but exhibit more angled molarwear. These analyses included comparisons of (i) rawaverage wear, (ii) molar wear rate and (iii) molar wearangle.

Raw average wear

Raw average wear scores were compared for each toothusing independent samples t‐tests to identify if grossdifferences in wear exist across the dentition. This is ameasure of the amount of wear on each tooth and canbe used for a general comparison to identify ifdifferences in the amount of wear exist betweensamples and which teeth specifically exhibit thesedifferences. Heavy wear (significant loss of the crown)is more commonly associated with groups practising adedicated foraging economy and is often found to begreatest on the anterior teeth (anterior loading),whereas dedicated agriculturalists often exhibit lighteror more variable wear in general, yet the heaviest wearis often associated with the posterior teeth amongagriculturalists (Molnar, 1971; Reinhardt, 1983; Smith,1984;Milner & Larsen, 1991; Kaifu, 1999; Deter, 2009).Occlusal surface wear was recorded for both sides ofadult maxillary and mandibular dentition in thesample, but only the left side was used in theanalyses. Occlusal wear was scored using ordinalscales following Smith (1984) for incisor, canine andpremolar teeth and following Scott (1979a) for molarteeth. No significant differences in wear rate wereobserved between right and left dentitions usingpaired‐samples t‐test; therefore, if a tooth was missingfrom the left side, the antimere was used to facilitatea larger comparative sample size.



Molar wear rate

A subsample of 112 paired first (M1) and second (M2)mandibular molars (n= 224) was selected to assess rateand angle of occlusal surface wear using attrition scoresbetween site locations and archaeological phases. Totalwear scores were compared between paired molarsusing principle axis analysis to identify if the rate ofwear differed. This test is designed to measure the rate(or speed) of occlusal surface wear exerted on themolars and identify if differences exist in how fastmolars wear on average between samples. Faster ratesof molar wear are often associated with harder dietsresulting from foraging wild foods and minimalprocessing, whereas slower although more variablerates of wear are more commonly associated withsofter diets and the consumption of agriculturalproducts such as domesticated cultigens, which areoften heavily processed (Smith, 1982, 1984; Larsen,1997; Lukacs, 1996; Sciulli, 1997; Kieser et al., 2001;Fujita & Ogura, 2009).Occlusal wear was scored on each quadrant of the

molar surface using the 10‐point ordinal scale devel-oped by Scott (1979a). In this method, each of thefour molar surface quadrants is given a wear scoreranging between 1 and 10 based on relative enamelloss. Scores for all four quadrants are added to give theoverall wear score for the tooth, ranging from 4 to 40.Smith (1972) proposed the use of a method modifiedfrom Miles (1963, 2001) to determine wear rate inskeletal samples that avoids the problems of agedependency inherent with dental attrition. Smith(1972) used correlation and regression analysis tocompare the differences in wear between the pairedfirst and second molars, utilising the staggeredapproximate 6‐year interval timing of molar eruptionas a proxy for age. As all of the teeth used from thesample represent adult individuals, Smith’s (1972)system provides an age‐independent assessment ofwear rates.Scott (1979b) further built upon Smith’s (1972)

approach and proposed the use of principle axisanalysis and successfully demonstrated that the slopeof the principle axis equation could be used as anindicator of the rate of wear, whereby a steeper slopeindicates a rapid rate of wear. Although interval datawould be preferable for statistical treatment, Benfer &Edwards (1991) were able to demonstrate that resultsof principle axis analyses using the Scott scoringsystem are similar to those produced using measure-ments of crown height and suggest that it is thereforean effective tool for assessing rates of occlusal surfacewear. Principal axis analysis (Scott, 1979b) was applied


to wear rates of left mandibular M1 and M2 betweencoast and valley interior sites and between early andlate archaeological phases within the lower AzapaValley sample.

