ojoa_355 407..428 RHIANNON E. STEVENS, EMMA LIGHTFOOT, JULIE HAMILTON, BARRY CUNLIFFE AND ROBERT E.M. HEDGES STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS Summary. Carbon and nitrogen isotope analyses were performed on human and animal bones recovered from pits within Danebury Iron Age hillfort. All results are within the range expected for European Holocene specimens and are similar to those from other Iron Age sites in central southern Britain. Our results indicate that the human diet included a significant amount of animal protein (meat and/or dairy products) consumed on a regular basis, but do not preclude a diet based heavily on cereal consumption. In comparison with the extensive heterogeneity visible in the animal isotope values, the homogeneity of the human values is rather striking. This may be a reflection of the much slower turnover rate of adult human collagen and may also indicate that the humans consumed a much greater variety of food than the fauna (thus averaging many isotopic sources). This is consistent with the role of hillforts as central places and locations for food distribution and exchange. introduction Once seen as largely defensive structures, hillforts have more recently been shown to be centres where a range of communal and ritual activities took place. Hillforts served as places of residence and performed a number of functions, including food storage and exchange. Many were also locations for overwintering stock and lambing/calving, and for processing, storing and redistributing grain from a wider area (Cunliffe 1984b; 1995). Danebury, occupied during the latter half of the first millennium BC, is one of the most significant and impressive Iron Age hillforts in southern Britain. Extensive excavations between 1969 and 1988 produced a wealth of faunal and botanical remains which provide indirect, qualitative information about the diets of the people living in the Danebury region (Cunliffe 1995). Because of its regional role, however, it is not possible to establish the extent to which this broad dietary information relates to the diets of the people who were buried in the hillfort. In this context, carbon and nitrogen stable isotope analysis of human and animal bone collagen can be especially informative as it provides a direct, long-term record of past diets at both the individual and population level. The application of this technique to Danebury is of considerable interest as the information obtained from the isotopic data can be integrated with OXFORD JOURNAL OF ARCHAEOLOGY 29(4) 407–428 2010 © 2010 Blackwell Publishing Ltd., 9600 Garsington Road, Oxford OX4 2DQ, UK and 350 Main Street Malden, MA 02148, USA. 407 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS the substantial archaeological evidence for diet and environmental information concerning the surrounding landscape. This technique has been applied to human populations from a number of Iron Age sites in Britain (e.g. Richards et al. 1998; Jay and Richards 2006; 2007; Jay 2008; Lightfoot et al. 2009), but only two of these sites are hillforts (Broxmouth, located in East Lothian, Scotland, and Poundbury, located in Dorset (Richards et al. 1998; Jay and Richards 2007)). At both Poundbury and Broxmouth the burial tradition differed significantly from that at Danebury as the majority of the human remains were recovered from cemeteries just outside the hillforts rather than from pits within them. Furthermore, at Poundbury the human remains have been broadly dated to the Late Iron Age/early Roman period and may not therefore be contemporaneous with the hillfort or the humans from Danebury. The excavations at Broxmouth have been published only in interim reports and therefore the isotopic results cannot be closely compared to the archaeological evidence for diet. Thus, an isotopic approach has not yet been applied to an Iron Age archaeological site akin to Danebury. This is the first in a series of studies investigating diet and economy at a number of Iron Age sites within the Danebury Environs study region by means of isotopic techniques. The aims of this study were thus: 1. to reconstruct the diet of the humans buried within Danebury hillfort as far as possible via isotopic analysis; 2. to compare and integrate the dietary information gained through isotope analysis with previous conclusions gained from the zooarchaeological and archaeobotanical remains; 3. to determine whether any isotopic differences within the hillfort population correlate with sex, age or burial practice; and 4. to compare the isotopic signatures of the humans found at Danebury with those at other types of Iron Age settlements in central southern Britain. background to study Reconstructing diet by stable isotope analysis Food sources contain different isotopic signatures which are transmitted through the food chain and recorded in the body tissues of the consumer. The composition of a human or animal’s body protein (such as bone collagen, studied here) primarily reflects its dietary protein intake (Ambrose and Norr 1993; Tieszen and Fagre 1993). Bone collagen, at least in adults, has a slow rate of formation and turnover, and its stable isotope composition therefore reflects the dietary intake over a period of years (Hedges et al. 2007). Carbon isotopes are used to detect variations in dietary inputs in terms of marine versus terrestrial protein (e.g. Schoeninger et al. 1983) or C3 versus C4 plants (e.g. Vogel and Van der Merwe 1977). Some studies suggest that a trophic shift between 0‰ and +2‰ occurs in carbon isotope signatures of bone collagen between diet and consumer, although +1‰ is more typically quoted (see Bocherens and Drucker 2003 for a review). Nitrogen isotopes primarily reflect the position of an animal in the food chain, as a +3‰ to +5‰ enrichment has been observed with each elevation in trophic level although the mechanism by which trophic level enrichment takes place is not well understood (Bocherens and Drucker 2003; Hedges and Reynard 2007). Nitrogen isotope ratios can be used to identify aquatic protein intake, as food chains are longer in both freshwater and marine ecosystems than in terrestrial ones (Schoeninger and DeNiro 1984). Unfortunately, it is impossible to distinguish between dietary protein sources derived from meat and milk of the same animal using carbon and nitrogen isotope bulk collagen analyses (O’Connell and Hedges 1999). 