Part-time farmers or hard-core sealers? Västerbjers studied by means of stable isotope analysis

Journal of Anthropological Archaeology 23 (2004) 135–162 www.elsevier.com/locate/jaa

€sterbjers Part-time farmers or hard-core sealers? Va studied by means of stable isotope analysis Gunilla Eriksson* Archaeological Research Laboratory, Greens villa, Stockholm University, S-106 91 Stockholm, Sweden Received 30 May 2003; revised 15 September 2003 Available online 27 February 2004

Abstract A case study of the Pitted-Ware site of V€asterbjers on Gotland in the Baltic Sea forms the starting point for a discussion on the cultural identity, economy, and chronology of this culture. Extensive and detailed stable isotope data on both the prehistoric fauna (87 samples from 20 faunal species) and human remains (65 samples from teeth and bones of 26 individuals) show that the V€asterbjers population, and most likely the whole Pitted-Ware Culture on Gotland, practised mainly seal hunting but no animal husbandry. The hypotheses that they belonged to the same group who practised farming (i.e., the Corded-Ware culture) can therefore be refuted. The Pitted-Ware Culture on Gotland evidently represented a separate group with a cultural identity of its own, and the seal was an important feature in that identity. Eighteen new radiocarbon dates suggest that the V€ asterbjers cemetery was in use for at least a couple of 100 years, during the period 2900–2500 cal BC, but there is no support for the proposed chronological division of the cemetery into two spatially separate halves. A calculation of the age offset caused by the marine reservoir effect for Middle Neolithic Gotland demonstrates a considerably smaller offset than previously suggested, 70
40 radiocarbon years. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Pitted-Ware Culture; Middle Neolithic; Gotland; Baltic Sea; Burial; Seal hunting; Stable isotope analysis; Palaeodiet; Ecology; Radiocarbon dating; Reservoir effect

Introduction During the Middle Neolithic, when agriculture had already been widely adopted throughout north-western Europe, large groups of fisher–hunter–gatherer people still coexisted in the Baltic region. These groups are generally referred to as representing the Pitted-Ware Culture (PWC)1 or (Pit-) Comb-Ware Culture in the western and eastern parts of the Baltic region, respectively. The PWC * Fax: +46-8-674-73-66. E-mail address: [email protected]. 1 Abbreviations used: ATA, Antikvarisk-topografiska arkivet (Archives of National Heritage Board and Museum of National Antiquities); SHM, Statens historiska museum (Museum of National Antiquities).

people typically inhabited coastal sites, living off seal hunting and other marine resources, but also inland sites in the East Baltic, living off fishing complemented by gathering and hunting. On the large island of Gotland, situated in the Baltic Sea between southern Sweden and Latvia, where preservation conditions for bone, teeth, and antler are particularly favourable because of the calciferous soils, several large PWC sites have been found, comprising extensive cemeteries and adjoining cultural layers. One of these sites, V€ asterbjers in the parish of Gothem, is the focus of this study (Fig. 1). Although the various PWC sites share many features, the ‘‘culture’’ itself remains difficult to define. The people have been described as everything from specialised and exclusive seal hunters to pig-herding farmers occasionally cultivating cereals and keeping cattle and

0278-4165/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jaa.2003.12.005

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G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Fig. 1. Location map showing the area in its Baltic context. The shoreline c. 4200 BP was calculated using a numerical model developed by the Geological Survey of Sweden (Ó Geological Survey of Sweden (SGU), permission 30-270/2003).

sheep (Browall, 1991; Carlsson, 1987; Knutsson, 1995; Lindqvist and Possnert, 1997; Malmer, 2002; Segerberg, 1999; Stor
a, 2001; Welinder, 1971; Wyszomirska, 1984). Their chronological stance vis-a-vis the farming Funnel– Beaker and Battle–Axe (i.e., Corded-Ware) Cultures and their possible interaction with these, are also poorly understood. It has even been questioned whether the Pitted-Ware Culture ever existed other than in archaeologistsÕ minds (Andersson, 1998; Carlsson, 1991, 1998; Edenmo et al., 1997; Persson, 1986). For the purpose of this paper, it will be assumed that the Middle Neolithic people buried at Gotland in fact had some things in common, whether it was a common cultural identity or just a common subsistence pattern. Extensive new stable isotope data and radiocarbon dates will provide an approach to exploring these issues.

Va¨sterbjers and the Pitted-Ware Culture on Gotland The Middle Neolithic graves found on Gotland number at least 180, distributed over several burial sites, usually with associated cultural layers, located mainly along the coasts (Burenhult, 2002; Taffinder, 1998). The most prominent in terms of the numbers of graves excavated are Ajvide, Visby, and V€asterbjers (Fig. 1). These are characterised by flat-grave inhumations, typ-

ically with grave goods such as Pitted-Ware pottery, worked boar tusks, pendants of seal, dog and fox teeth, awls, spears, harpoons and fish-hooks of bone, stone axes, tubular beads of dentalium and cylindrical bone beads (Burenhult, 2002; Janzon, 1974). Seal bone predominates among the faunal remains at most sites, V€ asterbjers being an exception, with its vast amounts of pig bone (Ekman, 1974; Stor
a, 2002). There is no consensus as to whether these should be regarded as domesticated pigs or as wild boar. Due to the excavation techniques, fish bones have been recovered in substantial amounts only at sites excavated during the latter half of the 20th century, but they are likely to have formed a significant portion of the faunal remains at the sites excavated earlier as well. Bones of domestic cattle and sheep/goats have been recovered at several sites, although in low numbers, leading most researchers to infer that some complementary animal husbandry was practised. Gotland was already an island in the early Postglacial, and due to this insularity the wild Stone Age fauna lacked many of the large mammals which are common at other contemporaneous sites, such as red deer and roe deer, elk (moose), and brown bear. There are a few finds of singular cervid bones from the Stone Age, but it is unlikely that these animals formed any permanent population on the island. They may be traces of occasional occurrences of the animals, or else the

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

bone was brought to the island as such (Ekman, 1974; cf. Stor
a, 2000 for a discussion of a similar situation on
€ the Aland islands; Osterholm, 1989). The V€asterbjers site is situated on a gravel ridge that is nowadays located slightly inland from the north-eastern coast of Gotland. In previous research it has regularly € been regarded as an inland site (Janzon, 1974; Osterholm, 1989), but the latest shoreline displacement data (P
asse, 2001) suggest that it was located on the southern shore of a long narrow inlet of the Baltic at the time of the burials (Fig. 1). It comprises more than 50 flat graves, mostly single burials, and extensive cultural layers. The site was first discovered in the late 19th century, when some Stone Age objects were uncovered in a small gravel pit, but the extent of the cemetery and cultural layers was not realised at that time. It was not until the 1930s, when gravel extraction was being pursued on a larger scale, that actual excavations took place. The first 3 years of excavations, during which some 30 graves were uncovered, were conducted first by Erik Floderus and then by Erik Bellander (Bellander, 1934; Floderus, 1932, 1933), after which M
arten Stenberger continued to dig for another 6 years (Stenberger, 1935, 1936, 1937, 1939, 1942), finding another 20 graves. A few additional graves and parts of the cultural deposits were excavated in the 1950s and 1960s in connection with extended quarrying and construction work at the V€asterbjers farmstead (Janzon, 1974). A monograph, The V€asterbjers cemetery (in German), was published in 1943, and the graves excavated later were included in the publication The Middle Neolithic Graves of Gotland (in Swedish) (Janzon, 1974; Stenberger et al., 1943). In addition to graves, the site included several hearths and a few postholes, pits, and ‘‘finding-places’’ (Fig. 2; all the structures, including graves, were numbered consecutively, which explains the high numbers assigned to certain graves). Two areas in the northeastern part of the site with particularly numerous finds of artefacts and of structures interpreted as hut floors were designated as the ‘‘eastern dwelling’’ and ‘‘western dwelling,’’ respectively (Fig. 2). The gravel often made it difficult for the excavators to observe any distinct limits to the graves or other structures. Moreover, it is clear from the original excavation reports that the cultural layers were greatly disturbed by modern agricultural activities (the terms refuse layers, occupation layers, cultural layers or cultural deposits are used here synonymously, not implying any interpretation as to what kinds of activities led to their formation). The cultural layers varied in thickness up to 0.4 m and consisted of dark soil and numerous, mostly unburnt, animal bones, potsherds, and stone artefacts. They were not found over the whole site, and it could not be determined whether they had originally been present throughout. It is clear, however, that where present, the cultural layers were always superimposed on graves and never the other

137

way around. In some areas there were only graves and no hearths or any other structures, whereas in others the latter were intermingled with the graves, or else there were areas with exclusively hearths. The eastern part of the site in particular included several graves which had apparently been disturbed during prehistoric times, and a number of graves were superimposed on others, indicating that there had been nothing to mark the graves on the surface and that the cemetery may have been in use for a considerable time. A conspicuous example is grave 67:1, a double burial with an adult woman and a young child resting on her left arm, carefully laid out but superimposed on grave 67:2, an accumulation of disarticulated bones from an older child and an adult man together with regular grave goods (Fig. 3). Excavation conditions at V€ asterbjers were far from ideal, since archaeologists were not sent for until after the quarrying had already started and some artefacts and human remains had been exposed. Furthermore, the extent of the excavation area was determined each year by how large an area of gravel would be quarried. The full extent of the site has never been established, let alone excavated. Even disregarding potential graves that were never uncovered, it is difficult to define exactly how many graves V€ asterbjers comprises—not only because of damage caused by quarrying and agricultural activities, but also evidently on account of activities during prehistoric times, when human bones were dispersed in the cultural layers. Another problem is that some structures were seemingly without skeletal remains (although ongoing research indicates that some of these may have contained infant bones which were not identified until recently, pers. comm. Torbj€ orn Ahlstr€ om, Department of Archaeology and ancient history, Lund University, Sweden). In summary, at least 60 individuals have been recovered, including three found in connection with the present study. The adult females and males were roughly equal in numbers, while children constituted approximately one fifth of the burials. There is no clear picture of the relationship between the graves and the cultural layers and structures, partly on account of the excavation history of the site, of course, and partly because many researchers have focused completely on the graves, regarding V€ asterbjers solely as a cemetery and either trying to fit the features of the site into that rather static category or completely disregarding the cultural layers and other structures. According to StenbergerÕs (Stenberger et al., 1943) account and interpretation, the occupation layers, though thicker in the centre of the area, were originally of the same extent as the cemetery and were contemporary with the graves. In view of the high number of graves, the frequent hearths and the occurrence of well-developed cultural deposits, he interpreted the V€ asterbjers site as a year-round settlement of considerable longevity. Malmer (1975), on the other hand, treated V€ asterbjers

138

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Fig. 2. Plan of the V€asterbjers site. Adapted from Janzon (1974).

only as a cemetery, dividing it into two halves that allegedly represent two chronological phases, based on the presence of certain artefacts in the graves, the northern, earlier part comprising all the graves containing battleaxes, flint axes, arrowheads of either flint, slate or bone,

or bone plaques, while the graves in the southern, later part were designated as ‘‘poorer’’ and had grave goods consisting of stabbing weapons of deer antler, hollowedged axes, bone awls, and perforated discs of bone (Malmer, 1975) (Fig. 2). Janzon (1974), in her work on

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

139

Fig. 3. The double burial 67:1 was superimposed on grave 67:2, which consisted of the partially disarticulated remains of two individuals. Adapted from Stenberger et al. (1943).