Molar wear angle

Summed wear scores were compared between buccalcusps of the first molar (M1) and lingual cusps of thesecond molar (M2) using principle axis analysisfollowing Chattah & Smith (2006) to identify if theangle of occlusal wear differed between locations orarchaeological phases. This test is designed to measurethe angle of occlusal surface wear exerted on the molarsand to identify if differences exist in howmolars wear onaverage between samples. The development of theocclusal surface wear plane, or angle, is largely the resultof the juxtaposition of hard versus soft diets and theconsistency of foods consumed regularly. Flat molarwear angles are often the result of harder diets associatedwith foraging wild foods and minimal processing,whereas steeper molar wear angles are often the resultof softer diets and increased tooth‐on‐tooth contactassociated with the consumption of agricultural prod-ucts that are often heavily processed (Molnar, 1971;Scott, 1979b; Smith, 1984; Chattah & Smith, 2006;Watson, 2008b; Deter, 2009; Fujita & Ogura, 2009).This methodology is a further modification of

Scott’s (1979b) approach and has the advantage ofcomparing both the rate and angle of molar occlusalsurface wear. It employs the functional differential inwear based on order and timing of eruption betweenM1 and M2 and measures the differential in wear ratebetween paired buccal versus lingual cusps. Thepotential exists to underestimate the degree of wearangle in younger individuals where M2 exhibitsminimal wear; however, this also makes the test robustand less susceptible to the affects of idiosyncratic wearon M1. This technique was also chosen because of itsflexibility, ease of application and comparability in theplace of more technically complex or time‐consumingtechniques such as morphometric (i.e. Bailey, 2004) orthree‐dimensional surface or image analysis (i.e.Mayhall & Kageyama, 1997). More specifically, theseresults are directly comparable with that of similarstudies in other regions of the world that haveconsidered the effects of dietary changes associatedwith the introduction of agriculture using wear ratesand planes (Molnar, 1971; Smith, 1984; Pechenkinaet al., 2002; Chattah & Smith, 2006; Watson, 2008b;Deter, 2009).Principal axis analysis was employed in the last two

analyses because it does not assume a causal relationship



between variables and does not assume that the X‐axis isuniformly measured without error (Scott, 1979b;Chattah & Smith, 2006). Bivariate normality (p> 0.10)was found for all subsamples. In comparing wear rate,the principal axis equation was determined byplotting the wear score of M1 on the Y‐axis andM2 on the X‐axis. For the comparison of wear plane,the principal axis equation was determined byplotting the wear score of the M1 buccal surface onthe Y‐axis and the wear score of the M2 lingualsurface on the X‐axis. A steeper principal axis slope(b) indicates a faster wear rate or steeper wear planeangle. Following Scott (1979b), bivariate plots of thedata were prepared.Intra‐observer error was assessed by repeating

analysis on 30 random dentitions 4 months after theoriginals were conducted. The mean difference in wearscores of the occlusal surface was two (standarddeviation of 2). In each case, error variances were lessthan 10% of total observed variation, confirming thatthey were small and unlikely to bias results. Allstatistical tests were performed using the SPSS 14.0 forWindows programme (Statistical Package for SocialSciences, Chicago, IL).

Results

Raw average wear

Tables 2 and 3 summarise descriptive statistics andhypotheses tests for attrition scores of left maxillaryand mandibular dentitions. The t‐test comparisonsidentify several teeth for which attrition differssignificantly between subsamples. Wear scores werehigher on average among coastal residents, but onlythe molars (UM1, UM2, UM3, LM2 and LM3)demonstrated statistically significant differences. Thispattern of greater wear on the molars is indicative of

Table 2. Descriptive statistics and t‐tests for left maxillary attrition by

Coast Valley p‐value

n Mean SD n Mean SD

UI1 16 3.63 1.20 30 3.50 1.33 0.756UI2 21 3.48 1.12 36 3.78 1.46 0.418UC 37 3.54 1.22 51 3.57 1.53 0.926UP1 42 3.90 1.39 53 3.64 1.73 0.426UP2 46 3.89 1.35 57 3.86 1.72 0.919UM1 59 5.83 1.54 61 5.02 1.47 0.004*UM2 56 4.93 1.50 65 3.63 1.34 0.001*UM3 30 3.83 1.16 43 2.28 1.23 0.001*

*Significant at the 0.05 level.