408 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. Although diet is the primary factor determining bone collagen isotope values, climatic and environmental parameters (temperature, water availability, salinity, manuring, etc.) can influence the isotope signatures of the local plants resulting in isotope variation within the herbivores, omnivores and carnivores that live within the ecosystem (Heaton 1999; Stevens and Hedges 2004; Bogaard et al. 2007). Therefore, it is necessary to sample contemporaneous fauna from the site in order to determine the isotopic signatures of animals potentially consumed by the human population. These in turn provide some indication of the isotope signatures of some, but not necessarily all, of the plants also potentially consumed by the humans. Analysis of associated fauna has in recent years become more routine; however, the number of associated fauna analysed at Danebury and reported here is unprecedented. Information on husbandry practices and landscape use can potentially be gained through such extensive isotopic investigations. However, a discussion of the animal isotope signatures in this context is beyond the scope of this study and will be the focus of a future paper. The Danebury landscape The following summary of the Danebury landscape is based on Cunliffe (1984a; 1993; 1995). Located near Stockbridge in Hampshire, Danebury hillfort sits only 145 m above sea level, but as the surrounding region rarely exceeds 100 m in altitude it dominates the landscape. It is located within chalkland, which falls away to the north to a scarp slope 24 km away, overlooking the valley of the River Enborne, a tributary of the Thames. The chalk dips gradually to the south until it disappears beneath clays and sands in the Hampshire Basin. The chalk is mainly covered with a thin light soil 200–300 mm thick, but in places patches of clay-with-flints cap the hilltops. The river valleys in the area surrounding Danebury are filled, to varying depths, with colluvial and alluvial deposits. This landscape would have been appealing for settlement as the gentle slopes and light soils lend themselves to cultivation with a prehistoric ard. Upland pastures were suitable for grazing sheep, whilst the wide flood plain of the River Test contained water meadows that were appropriate for grazing cattle. Areas of woodland on the steeper slopes would have provided a suitable habitat for herds of swine. The archaeobotanical and zooarchaeological record of subsistence at Danebury The majority of the archaeobotanical remains at Danebury were preserved as carbonized assemblages in pits. The archaeobotanical record is dominated by annual seed crops to the virtual exclusion of other food plants (Jones 1995). Spelt wheat (Triticum spelta) was the most common species in the assemblage followed by hulled six-row barley (Hordeum polystichum) (Jones 1984). Other crops included emmer (Triticum dicoccum), bread wheat (Triticum aestivocompactum) and hazelnut (Corylus avellana). Taxa, such as wild carrot (Daucus carota), could have been grown as crops but alternatively may have grown as weeds. Although other plants were utilized, cereals are likely to have accounted for the vast majority of the plants consumed by the human population. During the main period of occupation of the hillfort there was no obvious change in the composition of the palaeobotanical record. Analysis of the botanical remains has indicated that grain was being brought to the site either threshed or in the ear ready for threshing (Jones 1984; Jones and Nye 1991; Jones 1995). The quantity and abundance of carbonized cereal and arable weeds indicate that extensive cereal processing (the later phases: threshing, winnowing and storage) was taking place within the hillfort (Cunliffe OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 409 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS 1993; Jones 1995). Processed cereal grains were then stored in pits and granaries. Crops from several sites may have been mixed during storage at the hillfort. The storage capacities of the site were greatly in excess of the needs of the resident population, supporting the argument for Danebury’s role as a focus in a redistribution network (Cunliffe 1995). The following account of the zooarchaeological remains at Danebury is based on Grant (1984; 1991) and Cunliffe (1995). The zooarchaeological analysis indicated that many species were utilized including cattle, sheep, horse, pig, dog, goat, cat, red deer, roe deer, fox, badger, fish and birds. Only a few of these species, however, were economically important and were frequently consumed by the human population. Based on estimates of the minimum number of individuals, sheep dominated the faunal assemblage (c.60 per cent to 70 per cent), with both cattle and pig being abundant (c.10 per cent to 15 per cent), The age/sex profiles for cattle and sheep suggest that secondary products, such as milk, wool and traction, were more important than meat in management strategy, while pigs were clearly raised for meat. Thus the percentage meat calculations are not indicative of the amount of protein obtained from each animal as dairy products may have played an important role in the human diet. The scarcity of finds of goat, cat, red deer, roe deer, fox, badger, fish and bird bones, and the infrequent butchery marks, indicate that these species were not of economic importance at Danebury. Almost two-thirds of the bones recovered were identified as belonging to sheep, clearly showing that the livestock economy centred on sheep. The distinction between sheep and goat is not possible for all skeletal elements; however, the examination of clearly diagnostic bones suggested that only a very small amount of the ovicaprid remains were goat. The butchery marks suggest that the vast majority of the sheep remains were food refuse, but husbandry aims were also strongly focused on the production of wool, milk and manure. Although sheep bones were considerably more numerous than the bones of the other species, estimated meat and offal yields indicate that sheep may have only contributed an average of 27 per cent of the meat to the diet. Cattle made up approximately one-fifth of the bones recovered from the site. Although kept in much smaller numbers than sheep, estimated meat and offal yields indicate that cattle contributed an average of 46 per cent of the meat to the diet and are therefore thought to have been the major meat contributor. The mortality profiles indicate that the majority of cattle were mature animals, although the relatively high number of very young cattle indicates that Danebury may have been a centre for cattle breeding. Only mature cattle appear to have been slaughtered for food. Cattle, like sheep, are likely to have been exploited for their secondary products (Cunliffe 1993). Pot residue analysis has shown the presence of dairy fats adhering to many pot sherds recovered from Danebury, indicating