Applying Zooarchaeological Methods to Interpret Mortuary Behavior and Taphonomy in Commingled Burials: The Case Study of the Late Neolithic Site of Bolores, Portugal

Applying Zooarchaeological Methods toInterpret Mortuary Behaviour andTaphonomy in Commingled Burials: TheCase Study of the Late Neolithic Site ofBolores, PortugalJ. E. MACK,a A. J. WATERMAN,a,b A-M. RACILA,a J. A. ARTZa,c AND K. T. LILLIOSa*a Department of Anthropology, The University of Iowa, Iowa City, IA 52242, USAb Department of Natural and Applied Sciences, Mount Mercy University, Cedar Rapids, IA 52402, USAc Earthview Environmental, Coralville, IA 52241, USA

ABSTRACT The rock-cut tomb of Bolores in the Portuguese Estremadura dates primarily to the Late Neolithic/Copper Age(2800–2600 BC) and, in a series of recent excavations, has yielded thousands of fragmented, commingledhuman bone specimens. The primary goals of the present study were to determine the minimum number ofindividuals interred in the tomb and to analyse spatial patterns in fragmentation intensity to identify naturaland anthropogenic taphonomic processes. To investigate these research questions, the authors employeda simplified version of an established method in zooarchaeology to the study of human remains. Human bonespecimens were recorded by the presence of osteological landmarks rather than the zones used in similarstudies. This recording system allowed for calculation of the minimum number of individuals (further refinedthrough dental analysis) and generated the NISPs (Numbers of Identified Specimens), minimum number ofelements, fragment counts and landmarks sums essential to the conjoining and fragmentation studies. Frag-mentation analysis led to the identification of four possible use areas in the tomb: two for primary inhumationsand two for secondary deposits created by cleaning out the burial chambers at Bolores. We found that theapplication of multiple zooarchaeological methods to the study of commingled human remains has the poten-tial to provide a more fine-grained understanding of site biography and taphonomy than human osteologicalmethods alone. Copyright © 2015 John Wiley & Sons, Ltd.

Key words: mortuary studies; commingled remains; osteological landmarks; taphonomy; MNI; zooarchaeology;neolithic; Portugal

Introduction

Excavations at the Late Neolithic/Copper Age rock-cuttomb of Bolores (Torres Vedras) were initiated to bet-ter understand the lifeways of Late Neolithic/CopperAge populations of the Portuguese Estremadura duringa period of profound change in the Iberian Peninsula,which included population aggregation, agricultural in-tensification, long distance exchange, craft specialisa-tion and monumental tomb construction (Chapman,2003; Díaz-del-Río & García Sanjuán, 2006; Cardoso,2007). Despite these hallmarks of social complexity,

the collective burials typical of the period have made itchallenging for archaeologists to assess the impact ofthese social and economic changes at the level ofindividuals. Skeletal remains are generally commingledand highly fragmented, and in some regions, such assouthern Portugal, acidic soils result in poor bone pres-ervation altogether. Although published references toBolores exist from the 19th century (Torres, 1861: 23),archaeologists first became aware of the collectiveburial in 1986, when testing was conducted and its LateNeolithic/Copper Age date was determined throughdiagnostic material culture (Zilhão, 1987; Kunst &Trindade, 1990:38–41, Plate 4–5). In 2007, a teamunder the direction of K. Lillios initiated work at the site,and four seasons of excavations were conducted between2007 and 2012 (Lillios et al., 2010; Lillios et al., 2014).

* Correspondence to: Katina Lillios, 114 Macbride Hall, Department ofAnthropology, University of Iowa, IA 52242, USA.e-mail: [email protected]

Copyright © 2015 John Wiley & Sons, Ltd. Received 12 August 2014Revised 19 January 2015

Accepted 22 February 2015

International Journal of OsteoarchaeologyInt. J. Osteoarchaeol. (2015)Published online in Wiley Online Library(wileyonlinelibrary.com) DOI: 10.1002/oa.2443

