Journal of Archaeological Science 38 (2011) 925e933

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Journal of Archaeological Science

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Stable isotope analysis of a medieval skeletal sample indicative of systemic disease from Sigtuna Sweden

Anna Linderholm a,1, Anna Kjellström b,* a Archaeological Research Laboratory, Department of Archaeology and Classical Studies, University, 106 91, Stockholm, Sweden b Osteoarchaeological Research Laboratory, Department of Archaeology and Classical Studies, , Lilla Frescativägen 7, SE-106 91, Stockholm, Sweden article info abstract

Article history: In Sigtuna, Sweden, several medieval cemeteries have been excavated, from which approximately 800 Received 1 July 2010 skeletons have been excavated and analysed. Archaeological finds and anthropological analyses have Received in revised form exposed social differences between the cemeteries. Stable isotope analyses have shown that the 22 November 2010 inhabitants of the town consumed a mixed diet. Significant differences in dietary patterns between the Accepted 25 November 2010 cemeteries may be related to social stratification. In the outskirts of a churchyard excavated in 2006, bone changes showing systemic inflammatory Keywords: disease indicative of leprosy were observed in six individuals. The burial location suggests that the Systemic disease Leprosy affected belonged to a lower social stratum. Bone samples were taken from these six individuals, 19 other fi Tuberculosis human skeletons and ve animals from the same cemetery for analysis of the stable isotope composition Social classes of carbon (C), nitrogen (N) and sulphur (S). Diet The results showed no significant differences in d13C and d15N values between the groups, i.e. the Stable isotopes seemingly healthy humans and the humans affected by severe inflammatory disease appear to have had Carbon similar diets. Nor was a significant difference observed in d34S data between the six affected individuals Nitrogen and the rest of the sample, implying that no difference in origins could be observed between the two Sulphur groups studied. However, a comparison between the present study and the previous analysis resulted in significant differences in carbon values. Based on the results obtained in this investigation it is suggested that if a dietary difference existed between people in the outskirts of a cemetery (for example those suffering from leprosy) and people buried in higher ranked regions, it was not a difference in food source but rather in other parameters. Instead dietary differences and possibly social variations are demonstrated between cemeteries. The results from the present study highlight the hierarchical arrangements of social classes in the early medieval society. Ó 2010 Elsevier Ltd. All rights reserved.

1. Introduction or outcasts (Gejvall, 1969: Daniell, 1997). A similar location for people with skeletal changes of leprosy, showing their low social Individuals with leprosy have been documented in Sigtuna. In position in society, has been documented in medieval Lund, in the a grave excavated in 1995 associated with the church known as south of Sweden (Arcini, 1999). “Church 1” (Kjellström, 2005), an affected individual was identified. The present study considers the diet and origins of six individ- The grave was located in the periphery of the churchyard. The uals also discovered in the outskirts of a medieval churchyard in placement of the graves is in line with coeval Scandinavian burial Sigtuna. Skeletal changes indicate that the group had suffered from regulations (for example the Norwegian law Eidsivatingslagen), systemic disease. Their burial location implies that these individ- which assigned the areas most distant from the church to the poor uals also belonged to a low social stratum. Previous studies have shown that dietary differences, most likely related to social hier- archy, already existed between groups during the initial phase of the town’s establishment (Kjellström et al., 2009). Although * þ þ Corresponding author. Tel.: 46 8 161287; fax: 46 8 164476. knowledge of the current church and churchyard is low it was most fl E-mail address: anna.kjellstrom@o .su.se (A. Kjellström). fi 1 Present address: Department of Archaeology, Durham University, South Road, likely not a formal nursing institution. (A hospital was rst estab- Durham DH1 3LE, . lished in Sigtuna in A.D. 1287, around the time of the abandonment