differential loading on the posterior teeth amongcoastal residents. However, most prehistoric foragingpopulations present differential loading in the anteriordentition, much of which is commonly associated withthe non‐masticatory use of anterior teeth, such asgrasping fibres (Molnar, 1971; Reinhardt, 1983; Smith,1984; Milner & Larsen, 1991; Kaifu, 1999; Deter,2009). The pattern of posterior loading observed in thecoastal samples may reflect a difference in the specificforaged resources consumed (i.e. marine resources) orin processing techniques compared with other groupsprincipally invested in foraging, specifically comparedwith terrestrial foragers.When the samples were pooled across locations and

compared by archaeological phase, raw average wearscores were generally higher in the early phase, withdifferences in wear on three posterior maxillary teeth(UP1, UP2, UM2) and four mandibular teeth (LC,LP1, LP2, LM2) being statistically significant. Despitesmaller sample sizes, and although attrition scores varyacross more teeth by archaeological phase, to someextent the pattern is indicative of greater total wear atthe beginning of the Formative period in the lowerAzapa Valley. Other studies of dental attrition andsubsistence patterns typically associate greater overallwear with foraging and limited processing of consumedresources (Smith 1982, 1984; Sciulli, 1997; Kieser et al.,2001; Deter, 2009; Fujita & Ogura, 2009). The patternof greater overall wear observed during the early phasemay reflect greater investment in foraging resources atthe beginning of the Formative period, whicheventually gave way to a more balanced, mixedsubsistence economy.

Molar wear rate

Table 4 shows the results of the principle axis analyseson paired left mandibular molar wear scores. The rate ofaverage molar occlusal surface wear, as measured onM1

site location and archaeological phase

Early Late p‐value

n Mean SD n Mean SD

9 3.56 1.33 36 3.56 1.30 0.99910 3.40 1.26 47 3.72 1.36 0.49311 3.82 1.40 77 3.52 1.40 0.51012 4.75 1.54 83 3.61 1.55 0.020*12 4.75 1.48 91 3.76 1.54 0.037*12 5.94 1.54 108 5.36 1.55 0.22314 5.13 1.80 107 4.11 1.49 0.021*9 3.47 1.16 64 2.84 1.44 0.213


Table 3. Descriptive statistics and t‐tests for left mandibular attrition by site location and archaeological phase

Coast Valley p‐value Early Late p‐value

n Mean SD n Mean SD n Mean SD n Mean SD

LI1 15 3.87 1.06 27 3.96 1.81 0.851 5 4.60 1.67 37 3.84 1.55 0.314LI2 18 4.28 1.36 33 3.79 1.47 0.250 6 4.83 0.98 45 3.84 1.46 0.115LC 27 3.96 1.13 36 3.69 1.39 0.415 8 4.75 1.04 55 3.67 1.26 0.025*LP1 39 4.00 1.24 42 3.81 1.70 0.568 10 5.00 0.94 71 3.75 1.49 0.012*LP2 38 4.03 1.26 49 3.67 1.52 0.251 10 5.00 1.15 77 3.68 1.38 0.005*LM1 41 5.71 1.31 40 5.20 1.41 0.098 10 6.25 1.34 71 5.35 1.35 0.051LM2 45 4.85 1.48 40 4.00 1.53 0.011* 11 6.00 1.50 74 4.22 1.43 0.001*LM3 38 3.60 1.17 37 2.95 1.38 0.032* 6 3.46 1.08 69 3.26 1.34 0.732

*Significant at the 0.05 level.


against M2, mirrors those trends observed in attritionscores between locations. Residents of the coastal siteshad a steeper principle axis slope compared with thosefrom valley interior sites (Figure 3(a)) indicating aslightly faster rate of wear; however, the difference wasnot statistically significant (p> 0.05). A faster rate ofwear is consistent with other studies of dental attritionamong prehistoric foraging groups (Smith 1982, 1984;Walker & Erlandson, 1986; Larsen, 1997; Lukacs, 1996;Sciulli, 1997; Kieser et al., 2001; Deter, 2009; Fujita &Ogura, 2009) and, although non‐significant, mayreinforce the results observed in the raw average wearscores.When samples were pooled across locations and

compared by archaeological phase, the early phasedisplayed a slightly higher, but non‐significant, rate ofwear when compared with that of the late phase(Figure 3(b)). This pattern also matches the greateroverall wear observed in the raw average scoresobserved in the early‐phase samples and suggests thatalthough the rate of wear may be similar over time, it isgenerally greater early in the cultural sequence. Again,although non‐significant, a faster rate of wear is mostlyseen among foraging groups that consume a minimallyprocessed diet and therefore could be indicative ofgreater investment in foraging resources during theearly phase in the lower Azapa Valley.