Bolores is a natural, east-facing rock shelter in Jurassicsandstone, which was enlarged to make a more accom-modating burial space. The site is small, approximately5.5m long and 1.5m wide, with a floor-to-ceilingheight of 1.5m. Over time, slabs and stone partitionswere added inside the chamber to divide the space intothree distinct zones: Zones I–III (Figure 1). Elevenaccelerator mass spectrometry radiocarbon dates (BetaAnalytic, Inc., Miami, FL, USA) were obtained from11 different individuals recovered at various depths inthe mortuary deposit. A Bayesian model was imple-mented inOxCal (Bronk Ramsey, 2009), using 1millioniterations on 10 of the radiocarbon dates. These analy-ses returned dates of 2900–2500 BC and represent thefirst phase of the site’s use. One sample, from a subadultfound close to the surface (0–5cm depth), returned a

date of 3530±40 BP (Beta 235487) (1800 BC). Its dateappears to be sound, given that its 13C/12C ratio is notconsistent with bone depletion/contamination (RonHatfield, personal communication 2013). Thus, as inother Late Neolithic/Copper Age sites in the IberianPeninsula, it appears that the site was sporadically usedin the Early Bronze Age, as well.Osteological analysis was hampered by the com-

mingled, fragmentary state of the remains. Standard hu-man osteological data collection protocols (Buikstra &Ubelaker, 1994; Bass, 1995; White et al., 2012), devel-oped primarily for recording largely complete skeletonsfound in discrete contexts, could only be fully appliedto the four partially articulated individuals and thedental remains. In order to better understand the taph-onomic processes and the interactions between the

Figure 1. Map of Bolores tomb, showing stone partitions and Zones I–III.

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Copyright © 2015 John Wiley & Sons, Ltd. Int. J. Osteoarchaeol. (2015)

living and the dead at the site, additional methodsfor determining the minimum number of individuals(MNI) and assessing fragmentation were needed. Toaddress these questions, we turned to zooarchaeo-logical methods which were designed specifically forrecording commingled and fragmentary faunal remains(Lyman, 1994; Morlan, 1994; Grayson & Frey, 2004;Reitz & Wing, 2008). The distinction between thetwo types of analyses lies not only in the state of thematerial to be analysed but in the data produced. Hu-man osteological analyses primarily yield biologicalprofiles and life histories, while zooarchaeologicalstudies yield additional information concerning whathappens to the bodies of fauna in the perimortem andpostmortem periods. These observations allow for amore precise quantification of a highly fragmentedcollection.The method we applied at Bolores does have a pre-

cedent. Outram and Knüsel developed a system forapplying zooarchaeological analysis to both humanand animal remains recovered from the same contextsin order to differentiate between cannibalism, second-ary burial and disturbance of primary burials at VelimSkalka, a Middle Bronze Age ritual enclosure in theCzech Republic (Knüsel & Outram, 2004, 2006;Outram et al., 2005; Harding et al., 2007). The researchquestions at Velim, however, were different from thoseof the present study. Because very little faunal materialwas recovered from Bolores, direct comparison of thecondition of the human remains with contemporaryprocessed animal remains was not necessary. In thispaper, we present a simplified method for applyingzooarchaeological principles to an exclusively humanmortuary context.

The Bolores assemblage

The bone bed within the Bolores tomb is typical ofNeolithic/Copper Age collective burials in the IberianPeninsula (e.g. Carvalho, 2014). The bones at Boloreswere found commingled and fragmented to varying de-grees, with relatively few articulated segments. A fewpartially articulated individuals were identified, as wellas one bone bundle, but the majority of the skeletalelements were not found in anatomical position or inany anthropogenic arrangement that was discerniblein the field. Despite fragmentation, the human remainsdisplay relatively good preservation of the mineral con-tent of the bone, which is likely related to the calciumcarbonate content of the soil in which they were bur-ied. Although most of the site was excavated to theshale floor, approximately 20% of the original bone

bed remains unexcavated due to safety concerns re-garding the unstable roof overhang.In all, 5773 human bone specimens were recovered

at Bolores. Due to post-depositional processes, mostspecimens were not intact and were recovered ascollections of fragments (31793 fragments total). Thenumber of specimens identifiable to bone element is4765 (82.5%); the remaining 1008 human specimensare classified as ‘indeterminate’ (11.3%) or ‘long bone’(6.2%) fragments.