0305-4403/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jas.2010.11.022 926 A. Linderholm, A. Kjellström / Journal of Archaeological Science 38 (2011) 925e933 of the excavated churchyard [Kjellström and Wikström, 2008]). The groups (Kjellström et al., 2009). Significant differences (P < 0.001) hypothetical notion that these individuals were treated differently in nitrogen values between women at the burial ground Nunnan or that they came from another region is tested in this paper. (d15N mean ¼ 10.73&, s.d. ¼ 1.52) and the (supposedly high status) women at a churchyard called “Church 1” (d15N mean ¼ 13.06&, ¼ 2. The history of Sigtuna s.d. 0.68) were observed. One of the samples (Church 1, phase 2) was contemporary with the skeletal assemblage in the Humle- Sigtuna was founded in the 10th century AD on the shore of Lake gården block presented below. Mälaren, near the coast of the Baltic Sea in east central Sweden, (Fig. 1). Approximately 800 skeletons from several medieval 3. Stable isotope analysis in archaeology cemeteries in the town have been analysed to date. The graves are dated to three burial phases; signifying the establishment of the Stable carbon and nitrogen analysis is a well-established town (Phase 1 c. 900e1100), its peak of prosperity (Phase 2 c. method for examining prehistoric diet (Schwarcz and Schoeninger, 110 0e1300), and its decline (Phase 3 c. 1300e1530) (Kjellström 1991; Katzenberg, 1992; Sealy, 2001; Kellner and Schoeninger, et al., 2005; Wikström, 2008). 2007; Linderholm, 2008; Eriksson et al., 2008; Linderholm et al., During the Viking Age Lake Mälaren was still a bay of the Baltic 2008a and 2008b). The central principle behind this method is Sea, and seagoing vessels could sail up it far into the interior of that “you are what you eat”, namely that skeletal tissue is formed Sweden. However, around 1200 AD the bay became a lake due to from components in the diet. The main protein in the skeletal tissue post-glacial rebound and today the lake’s surface averages 0.7 m is collagen, and it is made up of amino acids which are synthesised above sea level. directly from the diet. Analysis of this collagen will consequently Sigtuna was from the beginning a highly stratified society where reflect an individual’s diet during the 10e to 15 years prior to death the first Christian kings both planned the topography of the town (Fischer et al., 2007). Collagen can survive in the skeleton for and controlled the population living within its limits (Tesch, 1990, thousands of years under good preservation conditions 2000, 2001; Zachrisson, 1998; Kjellström et al., 2005). Wide- (Ovchinnikov et al., 2001; Götherström et al., 2002; Smith et al., ranging contact with other European countries is demonstrated in 2005). Several experimental studies have shown that it is mainly artefacts and designs from northern , , England, the protein portion of the diet that is reflected in collagen isotopic Holland, , , Germany, Byzantium and Kiev (Karlsson, data (Ambrose and Norr, 1993; Howland et al., 2003; Jim et al., 1989; Larsson, 1990; Roslund, 1990, 2001). Although small 2004; Tiesze and Fagre, 1993). The carbon isotope ratio, d13C, compared to contemporary international towns, Sigtuna had an distinguishes protein from different sources; it can distinguish urban character, lacking agrarian constructions such as stables or between protein from terrestrial or freshwater environments and barns (Högrell, 1990; Petterson, 1990). The surrounding country- protein from marine environments, or C4 plants from C3 plants side provided the citizens with meat. In the cultural layers the (Schoeninger and DeNiro, 1984). C4 plants are found in tropical or zooarchaeological data contained bone remains from domestic subtropical environments and are not thought likely to have animals such as cattle, sheep, goat and pig (Hårding, 1990)aswell contributed to the diet in medieval Sigtuna. This means that all as game animals, wild fowl and fish (Jonsson, 1989; Hårding, 1990; terrestrial protein is considered to derive from C3 plants in this Vretemark, 1997). In addition to the most basic crops, fossil plant study. The nitrogen isotope value, d15N, on the other hand, will remains show that a diversity of vegetables, fruits and herbs were increase for each step in the food chain by approximately 3&, and cultivated (Hansson, 1997). Stable isotopic analyses have verified one can thus discriminate between trophic levels in the food web that the diet contained a combination of both terrestrial and marine (Minagawa and Wada, 1984; Schoeninger and DeNiro, 1984). Both protein but was generally predominantly terrestrial in origin the carbon and the nitrogen isotopic values are measured against (Kjellström et al., 2009). Variations in the intake of vegetable international standards and are expressed in per mil, &, i.e. parts protein, most likely socially motivated, were discernable between per thousand.

