Pannage, Pulses and Pigs: Isotopic and Zooarchaeological Evidence for Changing Pig Management...

234

© Society for Medieval Archaeology 2012 DOI: 10.1179/0076609712Z.0000000008

Medieval Archaeology, 56, 2012

Pannage, Pulses and Pigs: Isotopic and Zooarchaeological Evidence for Changing

Pig Management Practices in Later Medieval England

By JULIE HAMILTON1 and RICHARD THOMAS2

ZOOARCHAEOLOGICAL ANALYSIS OF a substantial assemblage of animal bones excavated from Dudley Castle, West Midlands, suggests that a significant change in pig management occurred during the 14th century. A dramatic decrease in the relative abundance of pigs, combined with an increase in the size of post-cranial bones and teeth, and a higher proportion of neonatal individuals, raises the possibility that greater control over breeding and feeding was being exerted in this period through the emergence of enclosed husbandry practices. Carbon and nitrogen stable-isotope analysis of a sample of 41 pig mandibles from two tightly dated phases of occupation supports this interpretation. Between the late 13th century and later 14th century there was a statistically significant decrease in δ15N, but not in δ13C, and pig dietary diversity probably also decreased. This paper discusses several explanations for these patterns, all consistent with a major change in pig management at this time.

Pigs occupied a central role in medieval animal husbandry regimes. Their omnivo-rous and foraging habits made them highly effective converters of a wide variety of plants and animals (including those inedible to humans and other animals) to meat and fat. Coupled with their fecundity and limited management requirements, these animals were a highly productive source of food that was especially amenable to preservation.3 It is perhaps unsurprising therefore that pork was the second most common form of meat consumed (by weight) on many medieval sites.4 In aristocratic households, in particular, the remains of pig bones are often abundant, a consequence of elite dietary preference, the potential of aristocratic estates to keep large numbers of pigs, the use of pigs as food rents, and the fact that pigs were not multi-purpose animals and were only exploited for meat.5

1 Research Laboratory for Archaeology and the History of Art, University of Oxford. [email protected]

2 School of Archaeology and Ancient History, University of Leicester. [email protected] As Bennett (1970, 227) notes, sows can breed at least twice a year, they have a gestation period of only 112–15

days, they are mature enough to breed after only a year, and an older sow can give birth to as many as 15 piglets. Even medieval agricultural writers, such as Walter of Henley, observe that sows should farrow three times a year (Lamond 1890, 29); Albarella 2006, 72; Wiseman 2000, 37.

4 Albarella 2006, 73.5 At Barnard Castle, Northumberland, for example, between 1095 and 1471 the proportion of pig bones ranged

from 31–51% out of the total number of identified specimens (Jones et al 1985, tab 2); Sykes 2007, 42.

235pannage, pulses and pigs

The stereotypical image of medieval pig husbandry is the pannage system, whereby pigs were loosely managed and seasonally driven into woodland to feed upon beech mast, acorns, rhizomes and roots. While this strategy was common in the Anglo-Saxon period,6 it was not the only husbandry regime available, partly because pannage only provided a seasonal and unreliable resource. Indeed, Rackham has gone so far as to argue that ‘by 1086 wood-swine had become swine of the imagination; real pigs were . . . fed in other ways’.7 Other documented practices include grazing upon waste, marshes and pasture, and using stubble, food leftovers and household rubbish in the absence of manorial woods, wastes and marshes; household waste was also recommended for feeding the weakest pigs or recently farrowed sows.8 Markedly different husbandry regimes existed in manors that formed part of the same estate.9 Even where pannage was practised, it is clear from documentary sources that it declined in importance from the 11th or 12th century as the extent of woodland gradually diminished and the length of the pannage season was restricted.10 By the later medieval period, traditional forms of free-range husbandry were beginning to be replaced by sty feeding on ‘legumes, cereals, house-waste and even by-products of the dairy and brewery industries’.11 Documentary sources from the Peterborough Abbey estate exemplify this: by the early 14th century, pigs were kept in sties and partly fed upon grains and legumes specifically grown for this purpose.12

Zooarchaeological evidence from sites in Britain and elsewhere in Europe is now adding weight to the idea that enclosed pig husbandry had begun to replace extensive management strategies by the later medieval period.13 In this paper, we will consider the evidence from Dudley Castle, a multi-period site with a large collection of well-dated pig remains that allows changes in practices to be investigated using traditional zooarchaeological and isotopic methods.

MATERIALS

Dudley Castle is located in the West Midlands, England, 15 km north-west of Birmingham (Fig 1). Excavations within the keep and the confines of the inner bailey between 1983 and 1993 identified ten phases of occupation spanning the 11th to the mid-18th century ad.14 This site was selected for this study because: (1) excavations over a ten-year period generated a substantial sample of pig bones that has already been subjected to detailed scrutiny;15 and (2) a pilot ancient DNA study from the site demon-strated excellent bone collagen preservation,16 an essential requirement for stable-isotope studies. Only bones from the mid-13th to the mid-18th century are discussed in this paper due to the restrictions of sample size: phase 5 (1262–1321); phase 6 (1321–97); phase 7 (1397–1533); and phases 8 and 9 combined (1533–1750). This phasing was established following archaeological confirmation of historically attested periods of building activity and has been independently verified by ceramic spot-dating.17

6 Trow-Smith 1957, 53.7 Rackham 1986, 75.8 Lamond 1890, 113, Trow-Smith 1957, 53, 81.9 For example, on the Peterborough Abbey estate in the 12th century, the manor of Oundle was practising

intensive pig management, while at Cottingham an extensive system of pig management was still practised (Biddick 1984, 166–7).