Methods

General

Basic identification of the collected bone specimensoccurred in the field, at which time specimens wereassigned catalogue numbers preserving provenience in-formation. In the laboratory at the University of Iowa,these numbers were entered into a database along withall available information, including field notes, frag-ment count and weight. Specimens were identified asto element, side and adult/subadult, with age and sexestimates recorded where possible. All fully fused orgenerally ‘adult-sized’ bone fragments and all perma-nent teeth with closed root apices and blunting ofcusps were classified as adult. Deciduous teeth, unde-veloped permanent teeth, bones with unfused portionsand all bones that were clearly too small to be adultwere classified as subadult (newborn to 20 years).Subadult age-at-death was calculated by dental devel-opment (Schour & Massler, 1941; Smith, 1991;AlQahtani et al., 2010), by epiphyseal fusion ordiaphyseal length (Scheuer & Black, 2000; Baker et al.,2005) or by comparison with France Casting’s GrowthSeries #SA350 (perinatal, 0.5–1.5 years, 1–2years and7.5–8.5 years). Because many elements finish fusing inmiddle to late adolescence, it is possible that somebones from 14–20-year-olds were incorrectly assignedto the adult category.Each entry for identified specimens also included

coding for the presence or absence of certain portions.In human osteological studies, fragmented specimensare usually recorded by the presence of large segments,for example, distal epiphysis and proximal third ofdiaphysis (Buikstra & Ubelaker, 1994), with additionalnotes providing more detailed but non-standardisedinformation. In order to create a more comprehensive,standardised recording system for the Bolores collec-tion, we modified the approach developed by Knüsel& Outram (2004). In their integrated approach to mixedhuman and faunal assemblages, they divided each

Applying Zooarchaeological Methods to Interpret Mortuary Behaviour


element into between 3 and 15 ‘zones’ and recorded thenumber of zones present on each specimen. However,direct comparisons between human and faunal bonewere not necessary for the Bolores study. For the pur-pose of documenting an exclusively human assemblage,elements were coded primarily for the presence of land-marks, which can be quantified less subjectively thanzones. These landmarks were selected from the stan-dard anatomical features listed in human osteologyand anatomy textbooks, such as the styloid processof the ulna (Gray, 1989; White et al., 2012). Thechosen landmarks (Figure 2, Figures S1–S29) are dis-tributed across the entire element, and the majority ofthe landmarks are relatively invariable in expressionand discrete, such as tubercles, articular surfaces andprocesses. Other anatomical sections that are not truelandmarks but which have clearly defined boundaries(e.g., the lateral border of the scapula) were also coded.In addition to these discrete bone features, a few fea-tureless but recognisable long bone shaft segments werealso coded as ‘landmarks’, similar to the ‘portions’ inMorlan’s (1994) bison bone study.For each element, the landmarks were coded as pres-

ent or absent (1 or 0). A landmark was coded as presentif more than 50% of the landmark was observed. Land-marks were not assigned to the carpals or tarsals, exceptthe talus and calcaneus. Metacarpals, metatarsals and allphalanges were divided into three portions: base, shaftand head. Teeth were recorded by type, for example,maxillary canine and mandibular first molar. Furtherdetails on the employed recording methods will bepublished in Lillios et al. (in press).

Minimum number of individuals

When data entry was complete, the database was sortedby element, with each category further divided by sideand age class (adult/subadult) before landmarks were

summed. The minimum number of elements (MNE)was determined by establishing the largest numberof non-repeating landmarks, such as femoral heads(Lyman, 1994). The MNI was determined by identify-ing the largest MNE from a single side, with adult andsubadult remains considered separately. The elementsused for these calculations were the cranium (recordedas a single element), teeth, atlas, axis, clavicle, scapula,os coxae, patella, talus, calcaneus, metacarpals, metatar-sals and all long bones. In these analyses, the entiremortuary site was treated as a single continuous fea-ture, as the zones observed within the tomb couldnot be proven closed contexts.The absolute MNI was further refined by physical