Fig. 1. Map of Sweden and Sigtuna with the location of some of the excavated churchyards (the Humlegården block ¼ Church 2). A. Linderholm, A. Kjellström / Journal of Archaeological Science 38 (2011) 925e933 927

4. Sulphur analysis as a tool for provenience determination significantly higher frequencies of several pathologies were observed (Kjellström and Wikström, 2008). Six skeletons showed During the last ten years analysis of the stable isotopes of sulphur signs of severe systemic disease not observed in the rest of the (d34S), has successfully been applied to several archaeological studies skeletal collection (Kjellström, 2010). Two of three individuals with (Richards and Hedges, 1999; Richards et al., 2001, 2003; Leach et al., preserved facial bones demonstrate signs of rhinomaxillary 2003; Craig et al., 2006; Privat et al., 2002; Linderholm et al., 2008a remodelling. Five of the affected exhibit bilateral periosteal new and 2008b; Fornander et al., 2008; Nehlich and Richards, 2009; bone formation, severe remodelling of the phalanges of the feet and Nehlich et al., 2010). Plants derive the majority of their sulphur pencil shaped metatarsals. Additionally one of the individuals had from the soil and the soil’s d34Ssignalisderivedfromthelocal lytic lesions confined to the lumbar spine, which had resulted in an bedrock. A small part of the sulphur intake will be derived from angular kyphosis. In at least two individuals lepromatous leprosy atmospheric depositions and microbial activities in the soil but to and tuberculosis could be confirmed respectively. Although the a much lesser extent. Terrestrial sulphur isotopic conditions thus vary remaining four skeletons exhibited severe bone atrophy in their feet depending on geological setting. The d34S values of sedimentary rocks (and three of them showed mild bone alterations in their hands) range from 40 to þ40&, European granitic rocks have d34S values characteristic of leprosy, other diseases could not be ruled out. that range from 4toþ9&,maficrockd34S values are close to 0&, and metamorphic rocks exhibit d34S values between 20 and þ20& 6. Methods (Krouse, 1980; Faure and Mensing, 2005). By comparison, the d34S value for the oceans are rather uniform, averaging 21&, with marine 6.1. Osteological methods vegetation having d34S values between þ17& and þ21& (Peterson and Fry, 1987). As a result of the reduction of sulphate ions (SO4 )to The skeletal assemblage was sexed and aged according to current 34 hydrogen sulphide (H2S), the d S values in freshwater systems are standard anthropological techniques (Moorrees et al., 1963a and much more dispersed ranging from 22 to þ20& (Krouse, 1980; 1963b; Phenice, 1969; Stloukal and Hanáková, 1978; Stewart, 1979; Faure and Mensing, 2005). Because of this terrestrial and fresh- Novotný, 1982; Brothwell, 1981; Lovejoy et al., 1985; Meindl and water d34S values vary far more than marine ones. The isotopic frac- Lovejoy, 1985; Pearson, 1917-19 in Bass, 1987:219;Ubelaker, 1989; tionation between food and consumer is relatively small (1& to Brooks and Suchey, 1990; Buikstra and Ubelaker, 1994; Scheuer þ2&), meaning that the d34S value in bone reflects the sulphur and Black, 2000; Bruzek, 2002). The measurements were taken isotopic composition of the diet which in turns reflects the geology of according to definitions set up by Buikstra and Ubelaker (1994). the food origin (Peterson et al., 1985; Bol and Pflieger, 2002; Sharp Differential diagnosis of leprosy was carried out following criteria et al., 2003; Richards et al., 2003; Fraser et al., 2006; Buchardt et al., presented by Andersen and Manchester (1992); Andersen et al. 2007; Nehlich and Richards, 2009). Thus any detected variation in (1994); Aufderheide and Rodríguez-Martín (1998); Ortner (2003); the d34S data could indicate geographical origins of the food and with Resnick and Niwayama (1988). this information migration patterns may be elucidated. In addition to the six skeletons with bone changes associated with systemic disease a control group of 19 adult individuals of 5. Materials both sexes (ten women and nine men) were picked out. Except for degenerative changes of the joints and signs of trauma on some of In the summer of 2006 Sigtuna museum conducted an excavation the individuals, the skeletons in the control group displayed no of the southern parts of the Humlegården block (Wikström, 2008). signs of systemic infectious diseases (Fig. 2). In addition, as The excavation covered 160 m2 and included 220 east-west oriented a reference, bone samples were taken from cattle (Bos taurus), cat graves with 227 skeletons. The same churchyard has been investi- (Felis catus), pig (Sus domesticus) and pike (Esox lucius). gated in 1991 when 99 skeletons were documented (Kjellström, 2005). The name of the church is unknown, but in the earlier 6.2. Bone sampling and collagen extraction investigation it was called Church 2, which is used henceforth in this study. The skeletons exhibited a variety of skeletal changes The long bones used in this part of the study were first cleaned and in comparison with other cemetery assemblages in Sigtuna, and bone powder was then obtained by use of a dentist’s drill.