Table 4. Principle axis slope (b), equation and 95% confidence limit

b

Coast M1 vs M2 0.726Valley M1 vs M2 0.664Early M1 vs M2 0.745Late M1 vs M2 0.683Coast M1 buccal vs M2 lingual 0.809Valley M1 buccal vs M2 lingual 0.613Early M1 buccal vs M2 lingual 1.050Late M1 buccal vs M2 lingual 0.662


Molar wear angle

Wear was greater on the molar buccal cusps in groupsfor all comparisons (Table 4). Principle axis analysis ofM1 buccal cusps wear scores against M2 lingual cuspswear scores demonstrate a steeper principle axis slopeand therefore a greater occlusal wear angle in molarsfrom coastal sites (Figure 4(a)). There is considerablevariability in the wear plane angles of both coastal andvalley interior residents; therefore, the difference inslope by site location is not statistically significant(p> 0.05). However, it is interesting that the molarwear angle is steeper among the coastal group becausemost studies of attrition patterns associate flat molarwear with foraging and limited processing of consumedfoods compared with more angled molar wear amongagriculturalists consuming softer, more processed diets(Smith 1982, 1984; Larsen, 1997; Sciulli, 1997; Kieseret al., 2001; Watson, 2008b; Deter, 2009; Fujita &Ogura, 2009). Although non‐significant, the patternobserved here is suggestive of dissimilarity in dietaryconsistency among the coastal foragers of the lowerAzapa Valley compared with terrestrial foragers inother parts of the globe.The principle axis analysis also demonstrated a

steeper slope and therefore greater occlusal wear anglein molars associated with the early phase (Figure 4(b))

s

Principle axis equation CL (95%)

2.499+0.726y 0.487<b<0.9662.492+0.644y 0.446<b<0.8822.977+0.745y 0.246<b<1.2442.476+0.683y 0.520<b<0.8466.676+0.809y 0.481<b<1.1387.557+0.613y 0.367<b<0.8595.842+1.050y 0.216<b<2.1907.363+0.662y 0.472<b<0.852


Figure 3. (a) Scatterplot of average wear scores of M1 and M2by site location, shown with regression lines. (b) Scatterplot ofaverage wear scores of M1 and M2 by archaeological phase,shown with regression lines.

Figure 4. (a) Scatterplot of M1 buccal cusps and M2 lingualcusps wear scores by site location, shown with regression lines.(b) Scatterplot of M1 buccal cusps and M2 lingual cusps wearscores by archaeological phase, shown with regression lines.Note steeper slope for early‐phase subsample.


in the lower Azapa Valley. Although similar variabilitycan be observed in early‐phase and late‐phase group-ings, the respective principle axis slopes are sufficientlydispersed from each other to be statistically significant(p< 0.05). As mentioned above, steeper molar wearplanes are principally associated with an agriculturallifestyle and a softer, more processed diet (Smith,1984; Sciulli, 1997; Deter, 2009). If the patternsobserved in this study reflect similar adaptations, thenone could conclude that the residents of the lowerAzapa Valley were heavily invested in domesticatedproducts or were heavily processing foods at thebeginning of the Formative period but reverted toutilise more foraged resources or limited processingduring the late phase. This seems like an unlikelyinterpretation given heavier wear and slightly fasterrates and angles during both the early phase and


among the coastal residents. Steeper molar wear duringthe early phase may instead be interpreted to indicate adifference in dietary consistency compared with otherforaging groups, specifically compared with terrestrialforagers.The limited sample size for the early phase,

particularly from the valley interior (n= 5), couldcontribute to the results obtained here, wherebyheavier wear, experienced by coastal foragers duringthe early phase, could be masked when pooled withlater‐phase coastal samples but reflect a stronger signalover the valley interior sample of the early phase.Unfortunately, sample sizes are too small to compareearly‐phase with late‐phase coastal samples and early‐phase with late‐phase valley interior samples. However,given that sample sizes are somewhat limited,



particularly for the early phase, those differencesobserved in attrition that are statistically significantare likely strong and therefore meaningful.Figure 5 shows a typical pattern of wear common

among Formative period coastal groups versus valleyinterior groups in the lower Azapa Valley. The figureillustrates those patterns observed in the data: heavyposterior wear, at a relatively faster rate and with aslightly steeper molar occlusal angle at coastal sites,compared with overall less severe wear, at a slower rateand with more cupped, but less angled, molar occlusalsurface wear at valley interior sites. These patterns alsohold true—and are statistically significant—during theearly phase. An additional phenomenon that wasobserved to differ between locations was an extensiveamount of chipping (damage) to dental crowns amongthe coastal residents (37.9%) compared with thosefrom the valley interior (5%; p< 0.001). Damage to thecrown can further exacerbate differential wear, espe-cially between molar surfaces (Scott & Winn, 2011).Enamel chipping was recorded as part of the largerdental analysis by simply counting the number of chipspresent that were clearly antemortem (those with somewear on the edges of the damaged surface comparedwith sharp edges likely due to postmortem damage).Chipping of the crown can be observed on the lingualedge of the lingual–distal cusp of M1 in Figure 5. Inaddition, the figure displays exposure of the pulpcavity in a molar from both dentitions; however, theexposure in the individual from the coast is the resultof heavy wear, whereas the exposure in the individual