inspection of the selected elements. During the con-joining study (see subsequent discussion), all specimensof a single element were examined together and MNEswere recounted, taking unique characteristics such asage, size, robusticity and pathology into account. Wa-terman separately examined and established the MNIfor the dental remains, using groups of in situ or spa-tially related teeth. Duplicate tooth types, overlappingmandibular or maxillary portions, age-at-death estima-tions, provenance and dental morphology were all usedto distinguish distinct individuals in the tomb. Theisolated teeth were identified by the criteria outlinedin White (2012), and supplementary texts—Hillson(2005) and Steele & Bramblett (1988)—were consultedas needed. In order to produce the dental MNI, tabula-tions of distinct, dentally identified individuals werecombined with the isolated tooth counts.

Conjoining study

A conjoining exercise was conducted on a limitednumber of elements, including the humerus, radius,ulna, os coxae, femur, tibia, fibula and calcaneus. Print-outs of landmark coding entries were used as tools to

Figure 2. Right scapula, anterior (left), lateral (middle) and posterior (right) views, with coded landmarks illustrated.

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predict possible refits. When entries in the databasewere sorted by element, it was possible to visualisewhich specimens had complementary, non-repeatinggroups of landmarks by scanning the columns for 1’sand 0’s. Refits of fragments collected together as asingle specimen were not counted in this study, butall refits between separately collected specimens wererecorded. Because all excavated specimens were map-ped with a total station before collection, the distancebetween the findspots of conjoining specimens couldbe calculated using the ‘measure’ tool in ArcGIS (ESRI,Redlands, CA, USA).

Fragmentation analyses

Three methods were used to examine the level of frag-mentation in the collection and the spatial distributionof fragmentation across the site. The data employedfor these calculations—landmark counts, NISPs, MNEsand fragment counts—were generated using the re-cording database. These three calculations allowedus to compare the spatial variations in fragmentationlevels between identified appendicular elements as wellas unidentified fragments. Axial elements (sternum, ribsand vertebrae) were not included in these analyses, be-cause fragmentation due to decomposition of thin cor-tical bone could not be distinguished from breakagecaused by other taphonomic factors.The Percentage Completeness, developed byMorlan

(1994) for zooarchaeological analysis, is calculated bytaking the average number of ‘portions’ (in our case,landmarks) present on each identified specimen anddividing that number by the maximum number of por-tions possible on that element. For instance, a completehumerus has 14 landmarks present. Two recoveredhumeri, one complete and one incomplete, have a totalof 21 landmarks. This figure, divided by the number ofhumeral specimens (n=2), gives an average of 10.5landmarks per specimen. When this average is dividedby the maximum number of possible landmarks (14),the result is 0.75 or 75%.Although Percentage Completeness is a useful index

for illustrating overall preservation and fragmentationwith dispersion, the method is not designed to measurein situ fragmentation. A single humerus specimen, with10 of 14 possible landmarks observable, would be rep-resented as nearly complete, even if the specimen werecollected as 25 fragments. Percentage Completenessdemonstrates how much of each element is present,not how fragmented the elements are.To address the issue of fragmentation more directly,

another index commonly used in zooarchaeologywas employed. This method divides the number of

identified specimens of a given element by the mini-mum number of that element present, NISP:MNE(Lyman, 1994). Because the Bolores ‘specimens’ arenot usually single fragments but, rather, collectionsof fragments found together in situ, the index wasadapted slightly. The number of fragments makingup the NISP was divided by the MNE for each ele-ment. The larger the resulting number, the higherthe level of fragmentation. In order to evaluate break-age patterns across and between zones, one-way anal-ysis of variance and Kolmogorov-Smirnov statisticaltests were employed to test the data from both thePercentage Completeness and the Fragmentation In-dex calculations.Both of these calculations are biased in that they

only incorporate data from identified specimens. Mean-while, the bones experiencing the highest degree offragmentation are rendered unidentifiable. FollowingOutram’s (2001) recommendation that indeterminatefragments should not be ignored, these were also exam-ined. They were sorted by size class, based on maxi-mum dimension, and counted. The size classes usedwere 0–20, 21–40, 41–60, 61–80, 81–100 and 100+mm. The counts were summed first by arbitrary excava-tion unit and then combined according to zone.