Fig. 2. (a) The feet of an adult woman (Case 2); (b) Acroosteolysis of the right fifth metatarsal; (c) A “pencil and cup” deformity of the first metatarsal and proximal phalanx on the right side; (d) A “pencil and cup” deformity of the right first metatarsal and proximal phalange the left side; (e) Acroosteolysis of the left fifth metatarsal. 928 A. Linderholm, A. Kjellström / Journal of Archaeological Science 38 (2011) 925e933

Collagen was extracted from skeletal elements according to Brown SPSS for windows (version 16.0) and P values <0.05 were consid- et al. (1988) in a designated bone laboratory at the Archaeological ered significant. Research Laboratory, StockholmUniversity. The samples were demineralised in a 0.25M HCl solution for 48 h at room tempera- fi ture, ltered and washed twice with deionised water through 7. Results a glass filter. After an addition of 0.01M HCl, the samples were incubated at 58 C overnight in order to dissolve the organic 7.1. Preservation material. The dissolved organic residue was then filtered and fi washed with deionised water through an ultra lter (30,000 MWCO Post-mortem degradation of bone occurs in at least three ways: fi Amicon Ultra-15 Centrifugal lter device (Millipore)), removing chemical deterioration of the organic phase, chemical deteriora- particles of less than 30kDaltons. Particles larger than 30kDaltons tion of the mineral phase and microbiological attack on the overall are likely to be undamaged collagen. The residual solvent was then composition (Collins et al., 2002; Hedges, 2002). In addition, transferred to a 2 ml Eppendorf tube and frozen at 80 C, after several parameters are involved in the loss of collagen from bone which the sample was freeze-dried and weighed. material, the main ones being time, temperature and pH (Collins d13 d15 For the C and N measurements approximately 0.5 mg of et al., 2002; Hedges, 2002). In order to control for diagenetically collagen was weighed into tin capsules for combustion in a PDZ altered bone we used the parameters put forward by DeNiro Europa ANCA-GSL elemental analyzer interfaced to a PDZ Europa (1985), Ambrose (1990), van Klinken (1999), which require that e 20 20 isotope ratio mass spectrometer (Sercon Ltd., Cheshire, UK). the C/N ratio should fall into the range 2.9e3.6, the collagen This step was performed at the UC Davis Stable Isotope Facility, should be 15.3e47% carbon and 5.5e17.3% nitrogen by mass, and Department of Plant Sciences, UC Davis, California, USA. Precision the collagen yield should be greater than 1%. The sulphur values & d13 & d15 d34 was 0.1 for C and 0.4 for N. For the S measurements were verified using the newly established criteria based on C/S and approximately 5 mg of collagen was used. The analyses were N/S ratios (Fornander et al., 2008; Nehlich and Richards, 2009). carried out at Iso-Analytical Limited, Crewe, UK using the EA-IRMS Two samples out of the 25 were discarded due to low C/N ratios. & d34 technique. Analytical precision was within 0.3 for the S. None of the samples were disregarded due to the C/S or N/S ratios A two-sample t-test was used for comparison of stable isotope (Table 1). None of the samples from faunal remains were discarded values between samples. Statistical analysis was conducted using (Table 2).

Table 1 Results of the stable isotope analysis of human bone samples from the Humlegården block 2008. Individuals affected by systemic disease are marked in grey.