10 Wiseman 2000, 39–40.11 Albarella 2006, 79.12 Biddick 1989, 121–3.13 Thomas 2005; 2006; Ervynck et al 2009.14 Thomas 2005.15 Ibid 2005.16 Campana 2008.17 Thomas 2005, 6.

236 julie hamilton and richard thomas

fig 1Location of Dudley Castle and other key sites mentioned in the text. © J Hamilton and R Thomas.

METHODS

zooarchaeological methodsOur study uses three zooarchaeological techniques to explore changing patterns of

pig husbandry at Dudley Castle: species abundance; age at slaughter; and the measure-ment of animal bones to indicate size.

Species abundance was calculated using the Number of Identified Specimens Present (NISP), which constitutes a count of the number of bone fragments belonging to each


taxon; this method is generally considered to be the least problematic technique for quantifying taxonomic abundance.18 We calculated the proportion of pigs, relative to the combined total of cattle, sheep and pig bones from the site (the three primary taxa that constitute 53% of the entire identified, hand-collected assemblage) to determine whether the frequency of pigs changed over time.

We estimated age at slaughter using two techniques: an assessment of the epiphy-seal fusion status of post-cranial bones; and determination of the relative frequency of deciduous mandibular premolars. To ease the interpretation of the fusion data, we grouped pig bones into three age classes: early fusing (0–24 months); middle fusing (24–30 months); and late fusing (36–42 months).19 The paucity of mandibles of sufficient completeness meant that it was not possible to confidently establish the eruption stage and wear pattern of mandibular teeth, which is the most reliable method for establishing slaughter age. However, calculation of the relative frequency of deciduous mandibular premolars provides a crude determination of the proportion of juvenile and mature animals in the assemblage.

We took measurements on pig bones and teeth using the standards of von den Driesch with amendments following Bull and Payne.20 To increase the size, and thus statistical relevance of the metrical dataset, we employed a log-scaling technique to allow different measurements to be combined on the same axis.21 This method involves convert-ing all measurements to logarithms by relativising each measurement against a standard. A positive value indicates that the archaeological specimen is larger than the standard, a negative value that it is smaller, while zero indicates that the standard and archaeological specimen are identically sized. For this study, we drew our standard from a Neolithic population of pigs from Durrington Walls.22 The statistical significance of temporal differ-ences in measurements was determined using a Mann-Witney U-test, because the data were not normally distributed.

isotopic methodsThe use of the stable isotopes of carbon and nitrogen in investigating human diet is

well established.23 The ratio of the heavier to the lighter isotope (13C/12C or 15N /14N) varies in characteristic ways across the food web,24 and is preserved and measurable in archaeological body tissues.25 Collagen, the major protein component of bone, is particu-larly useful for such measurements since it is resistant to diagenetic alteration and can often be extracted in useful quantities from small samples of bone. Here we apply this methodology to animals rather than people, expecting the isotope values to reflect the change from an extensive free-range management system to an intensive sty-based one where pigs were fed on agricultural produce.

Carbon-isotope patterning is mainly determined by plant use of carbon in photosyn-thesis, and is particularly useful in distinguishing diets based on marine or terrestrial foods,

18 Lyman 2008, 140; it should be noted here that the animal bones from Dudley Castle were recorded using a selective (one zone per bone) recording strategy, thus the NISP is equivalent to the Minimum Number of Elements (MNE; Thomas 2005, 9).

19 After Reitz and Wing 1999, tab 3.5.20 von den Driesch 1976; Bull and Payne 1988.21 Albarella 2002; Meadow 1999.22 Albarella and Payne 2005.23 Eg Müldner and Richards 2005, 2006.24 Sealy 2001.25 For convenience, stable isotope measurements are usually reported in parts per mil using the delta notation,

where eg δ13C = (((13C/12Csample)/(13C/12Cstandard))-1)×1000‰.


or on plants with different photosynthetic pathways (eg C4 maize versus C3 wheat), which may differ by up to 15‰.26 Wild C4 plants, adapted to hot, dry environments, are rare in the British flora, C4 crops such as maize and millet were not grown here in the medi-eval period, and Dudley Castle is a long way from the coast, so neither of these is likely to apply to pigs at this time and place. More subtle variations in plant δ13C that occur in response to environmental factors may be detectable, however. Plants growing in more shaded, wetter and/or cooler habitats may have lower δ13C values, and differences of up to 5‰ may be detected in the tissues of herbivores feeding on plants in different environ-ments.27 Pigs may also eat fungi that have higher δ13C values than photosynthetic plants.28 Feral boar sometimes eat fungi in large quantities,29 and have been recorded feeding on a wide variety of fungi, both saprophytic and mycorrhizal, including underground forms obtained by rootling.30 Suitable fungi would be much commoner in dense, old-growth and less intensively managed woodland, and would raise pig δ13C values rather than lower them, thus counteracting the effect of shade.31

Nitrogen isotope patterning depends on the δ15N of plants at the base of the food chain, which in terrestrial plants depends in turn on soil processes of nitrogen fixation and loss. Manuring tends to raise soil and hence crop δ15N,32 while legumes, which have their own symbiotic nitrogen-fixing bacteria in root nodules and consequently are useful in crop rotations and pasture because they improve soil nitrogen levels, have characteristically low δ15N values.33 Consumers at higher trophic levels (carnivores) have higher δ15N values, typically by 3–5‰ per trophic level.34 Omnivores such as pigs (or humans) have collagen δ15N values that are enriched over herbivore values by an amount that reflects the propor-tion of animal-derived protein in the diet. Physiological factors such as high growth rate, pregnancy and starvation, and environmental factors such as temperature and aridity, may also affect animal δ15N values.