Results

MNI

The adult MNI derived from the database is 19, basedon the presence of adult maxillary left first incisors(ULI1s). The left calcaneus provides the second high-est count, with two landmarks (the posterior talar sur-face and sustentaculum tali) occurring 15 times each.The subadult MNI was also calculated from dentalremains; 13 mandibular left deciduous 2nd molars(LLdm2s) were recovered from the site. The highestcount of subadults derived from postcranial remains iseight, based on the left femoral neck.The total MNI calculated from cranial and postcra-

nial landmarks (n=23) was considerably lower thanthe MNI derived from the counts of tooth types(n=32). During the physical examination of bonesperformed for the conjoining study, the postcranialMNEs of the humerus, radius, ulna, os coxae, femur,tibia, fibula and calcaneus were recalculated. Althoughthe minimum numbers were increased for many ele-ments (Figures 3 and 4), only one individual was addedto the postcranial MNI, a subadult represented by adistal left femur portion, which, based on size, didnot match any of the counted femoral necks.



Dental grouping did not increase the adult MNI butdid identify the presence of 17 subadults including 13children (0–10 years) and 4 adolescents (10–20 years).The discrepancy between this number and the 13 sub-adults represented by LLdm2s may be explained by thepresence of older children and adolescents who hadlost deciduous second molars premortem but were stillidentifiable in the collection by the underdevelopmentof permanent teeth. The MNI calculated from group-ing the dental remains is 36.

Conjoining study

For the purpose of this study, we counted only defini-tive conjoins between separately collected specimensand did not include refits among fragments collectedtogether as a single specimen. The total number ofrefits identified is 85, with 32 in Zone I, 19 in ZoneII, 32 in Zone III and two refits found betweenunprovenienced specimens. Although some refittingfragments were found as far apart as 25 cm, the vast

Figure 3. Adult minimum number of elements (MNE) values for the long bones, ossa coxae and calcanei.

Figure 4. Subadult minimum number of elements (MNE) values for the long bones, ossa coxae and calcanei.

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majority of conjoining specimens were found within1cm of one another, horizontally (Figure 5). In mostcases, these conjoining fragments were not recoveredtogether in the field due to a slight vertical separation,which caused the specimens to be collected in separatelots, sometimes during separate field seasons. Theseclose refits, like the fragments that were collected to-gether as single specimens, indicate breakage in situafter deposition. Only 12 refits suggest movement ofremains further than 5 cm after fragmentation. Interest-ingly, no refits were identified between zones.

Fragmentation analyses

The Percentage Completeness was first calculated for10 elements—humerus, radius, ulna, metacarpal, oscoxae, femur, tibia, fibula, calcaneus and metatarsal—with no separation by location, to get a baseline forcompleteness across the site. The resulting numbersare quite low. The major long bones do not exceed30%. The metacarpals and metatarsals are the mostcomplete bones, at around 60%.When the specimens were separated by zone, a pat-

tern appeared to emerge (Figure 6). For all elements,the specimens from Zone I are much less completethan those from Zone II, with those from Zone IIIfalling somewhere in between. This finding correlateswith the field observations made by the excavators.The Fragmentation Index was calculated by zone

for the same elements, and the spatial pattern offragmentation appeared similar, although less uniform(Figure 7). Zone I humeri, radii, ulnae, metacarpals,

femora, calcanei and metatarsals all exhibit at least amarginally greater level of fragmentation than the sameelements recovered from other zones. Zone II elementsare less fragmented than the bones from both otherzones, except for the humeri, ossa coxae and calcanei.The ambiguity of the data produced by the Frag-

mentation Index calculations may reflect the distribu-tion of breakage at the site more accurately than thepreservation patterns suggested by the completenesscalculations. While the data shows that Zone II hasthe highest level of completeness and Zone I has thelowest, when the general completeness and fragmenta-tion findings were tested within and between zonesusing one-way analysis of variance, no statistically sig-nificant differences were found in the breakage patterns(completeness F=2.339, p=0.116; fragmentationF=0.690, p=0.510). . Next, the Kolmogorov-Smirnov

Figure 5. Range of horizontal distances between refitting bone frag-ments. The vast majority of refitting specimens were found within1 cm of one another.