Middle Neolithic Gotland, drew attention to the possibility that the hearths, postholes, and other structures may have formed an important part of the burial ritual. As is evident from the above, there are a number of basic questions regarding economics, chronology, social organisation, and cultural identity which need to be resolved in order to understand the Pitted-Ware Culture on Gotland in general and at V€asterbjers in particular: 1. What was the dietary and economic focus for the V€asterbjers population? 2. Did it differ from that of other Pitted-Ware populations on Gotland, as suggested by the predominance of pig bone at V€asterbjers? 3. Were the pigs wild boar or domestic pigs? 4. Did the people practice animal husbandry? 5. How great was the importance of fish in the diet? 6. For what time was the cemetery in use? 7. Was there a chronological division of the cemetery into a northern and southern part, as suggested by Malmer? 8. What was the chronological and functional relationship between the graves and the cultural layers? 9. Do the Pitted-Ware sites on Gotland represent a separate group of people with their own cultural iden-

tity, or were they merely the hunting and fishing aspects of the Corded-Ware Culture (and of the preceding Funnel–Beaker Culture) during the Middle Neolithic?

Material and methods Three children, 10 female and 11 male adults and two adults of indeterminate sex, altogether 26 individuals, were analysed with regard to stable carbon and nitrogen isotopes (Table 1). These techniques, which have wide applications in archaeology and a number of other fields (for reviews, see e.g., Ambrose and Katzenberg, 2000; Griffiths, 1998; Lajtha and Michener, 1994; Schoeninger and Moore, 1992), are based on the observations that the proportions of the stable isotopes (13 C vs. 12 C and 15 N vs. 14 N) change in response to various physical, geochemical, and biological processes, a fact that can be used to study the dietary or migration patterns of prehistoric humans and animals, for example. The fractionation of stable carbon and nitrogen isotopes is to a great extent dependent on the ecology of the organism, that is, on its environment and position in the food web (or chain).

140

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Table 1 Human samples analysed from V€asterbjers Context

Sexa

Age category

Bone (n)

Quarry W dwelling Grave 2 Grave 3a Grave 4 Grave 6 Grave 11 Grave 12 Grave 20 Grave 24 Grave 31 Grave 32b Grave 61 Grave 63 Grave 65 Grave 66:2 Grave 67:1a Grave 67:2b By hearth 76 Grave 80 Grave 82 Grave 82 ‘‘Findingplace’’ 87 Grave 88 Grave 92 Grave 93

I I M F F F F M F F M M M M M M F I M F M I I

Adult Adult Adult Old adult Young adult Adult Adult Adult Adult Adult Adult Adult Old adult Adult Adult Adult Adult Older child Adult Old adult Young adult Young child Young child

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 2

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

F F M

Adult Old adult Adult

1 1 1

3 2 3

26

59

Total (n)

Teeth (n)

however, so that this difference can be disregarded for the present purposes. The stable isotope analyses are performed on collagen, the predominant protein present in skeletal tissue. Bone is constantly being remodelled during the organismÕs lifetime, and its stable isotope signature therefore reflects the average diet during a period of several years prior to death in the case of adults (although in growing individuals remodelling is apparently faster, see Liden and Angerbj€ orn, 1999 for a review on factors affecting collagen turnover). Teeth, by contrast, are formed early in life, and the dentine (the bony substance of teeth, partly covered by the enamel) is not subject to any collagen turnover, which means that the isotopic signal reflects the diet which prevailed when the teeth were formed, i.e., in childhood (Bada et al., 1990; Hillson, 1996). The dentine of teeth is laid down in angled layers starting from the crown down to the root (Hillson, 1996). All the teeth studied here were sampled at or just below the cervix (Fig. 4). Although this sampling strategy necessarily involved the inclusion of several consecutively formed layers of dentine, it excluded those portions of the dentine formed at the very beginning and end of tooth formation, thereby narrowing down the age

Key. F, female; M, male; and I, indeterminate. Notes. a Osteologically determined by Dahr (Stenberger et al., 1943), revised by Gejvall, 1974. b The skull was marked ‘‘grave 32?’’; NB! reliable stable isotope data were not available for all samples, see main text and Table 5.

Stable isotope values (d13 C, d15 N) are expressed in per mil (‰, parts per thousand), and calculated as ððRsample =Rstandard Þ  1Þ  1000‰, where R is the 13 C/12 C or 15 N/14 N ratio and the standard is PDB for carbon and atmospheric N2 for nitrogen. The d13 C value is higher (i.e., is less negative) in marine ecosystems than in terrestrial or freshwater systems, whereas the d15 N value increases approximately 3‰ for each step in the food chain. Another difference which is of archaeological significance is that between C3 plants (most terrestrial plants in forest and temperate zones) and C4 plants (mostly tropical and subtropical plants, such as millet, sorghum, and maize, a third category being CAM plants, mostly succulents). The C4 plants, like marine organisms, produce d13 C values which are higher than C3 plants because of their particular photosynthetic pathway (Boutton, 1991). There are no records of any C4 plants in the Baltic region during the Stone Age,

Fig. 4. Simplified cross-section of an incisor showing the dentine layering, which starts at the crown. All tooth samples were drilled from the same section of the tooth, just below the cervix, illustrated here by a first molar from the child in burial 67:2b € 56, top) and a third molar from the aged woman in burial (VAS € 45, note the heavy attrition). Adapted and redrawn 80 (VAS from Steele and Bramblett (1988).

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

span represented by each sample. Where possible, samples were taken from the skull bone and the first, second, and third molars of each individual, providing a total of 85 samples in all. Initially only adults were studied, since no skeletal material for children was available. However, since the teeth of adults are indicative of the childhood diet, this in effect expanded the material to include children who survived childhood, a group otherwise severely underrepresented in archaeological data. Moreover, three children came to be included because their skeletal remains were stored together with adult bones, two adults and one child were taken separately from three double burials (graves 66:2, 67:1, and 67:2), and one double burial (grave 82) yielded one adult and one child. Four individuals, three adults and one child, were from contexts which cannot be regarded as closed (the quarry, the W dwelling, the hearth 76 and the ‘‘finding-place’’ 87). The remaining 17 individuals were from single graves (Table 1). In addition to the human samples, 75 faunal samples from V€asterbjers, representing 18 species, and 13 further samples from the PWC site of Ire in the parish of Hangvar on the north-western coast of Gotland, representing five species, were analysed. The Ire site bears a close resemblance to V€asterbjers and consists of 10 excavated graves and adjacent cultural layers. Judging by the grave goods, V€asterbjers and Ire should be regarded as roughly coeval (Janzon, 1974, p. 118ff). The faunal analysis was performed in order to form a baseline record for evaluating and interpreting the

141

human stable isotope data, obtained by measuring those species which were either potentially consumed by humans or could produce isotopic end-values, i.e., maximum or minimum values for carbon and nitrogen. A further motive was to contribute to the discussion surrounding certain species which have aroused particular interest in previous research because of their specific association with the Neolithic people at Gotland, namely the pig, the dog, and the fox. Collagen was extracted from human and animal bones and teeth according to Brown et al. (1988), and the samples were analysed on a Carlo Erba NC2500 elemental analyser connected to a Finnigan MAT Delta+ isotope ratio mass spectrometer run in continuous flow, with a measurement uncertainty of
0.1‰ for both d13 C and d15 N. Collagen extracted from 11 humans and seven animals from V€ asterbjers was submitted for AMS radiocarbon dating (Table 2). Human bones from six graves had been dated earlier (Janzon, 1974; Sellstedt et al., 1967), producing dates ranging between 3765
115 BP (St-4302) and 4084
130 BP (St-4304) (uncalibrated). There were several reasons for dating additional material. One was to gain a better impression of the chronological variation—a larger number of dates can simply give better resolution—and another was to try to determine whether the cultural layers were contemporaneous with all or some of the graves or younger than all of them. Whereas the previous dates had been based on traditional b-decay dating methods, requiring large amounts of bone (c. 100 g), the new dates were produced

Table 2 Radiocarbon dates for human and faunal remains at V€asterbjers Context

14

Grave 4 Grave 12 Grave 24 Grave 61 Grave 65 Grave 67:1a Grave 67:2b Grave 80 ‘‘Finding-place’’ 87 Grave 88 By hearth 76 ‘‘Finding-place’’ 87 Grave 24 Grave 65 By hearth 76 ‘‘Finding-place’’ 87 By hearth 76 W dwelling

Ua-19394 Ua-19402 Ua-19395 Ua-19403 Ua-19396 Ua-19397 Ua-19398 Ua-19404 Ua-19406 Ua-19405 Ua-19399 Ua-19408 Ua-19927 Ua-19832 Ua-19831 Ua-19407 Ua-19400 Ua-19401

C lab ID

Species

Elementa

14

Human Human Human Human Human Human Human Human Human Human Human Grey/harp seal Pig Pig Pig Cattle Cattle Sheep/goat

Tooth Teeth Bone/tooth Bone/teeth Teeth Tooth Bone/tooth Teeth Bone Teeth Teeth Bone Boar tusk Boar tusk Tooth Tooth Bone Bone

4155
55 4125
55 4135
50 4370
70 4260
50 4200
55 4250
50 4340
65 4140
60 4175
55 4290
55 4275
60 4105
45 4140
55 4035
55 3095
65 3160
55 2815
50

Notes. a From which the dated collagen was extracted. b Values reported by the radiocarbon laboratory.

C age (BP)

d13 C (‰)b )14.8 )14.8 )15.4 )14.5 )14.2 )16.3 )15.0 )15.2 )15.3 )14.5 )16.2 )15.9 )21.2 )20.6 )20.6 )20.8 )21.4 )20.3

142

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

by accelerator mass spectrometry (AMS), which requires much smaller amounts (c. 100 mg of bone or dentine, i.e., about 1/1000 of what was needed earlier), thus reducing the harm done to the bones or teeth. It seemed reasonable to date the collagen that had already been extracted for the purposes of the stable isotope measurements. The previous dates had shown fairly large standard deviations, possibly related to the simplified chemical pre-treatment used for bone at the particular laboratory at that time (Edenmo et al., 1997, p. 182). It was hoped that the new radiocarbon dates would narrow these down, thus giving better precision, and hopefully also more accurate dates. The choice of samples for dating was based on the following three criteria: (1) Representativeness. Efforts were made to take samples from as many different parts of the cemetery and the cultural layers as possible, to ensure that various contexts were represented, and finally to make certain that humans of different sex, age, features, manners of deposition, and grave goods were dated. (2) Availability. Collagen samples that had already been extracted were preferred, in order to reduce damage to the bones and to minimize additional timeconsuming extractions. Nonetheless, a few additional samples were necessary to meet the other two criteria. (3) Methodology. One grave that had previously been radiocarbon dated was dated once more with AMS so as to assess the reliability of the previous dates. Moreover, since an earlier analysis of two V€asterbjers individuals (Liden, 1996) had shown a considerable amount of marine protein input in their diets, samples of both human and animal material from what were judged to be closed contexts were dated in order to estimate any age offset caused by the reservoir effect present in the samples and possibly to correct for it.