Figure 5. Photo of right mandibular posterior teeth highlightingwear and damage typical of Formative period sites in the lowerAzapa Valley. Top is of a 35‐ to 45‐year‐old man from the late‐phase coastal site of Playa Miller‐7 (individual CR‐133). Bottomis of a 30‐ to 40‐year‐old man from the late‐phase valley site ofAzapa‐75 (individual T‐123).


from the valley interior is the result of destruction by acarious lesion.

Discussion

In a recent related study, we identified higherfrequencies of caries and lost teeth among samplesfrom the valley interior and subsequently proposedthat this differential expression of oral pathology inclosely related groups was likely the result of greaterinvestment in agro‐pastoral resources and nicheconstruction by residents of the valley interior(Watson et al., 2010). This conclusion formulated theoriginal impetus for this investigation, and we testedthe hypothesis here that, concomitant with differencesobserved in oral pathology, in coastal groups consum-ing a greater percentage of foraged foods, occlusalsurfaces would have worn faster and exhibit flat molarwear, whereas among valley interior groups consuminga greater percentage of agro‐pastoral products, thesewould have worn slower but exhibit more angled molarwear. The results of our analyses demonstrated greateraverage tooth wear among coastal residents but limiteddifferences (not statistically significant) in rates ofattrition and wear angle in the molars compared withthat of the residents of the valley interior. Although weidentified some differences in wear, we reject ourhypothesis, with some caveats, that molar wear rateand angle demonstrated significant differences bylocation (coast vs valley interior). Instead, we foundsignificantly greater average wear and steeper molarwear angles and a minimally faster wear rate (notstatistically significant) in dentitions from the earlyphase of the Formative period.Two important patterns were therefore identified

from the analyses conducted on the dental sample fromthe lower Azapa Valley: (i) coastal residents exhibiteddifferential loading on the posterior dentition; and (ii)dentition from the early phase exhibited greater averagewear over the dental arch and steeper molar wear angles.Archaeological evidence (Dauelsberg, 1963, 1974;Muñoz & Chacama, 1982; Muñoz, 1989, 2004; Muñozet al., 1991; Arriaza & Standen, 2008) and patterns of oraldisease (Watson et al., 2010) indicated that the residentsof the coast continued to principally invest in marineforaging throughout the Formative period. In addition,the limited sample of early‐phase individuals from thevalley interior sites basically creates a ‘coastal’ signaturefor the subsample, one largely based on foraging marineresources. Therefore, the significant patterns of attritionobserved in both the coastal and early‐phase samplescan principally be attributed to a marine‐based diet.



This is significant because our results are partiallyopposed to patterns observed in most studies of dentalattrition among foraging groups, which are attributed toanterior loading, heavy overall wear and flat wear molarwear planes.Differences in occlusal surface wear have been shown

to generally correspond with subsistence practicesamong pre‐industrial populations (Molnar, 1971; Smith,1984; Larsen, 1997; Kaifu, 1999; Kieser et al., 2001;Deter, 2009; Fujita & Ogura, 2009; Liu et al., 2010). Theobservation that coastal groups exhibit more extensiveposterior tooth wear lends support, at least superficially,to dietary specialisation and the premise that coastalgroups were more heavily invested in marine foraging.However, most studies identify that foragers exhibitgreater anterior tooth wear relative to molar wearcompared with agricultural groups (Molnar, 1971;Smith, 1984; Kaifu, 1999; Deter, 2009), the reverse ofwhat was observed in the coastal samples examined inthis study. Greater anterior loading is commonlyassociated with using the front teeth for tool fabricationamong foragers (Macchiarelli, 1989; Larsen, 1997), butthe Azapa coastal sample lacks heavy anterior wear andevidence of task‐specific wear.Heavier and flatter tooth wear is also fundamentally