Figure 6. Percentage completeness values for long bones, ossa coxaeand calcanei, divided by Zone of recovery.

Figure 7. Fragmentation index values for long bones, ossa coxae andcalcanei, divided by Zone of recovery.



test was used to look for significant differences in thecompleteness and fragmentation patterns for differentskeletal elements recovered from the three zones, bycomparing distributions. Again, no significant differ-ences were detected between zones using this method(completeness, Zone 1 vs Zone 2: p=0.11, Zone 2 vsZone 3: p=0.11, Zone 1 vs Zone 3: p=0.975; frag-mentation, Zone 1 vs Zone 2: p=0.675, Zone 2 vsZone 3: p=0.975, Zone 1 vs Zone 3: p=0.975).Sorting indeterminate fragments by size yielded

limited information for the Bolores collection, as thevast majority (87%) was found to be less than 20mmin diameter. This finding was consistent across thezones and simply indicates that analysts were ableto identify most fragments over 20mm. The simplecounts of indeterminate fragments by zone support

the field observation that the remains in Zone I weremore highly fragmented than those in other areas;Zone I produced more than twice as many indetermi-nate fragments (n=9553) as either Zone II (n=3477)or Zone III (n=4729).Fragment counts were then summed by excavation

unit (eliminating those specimens which could not beassigned to a specific unit), and another pattern emer-ged (Figure 8). Units 1 and 16/17 yielded the highestnumbers of indeterminate fragments. These two unitsare found in the back corners of the cave, at the northend (Zone I) and south end (Zone III), respectively.When the indeterminate fragments of Unit 11, also inZone III, are divided between the northern and south-ern halves of the unit, the southern total is nearly twiceas high as the northern.

Figure 8. Map showing number of indeterminate fragments collected from each excavation unit. The highest numbers of fragments were found inUnit 1 and Unit 16.

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Discussion

Determination of MNI

The MNI calculated using the database of coded cra-nial and postcranial landmarks was refined by visualexamination of selected elements during the conjoiningexercise, with one subadult individual added to thecount. The general congruence of the results confirmsthat the landmarks selected for this study are effectivefor the tabulation of MNI. Not surprisingly, some ofthe MNEs that resulted from the visual inspection rep-resent a substantial increase over the database-derivednumbers. While some specimens were added to thecounts based on the expected distinguishing factors,such as size and robusticity, others were added due tothe presence of repeating portions that were not coun-ted as landmarks in this study.For the femur, the identifiable portion that is most

often preserved (13 right) is the area where linea asperatransitions into the gluteal tuberosity and meets withthe spiral and pectineal lines. Some shaft segments withthis portion include less than 50% of both linea asperaand the gluteal tuberosity and thus were not coded forthis area being present at all. Similarly, the identifiableportion that is most often preserved on the humerushas no formal osteological designation. The repeatingportion is the flat spot on the posterior surface of thedistal end, an area that was not counted in coding whenpreserved with less than 50% of the supracondylarridges or olecranon fossa. Although the increase inMNE for these two elements did not change the MNIin this case, it would be useful to add the two notedportions to the list of landmarks for future studies, be-cause both portions are easily recognised, and, havingrelatively dense cortical bone, are likely preserved inother fragmented collections. Three other recognisablelandmarks that were not coded but which slightly in-creased the MNEs were the neck of the fibula, thesupinator crest of the ulna and the oblique line of theradius. These additional landmarks are shown circledon the landmark coding illustrations in the SupportingMaterials.Ultimately, the MNI was determined from dental

remains, which yielded significantly higher numbers.The disparity between the results is particularly strikingfor the subadults, as the dental MNI is almost doublethe number of individuals identified by long boneanalysis. This finding is not surprising, because teethsurvive inhumation well, and even in undisturbed indi-vidual burials, the dense enamel of the crowns is oftenbetter preserved than the postcranial remains of sub-adult skeletons (AlQahtani et al., 2010). However, the