Results Stable isotope analysis of faunal remains from Va¨sterbjers The results of the faunal analysis are presented in Table 3 and Fig. 5. The faunal bones were generally of excellent quality and produced well-preserved collagen. Only one sample out of 75 yielded an insufficient amount of collagen for stable isotope analysis, a small € 93). The remaining samples yielvertebra of cod (VAS ded between 0.8 and 9.5% collagen (% by weight of whole bone or dentine). The few samples with low yields (below 1%) were deemed suitable for analysis based on their appearance (Ambrose, 1990) and the other quality criteria discussed below (cf. van Klinken, 1999). Atomic C/N ratios varied between 3.1 and 3.5, i.e., they were well within the limits of 2.9–3.6 for unaltered collagen (DeNiro, 1985). The carbon and nitrogen content (carbon 28.8–44.6%, nitrogen 10.2–16.5%) did not deviate

significantly from the normal for collagen from modern bone (Ambrose, 1990), with the single exception of a € 141), in which the carbon sample from a dog (VAS content was 20.7% and the nitrogen content 6.9%, but there were no other indications of diagenesis and both the C/N ratio and the visual appearance conformed to the accepted quality standards. Eleven duplicate samples from marine mammals (seals and porpoises) were treated with chloroform to test whether the elution of possible traces of lipids would affect the stable isotope signatures. Unfortunately, the chloroform proved to be contaminated, which made comparison of the stable isotope values with untreated samples pointless. GC-MS analysis of the compounds eluted in the chloroform, and of both treated and untreated collagen, nevertheless showed that the amount of lipids in the untreated collagen was of the order of 0.1% by weight (Isaksson, 2002), which is so infinitesimal that it is highly unlikely to have affected the stable isotope signature. A previous study of the d13 C differences between lipid-extracted and non-extracted bones demonstrated that the differences were <1‰ for each percent of lipids by weight in whole bone (Liden et al., 1995). Since the proportion of lipids in the collagen measured here would correspond to a maximum of 0.005% in whole bone, the stable isotope difference in this case could be expected to be far below the detection level. Cattle (Bos taurus), horses (Equus caballus), and sheep/goats (Ovis aries/Capra hircus) all had d13 C values between )21.8 and )20.3‰, which is typical of terrestrial herbivores, and the d15 N values ranged between 4.1 € and 5.8‰, apart from one tooth of a sheep/goat (VAS 84), where the d15 N of 8.3‰ is likely to represent a suckling animal. The portion of this first molar tooth that was analysed is formed early in the animalÕs life, and a lactation effect is therefore to be expected (cf. Bocherens et al., 1994; Fogel et al., 1989). The pigs (Sus scrofa) all fell within that same isotopic range, d13 C )21.6 to )20.6‰ and d15 N 4.5–6.4‰, which indicates that this omnivorous species was mainly feeding off plant material at V€ asterbjers, perhaps supplemented with insects and worms. The mountain hare (Lepus timidus; d13 C )22.5‰, d15 N 2.6‰) deviated somewhat from the rest of the herbivores, especially with regard to the stable nitrogen isotope value, which could be due to the particular physiology of lagomorphs (Pehrsson, 1983a,b). The d13 C values for the red fox (Vulpes vulpes) ranged between )20.0 and )18.1‰, and d15 N between 6.6 and 8.6‰, which is consistent with the carnivorous diet of this species, as the nitrogen values indicate one step up the food chain compared with the herbivores, and the carbon values indicate a minor marine influence, suggesting that sea-fowl, or more likely eggs of sea-fowl, or some other ‘‘seafood,’’ could have contributed slightly to their diet. The same goes for another carnivore, the

Table 3 Isotopic data for the V€asterbjers fauna Skeletal element

Context

Lab code

Bone/ dentine (mg)

Collagen (mg)

Collagen (%)

d13 C (‰)

d15 N (‰)

C/N

%C

%N

Bos taurus Bos taurus Bos taurus Ovis aries Ovis aries/Capra hircus Ovis aries/Capra hircus Ovis aries/Capra hircus Equus caballus Equus caballus Lepus timidus

Molar tooth Metacarpus Metatarsus Metatarsus First molar tooth

‘‘Finding-place’’ 87 N of hearth 76 N of hearth 76

€ VAS € VAS € VAS € VAS € VAS

171.6 124.4 99.7 103.1 64.8

7.1 11.8 3.6 2.2 2.8

4.1 9.5 3.7 2.1 4.4

)20.8 )21.0 )21.4 )21.0 )20.2

5.1 4.6 4.1 5.8 8.3

3.2 3.1 3.2 3.3 3.3

43.8 44.6 42.9 40.9 42.5

16.2 16.5 15.5 14.5 15.2

Phalanx

€ 85 VAS

54.0

4.2

7.8

)20.3

4.5

3.2

43.0

15.7

Molar tooth

W dwelling, hut floor By hearth 76

€ 89 VAS

77.6

1.3

1.7

)20.3

5.0

3.2

40.8

14.9

(Pre)molar tooth (Pre)molar tooth Tibia

W dwelling W dwelling W dwelling

€ 91 VAS € 92 VAS € 130 VAS

96.7 106.4 95.4

2.1 1.5 4.0

2.2 1.4 4.2

)21.8 )21.8 )22.5

4.6 5.4 2.6

3.3 3.2 3.4

41.7 39.6 44.2

14.9 14.5 15.3

Sus scrofa

Cattle Cattle Cattle Sheep Sheep/ goat Sheep/ goat Sheep/ goat Horse Horse Mountain hare Pig

Mandible

€ 115 VAS

113.1

4.3

3.8

)21.8

4.6

3.3

43.2

15.2

Sus Sus Sus Sus Sus Sus

Pig Pig Pig Pig Pig Pig

Canine Canine Canine Canine Canine Canine

Pig Pig Pig Red fox Red fox Red fox Red fox Golden eagle Pike Pike Pike Pike Pike Cod Perch Indet. fish

Boar tusk Boar tusk Incisor tooth Mandible Mandible Mandible Mandible Ulna

W dwelling, hut floor By hearth 76 By hearth 76 By hearth 76 By hearth 76 W dwelling E and N of hearth 76 Burial 24 Burial 65 By hearth 76 E or W dwelling Burial 5 Burial 67 Burial 22 By hearth 76

scrofa scrofa scrofa scrofa scrofa scrofa

Sus scrofa Sus scrofa Sus scrofa Vulpes vulpes Vulpes vulpes Vulpes vulpes Vulpes vulpes Aquila chrysaetos Esox lucius Esox lucius Esox lucius Esox lucius Esox lucius Gadus morhua Perca fluviatilis Pisces indet.

tooth tooth tooth tooth tooth tooth

Vertebra Vertebra Vertebra Vertebra Vertebra Vertebra Vertebra Fin rays

—

W dwelling

E or W dwelling W dwelling W dwelling N side of hearth 76 E or W dwelling — —

Burial 22

148 97 98 90 84

€ VAS € VAS € VAS € VAS € VAS € VAS

123 124 125 126 127 128

92.3 63.6 68.4 62.8 76.1 75.6

3.0 2.8 1.9 3.5 2.6 2.1

3.2 4.4 2.8 5.6 3.5 2.8

)20.6 )20.8 )20.9 )21.6 )20.8 )21.1

6.2 4.9 5.0 4.5 6.1 6.4

3.3 3.3 3.4 3.2 3.5 3.4

42.3 42.7 43.3 42.4 43.4 42.2

14.9 15.0 14.8 15.3 14.6 14.4

€ VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS

156 157 99 109 110 117 118 129

147.0 132.3 84.0 46.5 71.9 62.5 86.5 96.8

1.7 4.9 6.5 1.3 3.5 1.3 1.9 4.5

1.2 3.7 7.7 2.9 4.8 2.1 2.2 4.7

)21.2 )20.6 )21.2 )18.1 )18.7 )19.5 )20.0 )19.1

5.3 5.4 5.2 6.7 6.6 6.7 8.6 7.3

3.2 3.2 3.2 3.4 3.3 3.5 3.5 3.4

33.4 42.3 39.5 39.6 42.0 39.3 41.0 43.9

12.2 15.3 14.5 13.7 14.7 13.2 13.8 15.2

€ VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS

83 86 87 88 95 93a 94 96

73.2 81.4 50.0 62.5 77.8 92.7 70.5 203.9

1.5 1.8 0.6 1.3 0.8 0.1 0.9 2.3

2.1 2.2 1.2 2.1 1.0 0.2 1.3 1.1

)10.9 )12.1 )13.0 )11.6 )11.7

11.1 10.6 10.6 11.2 11.4

3.3 3.5 3.4 3.2 3.3

37.9 40.5 34.9 38.1 35.8

13.2 13.5 11.9 13.7 12.5

—

—

)14.1 )10.4

9.6 8.2

—

—

—

3.3 3.5

28.8 36.2

10.2 12.2

143

Common name

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Species

144

Table 3 (continued) Species

grypus grypus grypus grypus

Halichoerus grypus/ P. groenlandicus Pagophilus groenlandicus Pagophilus groenlandicus Pagophilus groenlandicus Pagophilus groenlandicus Phocoena phocoena Pusa hispida Pusa hispida Alca torda Mergus merganser Canis Canis Canis Canis Canis Canis Canis Canis

familiaris familiaris familiaris familiaris familiaris familiaris familiaris familiaris

d13 C (‰)

d15 N (‰)

C/N

%C

%N

1.7 0.7 2.1 2.4

2.1 1.0 3.1 2.4

)16.4 )15.7 )16.5 )16.3

13.3 13.9 14.5 13.4

3.4 3.3 3.3 3.2

40.1 40.2 40.4 42.8

13.7 14.1 14.1 15.5

97.1

1.6

1.6

)15.9

12.3

3.4

40.2

14.0

Skeletal element

Context

Lab code

Bone/ dentine (mg)

Grey Grey Grey Grey

Temporal bone Temporal bone Temporal bone Humerus

€ VAS € VAS € VAS € VAS

105 106 112 116

79.1 70.9 66.1 100.1

€ 149 VAS

seal seal seal seal

Collagen (mg)

Grey/harp seal Harp seal

Scapula

E or W dwelling N of hearth 76 W dwelling W dwelling, hut floor ‘‘Finding-place’’ 87

Temporal bone

E or W dwelling

€ 104 VAS

64.8

0.6

0.8

)15.5

14.1

3.3

33.8

12.0

Harp seal

Humerus

N of hearth 76

€ 108 VAS

47.3

1.4

3.0

)15.8

12.5

3.3

38.5

13.7

Harp seal

Temporal bone

W dwelling

€ 113 VAS

50.9

0.8

1.6

)17.2

13.7

3.3

37.5

13.3

Harp seal

Temporal bone

W dwelling

€ 114 VAS

85.5

1.1

1.3

)15.8

16.1

3.2

38.5

13.9

Harbour porpoise Ringed seal Ringed seal Razorbill Common merganser Dog Dog Dog Dog Dog Dog Dog Dog

