Journal Of Archaeological Science - Palaeo-Barn

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Journal of Archaeological Science 36 (2009) 2689–2699Contents lists available at ScienceDirectJournal of Archaeological Sciencejournal homepage: http://www.elsevier.com/locate/jasDietary patterns and social structures in medieval Sigtuna, Sweden, as reflectedin stable isotope values in human skeletal remainsqAnna Kjellström a, *, Jan Storå a, Göran Possnert b,1, Anna Linderholm c, 2aOsteoarchaeological Research Laboratory, Department of Archaeology and Classical Studies, Stockholm University, S-106 91 Stockholm, SwedenÅngström Laboratory, Box 534, Uppsala University, SE-751 21 Uppsala, SwedencArchaeological Research Laboratory, Department of Archaeology and Classical Studies, Stockholm University, S-106 91, Stockholm, Swedenba r t i c l e i n f oa b s t r a c tArticle history:Received 30 October 2008Received in revised form24 July 2009Accepted 31 August 2009Stable isotopes (d13C, d15N) have been studied in human burials from the medieval town Sigtuna inSweden. Dietary patterns of 80 adult individuals were analyzed on three cemeteries representing thephases of establishment, prosperity and decline of the town. All analyzed individuals were radiocarbondated. One of the cemeteries, Church 1, represents a population of higher social status than those at theother two cemeteries.The d13C values are homogenous and showed that the protein intake was mainly of terrestrial origin inthe whole population. d15N values varies more and they may indicate a higher input of vegetables in thediet at one of the cemeteries, the Nunnan block.Already in the initial phases of Sigtuna a social hierarchy had been established which is reflected indietary patterns. Apparently more animal protein was consumed among the high status population ofthe town. Furthermore, differences in dietary patterns between the sexes were noted. In all phases thefemales show more clustered values indicating a more homogeneous diet than that of the males.Ó 2009 Elsevier Ltd. All rights reserved.Keywords:Social statusSigtunaDietStable carbon and nitrogen isotopesRadiocarbon1. IntroductionThe town Sigtuna was established in the late 10th century AD inEastern Middle Sweden. Sigtuna was a hierarchic society anddeveloped into a true urban center with several religious institutions and a growing social stratification unique in Sweden at thetime (Fig. 1) (Hyenstrand, 1996; Zachrisson, 1998; Tesch, 2000).During the 10th and 11th century the town was founded in a ruralarea in connection to a royal manor. The period 12th–14th centuryrepresents the time of prosperity and throughout the 12th centurySigtuna was the only urban settlement in the eastern part ofSweden. Several stone churches were built and in the beginning ofthe 13th century Sigtuna was still flourishing with a strong religiousand social position. The last period of the Middle Ages (c.14thcentury – the Reformation) is characterized by stagnation andq Grant sponsorship: Magnus Bergvall foundation, Birgit and Gad Rausingfoundation.* Corresponding author. Tel./fax: þ46 8 161313.E-mail addresses: [email protected]fl.su.se (A. Kjellström), [email protected]fl.su.se(J. Storå), [email protected] (G. Possnert), [email protected] (A. Linderholm).1Tel.: þ46 18 4513059; fax: þ46 18 555736.2Tel.: þ46 8 162176; fax: þ46 8 6747366.0305-4403/ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.doi:10.1016/j.jas.2009.08.007a decline in the development of the town. The stagnation, mostlikely caused by the foundation of the nearby town Stockholm,seems to have started during the end of the 13th century when thepopulation declined in size and the town lost its former status as anurban center. However, the decline seems to have been a slowprocess and no signs of mass disasters like fires or major diseaseshave been identified.In recent years archaeological investigations have been performed at seven cemeteries, revealing a large collection of humanremains (Wikström, 2006). Approximately 775 skeletons have beensubject to osteological study (Kjellström, 2005; Kjellström andWikström, 2008). The burials have been subdivided into threechronological groups roughly corresponding to the formationphase, the time of prosperity and finally the period of decline ofSigtuna (Wikström, 2006). Some of the cemeteries contain burialsfrom all three phases while others were in use for a shorter periodof time and are represented by one or two phases only.In Sigtuna it is possible to follow a human population throughthe process of urbanization and through the development towardsa stratified society. Bioarchaeological investigations have revealeda trend of declining health through time in Sigtuna and a calculatedindex of health showed that the deterioration of health was moreobvious for women than men (Kjellström et al., 2005). The available(faunal) osteoarchaeological and historical sources give few direct