that milk was a common item. Note that it is not possible to distinguish between the milk fats originating from the different species of ruminant animal, and thus the relative importance of cattle versus sheep for milk production is not known (Copley et al. 2005). Around 12 per cent of the bones recovered were those of pigs, which provided only two main products – meat and manure. Calculations of the meat and offal yields indicate that pigs provided an average of 26 per cent of the meat consumed within the hillfort. As highly flexible omnivorous animals they are able to consume a range of foodstuffs. Although forest clearance by the Iron Age was extensive, the pigs are likely to have been turned out into the woodland that remained to forage during autumn and winter, spending their spring and summer on rough pastures or areas of heath (Cunliffe 1993). Within the forest they may have consumed fungi (which have distinct isotopic signatures), although the quantity is likely to have been substantially less than that consumed by pigs during the Neolithic period when woodlands, deadwood and fungi were more widespread (Hamilton et al. 2009). 410 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. Horses accounted for only 3 per cent of the bones recovered at Danebury and were evidently of much less importance to the nutritional economy than the previously discussed animals. Horses were kept to fulfil a few special functions such as pulling light loads. As Iron Age harnesses were simple, horses could not have been used for pulling ploughs (Cunliffe 1993). The horses’ mortality profile suggests that horse-breeding did not occur on site and, moreover, the majority of the horses seem to have been male. This situation is paralleled at other Iron Age sites and suggests that horses were not bred but were periodically rounded up to be broken in and trained for riding, light traction and as pack animals. The traces of butchery marks on the bones suggest that some of the horses were used as a meat source. A number of horses, however, were found in ritual deposits, and without butchery marks, indicating that horses were viewed differently to the other domesticates. Dog bones were only found in relatively small numbers (c.2 per cent) at Danebury. Dogs seem to have been present at the majority of Iron Age sites in Britain, where they are generally assumed to have been kept as guard dogs or sheep dogs. Gnaw marks on bones suggest that dogs would have had access to scraps and waste food, while butchery marks provide evidence that dogs were at least occasionally consumed by humans. Although approximately 240,000 faunal bone fragments were recovered from Danebury between 1969 and 1988, the calculated number of the animals represented for every year of occupation is very small (Grant 1991). Even when multiplied by two to account for the unexcavated area of the site such a calculation indicates that 8.4 animals were killed per year (Grant 1991). This represents a very small amount of meat and suggests that it may have only been consumed occasionally and that the diet may have focused more on cereals and secondary products. However, this calculation may not be meaningful as it is not possible to establish how much of the midden waste (including animal bones) was carried out of the hillfort to manure the fields. Mortuary practices at Danebury The final deposition of human skeletal material into pits at Danebury is the result of a number of processes linked to a range of beliefs and practices, but it is not considered to be the normative disposal pattern during the Iron Age (Cunliffe 1995). Almost all of the human remains recovered from Danebury were found in storage pits within the settlement area (Walker 1984). As such, they may be seen as being part of a tradition of burial recognized in upland central southern England where the construction of storage pits was an integral aspect of the local economic system (Whimster 1981; Walker 1984). It is likely that in the Iron Age the dead were normally disposed of in a way which has left little or no archaeological trace (Cunliffe 1995). Thus the bodies isotopically analysed for this study may not necessarily be representative of the entire population who inhabited Danebury. Moreover, the individuals to whom the archaeological bones belonged may not have been members of the population who occupied the site. They are likely to represent either individuals who died and for some reason were excluded from the normal disposal rites or were the victims of sacrifices (Cunliffe 1995). Such possibilities should be kept in mind when comparing the isotopic results of the human and animal remains recovered from Danebury. Six main burial deposition types were identified at Danebury (Table 1). In each of these categories the human bodies are thought to have been treated differently after death. The extent to which these different deposition types may reflect specific rituals or status during life is unclear (Walker 1984; Cunliffe 1995). OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 411 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS table 1 Burial types identified at Danebury hillfort and number of individuals analysed for this study from each burial type Category Mortuary practice No. of individuals A B C D E F Whole bodies in single or group burials Incomplete skeletons (individual depositions) Multiple, partially articulated skeletons in charnel pits Skulls or frontal bones Pelvic girdles Individual bones and bone fragments 24 5 13 12 2 1 Complete skeletons (type A) are thought to have been inhumed soon after death before the flesh had decayed sufficiently to allow the body to fall apart. With an absence of butchery marks or evidence of violent dismemberment on all but one specimen, the incomplete skeletons and individual bones (types B to F) are thought to have been deposited some time after the connective tissue had begun to rot (Walker 1984; Cunliffe 1991). The depositions of skulls (type D) and pelvic girdles (type E) were considered as separate deposition categories as they are likely to reflect socially distinct burial rites. One of the pelvic girdles displays the only direct evidence of human butchery found at the site (Walker 1984). Classical references have highlighted the symbolic importance of the skull to the Celts and have reported the removal of the heads of those killed during battle and their display as trophies as part of Celtic rituals (Polybius, Hist., III, 67; Diodorus Siculus, 29, 4–5; Strabo, IV, IV, 5; Lucan, I, 447; Livy, XXIII, 24; Whimster 1981, 185–6; Walker 1984). The cause of death cannot be determined for the majority of the skeletons, but a few skulls