Temporal bone

N of hearth 76

€ 107 VAS

56.2

2.0

3.6

)15.0

11.4

3.2

39.5

14.3

Temporal bone

E or W dwelling

€ 103 VAS

84.1

1.0

1.2

)15.6

12.8

3.1

36.3

13.4

Metatarsus

E dwelling, K3

€ 122 VAS

68.8

1.7

2.5

)16.6

11.1

3.3

41.6

14.8

Humerus Coracoid

W dwelling W dwelling

€ 145 VAS € 144 VAS

83.1 54.9

3.8 2.3

4.5 4.1

)15.2 )13.0

14.0 12.1

3.3 3.4

43.2 42.3

15.1 14.7

—

€ VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS

49.4 62.5 53.0 96.6 85.7 72.5 72.7 80.6

2.3 4.1 2.3 3.4 3.7 3.4 2.2 3.4

4.7 6.5 4.3 3.5 4.3 4.7 3.0 4.2

)12.0 )15.8 )14.6 )14.2 )14.3 )14.5 )14.2 )15.3

12.7 13.8 13.9 13.8 13.8 13.9 12.5 15.1

3.2 3.1 3.2 3.3 3.3 3.3 3.3 3.3

39.5 38.8 37.4 43.4 42.1 42.0 39.1 43.7

14.5 14.6 13.6 15.3 14.9 14.8 13.9 15.4

Humerus Skull bone Tibia Mandible Mandible Mandible Tibia First molar tooth

N side of hearth 76 Burial 5 Hearth 76 W dwelling W dwelling Burial 6 8 m NE of burial 67:1

100 101 102 111 119 120 121 131

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Halichoerus Halichoerus Halichoerus Halichoerus

Collagen (%)

Common name

Notes. a Insufficient amount of collagen for stable isotope measurement. Bones of the fore end of one dog found together in settlement layers. b

Canis Canis Canis Canis Canis Canis Canis Canis Canis Canis Canis

familiaris familiaris familiaris familiaris familiaris familiaris familiaris familiaris familiaris familiaris familiaris

Dog Dog Dog Dog Dog Dog Dog Dog Dog Dog Dog

Humerus Skull bone Canine tooth Mandible Third incisor tooth First molar tooth Skull bone First molar tooth Skull bone Humerus Molar tooth

Settlement layersb E or W dwelling E dwelling, K3 W dwelling Burial 22 E or W dwelling E or W dwelling W dwelling E dwelling, K3 E or W dwelling Burial 22

€ VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS

132 133 134 135 136 138 139 140 141 142 143

69.1 70.0 61.0 76.7 46.1 66.5 61.6 56.1 76.6 90.3 83.9

3.9 2.6 3.0 2.3 1.7 2.2 2.1 0.9 0.7 3.4 3.5

5.6 3.7 4.8 3.0 3.6 3.3 3.4 1.6 0.9 3.7 4.2

)14.5 )14.4 )14.6 )14.8 )15.4 )13.6 )14.5 )14.3 )15.9 )14.7 )14.5

12.4 13.9 15.3 14.0 15.7 15.8 14.0 15.3 13.4 13.9 15.3

3.3 3.3 3.4 3.4 3.2 3.4 3.3 3.2 3.5 3.3 3.2

44.3 40.9 41.5 40.6 40.2 41.2 41.2 37.2 20.7 42.2 41.8

15.5 14.5 14.4 14.0 14.5 14.1 14.5 13.4 6.9 14.9 15.0

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

145

golden eagle (Aquila chrysaetos), which had comparable stable isotope values, d13 C )19.1‰ and d15 N 7.3‰. It is not unlikely that these two species competed for the same prey to some extent. The d13 C values for the pike (Esox lucius) ranged from )13.0 to )10.9‰, and the d15 N values from 10.6 to 11.4‰, demonstrating the piscivorous nature of this species, which mostly feeds on other fish. Compared with the terrestrial food chains, aquatic (freshwater, brackish or marine) food chains are as a rule longer, and so it is not surprising that the d15 N for the pike is higher than that for the red fox, for instance. Two more fish samples, one perch (Perca fluviatilis) and one indeterminate fish, had lower d15 N values than the pike, 9.6 and 8.2‰, respectively, reflecting a mixed diet of both fish and invertebrates. These samples also extended the d13 C range for fish to a minimum of )14.1‰ (perch) and a maximum of )10.4‰. This latter sample consisted of fin rays deposited beside the feet of the deceased in grave 22, and regrettably could not be determined to species. Considering its d15 N value, it may well represent some kind of bottom feeder such as a flatfish. The total stable isotope ranges for seals were d13 C )17.2 to )15.5‰ and d15 N 11.1 to 16.1‰. Three species of seal were represented: the grey seal (Halichoerus grypus, n ¼ 4), harp seal (Pagophilus groenlandicus/ Phoca groenlandica, n ¼ 4) and ringed seal (Pusa/Phoca hispida, n ¼ 2). One additional sample was from either a grey seal or a harp seal. The considerable isotopic variability among seals (d13 C )16.0
0.6‰, d15 N 13.2
1.4, average
SD) is in all probability a result of their complex feeding and migratory patterns and their prey. Their feeding intensity is highly variable over the year, being lowest during the breeding, mating and moulting periods, i.e., in spring and summer. Moreover, juvenile animals have different feeding habits from older individuals (Nilssen et al., 1995; S€ oderberg, 1974). Whereas grey seals consume almost exclusively fish, the harp and ringed seals also include crustaceans in their diet (Lawson et al., 1995; Nilssen et al., 1995; S€ oderberg, 1974; Tormosov and Rezvov, 1978). The harbour porpoise (Phocoena phocoena) had an intermediate stable carbon isotope value relative to the fish and seals, )15.0‰, which goes well with the fact that the main prey of the present-day Baltic porpoise is known to be herring and cod. The d15 N value, 11.4‰, is somewhat lower than would be expected, although a stable isotope study of present-day Baltic porpoises points to considerable variability in this respect, with values ranging from 13.1 to 17.6‰ (Brandberg, 1999). The fact that fish exhibit d13 C values that are higher than for seals may seem surprising, but it is presumably an effect of their different habitats. The pike is a littoral species, i.e., it lives in the shallow waters close to the shore. From previous stable isotope studies of food webs in lakes, it is recognised that littoral and benthic

146

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Fig. 5. Plot of the faunal isotopic data (mean and SD; V€asterbjers and Ire pooled).

(bottom-living) organisms display elevated d13 C values relative to pelagic (open water) species (France, 1995). Even in freshwater environments some fish may exhibit d13 C values which are seemingly ‘‘marine,’’ although this appears to apply only in large basins (Dufour et al., 1999; Weber et al., 2002). The other birds measured here apart from the golden eagle were the razorbill (Alca torda, d13 C )15.2‰, d15 N 14.0‰) and the goosander (common merganser, Mergus merganser; d13 C )13.0‰, d15 N 12.1‰), with stable isotope signatures comparable to those of seals (razorbill) and carnivorous fish (goosander). Both species are known to feed mainly on fish, a fact that is consistent with their stable isotope signatures. The total number of dog (Canis familiaris) samples was 19, but the possibility cannot be excluded that some individuals were represented by more than one sample, since elements from different locations at the site were analysed. In view of the number of different elements and the isotopic values, one can nevertheless conclude that at least eight dogs were analysed. The dogs had a very clear marine input in their diets, with d13 C values ranging from )15.9 to )12.0‰ and d15 N from 12.4 to 15.8‰. There is a statistically significant difference in d15 N between teeth and bones (p < 0:0001, unpaired t test), in that all the d15 N values for teeth exceed 15.0‰, while no bone d15 N value is higher than 14.0‰. The elevated values for teeth are probably due to a lactation effect. The teeth were sampled close to the cervix, a part of the tooth which is evidently formed during suckling, and they therefore acquired elevated d15 N values caused by the higher trophic level. The stable isotope values for the dogs overlap to some extent with those for the seals, but the d13 C values were higher (less negative) and coincided more with fish such as the cod and herring.

Stable isotope analysis of faunal remains from Ire To improve the interpretation of the stable isotope results, the faunal data were supplemented with some additional samples from the Pitted-Ware site of Ire on north-western Gotland (Table 4, Fig. 1). An especially valuable addition to the data was the incorporation of cod (Gadus morhua) and herring (Clupea harengus) samples from Ire, two species which were potentially important for both seals and humans at V€ asterbjers, but were lacking among the V€ asterbjers faunal collections € 93, available to the present author (or in one case, VAS did not produce well-preserved collagen). The cod (d13 C )13.5
0.5‰, d15 N 11.3
1.3‰) had nitrogen values similar to those of the pike, reflecting partly piscivorous dietary habits, but the carbon values were lower. The herring (d13 C )14.6‰, d15 N 10.1‰) had the lowest (most negative) d13 C values of all the fish species, probably a reflection of its pelagic habitat, while the nitrogen isotope value is consistent with a diet of zooplankton and small invertebrates, occasionally supplemented with small fish. The seals at Ire had isotopic values similar to those reported above. The harp seal (d13 C )16.1‰, d15 N 14.0‰) fell within the same range as for V€ asterbjers, whereas the ringed seal had somewhat higher (less negative) d13 C values on average, )15.2‰
0.4, and similar d15 N values, 12.1
1.4‰. The Ire pigs (d13 C )21.0
0.6‰, d15 N 4.6
1.3‰), with one exception, had lower nitrogen isotope values than those reported for V€ asterbjers, possibly related to the fact that the measurements were made on bone, whereas the V€ asterbjers specimens were mostly teeth, which may have been affected by suckling during formation. On the other hand, this could be merely an effect of the omnivorous diet of this species, which was nevertheless purely terrestrial, as indicated by the carbon isotope values.