2690A. Kjellström et al. / Journal of Archaeological Science 36 (2009) 2689–2699the first Swedish Christian kings (Tesch, 2001a; Tesch and Vincent,2003). Later, probably in the beginning or middle of the 11thcentury, a wooden church was founded together with the, in theMälaren area, first Christian churchyard (Tesch, 2001a, 9ff; Teschand Vincent, 2003). Some decades later, approximately A.D. 1080,the region’s first stone church was constructed. The 28 m long and12.4 m wide church had an apse and possibly a crypt (Kjellströmet al., 2005). In 1993, the remains of a male buried with a crozierhead made of a morse ivory (walrus-tusk) were found close to thesouthern wall of Church 1 among graves dating to phase 2 (Tesch,2001b). The crozier-head, the oldest find with a liturgical connection in Sweden, implies that the man was at best an archbishop orat least an abbot (O’Meadhra, 2001). Furthermore, the remains ofa baptismal font, probably made by English or North Germancraftsmen, were recovered in the churchyard. The finds must beregarded as exceptional and prestigious objects denoting a royalfamily (Karlsson, 1989). In A.D. 995 the first Christian king, OlofEriksson, founded the first Swedish mint in the same block as thechurchyard. This is a strong indication, that the plot accommodateda ruling elite (cf. Hed Jakobsson, 2003). In comparison, the othercemeteries in Sigtuna seem to be more ordinary with a moremarginal location and absence of equivalent finds.2. The dietary background and the stable isotope ecologyof SigtunaFig. 1. Map of Sweden with Sigtuna.clues to dietary patterns in Sigtuna. Beyond a general knowledge ofanimal utilization, the diet in the town is largely unknown.However, differences between the households can be expected dueto social and economic conditions. Several archaeological observations indicate differences in social status between the cemeteriesand the churchyard at Church 1 stands out as exceptional. In the endof the 10th century the plot accommodated a royal manor housingFor better understanding of the isotopic data a general overviewof the possible food resources is provided. During the excavations inSigtuna no signs of agrarian character such as stables or barns havebeen identified indicating that the citizens were dependant on thefarms of the surrounding landscape (Kjellström et al., 2005).Generally, barley was the most important cereal during Late Ironand Middle Ages in Sweden (Myrdal, 1999). Province laws andcontemporary Scandinavian literature mention peas, beans,turnips, hemp, onions, apples, cabbage and flax and a variety ofother plants (cf. Hjelmqvist, 1961, 1965; Lange, 1965). Thus, it maybe assumed that, in addition to cereals, various roots, herbs, fruits,mushrooms, nuts and berries were consumed also in Sigtuna(Hjelmqvist, 1966; Lange, 1959, 1966).In accordance with most medieval zooarchaeological assemblages, the bone debris in the town layers indicates that the mostcommonly slaughtered animals were cattle, sheep and pig(Hårding, 1990). Contacts with the archipelago are reflected ina rather high frequency of bones from wild birds. In contrast to latermore developed towns the amount of wild fowl in Sigtuna exceedsthe frequency of domesticated birds (Vretemark, 1997). Theimportance of marine resources is reflected in the large quantitiesof local freshwater fish such as pike (Esox lucius), pike perch (Sanderlucioperca) and bream (Abramis brama) (Ericson, 1989). It is ofinterest though that a small amount of bones from herring (Clupeaharengus) and cod (Gadus morhua) have been identified indicatinga minor import of fish from the Baltic Sea area (e.g. Hårding,unpublished report).Sigtuna is located in a narrow bay of the Lake Mälaren, whichwas connected to the Baltic Sea until the 13th century. This suggeststhat the area had a more maritime character during the firstcenturies (phases 1 and 2). However, the isotopic differencesbetween fish from the Lake Mälaren in the two first phasescompared to the freshwater fish from the last phase are notbelieved to be very different (Westman et al., 1999). In addition, asmentioned above, the animal bone debris indicates thatconsumption of fish from the Baltic must have been limited.The factors that contribute to the variability in d15N values inhuman bone collagen are many, diverse and poorly understood.Except for being an indicator of the consumption of animal protein,