Mammalian isotope ratios vary with age and developmental stage. Before birth offspring reflect maternal values, but as soon as they start to suckle they are effectively consuming their mothers, so are at a higher trophic level, raising collagen values by 0.5–1‰ for δ13C and 3–4‰ for δ15N. It would take some time for bone collagen to reach these new values, depending on the rate of bone turnover, which is likely to be fast in small, rapidly growing animals. After weaning, these values would fall and begin to reflect diet as in older pigs. δ15N might even fall slightly below the adult mean in fast-growing juveniles.35

Samples of bone from Dudley Castle were taken from mandibles and maxillae of pigs, 20 from phase 5 (1262–1321), one of which was possibly from a wild boar,36 and 21 from phase 6 (1321–97). We used these elements because most of them could be at least approximately aged. The age profiles were quite different in phases 5 and 6 (see below), but using known-age material allowed us to separate out variation due to age.

Collagen was extracted from up to 1 gr of bone per sample using a standard proto-col.37 Any superficial material was removed from the bone by shotblasting, samples were

26 Buikstra and Milner 1991.27 Heaton 1999; Drucker et al 2008.28 Hamilton et al 2009.29 Hohmann and Huckschlag 2005; Skewes et al 2007.30 Schley and Roper 2003.31 Hamilton et al 2009.32 Bogaard et al 2007.33 Schoeninger and DeNiro 1984; Schoeninger et al 1998.34 Ambrose 1991.35 Fuller et al 2004; 2006.36 Determined on metrical grounds.37 O’Connell and Hedges 1999.


demineralised in 0.5M HCl at 4°C, rinsed with distilled water, and gelatinised in a pH 3 solution for 48 h at 75°C. The solution was filtered, frozen and freeze-dried. Between 2.5 and 3.5 mgr of dried collagen was loaded into a tin capsule for continuous flow combus-tion and isotopic analysis. Samples were analysed using an automated Carlo Erba carbon and nitrogen elemental analyser coupled with a continuous-flow isotope ratio monitoring mass spectrometer (PDZ Europa Geo 20/20). Each sample was measured in duplicate runs, using internal secondary standards (alanine and bovine liver standard), giving an analytical error of ±0.2‰. The pooled estimate of standard deviation, including both measurement and random error, is 0.33‰ for δ13C and 0.40‰ for δ15N, giving 95% confidence limits for any individual sample mean of ±0.5‰. Results are reported in unit per mil (‰) and δ13C and δ15N values were measured relative to the VPDB and AIR standards respectively.38 The collagen from all samples was well preserved: collagen yields were between 3 and 16%, and C:N ratios were 3.2–3.3 (Tab 1), well within acceptable limits.39

We performed an exploratory Principal Components Analysis on a subset of samples that had definite data for both age-class (see Tab 1) and size.40 This showed that size had no consistent relationship with isotope values, but age was important; once age was discounted, phase was important. Detailed age data were not available for all specimens, but it was possible to identify ‘juveniles’ consistently.41 The proportions of the other age-classes were similar in phases 5 (1262–1321) and 6 (1321–97). In order to include all the isotope data in the analysis, three groups were used: (1) phase 5 older (immature to adult; there were no juveniles in phase 5); (2) phase 6 older (immature to adult); and (3) phase 6 juveniles. Comparison of the first two groups would test for differences between older pigs in phases 5 and 6, and comparison between the last two groups for age-related effects in phase 6. There were not enough sexed individuals to take sex into account. Observed trends were statistically validated using Levene’s test to assess the equality of variance between samples and t-tests for samples with unequal variance to compare means.

The pig isotope data from Dudley Castle were compared with carbon and nitrogen values for cattle from Dudley Castle,42 and from eight published medieval sites in England, Wales and Scotland (Fig 1, Tab 2).

RESULTS

zooarchaeological analysisAnalysis of the relative frequency of pigs reveals a major decrease in abundance

between phases 5 (1262–1321) and 6 (1321–97),43 but not between later phases of occupa-tion (Fig 2). Declining pig abundance is well attested on English later medieval sites,44 but what is especially striking about Dudley Castle is its rapidity and scale: at other sites, a gradual reduction in the relative proportion of pigs is more typical.45

38 Mariotti 1983; Gonfiantini et al 1990.39 DeNiro 1985; Ambrose 1990. 40 The ‘size’ variable for each mandible was calculated as the mean log ratio for combined tooth width and length

measurements. The log ratio standard was derived from a sample of late Neolithic pig teeth from Durrington Walls (Albarella and Payne 2005).