associated with the particularly tough nature ofconsuming minimally processed foraged resources(Molnar, 1971; Smith, 1984; Larsen, 1997; Deter,2009). Our results not only certainly identified heavierwear among the residents of the coast from the lowerAzapa Valley (similarly for the early phase) but alsodetermined that they exhibited steeper molar wearangles more similar to agricultural groups consuming asoft, heavily processed diet, largely the result of greatertooth‐on‐tooth contact. Unlike tougher fibrous dietscommon to terrestrial foragers, foraging aquaticresources (Yesner, 1980) has been shown to createvariable, less predictable patterns of tooth wear(Walker & Erlandson, 1986; Macchiarelli, 1989;Littleton & Frohlich, 1993). The patterns of dentalattrition observed in coastal samples (and early phase)in the lower Azapa Valley samples are similar to thosedocumented among coastal groups in other parts of theworld (Walker & Erlandson, 1986; Macchiarelli, 1989;Littleton & Frohlich, 1993).We propose that a marine diet can be a variably

tough—or simultaneously soft and gritty—and canlead to more unpredictable tooth wear including heavywear, at variable rates, and greater molar wear angles(Macchiarelli, 1989; Littleton & Frohlich, 1993). Forexample, crustaceans, shell fish and meat from seamammals provide considerable resistance duringmastication, whereas meat from fish and sea urchin


provide almost no resistance and promote contactbetween opposing tooth surfaces. In addition, grit andusing teeth for processing hard components of the dietsuch as shells and fish bones can contribute to damageof the tooth crown and enamel chipping (Scott &Winn, 2011) as also demonstrated to be morecommon among the coastal residents of the lowerAzapa Valley.Another possible explanation for the patterns of

tooth wear observed in the lower Azapa Valley samplescould lie in the integration of agricultural products andfood processing technology that accompanied thebeginning of the Formative period in the region. Theaddition of domesticated cultigens to existing foragingsubsistence strategies increased carbohydrate consump-tion and created an increase, although minor, in theincidence of caries compared with the preceding coastalArchaic groups (Kelley et al., 1991; Watson et al., 2010).The relationship between dental caries and tooth wear isstill unclear, but Larsen (1997) suggested that groupswith high attrition rates often have low caries rates.Hillson (2002) was more cautious and advised that thisdoes not necessarily indicate a causal relationship.Populations with heavy attrition have been shown tomaintain greater frequencies of cervical caries, an areathat attrition is less likely to effect. This was not foundto be the case in the lower Azapa Valley where theresidents of the valley interior had significantly higherrates of cervical caries than the residents adjacent tothe coast (Watson et al., 2010). Occlusal attrition hasthe potential to remove fissure caries, but the normalprogression of fissure lesions is rapid and attrition canoften do little to prevent them. Although therelationship between dental disease and tooth wearis still unclear, the possibility does exist that a changein dietary proportions could have functioned tosimilarly alter wear patterns among the residents ofthe lower Azapa Valley, particularly with those livingalong the coast.In a study of oral pathology and dental attrition in

prehistoric groups along the Arabian coast, Littleton& Frohlich (1993) identified distinctive patternsamong groups practising mixed subsistence econo-mies. These were additionally unique from patternsobserved in dedicated coastal foragers and laterintensive farmers. They noted (i) high–moderaterates of attrition, calculus and abscesses, and low ratesof caries and antemortem tooth loss among mixedfisher–agro‐pastoralists; and (ii) low–moderate rates ofattrition and high rates of caries, calculus and abscesseswith severe antemortem tooth loss among mixed fisher–farming populations (Littleton & Frohlich, 1993). In bothcases, the practice of a mixed subsistence economy



resulted in reduced and more variable attritioncompared with the dedicated fishers. It is mostinteresting that the pattern observed among Arabianfisher–agro‐pastoralists closely mirrors that observedamong the fisher–agro‐pastoralists of the Formativeperiod in the lower Azapa Valley (Watson et al., 2010).Changes in subsistence technology, such as the