show evidence of warfare in the form of sword injuries. None of the depositions are associated with grave goods (Walker 1984). Some of the burials within each burial type (with the exception of type D) were accompanied by special animal deposits associated with ritual behaviour (Walker 1984). materials and methods In total, 205 bones from Danebury hillfort were sampled for isotopic analysis. Samples were taken from 58 humans recovered from deposits dating between ceramic phases 3 (c.470 to 360 BC) and 8 (c.50 BC to AD 50; see Table 2 for full details). Human bone samples were taken from all deposition categories with the exception of category F. Burial type, sex and age had been previously established for most individuals (Hooper 1984; 1991). In addition, samples were taken from 148 animals (39 cattle, two dogs, 18 horses, 30 pigs, 58 sheep and one roe deer). Faunal sampling focused on adult specimens; young and juvenile animals were avoided. The fauna were recovered from deposits also dating between ceramic phases 3 and 8 (see Table 3 for full details). Samples were prepared following the method in Privat et al. (2002). Collagen was extracted at the RLAHA, University of Oxford and at the McDonald Institute for Archaeological Research, University of Cambridge. Samples were isotopically analysed using an automated Carlo Erba carbon and nitrogen elemental analyser coupled in a continuous flow mode to an isotope ratio-monitoring (PDZ Europa Geo 20/20) mass spectrometer. Carbon and nitrogen results are measured in parts per mille (‰) relative to VPDB and AIR standards respectively 412 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. Sample no. Context Deposition Sex Age Growth Ceramic phase Burial category %C %N d13C d15N C:N DEH64 DEH77 DEH62 DEH89 DEH61 DEH60 DEH82 DEH68 DEH93 DEH59 DEH48 DEH50 DEH69 DEH76 DEH78 DEH80 DEH83 DEH90 DEH49 DEH84 DEH54 DEH71 DEH53 DEH85 DEH98 DEH91 DEH52 DEH94 DEH65 DEH105 DEH102 DEH86 DEH63 374/5 620/3 1114/5 G67 807/6 935/6H2 374/6 1015/6 587 1078/6 2218/2 582/4 2462/2 343/2 829 829 383/1 497 829 84/1 2100/2 489/2 2605/1 2223/3 120 37 2,4475 266 1993/6 1743 2509 1545/4 923/6 13x 25 241 58 27 44 14 46 24 49 222 23 240 12 28 29 16 22 30 6 248 21 259 223 7 3 239 10 214 224 245 199 34 Not determined Not determined Male Not determined Male Female Male Male Male Female Male Female Male Male Male Male Male Female Male Male Not determined Female Female Male Not determined Male Male Female Female Not determined Not determined Not determined Not determined c.3 c.5 c.12–13 c.15 17–22 17–25 17–25 20–25 20–25 21–25 25 25–35 25–35 25–35 25–35 25–35 25–35 25–35 30–40 30–40 35+ 35+ 50+ 50+ c.8 c.14–16 18–22 20–30 25–30 12 c.10–12 c.5–15 c.8–10 Infant Child Adolescent Adolescent Early adult Early adult Early adult Early adult Early adult Early adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Old adult Old adult Juvenile Adolescent Early adult Mature adult Mature adult Juvenile Juvenile Juvenile Juvenile 3 7 6 3 6 7 3 7 3 7 5 7 5 3 6 6 7 5 6 3 3 7 7 7 8 4 7 3 7 3 3 4 7 A A A A A A A A A A A A A A A A A A A A A A A A B B B B B C C C C 44.5 41.8 43.2 43.0 42.8 43.7 38.9 43.1 40.4 45.9 46.6 44.5 38.5 43.4 44.6 43.4 44.0 33.4 42.7 44.4 44.6 44.7 45.4 45.6 39.3 32.0 43.7 44.5 44.0 41.3 40.4 44.9 44.2 15.9 15.2 15.6 15.1 15.7 15.8 14.3 15.8 15.0 16.6 16.8 16.0 14.0 15.6 16.1 15.6 15.8 12.0 15.3 15.9 16.3 16.1 16.3 16.4 14.0 11.3 15.6 15.7 16.0 14.7 14.2 16.3 16.1 -20.7 -20.0 -20.3 -20.0 -19.9 -20.2 -20.1 -20.2 -19.6 -20.3 -19.7 -20.0 -19.9 -20.0 -20.1 -20.1 -20.3 -20.3 -20.1 -20.1 -20.0 -20.1 -20.2 -19.8 -20.0 -20.3 -19.9 -20.0 -20.0 -21.8 -20.2 -19.9 -19.9 10.0 7.7 9.3 8.1 8.7 7.8 7.5 8.4 8.3 8.1 8.4 8.0 7.8 8.3 8.0 8.1 8.0 8.8 8.7 8.6 8.3 7.7 8.2 8.6 7.8 8.8 8.7 9.8 7.8 5.3 7.6 8.5 7.7 3.3 3.2 3.2 3.3 3.2 3.2 3.2 3.2 3.1 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.3 3.2 3.2 3.3 3.2 3.2 3.2 3.3 3.3 3.3 3.3 3.3 3.2 3.3 3.3 3.2 3.2 RHIANNON E. STEVENS ET AL. OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. table 2 Human sample information and isotopic results 413 414 © 2010 Blackwell Publishing Ltd. OXFORD JOURNAL OF ARCHAEOLOGY Sample no. Context Deposition Sex Age Growth Ceramic phase Burial category %C %N d13C d15N C:N DEH51 DEH56 DEH67 DEH58 DEH79 DEH47 DEH81 DEH73 DEH70 DEH87 DEH92 DEH88 DEH97 DEH108 DEH100 DEH106 DEH99 DEH95 DEH96 DEH107 DEH101 DEH103 DEH104 DEH66 923/6 923/6 923 923/6 923/6 1078/6/5 935/6 923 2496/4 2509 23 2509 78 448 1530 2030 1530 27 639 2269 2383 1020 16 1156/1160 35 36 37 38 40 50 42 39 242 245a 1 245b 5 20 196B 215 196A 2 26 227 251 47 62 137 Not determined Not determined ?Female Male Female Male Male Male Not determined Not determined Not determined Not determined Female Female Male Female Male Male Male Female Not determined Male Female Not determined 14–16 14–16 16–20 20–25 25–30 25–35 35–40 35–45 Adult c.10–12 c.7–9 c.8–10 16+ 17–25 20–30 20–30 20–35 25+ 25–35 30+ Adult 18–25 <30 Adult Adolescent Adolescent Early adult Early adult Mature adult Mature adult Mature adult Mature adult Mature adult Juvenile Juvenile Juvenile Early adult Early adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Mature adult Early adult Mature adult Mature adult 7 7 7 7 7 7 7 7 7 3 7 3 7 5 7 6 7 7 6 7 7 3 3 6 C C C C C C C C C D D D D D D D D D D D D E E F 43.1 43.4 42.7 41.9 43.4 Failed 44.3 41.1 43.4 39.5 43.1 36.2 28.3 40.3 41.5 33.7 42.6 21.7 23.5 38.1 41.5 33.0 34.2 44.5 15.6 15.6 15.5 15.4 15.5 Failed 16.1 14.9 15.7 14.1 15.2 13.0 10.2 14.4 14.3 12.0 14.9 7.7 8.6 13.5 14.5 11.7 12.3 15.6 -20.3 -19.8 -20.1 -19.7 -20.2 Failed -19.9 -20.0 -20.2 -20.2 -20.1 -20.4 -20.2 -20.2 -19.6 -20.2 -20.5 -20.1 -20.3 -19.9 -20.0 -20.1 -20.2 -20.7 7.6 8.0 8.5 7.8 8.1 Failed 8.5 8.0 7.2 8.8 8.8 8.9 8.2 8.6 10.4 8.5 10.6 7.9 7.8 7.7 9.2 7.4 8.7 9.2 3.2 3.2 3.2 3.2 3.3 Failed 3.2 3.2 3.2 3.3 3.3 3.2 3.2 3.3 3.4 3.3 3.3 3.3 3.2 3.3 3.4 3.3 3.3 3.3 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS table 2 continued RHIANNON E. STEVENS ET AL. table 3 Faunal sample information and isotopic results Sample no. Species Ceramic phase Context details %C %N d13C d15N C:N DBH100 DBH103 DBH78 DBH79 DBH82 DBH85 DBH86 DBH87 DBH88 DBH89 DBH92 DBH96 DBH10 DBH13 DBH144 DBH147 DBH148 DBH17 DBH19 DBH20 DBH21 DBH22 DBH26 DBH39 DBH41 DBH44 DBH45 DBH49 DBH7 DBH104 DBH107 DBH108 DBH109 DBH110 DBH120 DBH126 DBH131 DBH133 DBH134 DBH8 DBH116 DBH53 DBH73 DBH75 DBH77 DBH81 DBH94 DBH95 DBH1 DBH11 DBH12 DBH14 DBH141 DBH143 Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Cattle Dog Dog Horse Horse Horse Horse Horse Horse Horse Horse Horse Horse Horse Horse Horse 3 3 3 3 3 3 3 3 3 3 3 3 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 8 4–6 4–6 7 8 3 3 3 3 3 3 3 7 7 7 7 7 7 DA71 P84 1 DA78 