12.9 13.4 13.7 14.3 11.4 12.5 12.1 14.4 13.0 10.8 14.7 13.9 13.9 37.0 40.8 42.3 40.3 33.7 34.3 35.2 40.5 36.5 34.6 39.3 39.6 42.3 3.3 3.6 3.6 3.3 3.4 3.2 3.4 3.3 3.3 3.7 3.1 3.3 3.5 6.9 4.2 3.8 3.7 4.3 10.1 9.9 11.4 12.4 13.5 14.0 11.1 13.1 )20.1 )21.2 )21.4 )20.7 )21.4 )14.6 )13.7 )14.0 )12.9 )16.7 )16.0 )15.5 )14.9 Pig Pig Pig Pig Pig Herring Cod Cod Cod Harp seal Harp seal Ringed seal Ringed seal Sus scrofa Sus scrofa Sus scrofa Sus scrofa Sus scrofa Clupea harengus Gadus morhua Gadus morhua Gadus morhua Pagophilus groenlandicus Pagophilus groenlandicus Pusa hispida Pusa hispida

Tibia Tibia Tibia Tibia Tibia Vertebrae Vertebra Vertebra Vertebra Temporal bone Phalanx Innominate Temporal bone

sq 62/S14 grave 2? grave 2 grave 4 sq 96/N2 Grave 4 Grave 4 grave 4 grave 4 sq 62/S14 sq 62/S14 sq 62/S14 Grave 2

IRE IRE IRE IRE IRE IRE IRE IRE IRE IRE IRE IRE IRE

04 06 07 51 52 56 53 54 55 01 02 03 05

63.4 76.8 68.1 75.9 78.3 289.3 131.6 110.3 157.0 82.0 63.6 78.1 64.7

1.5 1.8 1.7 2.1 0.9 2.0 1.3 2.9 1.5 0.8 1.8 2.6 1.4

2.4 2.3 2.5 2.8 1.2 0.7 1.0 2.6 0.9 0.9 2.9 3.4 2.1

d15 N (‰) Common name Species

Table 4 Isotopic data for the Ire fauna

Skeletal element

Context

Lab code

Bone/ dentine (mg)

Collagen (mg)

Collagen (%)

d13 C (‰)

C/N

%C

%N

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

147

Stable isotope analysis of human samples The preservation of the human skeletal material from V€ asterbjers was generally excellent. All 85 samples yielded enough collagen to allow stable isotope measurements. The mass spectrometry stable isotope analyses were run at two laboratories over a period of 3 years, but unfortunately the results from one of the laboratories showed inadequate precision, with inconsistency in replicate measurements, and they are therefore not reported here and were excluded from the statistical analysis. The values did show about the same range as those considered here, however. As a consequence of this, stable isotope data were available only for 67 out of the 85 samples, including two for which the atomic C/N ratio in the collagen was outside the acceptable range of 2.9–3.6, so that these also had to be excluded from the statistical analysis (Table 5, Fig. 6). The remaining 65 samples complied with the quality criteria discussed in the section on faunal data in terms of their C/N ratio and in all other respects. The total ranges for the human samples were )15.8 to )13.4‰ for d13 C and 14.3 to 17.3‰ for d15 N (d13 C )14.8
0.6‰, d15 N 15.7
0.7‰, average
SD). All the isotope signatures were indicative of a massive intake of marine protein, but there were differences within the population. Bone from male adults tended to have slightly higher d15 N values, 15.8
0.5‰ (avg
SD), than bone from female adults, 15.3
0.5‰, although the difference is not statistically significant (p ¼ 0:059, StudentÕs t test, unpaired). Apart from that trend, which should be interpreted with caution, no sex-based differential access to food could be demonstrated. While the bone results reflect the average diet for several years prior to death, it should be borne in mind that the isotope signatures for teeth from adults represent the childhood diet of individuals who survived into adulthood. The specific sections sampled on the first, second, and third molars could be estimated to correspond to three age categories, based on the timing of formation of each tooth section (cf. Fig. 4, Hillson, 1996; Reid et al., 1998). The stable isotope signature of the first molar (M1) would reflect the diet of a young child, aged approximately 2–4 years, that of the second molar (M2) an older child around 7 or 8 years of age, and that of the third molar (M3) an individual in early adolescence, around 13 years of age (Table 6). The ages assigned to each category should be regarded only as approximations, given that the timing of tooth formation varies between individuals and populations, and also because the sampling procedure involved a subjective element. The key point here is not the exact age of each category, but that the age categories are not overlapping, and that they follow in a sequence. Employing these categories, one finds interesting differences linked to age. In general, when infants are

148

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Table 5 Isotopic data for the V€asterbjers human remains Context

Skeletal element

Lab code

Bone/ dentine (mg)

Collagen (mg)

Collagen (%)

d13 C (‰)

d15 N (‰)

C/N

%C

%N

Quarry W dwelling Grave 2 Grave 2 Grave 2 Grave 2 Grave 3a Grave 4 Grave 5 Grave 6 Grave 6 Grave 6 Grave 6 Grave 11 Grave 12 Grave 20 Grave 20 Grave 20 Grave 24 Grave 24 Grave 24 Grave 24 Grave 31 Grave 31 Grave 31 Grave 31 Grave 32 Grave 61 Grave 63 Grave 63 Grave 63 Grave 63 Grave 65 Grave 65 Grave 66:2 Grave 66:2 Grave 66:2 Grave 66:2 Grave 67:1a Grave 67:1a Grave 67:2b Grave 67:2b Grave 67:2b Grave 67:2b By hearth 76 Grave 80 Grave 81 Grave 82 child Grave 82 child Grave 82 child Grave 82 child Grave 82 child Grave 82 adult Grave 82 adult Grave 82 adult

Parietal bone Mandible Parietal bone M1 M2 M3 Frontal bone Parietal bone M1 Parietal bone M1 P2 M3 Parietal bone P2 Parietal bone M1 P2 Parietal bone M1 M2 M3 Parietal bone M1 M2 M3 Skull bone Parietal bone Parietal bone M1 P2 M3 Parietal bone M1 Parietal bone M1 M2 M3 M1 M2 Skull bone M1 P2 (tooth germ) dm1 Parietal bone Parietal bone M3 Skull bone di1 dm1 dm2 M1 (tooth germ) Parietal bone M1 M2

€ VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS

104.9 100.0 68.3 40.6 43.5 58.8 74.9 68.9 46.6 101.3 68.8 41.1 53.6 85.2 40.4 73.3 43.6 44.6 75.2 66.2 67.2 52.6 84.4 39.2 55.8 45.4 70.8 96.6 87.1 63.7 58.4 38.6 67.3 45.8 62.4 59.9 45.6 42.3 67.5 51.9 84.7 54.0 45.3 35.8 86.3 72.1 43.2 159.4 32.5 43.5 46.9 60.0 44.6 54.0 51.4

1.5 1.7 1.5 2.1 1.3 1.0 1.0 1.1 1.0 3.5 3.5 2.1 2.6 1.2 2.3 2.9 1.6 2.0 4.1 1.5 1.9 2.1 1.0 2.5 3.1 2.8 1.3 1.1 0.9 1.0 1.0 0.9 3.4 2.7 1.3 3.4 2.2 2.3 2.6 2.4 3.2 2.8 2.3 1.9 0.7 1.8 1.8 5.0 0.4 0.6 0.7 2.9 1.3 2.6 3.0

1.5 1.7 2.2 5.2 3.1 1.7 1.3 1.6 2.1 3.4 5.1 5.2 4.9 1.4 5.7 3.9 3.6 4.6 5.5 2.2 2.9 4.0 1.1 6.4 5.5 6.1 1.8 1.2 1.0 1.6 1.8 2.4 5.0 5.8 2.1 5.7 4.7 5.4 3.8 4.7 3.8 5.2 5.0 5.2 0.8 2.5 4.2 3.1 1.2 1.3 1.4 4.7 2.8 4.8 5.8

)14.6 )15.7 )14.8 )14.6 )15.2 )15.1a )15.2 )15.5 )15.6 )15.7 )15.3 )15.3 )15.5 )15.3 )14.5 )14.6 )14.8 )14.3 )15.3 )15.4 )14.4 )14.5 )14.6 )14.7 )14.4 )14.5 )15.1 )14.4 )15.4 )15.5 )15.0 )15.1 )17.2a )14.9 )15.2 )14.7 )14.5 )14.4 )14.9 )14.9 )14.1 )14.0 )13.7 )14.3 )15.8 )14.7 )14.7 )14.2 )14.6 )13.8 )14.2 )13.4 )14.5 )14.3 )14.5

16.4 15.2 15.5 15.7 14.5 13.9a 14.6 15.2 14.7 15.6 14.9 16.1 16.2 16.1 15.7 15.1 15.2 15.2 15.6 15.1 15.6 16.3 15.6 15.3 15.6 15.7 16.2 15.9 16.5 15.6 16.3 16.2 15.7a 14.8 15.8 15.4 15.5 15.1 16.3 16.8 15.9 14.8 14.4 17.3 15.6 15.8 15.9 17.1 16.7 17.2 15.7 16.6 16.4 15.6 15.7

3.1 3.5 3.3 3.5 3.6 4.3 3.1 3.3 3.3 3.2 3.1 3.2 3.2 3.1 3.2 3.1 3.2 3.2 3.0 3.0 3.1 3.1 3.2 3.4 3.4 3.4 3.1 3.0 3.1 3.3 3.1 3.3 3.7 3.0 3.1 3.1 3.4 3.4 3.2 3.2 3.2 3.2 3.2 3.2 3.1 3.1 3.2 3.2 3.3 3.4 3.3 3.1 3.2 3.4 3.3

38.1 36.7 39.7 42.7 43.1 53.2 35.7 36.1 33.9 40.8 45.9 38.2 40.7 38.3 41.3 40.2 38.7 38.7 38.4 34.5 40.3 40.5 36.8 43.4 44.2 43.7 36.3 30.6 36.5 32.4 35.3 31.6 45.4 40.6 36.9 46.5 42.4 43.3 41.0 41.1 49.1 40.6 39.2 38.8 34.0 38.9 38.8 44.2 31.1 29.7 32.6 40.1 35.8 44.4 43.4

14.4 12.1 14.2 14.3 13.8 14.5 13.2 12.8 12.1 14.9 17.2 14.0 14.9 14.3 15.1 15.2 14.3 14.2 15.1 13.4 15.2 15.4 13.4 14.8 15.1 15.2 13.5 12.0 13.6 11.4 13.1 11.3 14.2 15.5 13.8 17.2 14.4 14.7 15.1 15.1 18.1 14.8 14.3 14.0 12.6 14.5 14.0 16.0 10.9 10.3 11.6 14.9 12.9 15.3 15.2

01 137 25 36 37 38a 02 66 67 62 51 52 53 04 74 05 58 59 09 08 06 07 10 39 34 35 11 12 16 47 14 46 17a 33 18 40 41 42 81 82 19 56 57 54 24 21 45 150 151 152 153 154 61 30 31

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

149

Table 5 (continued) Collagen (mg)

Collagen (%)

d13 C (‰)

d15 N (‰)

C/N

%C

%N

45.2 79.0

2.3 4.1

5.0 5.2

)14.0 )15.3

16.8 15.2

3.4 3.2

43.9 42.8

15.2 15.6

114.6

3.2

2.8

)15.4

16.0

3.3

42.9

15.4

60.9 48.1 85.4 44.0 41.1 55.3 53.3 44.9 53.5

1.8 2.2 1.5 2.3 2.3 2.1 2.8 3.0 2.5

2.9 4.7 1.7 5.1 5.6 3.7 5.3 6.7 4.6

)14.4 )15.8 )15.8 )14.4 )14.3 )15.8 )15.2 )15.4 )15.2

15.1 15.2 14.9 15.4 15.6 14.9 14.3 14.4 14.8

3.1 3.4 3.2 3.2 3.1 3.2 3.2 3.2 3.2

41.0 43.4 38.6 40.1 40.1 40.2 40.8 40.5 40.3

15.3 15.0 14.2 14.8 14.9 14.5 15.1 14.9 14.9

Context

Skeletal element

Lab code

Bone/ dentine (mg)

Grave 82 adult ‘‘Findingplace’’ 87 ‘‘Findingplace’’ 87 Grave 88 Grave 88 Grave 92 Grave 92 Grave 92 Grave 93 Grave 93 Grave 93 Grave 93