Lab # Id no. Sex d13C(&)%C d15N(&) %N C/N d34S(&) % S C/S N/S 1 3013 F 20.4 36.4 14.3 14.6 2.9 4.3 0.24 397 137 2 3014 F 20.9 39.6 13.1 14.1 3.3 6.6 0.25 418 128 3 3029 F 21.2 34.1 11.6 13.1 3 9 0.24 376 124 4 3045 F 20.8 38.9 14 14.7 3.1 6.8 0.29 358 116 5 3064 M 21.2 33.5 13.9 12.1 3.2 2.6 0.29 310 96 6 3068 M 20.5 34.4 14.4 13.4 3 5.2 0.32 287 96 7 3077 F -20,6 37,8 11,5 11,7 3,8 7,3 0,27 380 101

8 3092 ? -20,7 37,9 14,3 14,7 3 3,2 0,27 376 125

9 3093 M -21 39,9 13,8 14,4 3,2 9,8 0,24 451 140

10 3097 M 20.3 36.9 14.3 13.8 3.1 7.4 0.3 329 106 11 3134 M 21.1 36.1 13.5 13.7 3,1 4.7 0.27 362 118 12 3159 M -19,3 38,7 12,7 14,1 3,2 11,7 0,26 401 126

13 3195 F 20.3 34.1 14.2 13.5 2.9 5.1 0.44 207 70 14 3196 F 20 6 37.5 14.2 14.7 3 5.9 0.25 398 134 15 3225 M 21.3 37.6 11.2 14 3.2 11.6 0.27 376 120 16 3227 M 20.4 37.1 11.6 14.1 3.1 8.7 0.3 331 108 17 3233 M 20.4 38.3 11.2 14.5 3.1 9.5 0.34 301 98 18 3247 F 20.9 37.2 14.8 14 4 3 6.4 0.25 401 133 19 3250 M 19.3 35.4 13 14.3 2.9 8.7 0.33 290 101 20 3275 F 20.7 35.1 13.8 14.4 2.8 4.4 0.32 296 104 21 3281 M 20.2 36.8 14.6 14.8 2.9 7 0.25 385 133 22 3320 ? -20,3 37 13 14,8 2,9 8,4 0,26 376 129

23 3336 F 20.6 37.1 14.8 13.8 3.1 5.1 0.29 339 108 24 3401 M -19,5 36,1 12,7 14,6 2,9 8 0,26 371 129

25 3439 F 19.4 346 9.6 13.9 2.9 7.8 0.28 327 113 Mean 20.5 1.2 7 S.d. 0.6 1.4 2.4 A. Linderholm, A. Kjellström / Journal of Archaeological Science 38 (2011) 925e933 929

Table 2 Results of the stable isotope analysis of animal bone samples from the Humlegården block 2008.

13 15 34 Lab # Species d C %C d N %N C/N d SV-CDT % S C/S N/S (&) (&) (&) 26 bos 22.5 41.2 5.2 14.9 3.2 1.4 0.28 390 121 27 felis 22.1 41.1 10.7 14.4 3.3 5.6 0.32 343 103 28 esox 20.4 36.5 13.1 14.2 3 6.7 0.6 161 54 30 sus 21.9 37.9 9.5 15.5 2.9 6.5 0.28 363 127