41 Following O’Connor 1988.42 Fisher and Thomas in press.43 The phasing for the site was based on historically attested periods of building activity and independently

verified by ceramic spot-dating (Thomas 2005, 6).44 Grant 1988, 159; Albarella 2006, 74–6; Sykes 2007, 29; a reduction in the consumption of bacon (at the

expense of fresh beef) has also been observed in later medieval accounts (Dyer 1988, 28; 1991, 202; Woolgar 2006).

45 Sykes 2007; Albarella 2006.


46 O’Connor 1988.47 Thomas 2005, 51–2.

Table 1Results of isotope analysis. Age classes follow O’Connor.46

Sample Taxon Phase Age class Group δ13C (‰)

δ15N (‰)

C:N ratio

Collagen (%)

DC1 Pig 6 Immature-Adult 2 –21.7 6.1 3.26 4.9DC2 Pig 6 Sub-adult 2 –21.9 6.2 3.21 9.1DC3 Pig 6 Sub-adult 2 –20.8 4.4 3.19 8.1DC4 Pig 6 Sub-adult 2 –21.4 4.9 3.30 3.6DC5 Pig 6 Immature 2 –21.2 3.0 3.31 8.3DC6 Pig 6 Immature-Adult 2 –21.1 9.6 3.25 6.8DC7 Pig 6 Sub-adult 2 –21.0 3.6 3.28 6.0DC8 Pig 6 Immature-Adult 2 –21.2 4.6 3.24 5.6DC9 Pig 6 Immature-Adult 2 –21.3 4.2 3.25 3.4DC10 Pig 6 Sub-adult 2 –21.1 3.7 3.23 8.1DC11 Pig 6 Immature-Adult 2 –20.8 4.6 3.23 9.1DC12 Pig 6 Sub-adult 2 –21.5 8.7 3.30 3.7DC13 Pig 6 Juvenile 3 –19.7 12.6 3.18 11.2DC14 Pig 6 Juvenile 3 –21.0 7.0 3.22 13.6DC15 Pig 6 Juvenile 3 –19.8 10.6 3.20 13.8DC16 Pig 6 Juvenile 3 –21.0 6.0 3.22 11.8DC17 Pig 6 Juvenile 3 –21.0 3.3 3.27 10.5DC18 Pig 6 Juvenile 3 –20.9 10.0 3.22 9.0DC19 Pig 6 Immature 2 –20.7 3.7 3.28 7.1DC20 Pig 6 Juvenile 3 –20.3 9.6 3.24 10.4DC21 Pig 5 Sub-adult/Adult 1 –22.0 7.0 3.26 4.8DC22 Pig 5 Immature-Adult 1 –21.2 5.6 3.21 11.1DC23 Pig 5 Immature-Adult 1 –21.4 7.2 3.24 6.7DC24 Pig 5 Adult 1 –21.4 5.4 3.21 10.8DC25 Pig 5 Immature/Sub-adult 1 –20.4 6.3 3.21 5.7DC26 Pig 5 Sub-adult 1 –21.0 7.3 3.25 5.2DC27 Pig 5 Sub-adult 1 –20.6 6.5 3.20 13.3DC28 Pig 5 Sub-adult 1 –22.0 6.9 3.22 6.0DC29 Pig 5 Immature-Adult 1 –21.0 5.6 3.17 11.6DC30 Pig 5 Immature/Sub-adult 1 –22.2 7.5 3.28 4.4DC31 Pig 5 Immature/Sub-adult 1 –20.7 5.6 3.18 10.8DC32 Pig 5 Immature/Sub-adult 1 –20.3 4.7 3.26 4.3DC33 Pig 5 Sub-adult 1 –21.0 6.1 3.16 15.9DC34 Pig 5 Sub-adult 1 –21.5 5.4 3.21 16.0DC35 Pig 5 Sub-adult/Adult 1 –21.7 5.9 3.29 4.7DC36 Pig 5 Immature/Sub-adult 1 –20.8 7.3 3.19 7.8DC37 Pig 5 Immature-Adult 1 –22.6 8.8 3.23 4.2DC38 Pig 5 Adult? 1 –21.4 7.4 3.22 6.1DC39 Pig 5 Sub-adult 1 –21.7 3.8 3.24 12.5DC40 Wild

boar5 Immature 1 –21.9 7.0 3.27 4.3

DC41 Pig 6 Adult? 2 –20.7 5.8 3.25 3.3

Contemporary with this sharp decline in relative abundance is a statistically signifi-cant increase in pig size. This size increase was evident in tooth width measurements (Fig 3), as well as in tooth lengths and post-cranial bones.47 Another notable trend in the


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fig 2Relative proportion of cattle, sheep, and pig at Dudley Castle by phase (Total NISP = 7087).

© J Hamilton and R Thomas.

fig 3Comparison of log-scaled pig tooth width measurements between phases 5 (1262–1321; NISP = 187) and 6

(1321–97; NISP = 70) from Dudley Castle. The difference in the means between phases 5 and 6 is statistically highly significant (U = 2381; P = <0.0001). © J Hamilton and R Thomas.


metrical dataset is the greater dispersal of tooth and bone measurement values in phase 5 (1262–1321) compared with subsequent phases (Tab 3). This is partly the consequence of the inclusion of a number of very large specimens in phase 5 that are probably wild boar.48

In addition to changing abundance and body size, a notable shift in age at slaughter is evident in both dental and bone fusion data (Figs 4 and 5): a higher proportion of younger animals were slaughtered in phase 6 (1321–97) than phase 5 (1262–1321). Specifically, the proportion of animals slaughtered in the first three years of life is substan-tially higher in phase 6 than it is in phase 5. Moreover, in phase 6 there is a much higher proportion of animals that had died in the first month or two of life (Fig 6).

isotopic analysisAnalysis of the stable isotopes of carbon and nitrogen from the pig mandibles from

Dudley Castle reveals four clear patterns:

1. The mean δ13C for older pigs does not differ significantly between phase 5 (1262–1321) and phase 6 (1321–97; Fig 7; Tab 4). However, the range of values is wider in phase 5 (Fig 8); the variance of δ13C values differs almost significantly between the older phase 5 and older phase 6 pigs (Levene’s test P = 0.051).