P1129 1 DA76 P923 3 DA71 P84 2 DA76 P923 3 DA76 P923 6 DA76 P923 6 DA76 P923 6 DA76 P923 6/31 DA76 P923 6/33 DA78 P1030 6 DA71 P84 2 DA77 P955 2 DA77 P955 2 DA77 P935 6 DA77 P935 6 DA77 P935 6 DA82 P2155 2 DA77 P995 3 DA74 P582 4 DA82 P1996 4 DA73 P507 1 DA77 P995 7 DA77 P955 2 DA77 P955 2 DA74 P630 1 DA 74 P571 1 DA74 P751 1 DA82 P2155 2 DA78 P1078 3 DA78 P1078 1 DA78 P1078 1 DA78 P1078 1 DA78 P1078 1 DA78 P1078 4 DA87 P1900 1 DA87 P1900 1 DA74 P636 3 DA74 P619 3 DA82 P2155 2 DA78 P1078 2 DA78 P1030 7 DA76 P923 5 DA76 P923 6 DA76 P923 6/4 DA76 P923 3 DA78 P1030 9 DA71 P84 2 DA73 P507 1 DA77 P995 2 DA77 P995 1 DA77 P995 7 DA77 P935 6 DA77 P935 6 38.4 42.6 23.7 12.9 37.6 38.8 18.9 25.9 18.0 33.7 16.2 19.4 27.5 16.3 20.9 30.3 27.8 43.8 17.9 17.7 26.3 15.9 39.2 36.4 19.5 22.1 42.9 33.3 25.0 24.6 24.6 37.8 31.3 29.0 23.6 17.8 30.9 21.6 24.6 25.5 36.1 26.5 24.4 30.2 Failed 13.6 20.7 26.2 32.0 40.0 8.4 11.6 16.2 21.3 13.8 15.4 8.3 4.4 13.6 13.7 6.7 9.1 6.3 12.0 5.6 6.7 10.1 5.9 7.6 11.2 10.2 16.3 6.7 6.4 9.7 5.8 14.2 13.2 7.1 8.1 15.6 12.3 9.4 8.6 8.5 13.1 10.9 10.1 8.1 6.4 11.3 7.9 8.9 9.3 12.8 9.4 8.6 10.7 Failed 4.6 7.2 9.1 11.5 14.5 2.9 4.2 5.8 7.8 -21.2 -21.8 -22.4 -22.3 -21.5 -21.7 -22.1 -21.3 -21.6 -21.5 -21.9 -21.6 -21.5 -22.3 -21.1 -21.8 -21.5 -21.5 -21.5 -21.2 -21.4 -21.6 -21.6 -21.8 -21.5 -21.4 -20.7 -21.5 -21.2 -21.6 -21.5 -21.5 -21.5 -21.2 -21.7 -21.7 -21.9 -22.0 -21.3 -20.6 -20.1 -22.4 -22.2 -21.6 Failed -23.0 -22.6 -22.3 -22.4 -22.2 -22.8 -22.2 -21.7 -22.3 4.9 4.0 6.7 6.4 4.2 5.4 3.4 2.8 5.1 5.4 2.6 3.3 3.4 4.1 4.3 3.6 2.8 5.6 2.4 6.3 3.8 2.9 5.2 3.7 4.4 5.0 2.3 5.3 4.9 4.1 6.1 3.7 4.8 2.0 6.0 5.5 3.6 3.9 4.1 7.7 6.5 4.6 3.0 2.0 Failed 5.1 5.7 5.8 4.2 3.1 5.3 3.4 1.6 5.2 3.3 3.2 3.3 3.4 3.2 3.3 3.3 3.3 3.3 3.3 3.4 3.4 3.2 3.2 3.2 3.2 3.2 3.1 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.1 3.4 3.4 3.4 3.4 3.3 3.4 3.2 3.2 3.2 3.2 3.2 3.3 3.3 3.3 3.3 Failed 3.5 3.4 3.4 3.3 3.2 3.3 3.2 3.2 3.2 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 415 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS table 3 continued Sample no. Species Ceramic phase Context details %C %N d13C d15N C:N DBH46 DBH47 DBH106 DBH112 DBH114 DBH54 DBH55 DBH58 DBH59 DBH60 DBH62 DBH63 DBH65 DBH93 DBH98 DBH99 DBH145 DBH146 DBH16 DBH24 DBH25 DBH32 DBH34 DBH35 DBH36 DBH40 DBH48 DBH52 DBH122 DBH127 DBH129 DBH132 DBH135 DBH136 DBH138 DBH91 DBH101 DBH102 DBH56 DBH57 DBH61 DBH64 DBH66 DBH67 DBH68 DBH69 DBH70 DBH71 DBH72 DBH74 DBH76 DBH80 DBH83 DBH84 Horse Horse Horse Horse Horse Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Pig Roe deer Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep 7 7 8 8 8 3 3 3 3 3 3 3 3 3 3 3 7 7 7 7 7 7 7 7 7 7 7 7 8 8 8 4–6 4–6 4–6 4–6 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 DA74 P571 1 DA74 P630 1 DA78 P1078 1 DA78 P1078 1 DA78 P1078 5 DA76 P923 6 DA76 P923 3 DA76 P923 6 DA78 P1102 2 DA76 P923 1 DA76 P923 1 DA76 P923 2 DA78 P1060 4 DA78 1030 9 DA76 P923 6 DA78 1030 7 DA77 P935 6 DA85 P2447 5 DA77 P995 1 DA77 P955 2 DA77 P995 3 DA74 P571 1 DA74 P571 1 DA74 P571 1 DA73 P507 1 DA82 P2155 2 DA74 P630 1 DA 74 P630 1 DA78 P1078 5 DA78 P1078 3 DA78 P1078 1 DA74 P686 3 DA74 P649 1 DA78 P1058 5 DA74 P619 3 DA78 P1030 7 DA71 P84 1 DA78 P84 2 DA71 P84 2 DA78 P1030 5 DA76 P923 6 DA76 P923 6 DA76 P923 6 DA76 P923 6 DA76 P923 6 DA76 P923 6 DA76 P923 6 DA76 P923 1 DA76 P923 6 DA76 P923 4 DA76 P923 4 DA71 P84 2 DA78 P1102 2 DA78 P1102 2 24.5 35.2 33.6 27.8 36.2 25.6 28.8 31.8 33.7 34.7 27.6 33.2 26.9 20.0 28.5 27.0 19.7 27.7 23.7 21.4 42.5 29.7 35.6 28.2 30.5 19.5 38.7 25.3 40.0 28.7 30.4 28.2 31.8 22.3 29.1 27.5 25.6 23.5 35.5 45.1 26.0 41.2 33.5 40.1 25.9 15.5 20.5 34.2 42.0 39.8 24.4 23.0 26.7 25.5 8.8 13.1 11.8 9.6 13.0 9.1 9.9 11.3 12.1 12.0 9.5 11.5 9.4 7.0 10.0 9.5 7.1 9.9 8.7 7.7 15.3 10.7 13.1 10.4 10.9 6.9 14.2 8.9 14.0 10.2 10.9 10.3 11.6 8.1 10.7 9.7 9.0 8.2 12.5 16.1 9.2 15.0 12.0 14.4 9.0 5.4 7.2 11.6 14.9 13.7 8.6 8.0 9.3 9.0 -22.1 -22.2 -22.2 -22.4 -22.4 -21.4 -21.6 -20.8 -21.5 -21.7 -21.5 -21.6 -21.6 -20.9 -21.5 -20.8 -21.0 -21.1 -21.3 -21.4 -21.4 -21.8 -21.1 -21.7 -21.2 -21.6 -21.0 -21.3 -20.4 -21.7 -20.6 -21.4 -21.4 -21.0 -21.4 -21.1 -20.7 -21.5 -21.4 -21.2 -20.6 -21.1 -21.2 -20.5 -20.9 -21.4 -21.4 -21.7 -20.7 -21.4 -21.4 -21.4 -21.6 -21.9 3.9 2.8 3.9 4.9 3.6 7.0 5.4 6.3 7.2 6.3 5.9 6.6 6.6 3.9 6.7 5.4 6.4 5.8 7.3 6.9 7.6 6.3 6.9 6.1 5.6 7.1 6.8 5.8 5.9 9.9 7.5 6.7 6.5 6.7 6.7 2.0 4.1 5.8 4.8 5.1 3.1 4.4 4.8 3.4 3.3 4.1 3.8 4.3 5.0 4.8 4.9 5.8 4.1 6.0 3.3 3.1 3.3 3.4 3.3 3.3 3.4 3.3 3.3 3.4 3.4 3.4 3.3 3.3 3.3 3.3 3.2 3.3 3.2 3.3 3.2 3.2 3.2 3.2 3.3 3.3 3.2 3.3 3.3 3.3 3.3 3.2 3.2 3.2 3.2 3.3 3.3 3.3 3.3 3.3 3.3 3.2 3.3 3.2 3.4 3.4 3.3 3.4 3.3 3.4 3.3 3.3 3.3 3.3 416 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. table 3 continued Sample no. Species Ceramic phase Context details %C %N d13C d15N C:N DBH90 DBH97 DBH142 DBH15 DBH18 DBH2 DBH23 DBH27 DBH28 DBH29 DBH3 DBH30 DBH31 DBH33 DBH37 DBH38 DBH4 DBH42 DBH43 DBH5 DBH50 DBH51 DBH6 DBH9 DBH105 DBH111 DBH113 DBH115 DBH117 DBH118 DBH119 DBH121 DBH123 DBH124 DBH125 DBH128 DBH130 DBH137 DBH139 DBH140 Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep Sheep 3 3 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 8 8 8 4–6 4–6 4–6 DA71 P84 2 DA78 P1030 3 DA85 P2447 5 DA77 P955 2 DA77 P995 7 DA74 P571 1 DA77 P995 2 DA74 P582 4 DA74 P582 4 DA77 P955 2 DA77 P995 3 DA77 P955 2 DA77 P955 2 DA82 P1996 4 DA74 P522 7 DA74 P582 3 DA74 P582 2 DA82 P2155 2 DA74 P571 1 DA74 P 82 2 DA77 P955 2 DA74 P571 1 DA77 P995 3 DA74 P582 4 DA78 P1078 6 DA78 P1078 1 DA78 P1078 6 DA78 P1078 5 DA78 P1078 5 DA78 P1078 5 DA78 P1078 1 DA78 P1078 1 DA78 P1078 6 DA78 P1078 6 DA87 P1900 1 DA78 P1078 1 DA78 P1078 3 DA74 P619 3 DA78 P1058 5 DA74 P649 1 33.2 43.3 27.6 19.1 16.0 22.0 26.3 30.9 Failed 31.4 23.7 22.9 18.4 26.0 39.2 46.2 28.0 20.4 36.7 42.7 33.2 29.9 47.7 21.8 36.8 41.3 29.1 39.0 29.8 27.2 37.4 50.9 43.2 33.3 29.3 41.6 22.1 41.8 20.2 44.6 11.6 15.7 10.2 7.0 5.9 8.1 9.8 11.2 Failed 11.5 8.8 8.2 6.6 9.5 13.9 17.0 10.4 7.4 13.4 15.1 12.1 10.6 17.7 8.1 13.2 14.5 10.3 14.0 10.4 9.6 12.9 17.5 15.5 11.9 10.2 14.8 7.9 15.5 7.2 16.4 -21.3 -20.8 -20.4 -21.0 -21.5 -21.3 -21.6 -21.2 Failed -21.6 -21.6 -21.6 -21.3 -21.1 -21.7 -20.9 -20.7 -21.4 -21.4 -21.3 -21.6 -21.0 -21.3 -21.2 -21.2 -21.0 -21.2 -21.2 -21.1 -20.9 -21.4 -21.0 -20.3 -22.2 -21.3 -21.2 -21.6 -20.9 -21.2 -21.1 4.7 4.0 4.6 3.3 4.0 4.2 4.7 4.1 Failed 3.4 4.8 2.9 3.4 3.6 5.5 4.0 3.7 2.6 3.2 4.7 3.7 5.2 3.9 4.7 4.7 4.0 4.2 4.5 4.3 3.5 4.3 4.8 3.1 3.2 5.5 4.7 3.4 4.1 4.3 4.0 3.4 3.2 3.2 3.2 3.2 3.2 3.1 3.2 Failed 3.2 3.2 3.3 3.2 3.2 3.3 3.2 3.1 3.2 3.2 3.3 3.2 3.3 3.1 3.2 3.3 3.3 3.3 3.3 3.3 3.3 3.4 3.4 3.3 3.3 3.4 3.3 3.3 3.2 3.2 3.2 (Hoefs 1997). Each sample was run at least in