7.2. Isotope data

In all, the carbon and nitrogen values from the individuals with bone changes did not differ significantly from nearby skeletons in the control group from the same cemetery (Table 1, Fig. 3). The diet seems to have been rather homogenous with mainly terrestrial d13 ¼ & protein seen in the carbon values ( C mean 20.47 , Fig. 4. Scatter plot showing the distribution of d13C and d34S values for skeletons s.d. ¼ 0.57). The standard deviation of 0.57 is however slightly indicative of leprosy and a control group from the Humlegården block. higher than the postulated standard deviation of 0.3 said to represent a population with a homogenous diet according to Lovell et al. (1986), but low enough to infer a fairly homogenous diet. No Attempts to reconstruct the diet for the same period in Sigtuna significant differences can be detected between the affected and have been performed previously in 2005 (Kjellström, 2005; non-affected concerning either carbon (t (21) ¼1.283, P ¼ 0.213) Kjellström et al., 2009). A comparison between the contemporary or nitrogen (t (21) ¼0.084, P ¼ 0.934) values. When looking at assemblage from the previous study (of Church 1) and the present males versus females no significant differences can be seen in analysis resulted in significant differences in carbon values either the d13C(t(19)¼ 0.620, P ¼ 0.543) or d15N(t(19)¼0.489, (P < 0.001) but not in nitrogen values (Fig. 5). P ¼ 0.631) values. There is however a strong indication of a regular animal protein diet, shown in the high values of nitrogen (d15N 8. Discussion mean ¼ 13.19&, s.d. ¼ 1.38) (Table 1, Fig. 3). The sulphur data for the combined sample (d34S mean ¼ 7.11&, 8.1. Human diet during the medieval period in s.d. ¼ 2.41) fits in general with the surrounding bedrock signal (granite has a range from 4e9&). When divided into individuals In comparison with other dietary studies performed on similar affected (d34S mean ¼ 8.23&, s.d. ¼ 3.14) and not affected (d34S dated materials across Europe this set of dietary data conforms well mean ¼ 6.80&, s.d. ¼ 2.18) with systemic disease no significant (Privat et al., 2002; Polet and Katzenberg, 2003; Bayliss et al., 2004; difference is seen between the two groups (t (21) ¼1.186, Müldner and Richards, 2007; Fornaciari, 2008). In an early study of P ¼ 0.249) (Fig. 4). an Anglo-Saxon cemetery, Privat et al. (2002) showed that the diet When looking at the males (d34S mean ¼ 7.90&, s.d. ¼ 2.73) was based on terrestrial food with carbon values ranging from versus the females (d34S mean ¼ 6.33&, s.d. ¼ 1.45) no significant 20.7& to 19.1&. The nitrogen values confirmed this, having difference can be seen either (t (19) ¼ 1.565, P ¼ 0.134). (Table 1). a range of 8.4&e12.8&. It is clear though that some of the indi- The animals analysed show a range of d34S values from 1.44 to viduals studied here were supplementing their diet with some 6.74& (Bos 1.4&, Felis 5.6&, Esox 6.7& and Sus 6.5&). They are freshwater fish. Privat and colleagues also tested their data set to used as a baseline, a local point of reference for the interpretations examine if there were any differences in dietary composition of the sulphur values (Table 2, Fig. 4). between the sexes, but no such difference was observed (Privat