2. In phase 6 the mean δ13C of juveniles is higher than the mean for older pigs in the same phase by approximately 0.7‰ (P <0.01) and the variance differs significantly (P = 0.048, Levene’s test).

3. The mean δ15N value for older pigs in phase 5 is significantly higher than the mean for older pigs in phase 6, by 1.4‰ (P = 0.039; Figs 7 and 9). Variation is wider in phase 6 but the difference in variance is not statistically significant (P = 0.094, Levene’s test).

4. The mean δ15N of the youngest pigs in phase 6 is significantly higher than the value for older pigs in the same phase (P <0.01) by 3.2‰ (Tab 4); the data are also more variable although this is not statistically significant (Fig 9; P = 0.077, Levene’s test).

48 Ibid.

Table 3Coefficients of variation and sample sizes for selected bone and tooth measurements. Coefficients of variation approaching 0 indicate narrowly dispersed data, while those approaching 1 indicate

widely spread data.

Phase 5 (1262–1321)

Phase 6 (1321–97)

Phase 7(1391–1533)

Phase 8–9 (1533–1750)

First molar (width of anterior cusp)

0.133 (n = 37) 0.077 (n = 12) 0.067 (n = 21) No data

Second molar (width of anterior cusp)

0.088 (n = 36) 0.030 (n = 10) 0.063 (n = 18) 0.127 (n = 4)

Third molar (width of anterior cusp)

0.091 (n = 22) 0.046 (n = 5) 0.087 (n = 13) No data

Astragalus (greatest lateral length)

0.149 (n = 15) 0.073 (n = 8) 0.061 (n = 6) 0.014 (n = 6)


fig 4 Epiphyseal fusion data for pig.49 © J Hamilton and R Thomas.

Pig δ13C and δ15N values can be compared with those of cattle from the same phases (Fig 10). Cattle δ13C values do not change, and pig values are consistently higher than cattle by 0.8–1.0 ‰ (P <0.01, t-test). Cattle δ15N values are similar in both phases, while pig mean δ15N is 1‰ higher than cattle (P <0.01, t-test) in phase 5 (1262–1321) and 0.5‰ lower (not significant) in phase 6 (1321–97).

DISCUSSION

Taken together, the zooarchaeological and isotopic evidence strongly suggest that a major change in pig management occurred in the 14th century as manifested by a pre-cipitous decline in relative abundance, increased size, changed pattern of age at slaughter and altered isotope values.

Woodland clearance has traditionally been invoked as a possible cause of declining pig abundance.50 This hypothesis rests on the assumption that a reduction in woodland led to reduced availability of mast, which was used as an intermittent food source for pigs, particularly in the autumn to fatten the animals before slaughter,51 but possibly also in the

49 Fusion categories follow Reitz and Wing 1999, tab 3.5.50 Grant 1988, 159.51 Stamper 1988, 133.


fig 5Percentage of deciduous premolars at Dudley Castle by phase. © J Hamilton and R Thomas.

fig 6Percentage of neonatal pig bones at Dudley Castle by phase. © J Hamilton and R Thomas.


spring.52 There is local and national evidence for declining woodland in this period. Hemingway has estimated that the extent of woodland on the manor of Dudley con-tracted from 7.8 sq km in 1086 to 2.9 sq km by 1273.53 A key factor in woodland loss in this region was the creation of Pensnett Chase.54 King Henry III created this chase, which comprised the largest part of the manor of Dudley, out of Royal Forest sometime between 1216 and 1231.55 The creation of the chase relieved the land from the restrictions of for-est law and placed it in-common. Consequently, anyone with common rights could graze their animals on this land. This would have led to extensive woodland depletion because animals would have prevented sapling regeneration.56 While this predates the pig decline

52 Rogers 1866, 336.53 Hemingway 2009, 42.54 A chase was essentially a private forest.55 Hemingway 2009, 40.56 Ibid, 42.

fig 7Results of isotope analysis, with means and standard errors for the three groups. © J Hamilton and R Thomas.

Table 4Means and standard deviations of δ13C and δ15N values. Within each column, means followed by

different letters indicate a significant difference (t-test with unequal variance, P ≤ 0.05).

Group δ13C (‰) mean SD δ15N (‰) mean SD n

Phase 5 (1262–1321), older –21.3 A 0.61 6.4 A 1.16 20Phase 6 (1321–97), older –21.2 A 0.37 5.0 B 1.79 14Phase 6 (1321–97), juvenile –20.7 B 0.59 8.0 C 3.03 7


at Dudley Castle, the knock-on effect of the lifting of forest law restrictions was an increase in assarting (the conversion of woodland to agricultural land), which was especially common in this region,57 further reducing woodland coverage and requiring pigs to be fed in other ways. As Wiseman notes, the alternatives to the products of the forest were cereals and pulses, which were expensive and also required for human consumption.58 If one accepts this model, it is perhaps unsurprising that large-scale pig keeping of the kind witnessed at Dudley Castle in the 12th and 13th centuries became unsustainable.