duplicate. Replicate measurement errors on laboratory standards (comprising in-house standards of nylon and alanine calibrated against IAEA standards) were less than 0.2 ‰ over the period of analysis. results and discussion Sample preservation Out of the 205 samples, three (one human, one horse and one sheep) failed to produce enough collagen for isotope analysis. The successfully extracted collagen had C/N atomic ratios OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 417 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS between 3.1 and 3.5 (see Tables 2 and 3). This is within the range of 2.9 to 3.6 which indicates good collagen preservation (DeNiro 1985; Ubelaker et al. 1995). All of the collagen extracts contained percentage carbon and nitrogen that were higher than 8 per cent and 3 per cent respectively which, again, are considered to be indicative of well-preserved collagen (DeNiro 1985; Ambrose 1990). The d13C and d15N values of the humans and fauna analysed are listed in Tables 2 and 3. Faunal samples The analysis of faunal material from Danebury provided baseline isotopic data against which the human d13C and d15N values could be compared (Figs. 1 and 2). The d13C of the fauna ranged from -23.0‰ to -20.1‰ and the d15N ranged from 1.6‰ to 9.9‰. As no significant differences were observed between ceramic (temporal) phases for any species, the isotope results from the different phases were considered collectively (one-way ANOVA with post-hoc Bonferroni correction). The faunal d13C results are within the typical range observed for animals living in ecosystems dominated by C3 plants. The herbivores (cattle, horse and sheep) have similar mean d15N values, approximately 4‰. The cattle and horse d15N values are more variable than those of sheep, possibly indicating differential management strategies in the use of the 13 12 11 10 Danbury humans (n=46) δ 15N(‰) 9 Danebury fauna Yarnton humans (n=27) 8 Yarnton fauna Hampshire humans (n=22) Hampshire fauna 7 Glastonbury humans (n=11) Glastonbury 6 Poundbury humans (n=13) Eton humans ( n=5) 5 4 3 -23.0 -22.5 -22.0 -21.5 -21.0 -20.5 -20.0 -19.5 -19.0 -18.5 δ C(‰) 13 Figure 1 Mean d13C and d15N values of humans and animals from Danebury hillfort. Error bars show standard deviations from the mean. 418 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. 11 10 9 8 δ 15N (‰) 7 6 5 Humans (adults and adoloscents) Cattle 4 Horses Pigs 3 Sheep 2 Dogs Roe deer 1 -23.5 -23.0 -22.5 -22.0 -21.5 -21.0 -20.5 -20.0 -19.5 -19.0 δ C (‰) 13 Figure 2 d13C and d15N values of humans and animals from Danebury hillfort. landscape. The dogs have enriched d13C and d15N relative to the herbivores, indicating an omnivorous diet. In fact they are not dissimilar to the human isotope signatures, which might imply that the dogs scavenged human food waste or may have been actively fed by the local people. Compared to ruminants, pig d15N values are substantially enriched, whereas, unlike dogs, their d13C values are similar. This suggests, but is not entirely consistent with, the feeding of pigs at a higher trophic level than herbivores, such as household scraps including animal remains. Another possibility is the consumption of cereal that has been enriched in d15N through manuring. Human samples With the exception of a single specimen, the d13C of the humans ranged from -20.7‰ to -19.6‰ (mean = -20.1‰, s = 0.2‰) and the d15N ranged from 7.2‰ to 10.6‰ (mean = 8.4‰, s = 0.7‰) (Figs. 1 and 2). The excluded specimen (Outlier 1), previously identified as a child rib, had d13C and d15N values of -21.8‰ and 5.8‰ respectively (Figs. 2 and 3). These isotope values are substantially different to those of the other humans but are similar to those of the local herbivores, which strongly suggests a misidentification of the bone. This sample was excluded from all further analyses. The human d13C signatures indicate a diet based on a C3 terrestrial food chain, and suggest that neither marine nor, probably, freshwater resources were economically important. OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 419 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS 11 4 5 2 10 6 3 9 δ 15N (‰) 8 7 6 Infant Children Juveniles Adolescents Early adults Mature adults Old adults 1 5 4 3 -22.0 -21.5 -21.0 -20.5 -20.0 -19.5 -19.0 δ C (‰) 13 Figure 3 d13C and d15N values of humans from Danebury hillfort according to age categories as defined by Bogin 1999. Numbers 1 to 6 indicate outliers from the main group. This isotopic evidence is in concordance with the zooarchaeological evidence that fish remains are almost entirely lacking from the bone assemblage. The d15N values also confirm that neither marine nor freshwater resources were consumed regularly. The human d15N signatures indicate that the diet included a significant amount of animal protein (meat and/or dairy products) consumed on a regular basis. The mean human d13C and d15N values are 1.3‰ and 3.4‰ enriched respectively relative to the average of the main economic herbivore (cattle, sheep and pig) mean isotope signatures. Such an enrichment has been used to evaluate the trophic level, or rather the relative proportion of animal to plant protein, in the human diet. However, the evaluation depends on assumptions (see Hedges and Reynard 2007 for a discussion) which cannot be shown to hold for Danebury. Crucially, d15N for herbivore diets may well differ from d15N for the plants in the human diet, which are more likely to be cereal grain rather than forage plus waste material from cleaning and threshing. It is now appreciated that cereal grains may be enriched over other plant tissues, as well as through manuring (Heaton 1999; Bogaard et al. 2007). The values we report here therefore point towards a substantial fraction of animal protein, but do not preclude a diet based heavily on cereal consumption. Although a few humans had isotopic signatures that were slight outliers (Outliers 2 to 6) from the main group of isotope results, the human isotope data are tightly clustered and much less variable than those of the fauna (Figs. 2 and 3). This may be a reflection of the much slower 420 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. table 4 Age classes as defined by Bogin (1999) Age class Male Female Infants Children Juveniles Adolescents Early adults Mature adults Old adults 0 to <3 3 to <7 7 to <13 13 to <18 18 to <25 25 to <50 50+ 0 to <3 3 to <7 7 to <11 11 to <16 16 to <25 25 to <50 50+ turnover rate of adult human collagen, or may also indicate that the human diet was on average less subject to variability than the fauna (perhaps through a much greater variety of sources). Ceramic phase: No significant differences were observed between isotope