higher dental MNI cannot be solely attributed to differ-ential preservation. Subadult teeth allow for more fine-grained age estimation, and thus greater differentiationbetween commingled individuals, than is possible withfragmented postcranial remains. For these reasons,zooarchaeologists commonly rely upon dental remainsto construct subadult mortality profiles (Gillis et al., 2014).The disparity for adult remains, although less mark-

ed, suggested several possibilities. Some individualsmay have been brought to Bolores in an incompletestate. The deposition of isolated crania could explainthe higher proportion of teeth among the remains. Al-ternately, bones may have been removed from the siteover time, as part of cleaning and maintenance or forritual purposes. Both of these practices are known fromLate Neolithic/Copper Age burials in the Iberian Pen-insula (Gibaja et al., 2012). Loose teeth could have beenleft behind by these activities. The inconsistencies inthe MNIs might also be due to recovery and analysisbias. Because 20% of the cave remains unexcavated,much of the ‘missing’ material may still be on site. Ad-ditionally, the unaccounted for long bones may simplyhave been rendered unrecognisable by fragmentationprocesses that the smaller, more durable teeth survived.To determine whether or not any elements are

disproportionately represented in the collection, theMNEs were compared with the number of elementsthat should be present, given an MNI of 19 adults.Subadults were not included in the Bone Representa-tion Index (Figure 9) calculation due to the generally

Figure 9. Bone Representation Index based on adult MNI of 19.



https://www.researchgate.net/publication/227847876_The_London_Atlas_of_Human_Tooth_Development_and_Eruption?el=1_x_8&enrichId=rgreq-272ac3cc-ee65-4a26-986f-2cd0da796293&enrichSource=Y292ZXJQYWdlOzI3Mjg5MDQ5MjtBUzoyMjEwNzQ1OTY4NjQwMDBAMTQyOTcxOTY5OTE2Mw==

incomplete preservation of immature remains. Around70% of the adult crania, humeri and tali that shouldhave been present were identified in the collected ma-terial. While the crania would be highly representedin the first proposed scenario earlier, and the humeriwould be equally represented if bone bundles weredeposited in the cave, the high number of tali suggestscomplete inhumations. The fact that metacarpals,metatarsals and hand phalanges are represented in sim-ilar proportions to the long bones also points to com-plete bodies, as these labile articulations are less likelyto persist long enough for the elements to appear insecondary burials (Duday, 2011; Knüsel, 2014). Mean-while, the elements with the lowest percentages ofrecovery are mainly those of the axial skeleton, ele-ments with thin cortical bones that preserve morepoorly under any burial conditions. Although remains

may have been removed from the cave during cleaningepisodes, there is nothing in these numbers to suggestthat specific elements were being preferentially taken.Overall tooth representation was not incongruous withthat of the other elements; just over 50% of the maxi-mum number of teeth (693 of 1312) were recovered.

Fragmentation and spatial analysis

Heavy fragmentation is common in commingled mor-tuary contexts and is typically presumed to be caused,in part, by the movement of bones by ancient peoplesas part of their ritual activities or in making room fornew burials. Two other processes to which fragmenta-tion is often attributed—animal scavenging and inten-tional bone breakage—were eliminated as possibilitiesas Bolores. No rodent gnaw marks or obvious carnivore

Figure 10. Map of Bolores tomb showing Zones I–III and possible Zone IV.

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puncture marks were found on the bones. Intentionalbreaking of bones as part of mortuary activity seemsunlikely, as no anvil abrasions or percussion marks wereidentified during analysis.Although fracture type was recorded in the work

by Outram (2001) and Outram et al. (2005), this in-formation was not recorded during our analysis. Over-all, though, analysts observed no perimortem or freshbone fractures and noted that relatively few fracturesexhibit characteristics of bone breaking while somecollagen still remained. The majority of breakage ap-pears to have occurred on mineralized bone with littleor no collagen. Given the prevalence of mineralizedfractures, the close proximity of most conjoiningspecimens and the fact that no refits were identifiedbetween zones, it seems likely that much of the frag-mentation of identifiable bones occurred in situ, at thelocation where the bones were last deposited.Because the breakage appears to have occurred after

the bones were deposited in the tomb, the spatial dis-tribution of fragmentation can inform us about mortu-ary behaviour within that space. Field observationssuggested that Zone I, with its completely disorderedremains, was distinct from Zones II and III, which eachheld two articulated individuals in addition to com-mingled remains. The lack of statistically significantdifferences in fragmentation patterns between the threezones suggests that, although Zones II and III heldrelatively complete skeletons, the remainder of theidentifiable elements from those two zones exhibitedfragmentation similar to that in Zone I. This breakagemay be related to the activities that resulted in thedisarticulation of individuals previously placed in theburial chambers.Given that a larger amount of skeletal material in