The extent to which a decline in mast would have affected the number of pigs that could be kept has to be questioned, however. For example, in the 1273 Inquisition Post Mortem of Roger de Somery III (11th Baron of Dudley), it was noted that, ‘certain burgesses owe pannage for their hogs yearly, whether or not there be mast’ and also that ‘there is a wood called Penniak . . . and the pannage in the said wood is worth yearly 20s, although it rarely happens’.59 This implies that mast may have only provided an occa-sional contribution to the annual feed of pigs. Moreover, the woodland around Dudley

57 For example, in 1273 the Inquisition Post Mortem for the adjacent manor of Sedgley, located within the bar-ony of Dudley, records the annual rent of assarts as £5 10s 9d (Wedgewood 1911, 154). Further assarting occurred in 1338 when Sir John de Sutton (14th Baron of Dudley) was given a licence to assart in parts of Pensnett Chase belonging to the manors of Dudley, Sedgley, Swinford and Rowley-Somery (Hemingway 2009, 40).

58 Wiseman 2000, 41; while vetch could have been used, since it was cultivated solely for animal fodder, its cultivation was primarily restricted to S and SE England (Campbell 1988, 198).

59 Wedgwood 1911, 153.

fig 8Mean, one standard deviation and range of δ13C values. © J Hamilton and R Thomas.


Castle is perhaps better regarded as wood-pasture (ie a mix of woodland, often comprising pollarded trees and grassland grazing) than closed canopy forest,60 and was probably only used as an occasional seasonal resource in any case. Such woodland may have also been managed by coppicing, a practice that is unsuited to pannage.61 Indeed, the interpretation that the pigs supplied to Dudley Castle in phase 5 (1262–1321) — when they were more abundant — derived a major part of their diet from dense, shady woodland, can be firmly rejected following the analysis of the carbon isotopes, which mirrors the situation at other medieval sites: if the pigs had been kept in dense woodland, mean δ13C values would have been considerably lower.

It is more likely, therefore, that the decline in the relative proportion of pigs was driven by the changing nature of the agricultural landscape in the later medieval period. Grant argued that pigs were most abundant in the 12th and 13th centuries because they were the best way of maximising available resources, when grazing land for cattle and sheep was at a premium due to the intensification of arable farming. Thus, pigs were kept in the spring or summer on waste ground unsuitable for cultivation and then fattened upon cereal waste in the late summer and the products of the forest in the autumn.62 The 14th-century decline in the proportion of pigs witnessed at sites such as Dudley Castle can, in Grant’s model, be viewed as a consequence of the conversion of arable to pasture in

60 Rackham 1986, 121.61 Rackham 1980, 120.62 Grant 1988, 159.

fig 9Mean, one standard deviation and range of δ15N values. © J Hamilton and R Thomas.


the wake of the collapse of the grain market and population depletion after the Black Death, which made the raising of cattle and sheep for meat more attractive to farmers, since they were less labour intensive and more profitable.63 The fact that a degree of incompatibility exists between pigs and pasture, because of their destructive feeding habits, strengthens this argument.64 However, Grant’s evidence that the apogee of pig husbandry occurred in the 12th–13th centuries and subsequently declines is challenged by more recent zooarchaeological syntheses.65 These instead reveal that the peak of pig husbandry occurred in the Anglo-Saxon period and that the decline commenced gradually from the mid-12th century onwards. Given this changed chronology, it would appear that pigs were equally incompatible with intensified arable production, an idea supported by Redding and Sykes.66 Nevertheless, at Dudley Castle, the speed and particularly the timing of the decline in the relative abundance of pigs suggests that the rise of pasture may have been a significant factor.

While the declining proportion of pigs appears to be a national phenomenon, local explanations should not be ignored. For example, changes in tenancy at Dudley Castle may also have influenced the relative frequency of pigs in phase 6 (1321–97). In 1322 the de Sutton family inherited the barony of Dudley, after the former incumbent, John de

63 Ibid; Wiseman 2000, 40.64 Wiseman 2000, 31.65 Sykes 2007; Albarella 2006.66 Redding 1991, 22; Sykes 2007, 94.

fig 10Comparison of phase 5 (1262–1321) and phase 6 (1321–97) carbon and nitrogen stable-isotope values for

cattle and pig at Dudley Castle. © J Hamilton and R Thomas.


Somery, died without heir. John de Sutton inherited the estate through marriage; how-ever, many of the manors that belonged to the estate were split between the de Suttons, John de Somery’s wife and his second sister.67 Consequently, the barony of Dudley lost most of their Buckinghamshire manors as well as a number in the West Midlands, par-ticularly in Worcestershire and Warwickshire. This was offset by the acquisition of manors in Cheshire, Rutland, Derbyshire, Bedfordshire, Nottinghamshire, Oxfordshire, Essex and Wales. The changed emphasis in pigs may therefore reflect the inability of the manors to supply pigs in the same quantity,68 or the dietary preference of the new household.