M3 Femur

€ 32 VAS € 147 VAS

Temporal bone

€ 146 VAS

Parietal bone M2 Parietal bone M1 P1 Parietal bone M1 M2 M3

€ VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS € VAS

23 29 79 78 77 72 71 70 69

Key. P1, P2 ¼ first and second premolars, respectively; M1, M2, M3 ¼ first, second, and third molars, respectively, di1 ¼ first deciduous incisor; dm1, dm2 ¼ first and second deciduous molars, respectively. Note. a The sample did not conform to the quality requirements and was excluded from statistics.

life-history changes, i.e., variation in the values for particular individuals in the course of their lives. Such an analysis demonstrates systematic changes during life after infancy in many individuals, who display their lowest d15 N values as young children, reaching a maximum in early adolescence, and lower values as adults— although higher than in childhood (Table 7). Children under the age of two display the highest d15 N values, of course, reflecting breastfeeding, and their d13 C values are also elevated (less negative). Radiocarbon dating Fig. 6. Plot of the V€asterbjers human isotopic data. Table 6 Age categories assigned to the sampled teeth based on the formation of dentine Tootha

Formation ageb (years)

Age category

M1 M2 (P1, P2)c M3

3
1 7.5
2 13
2.5

Young child Older child Adolescent

Note. a First, second, and third molars (M1, M2, and M3). Of sampled section, cf. Fig. 4 (data from Hillson, 1996). c The timing of formation of the first and second premolars (P1 and P2) roughly corresponds to that of the second molars. b

excluded, young children exhibit the lowest d15 N values, while adolescents display the highest values. This is true on a general level, comparing the whole group of young children with the whole group of adolescents (p ¼ 0:02, unpaired t test), but it is even more interesting to look at

The radiocarbon dating generated some unexpected results (Fig. 7, Table 2). All 11 humans yielded dates ranging between 4370
70 and 4125
55 BP (uncalibrated), and the one seal fell within that range as well, being dated to 4275
60 BP. The three pigs had somewhat younger dates, however, between 4140
55 and 4035
55 BP, and the other domestic animals proved to be much younger: two samples of cattle were dated to 3095
65 and 3160
55 BP, and one sheep/goat sample to 2815
50 BP. Calibration identifies the cattle and sheep/goat with certainty as Bronze Age specimens (according to the Swedish chronology), so that they do not belong to the Stone Age occupation/use of the V€ asterbjers site. The Stone Age AMS dates were considerably earlier than those previously reported for V€ asterbjers. Although the b-decay radiocarbon dates overlap to some extent with the AMS dates, because of their large standard deviations, there seems to be a consistent difference of several 100 years. Grave 67:1, which has been studied by both methods, was now dated to 4200
55 BP

150

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Table 7 Intra-individual changes in d15 N, paired t tests Compared elements/age categories

Mean d15 N (‰)

SD d15 N (‰)

M1 (young child) vs. M3 (adolescent)

15.2 15.9

0.5 0.7

7

6

0.02

M1 (young child) vs. bone (adult)

15.2 15.5

0.4 0.5

11

10

0.03

n

df

p

Note.  Statistically significant.

Fig. 7. Calibrated radiocarbon dates for human and faunal material at V€asterbjers. A reservoir correction of 70
40 radiocarbon years was applied to the human dates prior to calibration.

(Ua-19397) as compared with the previously reported figure of 3765
115 BP (St-4302). A similar systematic difference between b-decay and AMS dates from the same laboratories has been demonstrated by Segerberg,

who related this to the pre-treatment procedures employed at the Stockholm laboratory in the 1970s and 1980s (Segerberg, 1999, p. 122). Only the AMS dates will be considered in the following discussion.

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Discussion The marine reservoir effect Calibration of radiocarbon dates is a relatively straightforward matter where herbivorous samples such as cattle and sheep/goats are concerned, but for samples with a marine influence, i.e., seals and humans, a marine correction should be applied before calibration. The marine reservoir effect is principally caused by upwelling of water from lower depths in large basins (oceans, seas or larger lakes) and its mixing with surface water. Because the water from deeper levels has not had the same carbon exchange with the atmosphere, it contains lower amounts of 14 C than the surface water and thus exhibits an apparent radiocarbon age (Taylor et al., 1996). It is well known that samples from the Baltic Sea may incorporate carbon with such reservoir ages (e.g., Olsson, 1986), and because of the complicated natural history of the Baltic, the extent of this effect has fluctuated over time, so that the discrepancy must be established separately for any given period. Moreover, it can be expected to have varied widely within the basin, both vertically and horizontally, due to the circulation system imposed by the topography, salt-water inflow, and freshwater runoff (Bonsdorff and Blomqvist, 1993; Ojaveer and Elken, 1997). A previous attempt to estimate the reservoir effect for Gotland in the Middle Neolithic was made by Lindqvist and Possnert (Lindqvist and Possnert, 1997; Possnert, 2002), who found a reservoir age offset of approximately 300 years in seals from burials at the Pitted-Ware site of Ajvide in the parish of Eksta, which led them to infer an age offset caused by the marine reservoir effect of some 200 years for humans buried at the same site. A comparison between the dates for humans and those for terrestrial fauna in the two graves at Ajvide for which

151

data have been published and the two V€ asterbjers graves presented here results in much smaller differences; around 70
40 years (Table 8). Applying this smaller correction to the dates for the humans, a much better match with the faunal dates is achieved (Fig. 8). The terrestrial fauna dated at Ajvide and V€ asterbjers consisted of boar tusks, and in one case half a mandible of a hedgehog (Erinaceus europaeus), evidently deposited as grave goods. Although there is always a risk that some or all of these grave goods had been in circulation for some time before deposition, this has to be balanced with the importance of dating a closed context, i.e., to have a reliable association between the interred human and the animal. Were the dated faunal remains to be much older than the burial, this would of course increase the actual reservoir age offset, even though it is rather unlikely that all the dated objects would have been in circulation for as long as 130 years, as presumed by the higher figure used by Lindqvist and Possnert (1997). As far as V€ asterbjers is concerned, apparently only those finds associated with burials that were considered ‘‘objects,’’ such as boar tusks, were meticulously catalogued and labelled in the archaeological museum collections, while other finds of animal material in graves were simply stored among the vast collections of faunal remains, not sorted by species, and at best packed in separate containers. It therefore proved impossible to trace the recorded finds of animal bones in graves that had initially been planned for radiocarbon dating. The recovery and subsequent dating of bones from the ‘‘finding-place’’ 87, where a cattle tooth ended up giving a date more than 1000 radiocarbon years younger than a human bone from the same context, clearly demonstrates the importance of using only closed contexts, even in cases where this is seemingly in conflict with the demand for material which could be expected to have been in circulation for only a short time.

Table 8 Radiocarbon age differences between Pitted-Ware humans and associated terrestrial faunaa Grave

14

Species

14

V€ asterbjers 24 V€ asterbjers 24

Ua-19927 Ua-19395

Pig Human

4105
45 4135
50

)21.3 )16.2

30
67

V€ asterbjers 65 V€ asterbjers 65

Ua-19832 Ua-19396

Pig Human

4140
55 4260
50

)23-3 )14.2

120
74

Ajvide 2 Ajvide 2

Ua-10429 Ua-10416

Hedgehog Human

4150
65 4235
75

)21.4 )16.5

85
99

Ajvide 29 Ajvide 29

Ua-10430 Ua-3538

Pig Human

4195
70 4235
65

)22.1 )15.3

40
96

C lab ID

C age (BP)

Mean offsetc a

Note. Ajvide data from Lindqvist and Possnert, 1997, p. 55. b Values reported from the radiocarbon laboratory. c Calculated using OxCal version 3.5 (Bronk Ramsey, 2000).

d13 C (‰)b

14

C age offset

68
40

152

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Fig. 8. Comparison between calibrated radiocarbon dates for terrestrial fauna (top) and humans from the same graves; data from Table 8. Two alternative reservoir-effect corrections have been applied to the human dates prior to calibration: 70
40 radiocarbon years (centre, according to the present study) and 200
70 radiocarbon years (bottom, according to (Lindqvist and Possnert, 1997)).

Chronology Discussions concerning V€asterbjers have been dominated by the notion of a horizontal distribution of graves representing two chronological phases (Fig. 2) ever since this was first suggested by Malmer (1962), although the hypothesis has never been tested (see e.g., Andersson,

1997; Janzon, 1974; Malmer, 2002). When scrutinising MalmerÕs arguments (1975), one finds that the hypothesis was based on two types of artefact, found in only five ‘‘graves,’’ two of which do not qualify as closed contexts (Table 9). Only two of these skeletons, both accompanied by antler stabbing weapons, have been examined osteologically, being reported as representing one male adult

Table 9 The basis for MalmerÕs (1975) chronological division of the V€asterbjers cemetery Grave/ structure 7 39 36 65 87

Context

Osteological data

Part of cemetery

Chronologically significant artefact

Not closed (‘‘grave completely destroyed’’) Grave Grave Grave Not closed (‘‘finding-place’’)

Skeleton not recovered

N

Battle-axe, early

Skeleton lost, never examined Adult indet.a Adult male, 30–40 yearsb Infant bones recently recovered among faunal remainsc

N S S S

Battle-axe, early Antler weapon, late antler weapon, late Antler weapon, late

Note. a Dahr (Stenberger et al., 1943). b Gejvall, 1974. c Ahlstr€ om unpublished.

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

and one adult of indeterminate sex. Unfortunately, it has not been possible to locate any of the skeletons with associated battle-axes. One was evidently destroyed during gravel quarrying and never recovered, and the other seems to have already been missing by the early 1940s, since it was not available for osteological examination (Stenberger et al., 1943). Consequently it was not possible to radiocarbon date any grave with battle-axes. The other artefact types found in all the graves do differ in their distribution between the northern and southern parts of the cemetery, but this does not have any chronological significance per se; it is a consequence of the division, not a prerequisite for it. Nevertheless, MalmerÕs hypothesis was tested using eight of the human dates after correction for the reservoir effect. The (uncorrected) dates of boar tusks from graves 24 and 65 were also included in the test. As demonstrated by the presence of Bronze Age cattle, ‘‘finding-place’’ 87 cannot be regarded as a closed context, and it was therefore excluded, as was hearth 76 for the same reason. Grave 67:2, one of the graves disturbed by a later burial, was also excluded from the test, since it could be assumed to be earlier than grave 67:1, but it was not known by how much. Following MalmerÕs division, the early group then included graves 4, 12, 24, and 61 and the late group graves 65, 67:1a, 80, and 88. Combination of the dates (using the OxCal 3.5 software, Bronk Ramsey, 2000) reveals no support in the data for any subdivision of the cemetery. Contrary to MalmerÕs ideas, the combined probability distributions for the groups overlap to a great extent, and if anything, the ‘‘early’’ group (2840–2580 cal BC, 2r) is later than the ‘‘late’’ group (2870–2680 cal BC, 2r), but the dates within each group show poor agreement (Fig. 9). Accordingly, there is nothing in the radiocarbon data to support the hypothesis. In a recent work, Malmer brings up the possibility of a gender-based division, in which ‘‘men were buried in the northern part of the cemetery and women in the south’’ (Malmer, 2002, p. 95). Although Malmer himself refutes this explanation, because there were evidently both females and males interred in both parts of the cemetery, it is interesting how he routinely presupposes that men must have been buried with battle-axes (and thus women with antler weapons), especially given the fact that the only sexed individual out of the five with these types of artefact was a male buried with an antler weapon (Table 9). Moreover, if the distribution of artefact types has any significance at all, it is puzzling that the only pertinent social or cultural categorisation Malmer can think of is one based on biological sex. The radiocarbon dates do, however, support the idea of two chronological phases, or at least use during an extended period of time, whether continuous or repeated. Combination of the three dates from boar material, for which no reservoir correction is needed, gives an