Fig. 5. Scatter plot showing the distribution of d13C and d15N values for the 2008 Fig. 3. Scatter plot showing the distribution of d13C and d15N values for skeletons sample from the Humlegården block (Church 2) and a control group from another indicative of leprosy and a control group from the Humlegården block. cemetery (Church 1) in the 2005 analysis. 930 A. Linderholm, A. Kjellström / Journal of Archaeological Science 38 (2011) 925e933 et al., 2002). They detected a stronger input of freshwater fish in the isotopic fractionation between food and consumer is relatively “poor” group relative to the “wealthier” population. When a medi- small (1& to þ2&) and the surrounding bedrock signal (granite eval monastic community from the coast of Belgium was examined, has a range from 4to9&) the sulphur signals obtained in this the mean values were 19.1 0.46& and 11.1 0.92& for carbon study appear to indicate a local origin. and nitrogen respectively. The carbon isotope values were indica- The sulphur values show no difference between individuals tive of a terrestrial based diet. Once again the nitrogen isotopic affected by systemic disease and non affected individuals, nor does values are high and can be explained by an input of freshwater fish there seem to be any difference between the different sexes. This or other marine products (Polet and Katzenberg, 2003). would indicate that there is no division between the affected and non-affected individuals. 8.2. Sulphur isotope values from Sigtuna and other parts of Sweden 8.3. Disease, religion and diet during the medieval period Since the number of investigations using d34S on archaeological material is low, there are not that many data sets to compare these In a study from 2004 Bayliss et al. investigated a medieval data to. The sulphur values obtained here show a rather dispersed cemetery in Norwich. It is a cemetery where healthy individuals are set of d4S values ranging from 2.6 to 11.7&, with a mean ¼ 7.1&, buried next to individuals affected by leprosy, thus resembling the s.d. ¼ 2.4. The d34S values are higher compared to two sets of cemetery investigated in this study (Bayliss et al., 2004). Even previously published d34S values from other places in Sweden; from though the focus of the paper was on the radiocarbon dates in Birka (in close proximity to Sigtuna) mean ¼ 5.2&, s.d. ¼ 2.5 conjecture with dietary offsets, similarities may be discerned (Linderholm et al., 2008a) and from Björned in the north of Sweden between the isotopic data obtained in this study and the ones from mean ¼ 5.4&, s.d. ¼ 3.4 (Linderholm et al., 2008b). The interpre- the Humlegården block. At Norwich the carbon values ranged from tation of the human d34S values is that they mostly fit with the 20.9& to 17.0& and the nitrogen values from 9.8& to 13.5&. surrounding geological signal stemming from the granite bedrock There seems to be no difference between the individuals showing (21 individuals fall between 4 and 9&). However there are some signs of leprosy and those who do not. The sample from the outliers that may well be from other places. There are for example Humlegården block has a much higher d15N signal than all the data two individuals with d34S values above 11& (11.6 and 11.7&). They presented in prior studies, and the amount of freshwater fish or both fall well above the granite signal for the surrounding area and other 15N-rich food digested seems fairly high. However, isotopic could possibly be from a different region altogether. Based on these values in accordance with those from Humlegården were obtained results we cannot say that all humans buried at the cemetery were in an investigation performed by Müldner and Richards in 2007 on local. It is interesting to note that the individuals with the highest a medieval English population (Müldner and Richards, 2007). In sulphur value represent both groups, this is also true for the indi- this material the religious impact on the diet is strongly demon- viduals with the lowest sulphur values. This supports the inter- strated and can be compared to our data set. Their study is based on pretation that there is no geographical difference between the two stable isotope analysis on populations from three different medi- groups investigated here. eval sites in Northern England: a friary, a mass grave, and a rural None of the 23 remaining human samples or any of the animal hospital. All of these new sites differ from prior investigations samples were disregarded due to low C/S and N/S ratios (Fornander performed on archaeological populations in one aspect; they all et al., 2008; Nehlich and Richards, 2009). Accordingly to Nehlich demonstrate enriched d15N values in combination with terrestrial and Richards (2009). Three of the samples showed a lower C/S carbon signals. The explanation given by Müldner and Richards for ratio (207, 287 and 290) and four samples showed a lower N/S ratio this phenomenon is that what is being measured is actually the (70, 96, 96, and 98) than would be expected. All of these values are impact of medieval fasting regulations. The results also point to the however in the range suggested by Fornander et al. (2008). For fact that there was little difference in diet between different social these values the indications for collagen preservation are within the groups. There is a slight difference within the populations; the documented ranges and are thought to be reliable (Table 1). priests and patrons have higher nitrogen values than the rest. Animal d34S values are traditionally used as a “local” reference. Basically what we can see in this study is an increase in freshwater In this study we have the cat (5.6&) and the pig (6.5&)as fish consumption in these medieval populations regardless of social a terrestrial reference, and a marine reference from the fish. Aquatic standing. The stable isotope values from the three sites range from animals have a different sulphur source and the 34S value for the 20.6& to 18.1& for carbon and from 10.5& to 14.9& for fish can thus be different because of this (6.7&). The very limited nitrogen (Müldner and Richards, 2007). These values are very amounts of animals analysed in this case study severely weakens similar to the values obtained in the current study and the expla- the construction of a local baseline/signal, however they are nation for the high nitrogen values in combination with extreme suggestive of a local signature. The pig analysed in this investiga- terrestrial carbon values may be the same. Hence, what we are tion could very possibly be a domestic one and if so, might have seeing in our data set is most likely evidence for medieval fasting been fed on human food waste. This would to some extent explain practices. the d34S values and the