Zone I was rendered unidentifiable due to fragmenta-tion, as demonstrated by the higher indeterminate frag-ment count, it is possible that this area was used as arepository for materials cleaned out of the central andsouthern burial chambers (Zones II and III). Due to thelack of refits identified between zones, however, it seemsmore likely that the remains in Zone I were simply sub-jected to a greater amount of movement/reordering.The uneven distribution of unidentified fragments inZone III, with a higher concentration in the southernportion, may also be due to the presence of a secondarydeposit area. The remains of individuals previously in-terred in Zone III may have been pushed against thesouthern wall during tomb cleaning activities, thus cre-ating a fourth zone or usage area similar to Zone I. Thishypothesis is supported by the fact that the only longbone bundle at the site was found in the southern endof Zone III (Figure 10).

Conclusions

Although the MNI for Bolores was determined throughin-depth analysis of the dental remains, the landmarkcoding system was found to offer several benefits.The method is fast and simple enough that studentscan assist in the time-consuming task of coding largecollections (excluding cranial and subadult remains).Specimen by specimen entry is more practical thantrying to sort a large collection by element in the lab,particularly when the originating site has no discretefeatures. Furthermore, the collected data—tallies oflandmarks, and NISP and MNE values—can be usedfor conjoining and fragmentation studies.One of the consistent characteristics of Late Neo-

lithic collective burials is extreme fragmentation. In or-der to interpret mortuary behaviour at Bolores andsimilar sites, it is essential that we understand the na-ture and the spatial distribution of this fragmentation.The application of zooarchaeological methods to thecollection allowed us to focus on taphonomic alter-ations of the individuals (rather than life histories),which in turn allowed us to make inferences aboutthe use of the mortuary space and the actions of the liv-ing community that interred their dead in the tomb.Future work could include the re-analysis of remainsfrom previously excavated Iberian mortuary sites (in-cluding caves and megaliths) and the comparison offragmentation levels to determine use of space in otherburials and whether or not rock fall makes a significantcontribution to bone fracturing. Although the use ofGIS data from Bolores permitted fine-grained spatialanalysis, material from older excavations could be usedfor a similar study, provided that specimens have suffi-cient provenience information.The application of multiple zooarchaeological me-

thods to the study of human remains offers a morefine-grained understanding of site biography and ta-phonomy than standard osteological analysis alone.Such a strategy offers the possibility of insights intosequence and ritual practice at ancient burials and,thus, knowledge of the diverse and intimate ways thatpeople in the past interacted with their dead. This isparticularly significant for studies of the Neolithic ofWestern Europe. The collective burials typical of thetime tend to be associated with aggregated interpreta-tions of their burial populations and, indirectly, anotion that these sites reflected an emphasis on com-munal identities (over individual identities). By inte-grating knowledge of ritual practices and taphonomichistory with traditional bioarchaeological methodsfocused on biographies, we can gain a more nuancedunderstanding of the culturally variable ways that social



difference was marked at death at the level of theindividual.

Acknowledgements

We are grateful for the support provided by the Na-tional Science Foundation (#1153568) and the Univer-sity of Iowa Social Science Funding Program andInternational Programs. We appreciate the advice andinput given to us, at different stages of this research,by Alan Outram andMatthewHill. We are also gratefulto the many students who helped with the study of theBolores remains, including Lily Doershuk, Leslie Nemo,Laura Ruebling, Tyler Perkins and Katie Thompson.

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Applying Zooarchaeological Methods to Interpret Mortuary Behavior and Taphonomy in Commingled Burials: The Case Study of the Late Neolithic Site of Bolores, Portugal

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