153

uneven probability distribution, showing a maximum 2r span of 2860–2490 cal BC (1r: 2850–2500 cal BC). These dates support the notion that V€ asterbjers was in use for some time, perhaps several hundred years. This is further supported by the presence of graves superimposed on each other. The pronounced cultural deposits, on the other hand, should not be taken as evidence for the duration of use, since they could well be of a later date, as indicated by the radiocarbon dates for cattle and sheep/goats. The human individuals in the cultural layers show no differences from those buried in regular graves with regard to diet, which could be taken as further evidence that these layers were in fact later intrusions, which caused the bones to disperse. Human diet Rather than employing a simple two-component linear model calculating the percentages of marine and terrestrial protein input to the diet of the humans, a graphic model was used here that shows ranges for isotopic expectancy values for subjects consuming different kinds of food, based on the faunal isotope data. This model was considered more suitable for the circumstances at V€ asterbjers, with at least three major potential protein sources (cf. Schwarcz, 1991). This approach finds further support in linear regression analyses of the stable isotope data. Whereas there is a highly significant correlation between the d13 C and d15 N values for the animals, excluding dogs (r2 ¼ 0:97, p ¼ 0:0000, n ¼ 59), this correlation is much weaker for the humans (r2 ¼ 0:11, p ¼ 0:0083, n ¼ 65), accounting for only 11% of the variation in each parameter and suggesting that there were more than two major protein sources. (Regression analysis of the isotope values for humans and dogs as one group shows no correlation at all between d13 C and d15 N values, r2 ¼ 0:001, p ¼ 0:77, n ¼ 84.) While the d15 N value for a consumer will be approximately 3‰ higher than that for the species consumed, due to isotopic fractionation (Minagawa and Wada, 1984; Schoeninger and DeNiro, 1984), there is a much smaller and less consistent, trophic-level shift in d13 C, in the vicinity of 1‰ (for a discussion, see Michener and Schell, 1994). Accordingly, the distributions of stable isotope values for fish, marine mammals (seals and porpoises), pigs and terrestrial herbivores (horses and hares, with cattle and sheep/goats excluded) were plotted with the corresponding trophic-level differences taken into account to allow for the expected isotopic shift in a person feeding completely on any one of these food groups (Fig. 10). As is evident, all the human values fall into the ‘‘seal-eating’’ category, revealing an overwhelming contribution of seals to the diet. Previous studies, and also unpublished stable isotope data from Ire, Visby, and Ajvide, suggest that this situation was prevalent all over Gotland at the time (Liden, 1996;

154

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Fig. 9. Combinations of radiocarbon dates for two groups of graves based on MalmerÕs division of the cemetery.

Lindqvist and Possnert, 1997, Eriksson, unpublished data). This predominance of seals in the diet is so extensive that it would be justifiable to describe the PittedWare people on Gotland as ‘‘the Inuit of the Baltic.’’ The occurrence of plant foods (including algae) in the diet at V€asterbjers appears to have been limited. Although it should be borne in mind that the stable isotope values for collagen reflect only the protein part of the diet (Ambrose and Norr, 1993), protein is present in

practically all foodstuffs, including vegetables, and any major contribution of vegetable protein would therefore be visible in both the carbon and nitrogen isotope values. It is true, though, that a comparison between plants foodstuffs and fish and mammal foodstuffs in terms of the total weight of food ingested will show a stable isotope underestimation of the vegetable input because plant foods in general contain lower percentages of protein than do animal foods. On the other hand, if the

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

155

Fig. 10. (A) Individual isotopic values for Stone Age faunal remains at V€asterbjers and Ire, grouped by category. (B) Humans and dogs plotted against isotopic expectancy values for individuals living entirely off any of four groups of potential foods.

contribution of different foodstuffs to the nutritional value is compared, the stable isotope signature will show only a minor underestimation of plant foods. There are no significant differences in diet between the individuals recovered from regular graves and those found in contexts that cannot be regarded as closed. Whether the latter should thereby be interpreted as bones from destroyed graves, or taken instead as evidence that the dispersal of bones from the dead was part of the regular burial ritual, is not clear. Disarticulated isolated human bones scattered in refuse layers is not an unusual phenomenon in Pitted-Ware contexts (e.g., G€ otherstr€ om et al., 2002; Knutsson, 1995; Olsson et al., 1994). Despite the occurrence of fish hooks and other fishing implements in burials, fish does not seem to have

been of significant dietary importance for the people at V€ asterbjers. On the other hand, judging from the isotope data, fish did contribute substantially to the diet of the dogs. Pigs, dogs, and foxes Ever since the first finds of Stone Age pig remains on Gotland, an intense debate has raged about whether they were domestic pigs or wild boar. Their size is closer to that of wild boar, but judging from other morphological characters they could be either. It is apparent that they were introduced onto the island by human agency, a fact which together with other arguments (concerning the relative abundance of skeletal elements)

156

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

has led Lindqvist (Lindqvist and Possnert, 1997) and Jonsson (1986), for example, to favour the domestic pig hypothesis, whereas Ekman (1974) and Rowley-Conwy (Rowley-Conwy and Stor
a, 1997) have argued for them being wild (for a review of the different arguments, see Rowley-Conwy and Stor
a, 1997, pp. 121–124). Although there is no single, irrefutable definition of domestication, it generally includes selective breeding, i.e., human control over reproduction (A Dictionary of Zoology, Oxford). Lepiksaar (1986) discusses how initially wild pigs feeding on refuse heaps at human habitations could have developed mutualism, a form of predomestication, and suggests that in the case of Gotland the Middle Neolithic people kept semi-wild ‘‘freeland pigs,’’ forming herds that fed and bred in the woods surrounding the settlement. The human influence in that case would only have involved some limited guarding and occasional winter feeding (Lepiksaar, 1984, 1986). Pigs are omnivorous, i.e., live off both plant and animal foodstuffs, as opposed to herbivores such as cows and sheep, which eat only plant foods. If winter fodder was required for the ‘‘freeland pigs,’’ it would of necessity have to have included what was available to humans, i.e., marine resources. The same goes for mutualistic and domesticated pigs, which would have consumed a significant amount of marine protein. Wild boar, on the other hand, would have fed either completely on terrestrial resources, or, on rare occasions, on marine refuse heaps. It is clear from the stable isotope analyses that none of the pigs at V€asterbjers had any marine input in their diet (d13 C )21.1
0.4, d15 N 5.4
0.7, average
SD). At least eight individuals, both female and male, juvenile and adult animals, from various contexts, were represented, and their Middle Neolithic origin has been confirmed by radiocarbon dating. The five pigs analysed from Ire, originating from both grave and settlement layers, were similar to the V€asterbjers pigs, i.e., they had had completely terrestrial diets. On the whole, the evidence indicates that the Middle Neolithic pigs, regardless of age or sex, or whether deposited in graves or in cultural layers, had essentially the same diet, and that this diet did not include marine resources to any notable extent. Consequently, there is nothing to suggest either domestication or mutualism. There then remain only the ‘‘freeland pig’’ and wild boar alternatives. Although it is quite possible that winter feeding of ‘‘freeland pigs’’ took place on Gotland, none of the 13 pigs analysed show any traces of this. Besides, winter feeding seems rather remote from any human control and cannot seriously be regarded as a form of domestication. According to A Dictionary of Zoology (1999), ‘‘[s]ome authors make these distinctions: wild species, subject to natural selection only; domestic species, subject to selection by humans; and feral species, formerly domestic species which are now, as escapees,

subject once again to natural selection.’’ Following these definitions, feral would be a more correct term. It is quite possible that the Gotland pigs were once domesticated but had become feral by the Middle Neolithic, whether ‘‘freeland pigs’’ or not. On the other hand, it is equally possible that they were just wild boar—the present analyses unfortunately cannot distinguish between feral pigs and wild boar, so this will have to remain unclear. It is obvious from the stable isotope analysis, however, that they were not domesticated. It is furthermore apparent from the stable isotope analyses of human samples that pork was not consumed to any substantial degree. Nevertheless, pigs were obviously important to the people at V€ asterbjers, as demonstrated both by the many deposits of worked boar tusks in graves, and by the large amounts of skeletal remains of pigs found in the cultural layers at the site. Either pork was only consumed on particular (ritual) occasions, or the animals were sacrificed without being eaten at all. There is nothing in the isotopic data to imply that pigs were used at times of food shortages (or maybe food shortages were rare), although it cannot be ruled out. It is quite clear, on the other hand, that pigs were of ritual significance. This discrepancy between ritual importance and importance in the diet is striking, although in no way unique. It could be argued that if more archaeological sites were scrutinised following the same methodology, one would find that it is quite common to find such ‘‘double standards.’’ A conspicuous example is the Zvejnieki Stone Age cemetery, situated on a former island in Lake Burtnieki in northern Latvia, where the grave goods showed great emphasis on big-game hunting while in practice people consumed mostly freshwater fish (Eriksson et al., 2003). By contrast, the dogs at V€ asterbjers were unquestionably domesticated, as is also evident from their diet. As demonstrated by the consistent difference between the bones and teeth from dogs, the values for the teeth evidently represent suckling pups. Taking into account only the bone samples (d13 C )14.5
0.9, d15 N 13.5
0.6‰, average
SD), the d15 N values are on average lower than for humans and the range in d13 C values is wider, suggesting a more varied diet, possibly because the dogs fed on scrap food and did not have the ‘‘first choice’’ of food, as suggested by Chu (1998) in her study of the prehistoric Ekwen Inuit along the Bering Strait. Although many Inuit people are recorded as not consuming fish to any great extent (e.g., Eidlitz, 1969, and references cited therein), the practice of feeding fish to dogs is well attested among many populations (Whitridge, 2001). A glance at the plot of isotopic expectancy values (Fig. 10) suggests that most dogs at V€ asterbjers probably consumed a mixture of fish and seal meat, possibly also including some occasional terrestrial food sources. Could this be where the pork went?