higher d15N value. The pigs would most So, in order to explain the high d15N ratios seen in this study in likely have been fed some fish scraps if fish were consumed at the combination with totally terrestrial carbon signals one has to look site. Furthermore, it is possible that the pigs fed on plants affected at some possible explanations. These could be a diet based on by sea-spray aerosols as a result of, for example, a higher exposure freshwater resources, migrating birds, suckling animals or on pork to wind (cf. Angerbjörn and Pehrson, 1987). Only very small traces from animals that had themselves consumed large quantities of of a sea spray effect might be observed in our samples; it might animal products (Privat et al., 2002; Rubenstein and Hobson, 2004; explain the pig and some of the range of our d34S values. Since we Jay and Richards, 2006). The latter scenario seems rather unlikely cannot detect it in any profound way it is unlikely to have a large based on data from the single pig analysed and thus cannot account effect on or data. The only “non-local” value among the animals for the high d15N ratios obtained. Discoveries of bone debris from tested seems to be the cattle sample (1.4&). Excluding the cattle migrating birds and juvenile livestock have been made in Sigtuna sample would give the animals a d34S mean ¼ 6.3&, s.d. ¼ 0.6. This but the explanation of a high input of freshwater fish in the diet “local” signal fits very well with the mean value obtained for the seems far more plausible. It has been shown in prior studies that human individuals tested (d34S mean ¼ 7.1&). Given that the a large part of the diet in medieval populations was based on A. Linderholm, A. Kjellström / Journal of Archaeological Science 38 (2011) 925e933 931 freshwater fish (Privat et al., 2002; Polet and Katzenberg, 2003; material is unearthed and analysed, it is becoming possible to Müldner and Richards, 2007). In a recent paper by Grupe et al. examine the diet in a more direct way. From the few comparable (2009) stable isotope analysis was performed in order to evaluate isotopic studies performed on medieval populations (Privat et al., the brackish water aquatic food web. Here they clearly show that 2002; Polet and Katzenberg, 2003; Bayliss et al., 2004; Müldner and freshwater fish can be depleted in their d13C values. They also Richards, 2007; Fornaciari, 2008), the results indicate a diet based observed raised d15N values for carnivorous, top-consuming fish on terrestrial sources with a rather large input of freshwater fish. It has species (i.e. cod), which could explain the high d15N values obtained also been possible to investigate potential differences in diet between in this study. This is also corroborated with the fact that religious social groups and, as in this study, between healthy individuals and beliefs dictated that fish should be eaten during the fast on certain those affected by systemic disease. days (up to one third of the year) (Montanari, 1999). When analysing the sulphur isotope composition, no differences Based on the medieval religious doctrines concerning a “spiritual could be ascertained in either affected versus non-affected groups geography”, the burial locations of the individuals possibly affected or females versus males. This would indicate that the people buried by leprosy suggest a socially stratified society. Severe pathological at Humlegården originated from the same region or at least that no changes are seen in skeletons in the outskirts of the cemeteries and clear distinctions can be made between the origins of the two not in the parts located near the churches. Furthermore, previous groups. Comparing the animal reference d34S measurements with studies of skeletal medieval samples from the same site have shown the human d34S values, the origin of the people buried here seems differences in dietary patterns, most likely based on social stratifi- to be predominantly local but with a few exceptions. This all fits cation. Surprisingly, a clear social dichotomy is not observed in the with Sigtuna’s status as a town and trading centre with people from diet of the affected. Individuals with bone changes indicative of around the Baltic Sea. systemic diseases such as leprosy had the same diet as the (at least The burial locations of the affected suggest a socially stratified seemingly) unaffected community at the same cemetery. On the society and social stratification has been indicated in previous other hand, the individuals buried in the same area as the six studies. No dietary differences were observed between affected and possible cases of leprosy could have been sick for a long time from non-affected individuals or between females and males. Differences diseases that do not affect the skeleton. Hence, comparisons were only found when comparing the total sample with a contem- between skeletons with and without skeletal changes are not porary cemetery. Given that socially defined diets existed these may necessarily the same as comparisons between unhealthy and have been expressed as differences in food quality rather than food healthy individuals. However, leprosy affected could, according to source. The results from the present study highlight the hierarchical historical sources, be seen as a group of their own, with a more arrangements of social classes in the early medieval society. severe social stigma than others. It is possible that the sample is spatially biased, and that a different result would have been Acknowledgements obtained had individuals buried within the church building (clearly signifying higher status) been included. With the results in mind, it is We would like to thank Sigtuna museum for access to the Sig- therefore suggested that if there existed a dietary difference tuna skeletons. We would also like to thank the anonymous between infected and seemingly healthy people it was not a differ- reviewer for the comments. ence in food source but rather in other parameters, i.e. the same type Grant sponsorship: Berit Wallenberg foundation. of food was consumed but in varying quality and freshness. Both the archaeological and the rare historical records indicate References that different social groups in society used the churchyard at the Humlegården block and the one belonging to Church 1 (Kjellström Ambrose, S.H., Norr, L., 1993. Experimental evidence for the relationship of carbon et al., 2005; Wikström, 2008). Comparing the sample from Humle- isotope ratios of whole diet and dietary protein to those of bone collagen and gården (Church 2) as a whole with a sample from a contemporary carbonate. In: Lambert, J.B., Grupe, G. (Eds.), Prehistoric Human Bone: Archaeology at the Molecular Level. 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