signatures of the humans dating to different ceramic phases, suggesting that during the occupation the diet of the humans did not change substantially. Age: No significant difference was observed between the mean isotope signatures of the different age categories (Juveniles to Old Adults: as defined by Bogin 1999, table 4). It should be noted, however, that Outliers 3 to 6 are all mature adults (Fig. 3). Dietary differences may have existed between these individuals and the other humans. The single infant (Specimen DEH64; Outlier 2) had depleted d13C and elevated d15N values relative to the majority of the adult humans which is likely to be due to its consumption of maternal milk. This phenomenon has been widely observed in very young humans and other animals (Fogel et al. 1989; Balasse et al. 1997; Schurr 1997) (Fig. 3). By contrast the single child isotopically analysed (DEH77) had isotopic signatures similar to those of the majority of the adult humans analysed, indicating that by c.five years old this individual had been weaned (Fig. 3). Sex: With sex determined for 39 individuals (15 females, 24 males), it was possible to compare male and female carbon and nitrogen isotope values (Fig. 4). Although no significant difference was observed between the mean d13C and d15N values of males and females, some patterning is detectable in the isotope signatures of the two sexes. Firstly, the female carbon and nitrogen isotope signatures are more clustered than those of the males (Fig. 4). Secondly, specimen DEH94 was identified as a slight isotopic outlier (Outlier 6) from the main group of human isotope results (males and females collectively). When plotted by sex it is noticeable that this specimen’s d15N value is considerably enriched relative to those of the other females. Thirdly, none of the females have d13C values greater than -19.9‰ whereas six males have values that are higher. Although these patterns could reflect small differences in the mean isotopic signatures of their diet, the difference in diet composition might be substantial but not detectable through isotopic analyses. The variation within the population is small and could alternatively be due to natural variation. Burial type: The mean d13C and d15N values of the humans did not significantly differ between burial deposition types. In particular, the mean isotope signatures of the humans belonging to those deposition types thought to reflect socially distinct performances (burial deposition types OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 421 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS 12 11 4 5 δ 15N (‰) 10 6 9 Females Males 8 Average female Average male 7 6 5 -21.0 -20.8 -20.6 -20.4 -20.2 -20.0 -19.8 -19.6 -19.4 -19.2 -19.0 δ 13C (‰) Figure 4 d13C and d15N values of humans from Danebury hillfort according to sex. Numbers (4 to 6) indicate outliers from the main group. Error bars show standard deviations from male or female means. D and E) did not differ from those not thought to reflect socially distinct performances. It should be noted that two of the four adults with outlier isotope signatures (Outlier 4 (DEH99) and Outlier 5 (DEH100)) belong to burial type D (Fig. 5). The two other outliers (Outlier 6 (DEH94) and Outlier 3 (DEH66)) belong, however, to burial types B and F respectively, which do not reflect socially distinct performances. Thus the results suggest that the individuals with socially distinct burial practices consumed isotopically similar diets to those without socially distinct burial practices Outliers: The isotope signatures of two out of the six outliers are easily explicable. Outlier 1 is thought to be a misidentified animal, and Outlier 2 is an infant whose isotope signatures have been affected by the consumption of breast milk. The four remaining outliers (Outliers 3 to 6) are all mature adults, two of whom are males (Outliers 4 and 5), one of whom is female (Outlier 6) and one whose sex is not determinable (Outlier 3). Both males represent burial type D (i.e. skulls or frontal bones) and therefore reflect socially distinct performances. The female represents burial type B and the unsexed adult represents burial type F, neither of which reflects socially distinct performances. Thus the outliers from the main group do not have many common characteristics apart from being mature adults. Their distinct isotopic signatures could indicate that they had different access to resources compared to the rest of the population buried at Danebury. Alternatively it might indicate that they lived in another community where they 422 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. 12 11 4 5 δ 15N (‰) 10 9 6 3 8 Burial type A 7 Burial type B Burial type C 6 Burial type D Burial type E Burial type F 5 -21.0 -20.8 -20.6 -20.4 -20.2 -20.0 -19.8 -19.6 -19.4 -19.2 -19.0 δ 13C (‰) Figure 5 d13C and d15N values of humans from Danebury hillfort according to burial type. Numbers (3 to 6) indicate outliers from the main group. consumed an isotopically different diet, then came (or were brought) to Danebury some time before their death or as body parts after death. Other isotopic techniques such as oxygen and strontium isotope analysis could in future be used to test this possibility. If demonstrated to be ‘immigrants’ these individuals may represent trophies of war or may have been slaves. Inter-site comparison Previous isotopic studies of Iron Age sites have indicated that diets were based upon the C3 terrestrial food chain; however, marked regional differences in the isotope signatures of the associated herbivores indicate variation in the underlying baseline values due to local environmental conditions (Jay and Richards 2007). We have therefore restricted our inter-site comparison to sites in central southern England including Yarnton (Lightfoot et al. 2009), Hampshire (Winnall Down and Micheldever Wood) (Jay and Richards 2007), Glastonbury (Jay 2008), and Eton Boat Lake (Stevens et al. in prep.). Isotope data from associated herbivores are not currently available from Poundbury, and are limited from Eton (six cattle and one sheep). The Danebury human d13C signatures are most similar to those at Eton and Yarnton, and with less than 1.5‰ variation in the mean human d13C values the inter-site variation is not substantial (Fig. 6, Table 5). Greater inter-site variation is seen in the mean human d15N values, with around 2.5‰ difference detected between sites. The Danebury human d15N signatures are OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 423 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS 13 12 11 10 Danbury humans (n=46) δ 15N(‰) 9 Danebury fauna Yarnton humans (n=27) 8 Yarnton fauna Hampshire