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

Earlier claims that dogs could be used as isotopic ‘‘proxies’’ for humans (Clutton-Brock and Noe-Nygaard, 1990; Noe-Nygaard, 1988) have proved to be grossly exaggerated, as shown by evidence from the Zvejnieki Stone Age complex in Latvia (Eriksson and Zagorska, 2003). This is furthermore apparent from various other stable isotope studies of dog and human remains (e.g., Coltrain et al., 2004; Katzenberg, 1989; White et al., 2001; White and Schwarcz, 1989). Although the V€asterbjers dog data do partly overlap with the human data, there are significant differences in d15 N (p < 0:0001, unpaired t test), and caution should consequently always be taken in habitually inferring the human diet from the dogsÕ diet. Dogs can have various roles and functions, both ritual and practical, none of which are mutually exclusive (Olsen, 2000; Serpell, 1995), and the nature of their relationship to humans is likely to affect their diets. Therefore dogs cannot be expected to exhibit homogeneous diets even within one community, a conclusion supported by the V€asterbjers isotope data for dogs. Janzon (1974) has drawn attention to the great number of dogs needed to produce the set of tooth pendants found in some graves, e.g., double burial 67:1, where the teeth had been collected from at least 32 dogs, some of which were apparently of great age. Janzon remarks that these teeth must have taken several (human) generations to assemble (Janzon, 1974, p. 88). This seems to me a vague line of argument, based on the implicit premises that one person was the owner of only one dog, while in reality we do not know the dog-topeople ratio, or even whether people claimed personal, communal or any ownership at all over dogs. Provided the V€asterbjers population possessed several dogs simultaneously, collecting their canine teeth post-mortem (facilitated by decay, causing the teeth to lose their attachment to the jaw) and piercing them may well have taken only a relatively short time. It has been suggested that in some cases foxes were kept in captivity on Gotland during the Middle Neolithic (Ekman, 1974; Janzon, 1974). It is likely that such animals would be fed approximately the same food as dogs, and therefore would exhibit similar stable isotope values. None of the four foxes analysed from various contexts at V€asterbjers show anything like these values, however. This does, of course, not rule out the possibility that other foxes were kept in this way. Finds of cattle and sheep/goats at PWC sites on Gotland It has not been possible to go through all the relevant material in detail, but so far I have found no secure, positive evidence of the occurrence of cattle or goats in a Pitted-Ware context on Gotland. Four fragments of sheep in burial 82 at V€asterbjers (Gejvall, 1974), along with the sheep bone (pers. comm. Jan Stor
a, Osteoar-

157

chaeological Research Laboratory, Stockholm University, Sweden) deposited with a collection of objects next to burial 7 at Ajvide (Burenhult, 2002), are so far the most prominent evidence, although none of these have been radiocarbon dated. It may be suggested that these bones can be seen as parallels to other CordedWare objects deposited in Pitted-Ware graves, such as the battle-axes or antler stabbing weapons, and that the use of individual elements does not imply adoption of the whole ‘‘cultural package’’ (cf. Damm, 1991; Hallgren, 1996). A few finds of domesticated animals have been recorded at Ire on the north-western coast of Gotland: two bones of cattle and 10 bones of sheep/goats (Ekman, 1974), but all of these were recovered in or just beneath the topsoil or during the sieving of dumps, which can hardly be considered closed contexts. Bearing in mind the Bronze Age intrusions at V€ asterbjers, they cannot therefore be regarded as evidence of animal husbandry at Ire during the Middle Neolithic. The same goes for the numerous finds of domestic animals allegedly associated with Pitted-Ware burials in the town of Visby (Flyg, 2002; Nihlen, 1927). This site has been subjected to severe interference from the extensive medieval layers and later intrusions. The gravel matrix makes stratigraphical observations problematic, and until a radiocarbon date for the cattle or sheep/goat remains is presented that firmly links the occurrence of these animals to a Pitted-Ware context, I find it hard to trust the connection. Lindqvist and Possnert (1997) mention a few cattle or sheep/goat bones from Gotland that have been dated by radiocarbon to the Early Neolithic and in one case to the Middle Neolithic, but they report only isolated dates in cal BC and fail to give any data on radiocarbon ages, standard deviations or lab numbers, thereby making it impossible to assess the relevance of their dates. They also report, however, on numerous finds of domestic animals in Middle Neolithic layers which, when radiocarbon dated, have turned out to be intrusive, originating from the Bronze or Iron Age. These cases are evidently parallels to the Bronze Age bones at V€ asterbjers. It may well be that most finds of cattle and/or sheep/ goats in PWC contexts on Gotland are actually later intrusions. Previous studies have often taken the Middle Neolithic date of domestic animals for granted, either omitting to take the detailed archaeological context into account or acknowledging it but not making use of it (e.g., Ahlfont et al., 1995; Ekman, 1974; Lindqvist and € Possnert, 1997; Osterholm, 1989; Wallin and Martinsson-Wallin, 1992). A refreshing contrast to this is the paper by Stor
a (2000), who examined the context and anatomical representation of finds of domesticated ani
mals on the Aland Islands (cf. Fig. 1) during the Neolithic, including various PWC sites. By radiocarbon

158

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

dating the finds as well, he demonstrated that, contrary to previous beliefs, cattle and sheep/goats did not occur until the Late Neolithic, when they were accompanied by Corded-Ware stylistic elements on the pottery. The previous and present analyses and discussions have shown that cereals were never a staple food for PWC populations (Jennbert, 1984; Liden, 1996), and it may be claimed that the same is true of domesticated animals. In fact, when dissecting the evidence for animal husbandry at PWC sites, it becomes evident that it was not only rare but probably non-existent in most cases. Stenberger (Stenberger et al., 1943), in his account of the V€asterbjers excavations, stated that all the animal bones from the topsoil layer were discarded because of the risk of modern intrusions. This was wise, of course, but it did not prevent the prehistoric intrusions from being included. Given the complex history of the use of many archaeological sites, on Gotland and elsewhere, attention must always be paid to the risk of prehistoric intrusions.

Part-time farmers or hard-core sealers? To sum up, the evidence for Pitted-Ware farming on Gotland is very limited, to say the least. The contextual data and radiocarbon dates demonstrate no evidence for the existence of either cattle or sheep/goats, and the pigs were most probably wild boar, or possibly feral, but the stable isotope evidence rules out the possibility that they were domesticated. It has been suggested that the PittedWare and Corded-Ware cultures were traces of the same people, and that the emphasis on marine resources at Pitted-Ware sites was only ritual/ideological while in reality the people were part-time farmers, commuting between inland areas and the coast (Andersson, 1998, p. 73; Carlsson, 1991; Carlsson, 1998, p. 59ff; Persson, 1986). The human stable isotope data for V€asterbjers nevertheless show unequivocally (1) that neither cattle nor sheep/goats, nor wild boar, for that matter, could have formed any vital part of the human diet, (2) that seals were the primary source of protein for both adults and children, and (3) that although the diet changed somewhat with age, people retained their seal protein focus throughout their lives, showing no indications of migration or frequent travel between the coast and places further inland. Both published and unpublished stable isotope data for other Pitted-Ware sites on Gotland indicate that the situation was similar all over the island. Another proposal put forward is that fish rather than seals were of primary importance in the diet of the Pitted-Ware people, and that seals have been overemphasised in previous research for taphonomic reasons (e.g., Lindqvist, 1997; Segerberg, 1999; Stor
a, 2001). However, relative to the extensive faunal stable isotope

baseline, the human stable isotope signatures show that fish was of secondary importance to the people at V€ asterbjers, although it does seem to have formed an important part of the diet for some dogs. This fact coincides with ethnographic data on various Inuit populations, who are reported to feed their dogs on fish, which are of limited importance for the human diet. It is also quite possible that fish was the first food that children caught from the wild on their own (Whitridge, 2001), which could possibly account for the relatively lower d15 N values at younger ages at V€ asterbjers, although this needs to be explored further. Marine birds are another important potential source of food, although they cannot be distinguished from fish and seals in the present stable isotope data. Evidence from Ajvide bears further witness to the importance of seals to the people of Gotland during the Pitted-Ware period. An extensive blackish occupation layer, up to 0.4 m in depth and of oblong extent, c. 10  20 m in size, was found among the PittedWare graves. This layer, which was saturated with seal train-oil and featured numerous seal bones and artefacts, was interpreted as a ‘‘seal altar’’ (Gotl. k€ autaltare), a ‘‘ritual seal-butchering area,’’ demonstrating the ritual importance of seals to the Pitted-Ware people in € addition to their economic significance (Osterholm, 2002). Stor
a (2001) has demonstrated a differential treatment of seal skulls and other parts of the carcass
and has sugat both Ajvide and Jettb€ ole on Aland, gested that the supposedly anthropomorphic clay figurines found at Jettb€ ole may in fact bear the merged shapes of a seal and a human being (Stor
a, 2001). In the light of these facts together with the stable isotope evidence, I would argue that the Pitted-Ware Culture on Gotland in fact did represent a separate group with a cultural identity of their own, and that seals played an important role not only in their diet but also in their identity.

Conclusions Although a wide range of potential food sources were available, the Pitted-Ware populations chose to use only a limited part of these. This could be considered a universal law: what is considered edible in a given society is not predictable from the accessible resources alone. Not even the resources that are obviously exploited are necessarily eaten, as demonstrated by the vast amounts of pig bones at V€ asterbjers. The extensive and detailed stable isotope measurements performed here on both faunal and human remains and the supporting evidence all indicate that the V€ asterbjers population, and most likely the whole Pitted-Ware Culture on Gotland, relied on seal hunting for its livelihood, practising no animal husbandry.

G. Eriksson / Journal of Anthropological Archaeology 23 (2004) 135–162

The hypotheses that they belonged to the same group of people who practised farming (i.e., the Corded-Ware Culture) can therefore be refuted. The new radiocarbon dates suggest that the V€asterbjers cemetery was in use for some time, at least a couple of hundred years, during the period 2900–2500 cal BC, but there is no support in the radiocarbon dates for the chronological division of the cemetery into two spatially separate halves as suggested by Malmer, although there may well have been a short gap in its use for burial purposes. The occurrence of intrusive Bronze Age finds in the cultural layers implies that some or all of the deposits were accumulated later than the Middle Neolithic, and that the Neolithic finds in these layers were traces of disturbed graves or other structures. As a result of the new radiocarbon dates a calculation of the age offset caused by the reservoir effect for Middle Neolithic Gotland could be made, demonstrating a considerably smaller age offset than previously suggested, 70
40 radiocarbon years. Since the renewed radiocarbon dates cast doubt on previous ones, not only for V€asterbjers, but also those for Visby and Ire, this should be a matter for future investigations. A further detailed analysis should also be made of the grave goods and contextual data for each individual analysed at V€asterbjers, Ire and Visby and contrasted with the stable isotope data. This should be facilitated by ongoing attempts at identifying molecular sex by DNA analysis.

Acknowledgments I am most grateful to Kerstin Liden for her feedback and advice, and to Janne Stor
a for the identifications of mammals and for valuable discussions. I also wish to thank Sven Isaksson, Per Ericson, Tero H€ark€ onen, Carina Olsson, Jonathan Lindstr€ om, Torbj€ orn Ahlstr€ om, and Christian Lindqvist, who contributed vital information and data, Anna Linderholm, Mia Arvidsson, Anders G€ otherstr€ om, and Sara Patriksson, who provided essential laboratory assistance at various points in the project, Heike Siegmund and Bo Edlen, who ran the mass spectrometers, Maud S€ oderman and G€ oran Possnert, who performed the radiocarbon dating, and Leif Andersson, who produced the shoreline map. Many thanks go to Malcolm Hicks for revising the language of the manuscript. Thanks also go to the Swedish Museum of National Antiquities (SHM), which gave permission to analyse and publish photographs of the material, especially to Leena Drenzel who administrated the access. This research was primarily funded by the Swedish Research Council (VR, formerly HSFR) and the Archaeological Research Laboratory, Stockholm University, with additional support from M
arten Stenbergers stipendiefond.

159

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