A. Kjellström et al. / Journal of Archaeological Science 36 (2009) 2689–2699nitrogen isotope ratios may also be affected by an intake of leguminous or nonleguminous vegetables (Commisso and Nelson,2006, 2007, 2008), specific dairy products (Minagawa, 1992),suckling animals (Jay & Richards, 2006), migrating birds(Rubenstein & Hobson, 2004), aridity (Schwarcz et al., 1999) anddifferent types of meat or freshwater fish (e.g. Katzenberg, 2000).This suggests that interpretations based on the isotopic nitrogensignature must be made with caution. Furthermore, the food chainsin water are longer than on land and are thus affecting the d15Nvalue for different fish species (Eriksson et al., 2008). Hence,carnivorous fish such as Pike will get very high d15N values andeven a low intake may affect the human bone collagen. To someextent it is possible to distinguish between freshwater and marinefish due to the isotope signatures (Eriksson and Zagorska, 2003),however, both groups show a large variation depending on speciesand habitat.According to Katzenberg (1992) the isotopic values for a dietwith a large intake of terrestrial food and without any aquaticcontributions, would result in d13C values less than 19.00&. Asa reference for the present analysis previous studies from thenearby settlement Birka (A.D. 750–950), also located in the LakeMälaren area, have shown that cattle range from 22.0 to 21.8&for d13C and 4.0–5.1& for d15N (Linderholm et al., 2008a). At thesame sites the values for omnivores such as pigs range from 21.3to 19.9& for d13C and 9.7–13.8& for d15N. No terrestrial carnivores or fish bones have been analyzed at Birka. However, sites atÖland (also on the east coast of the Baltic Sea) may be used asa reference (Eriksson et al., 2008). Values from a wild cat (Felissilvestris) show a d13C value of 16.4& and of 9.4& for d15N. Thefish bones come from pelagic species and show marine isotopicvalues ranging from 16.6 to 10.8 for d13C and 8.8–11.2& ford15N. As a reference for freshwater fish in the Bothnian Bay area,a pike (Esox lucius) from Zvejnieki, Latvia, is used, showing a d13Cvalue of –23.6& and of 11.7& for d15N (Eriksson and Zagorska,2003). It is not ideal to use reference samples of different date andcontext due to variation in particular ecology, however, this helpsestablishing the approximate isotopic signature for fauna in theregion.In recent years many studies utilizing stable isotope data andtrace element analyses of human remains as well as chemicalanalyses of organic residues on pottery have shed new light onhuman dietary patterns in Sweden during the period preceding theestablishment of Sigtuna. (Arrhenius, 1990; Lidén and Nelson, 1994;Iregren et al., 2000; Isaksson, 2000; Isaksson et al., 2004;Linderholm et al., 2008a; Linderholm et al., 2008b). The resultsindicate a diet mainly comprising proteins of terrestrial origin(Lidén and Nelson, 1994), however, with an apparently high inputof vegetable items (Isaksson, 2000). Interestingly, in the Late VikingPeriod animal foods seem to have been consumed mainly inritualized situations and contexts (Isaksson, 2000).Of interest for the present study was to evaluate the level ofanimal foods in the diets that can be used as a marker for highstatus in Sigtuna. The relationship between diet and chemistry ofbone has proved to be a valuable clue in the study of ancientdietary patterns revealing information otherwise unavailable.Many studies have examined dietary patterns in relation to socialhierarchy (e.g. Aufderheide, 1989; Aufderheide et al., 1988; Baraybar and de la Rua, 1997; During, 1994, 1997; Eriksson, 2003;Honch et al., 2006; Iregren et al., 2000; Jay and Richards, 2006;Katzenberg, 2000; Katzenberg et al., 1995; Lidén, 1995; Lidén andNelson, 1994; Mays, 1997, 2000, 2003; Müldner and Richards,2005; Olsson and Isaksson, 2008; Papathanasiou, 2003; Polet andKatzenberg, 2003; Privat et al., 2002; Richards et al., 1998; Richardset al., 2006; Sandford and Weaver, 2000; Schutkowski, 1995;Schutkowski et al., 1999; Ubelaker et al., 1995; Vuorinen et al.,26911996; Waldron, 1981; White, 1994; White et al., 1993). Our mainobjective is to examine dietary patterns in Sigtuna throughchemical analyses of human remains using stable isotopes. Morespecifically, we examine dietary changes related to time, andwithin each time period, dietary changes related to sex and ifpossible, social status. In Sigtuna the burials chosen for analysiswere initially dated through archaeological criteria (Wikström,2006) but in order to confirm the chronology all samples wereradiocarbon dated. In most previous studies, the analyzed sampleshave seldom been radiocarbon dated rendering the chrono