humans (n=22) Hampshire fauna 7 Glastonbury humans (n=11) Glastonbury 6 Poundbury humans (n=13) Eton humans ( n=5) 5 4 3 -23.0 -22.5 -22.0 -21.5 -21.0 -20.5 -20.0 -19.5 -19.0 -18.5 δ C(‰) 13 Figure 6 Mean d13C and d15N and standard deviation of humans and fauna (cattle, sheep and pig only) from Iron Age sites in the British Isles: Yarnton (Lightfoot et al. 2009), Hampshire (Winnall Down and Micheldever Wood), Glastonbury (Jay 2008), and Eton Boat Lake (Stevens et al. in prep.). No fauna included from Eton Boat Lake as no Iron Age pig isotope data are currently available from this site. table 5 Difference between mean adult human and mean fauna (mean of cattle, sheep and pig, and mean of cattle and sheep) isotope values Site Cattle, Sheep, Pig 13 Danebury Hampshire Yarnton Glastonbury Eton Cattle, Sheep 15 Reference D C D N D13C D15N 1.3 1.2 1.5 1.3 3.4 3.6 3.5 3.0 1.3 1.3 1.4 1.2 1.7 4.1 4.2 4.0 2.9 5.1 This paper Jay and Richards 2007 Lightfoot et al. 2009 Jay 2008 Stevens et al. in prep. most similar to those at Poundbury and in Hampshire. It is clear that where associated fauna are available the inter-site variation in the human isotope signatures mimics that observed in the fauna (Fig. 6). Thus much of the inter-site variation in the Iron Age isotope signatures is unlikely to be linked to human dietary choice but rather linked to parameters that affect each ecosystem differently, such as the local micro-climate. 424 OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. RHIANNON E. STEVENS ET AL. We can gain further insight into dietary difference between sites through comparison of the offset between the mean isotope signatures of the humans and that of the major economic herbivores (cattle, sheep and pig) (Table 5). At Danebury, Hampshire and Yarnton both the carbon and nitrogen offsets are similar, indicating consumption of a comparable level of animal protein. At Glastonbury the nitrogen isotope offset is around 0.5‰ less than at the other sites. This difference could be due to the fact that the nitrogen isotopes at Glastonbury indicate that the pigs are herbivores whereas at the other three sites they indicate that the pigs are omnivores. However, when the pigs are excluded from the offset calculations, the difference between the nitrogen offset at Glastonbury and the other sites is increased (Table 5). This indicates the consumption of a lower level of animal protein at Glastonbury than at Danebury, Hampshire and Yarnton. Although Eton appears to have a high level of animal protein consumption, given the low number of faunal results available (six cattle, one sheep and no pigs) any interpretation of these results is highly speculative. We therefore conclude that the level of animal protein consumption at Danebury is typical for the region. The Iron Age studies discussed above comprise samples from various burial practices and types of site. At Danebury the human remains were recovered from pit burials within the hillfort. Poundbury is the only other hillfort site, but here samples were taken from the cemetery at the base of the hillfort (and may not be Iron Age in date) (Richards et al. 1998). All the other sites are small with varying amounts of evidence for human settlement, with human remains recovered from graves, pits, ditches and other features (Jay and Richards 2007; Jay 2008). Yarnton, however, is the exception as this small settlement site has an associated formal cemetery which was in use for around 100 years (Lightfoot et al. 2009). Given the variety of sites and burial practices one might expect a greater amount of dietary variation to be indicated via isotopic analyses. Although isotopic signatures indicate that diet in the Iron Age was relatively homogeneous, subtle variations may not be detectable in the isotope signatures due to the averaging effects of collagen turnover and the bias towards animal protein. Nevertheless, substantial intra- and inter-site isotopic variation between individuals has been observed in Britain during other time periods (Müldner and Richards 2007; Privat et al. 2002; Richards et al. 2005; Stevens et al. 2010) and it therefore seems most likely that Iron Age peoples throughout the region ate rather similar diets based on terrestrial resources. conclusions In summary, isotopic techniques have allowed us to investigate the dietary patterns of the humans buried at Danebury with regard to age, sex and burial deposition type. The most notable feature of the human and animal isotope data from Danebury is the homogeneity of the human isotope values as compared to the extensive heterogeneity of the animal isotope values. This may be a reflection of the much slower turnover rate of adult human collagen, or may also indicate that the human diet was on average less variable in isotopic composition than that of the fauna. This may indicate that the humans consumed a much greater variety of food (thus averaging many isotopic sources), which is consistent with the traditional role of hillforts as central places and/or redistribution centres. The human isotope data from Danebury are broadly similar to those at other Iron Age sites in central southern England and this is even more apparent when intra-regional variation in baseline isotope values is taken into consideration. OXFORD JOURNAL OF ARCHAEOLOGY © 2010 Blackwell Publishing Ltd. 425 STABLE ISOTOPE INVESTIGATIONS OF THE DANEBURY HILLFORT PIT BURIALS Acknowledgements The authors would like to thank Kay Ainsworth at Hampshire Museum stores for providing access to the material, records and unpublished information. Jessica Pearson is thanked for her help with sampling the human remains. Peter Ditchfield, RLAHA, is thanked for his assistance with the isotopic analyses. Tamsin O’Connell and Linda Reynard are thanked for useful discussion. (Corresponding author) (RES) McDonald Institute for Archaeological Research University of Cambridge Downing Street Cambridge CB2 3ER E-mail: res57@cam.ac.uk (EL) Department of Archaeology University of Cambridge Downing Street Cambridge CB3 3DZ (REMH, JH) Research Laboratory for Archaeology and the History of Art University of Oxford Dyson Perrins Building South Parks Road Oxford OX1 3QY (BC) Institute of Archaeology University of Oxford 36 Beaumont Street Oxford OX1 2PG references ambrose, s.h. 1990: Preparation and characterization of bone and tooth collagen for isotopic analysis. Journal of Archaeological Science 17, 431–51. ambrose, s.h. and norr, l. 1993: Experimental evidence for the relationship of the carbon isotope ratios of whole diet and dietary protein to those of bone collagen and carbonate. In Lambert, J.B. and Grupe, G. 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