introduction and use of ceramics, as well as dietarycomposition could have played an equally importantrole in altering wear patterns during the Formativeperiod along the coast. Crude ceramic vessels areintroduced relatively early in the Formative periodalong with the suite of domesticates (Rivera et al.,1974; Santoro, 1980b, 1980c; Muñoz, 1989, 2004;Rivera, 1991). New technology in food processingusing ceramic vessels, even within the confines ofmarine foraging, would certainly affect grit contentand food consistency. Mølleson et al. (1993) andSciulli (1997) found that dental wear rates declinedmarkedly with the development of ceramic cookingvessels. The use of ceramic vessels for cookingdramatically decreases food consistency and causesmore tooth‐on‐tooth contact that functions to createsteeper molar occlusal surface wear planes, such asthose observed in the early phase of the lower AzapaValley. However, it is curious that the angle decreasesin the samples over the course of the Formative period.Although the introduction of ceramic vessels may be acontributing factor to the wear patterns observed here,greater investment in foraging marine resources alongthe coast, as is likely the case among the early‐phasesamples, appears to be a more parsimonious explan-ation in this case.The variability in patterns of dental wear observed

among the residents of the lower Azapa Valley appearsto fundamentally be the result of an extremely dynamicsubsistence adaptation. The variable consistency of amarine diet, perhaps in conjunction with changes infood processing (i.e. the introduction of ceramiccooking vessels), could have produced the heavy wearand steep molar occlusal surface angles observedamong the coastal and early‐phase residents of thearea. The introduction and investment in domesticatedcultigens and animals, while still maintaining aconsiderable degree of reliance on marine resourcesas suggested by bioarchaeological data, could havelimited wear rate and angle among residents of thevalley interior (and the late phase) while simulta-neously creating more dental decay. What is mostlikely in both cases is that the variability in wearobserved among these groups can be specifically relatedto the amalgamation of a marine–agro‐pastoral econo-my. It is important to also note that the Andean coast is


the only location in the Americas where thesecircumstances occur. The remaining shoreline of theAmericas lacked investment in pastoralism. It is alsolikely that the interplay of investment in these variedresources changed over the course of the Formativeperiod, and as control over, and of, these resources (oldand new) stabilised, groups in the lower Azapa Valleycanalised production roles in their respective niches bythe later phase.

Conclusions

This study used wear scores from 200 Formative periodindividuals from the lower Azapa Valley along thenorthern Chilean coast to test the hypothesis that,concomitant with differences in dental pathology,occlusal surfaces would wear faster and exhibit flatmolar wear in coastal groups consuming greaterquantities of foraged foods, compared with slowerwear rates but more angled molar wear among valleyinterior groups consuming greater quantities of agro‐pastoral products. Differences in overall wear patternsbetween coastal and valley interior locations and inmolar wear plane were observed between the early andlate archaeological phases. Traditional explanatorymodels failed to encompass the multidimensionalpatterning identified in the data. Initially, the resultsdo not appear to support significant differences intooth wear by site location, and we reject ourhypothesis. However, these results are significantbecause they indicate a great deal of complexity tothe interaction between tooth wear, dental disease anddiet, particularly among groups that regularly exploitmarine resources.People living along the Andean coast practised

stable marine foraging for several thousand years priorto and after the Formative transition. However, theintroduction of agriculture added new dimensions andresources for exploitation in existing subsistencesystems. There are clear links between coastal andvalley interior groups, with little distinction for theduration of the Formative period. Both groupspractised a mixed subsistence economy, utilising therich marine resources along the coast and investing inagro‐pastoral production in the fertile river valleys.Here, we argue that the nuances of tooth wearobserved in the data result from the variability inherentin a marine foraging diet and the incorporation of amore inclusive mixed subsistence adaptation. Moreover,the appearance and use of pottery among coastal groupscould have played an additional significant role inaffecting patterns of wear in these samples.



Acknowledgements

This work was supported by the William J. FulbrightVisiting Scholar Grant, the Commission for theInternational Exchange of Scholars, the FulbrightCommission Chile, the Universidad Tarapaca de Aricaand the Museo Arqueológico San Miguel de Azapa.Study of the collections from Azapa was conductedunder the auspices of the project ‘Túmulos funerarios:Monumentos del paisaje desértico indicadores de laorganización territorial de las poblaciones Formativasde los valles occidentales del norte de Chile y sur delPerú’ (Fondecyt 1085106; Universidad de Tarapacá,Chile). We are grateful to Raul Rocha for producingFigures 1 and 2 and to Misty Fields, Alexis Gray andNathan Harper for providing comments on earlierversions of the manuscript. We would also like tothank the journal editor and the anonymous reviewersfor providing critical review and insightful commentsthat greatly improved the manuscript.

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