Whatever the precise cause of the change in pig abundance, other zooarchaeological evidence strongly suggests that a change in management occurred simultaneously. For example, the significant increase in the size of pigs in phase 6 (1321–97; Fig 3) provides an important indicator of more closely managed breeding. Size changes in domestic animals can occur for two reasons: (1) changes to genetic constitution (through the intro-duction of new bloodstock and/or selective breeding); and (2) improvements to upkeep (enabling animals to reach their genetic potential). The first of these possibilities affords a more convincing explanation for the pattern observed at Dudley Castle because both pig teeth and post-cranial bones were larger in phase 6 (1321–97) than in phase 5 (1262–1321) and tooth size is primarily dictated by genetics rather than age, sex and environmental conditions during development; conversely, the size of the post-cranial skeleton is influ-enced by both genetic and environment factors.69 If pigs were managed extensively and allowed to roam freely during the pannage season, which coincides with the main mating season in late autumn, then little control over breeding could be exerted.70 However, the identification of a significant increase in the size of pig teeth suggests that closer manage-ment of the pig breeding had occurred in phase 6, most probably through enclosure.71 By implication, therefore, it is possible to argue that the pigs in phase 5 (1262–1321) were more extensively managed. Independent support for this is provided by the presence of large ‘outliers’ in the metrical datasets and greater coefficients of variation in phase 5 (Tab 3). The latter data not only point to the presence of wild boar, but also the possibility that interbreeding between wild boar and domestic pigs was taking place.72 One presumed consequence of the keeping of pigs in a more enclosed environment would have been a reduction in the maximum number of animals that could be supported.

The age data further support the notion that closer management of pigs occurred in phase 6 (1321–97). The greater proportion of pigs slaughtered within the first three years of life in phase 6 may reflect the larger size of the animals: as Albarella notes ‘larger animals were likely to grow faster and provide a greater output of meat’,73 so it would be possible to slaughter these animals at an earlier age. More telling, however, in phase 6 (1321–97) there was a much higher proportion of animals that had died within the first month or two of life (Fig 6). These data support the idea that in the latter half of the 14th century pigs were being reared closer to the site, rather than in more distant locales. Such animals may have become incorporated into the archaeological record following neonatal fatalities; alternatively, controlled access may have simplified the acquisition and consumption of suckling animals.

67 Hemingway 2006, 47.68 It is also possible that the absolute numbers of pigs remained the same but that the numbers of cattle and sheep

increased significantly.69 Albarella 2002, 54.70 Wiseman 2000, 36.71 This change in management was predicted by Wiseman (2000, 42).72 Thomas 2005, 49.73 Albarella 2006, 85.


The isotopic evidence consolidates the argument that the pigs in phase 5 (1262–1321) were more extensively managed than subsequently. The range of δ13C values seen in phase 5 is much wider than in phase 6 (1321–97), which could reflect more varied individual diets, as might be expected of opportunistic feeders in habitats that vary spa-tially and temporally. It is also possible that, as a consumer site, the castle was receiving pigs from a wider range of environments in phase 5 (perhaps from all the different manors before the estate was broken up through inheritance), and then moved to more local, restricted production. There is a noticeable tail of depleted values in the phase 5 data, which could reflect some use of shadier or wetter habitats (Fig 7). The possible wild boar individual is in this tail, but not the lowest. Fungus consumption affects δ13C values in the opposite way to shade and, like mast, would be a seasonal resource with considerable year-to-year variation in availability. Since the pigs investigated were mainly quite young (Tab 1) with rapid bone turnover, their collagen isotope ratios would mainly reflect diet in the months before death, which might sometimes include large amounts of fungi leading to higher δ13C values in some individuals.

δ13C values in pigs are consistently higher than in cattle in both phases 5 (1262–1321) and 6 (1321–97; Fig 10). This is not easily explained by the different digestive physiologies of cattle (ruminants) and pigs (non-ruminants), because that should act in the opposite direction, causing ruminants to be relatively enriched, since the methane they produce is depleted in δ13C.74 If cattle spent much more time feeding in dense woodland than pigs in both periods, cattle δ13C values might be depleted relative to pigs, as observed. However, in that case the lack of change in pig δ13C values, either absolutely or relative to cattle, is surprising, as we would expect them to be using woodland in phase 5 but not in phase 6. As noted above, use of woodland might lead to either higher or lower pig δ13C values, so perhaps it is the wider range of values that is important here rather than the mean. In any case, the existence of such dense woodland is doubtful in either phase. However, cattle might have fed on wetter pasturage than pigs, or on fodder grown in wetter areas such as riverside hay meadows,75 which could also lower δ13C. The fact that pigs show clear changes in stable-isotope ratios, while cattle do not, supports the link with changes in management and diet, rather than some overall climatic or environmental change that would affect all species.

The significantly higher δ13C values for the youngest pigs in phase 6 (1321–97) are consistent with a suckling effect. Values will rise from that of the mother at birth, and decline towards adult values as other foods are included in the diet, at a rate that reflects bone turnover, so the wide range is not surprising. The mean δ15N value of the youngest group in phase 6 is also higher than that of the older pigs (P<0.01) by 3.2‰, as expected for a suckling signal. As for carbon, the wide range can be explained by the rapid changes taking place in this age group as the piglet is born, suckled and weaned.

Comparing mean δ15N values in the older groups of pigs, it is clear that there was a significant decrease between phase 5 (1262–1321) and phase 6 (1321–97). We can offer three explanations of this change in δ15N values. The first suggests that phase 5 pigs had diets richer in animal-derived protein (eg insects and worms) because they were free to select the best available resources, while phase 6 pigs were more constrained and this was not compensated for through the consumption of waste high in animal-derived protein. The second suggests that, whether or not the proportion of animal-derived protein in the diet was higher in phase 5, it was richer in 15N because of the effects of manuring. The third suggests that δ15N values were lower in phase 6 because pig diet included a high proportion of legumes, which typically have depleted 15N values.

74 Hedges 2003. 75 Lynch et al 2008, 1032.


Pig δ15N values were significantly higher than those of cattle (which did not change) in phase 5 (1262–1321) but not in phase 6 (1321–97). The diet of extensively managed pigs in phase 5 could have included animal protein derived from worms and insects obtained by rootling, and if they were allowed to scavenge around habitations possibly also human food waste (including excrement) and rubbish, all of which would have raised pig δ15N relative to cattle. If their freedom to roam were curtailed by more intensive management, the proportion of these foods in pigs’ diets might be reduced, thus reducing their degree of omnivory relative to cattle. It is not certain to what extent the waste from food preparation or processing (eg dairying, brewing or milling) might have been fed to pigs in either phase at Dudley Castle, but it is unlikely that it would have happened in phase 5 and not in phase 6 — if anything, the reverse seems more likely. The change in proportion of these foods in pig diets would need to be quite large to account for the change in δ15N values.

Another possibility is that in phase 5 (1262–1321) pigs, but not cattle, were allowed to feed on manured areas after harvest, and so obtained plant and invertebrate food that was enriched in δ15N.76 Pigs might be useful by both turning and manuring the soil, and by removing crop pests that overwinter in soil. It seems unlikely, however, that cattle would not also be allowed to graze on crop remains on manured areas, and it is also unlikely that this relatively small seasonal resource would be enough to account for the difference in δ15N between pigs and cattle or pigs in phase 5 and phase 6.

The most obvious explanation is that with closer management of pigs in the later medieval period there was increased use of legumes as a fodder crop, which would have depressed pig δ15N values.77 While documentary and archaeobotanical evidence exists for the cultivation of peas, beans and vetch for fodder,78 it is not currently known whether greater emphasis was placed upon these in the later medieval period. However, documen-tary sources do reveal something of the type and quality of nitrogen-fixing fodder crops used for fattening pigs. For example, Rogers estimates that two to four bushels of grain or pulse per pig per year were required.79 In 1306–7 on a manor of the abbey of Bec at Combe, Hampshire, young pigs were fattened with beremancorn (a maslin of wheat, barley and rye) and brotcorn (a maslin of oats and peas and/or vetches).80 At the manor of Stevenage, Hertfordshire, in 1274 pigs aged 18 months were fattened for the table on pea chaff (ie threshed pea-pods),81 while at Wellingborough, pig feed was supplemented with peas and vetches; the latter were fed in both summer and winter because of illness.82 On the Peterborough Abbey estates in the early 14th century, legumes were the crop most commonly fed to pigs, with a much smaller proportion of oats, barley and dredge (mixed grains). Approximately one-third of the legume harvest was fed to pigs on the six core manors and in 1309–10 the abbey planted on average 10% of its demesne acres with legumes.83 Using these figures, 70–80% of pig diet would have been legumes, and this would account well for the observed change in mean δ15N values at Dudley Castle between phases 5 and 6.84

76 Bogaard et al 2007.77 Although historical records indicate the use of household and dairy waste to feed pigs in the later medieval

period (eg Albarella 2006, 79), this would have lead to an increase in δ15N values.78 Moffett 2006, 53; Stone 2006, 12–13; turnips (Brassica rapa) were probably also cultivated for human and

animal consumption, but their seeds can be difficult to distinguish from other brassicas (although see Kenward et al 1994 for an exception).

79 Rogers 1866, 336–7.80 Trow-Smith 1957, 117; maslin definitions follow Pretty 1990, tab 5.81 Trow-Smith 1957, 126.82 Ibid, 117–18.83 Biddick 1984, 175; 1989, 122–3.84 Using the model developed by Hamilton et al 2009.


We argue that both the zooarchaeological and isotopic evidence point to a major change in pig husbandry between phase 5 (1262–1321) and phase 6 (1321–97), from an extensive system using a variety of resources (which may have included pannage in wood-land areas) to an intensive system where smaller numbers of pigs were reared under more confined conditions, with legumes grown especially for that purpose providing a major part of pig diets.

How do our results compare with studies from other sites? It is useful to look at both pig and cattle values, particularly when comparing sites from different periods or regions, because wide-scale environmental effects such as variation of δ13C with climate,85 or variation between sites in local soil conditions and hence δ15N values, should affect both species similarly, while changes in management regimes may not.

Comparison of the isotopic values from Dudley Castle with broadly contemporary sites (Tab 2, Fig 11) reveals that the phase 5 (1262–1321) pigs are isotopically most simi-lar to those from early and later medieval sites in Yorkshire, particularly the rural sites of Wharram Percy and St Giles (Brompton). This may well reflect a ‘free-range’ management regime at these rural sites, using woodland and waste resources opportunistically. The pigs from Orkney and Whithorn Cathedral Priory are likely to have consumed marine food and/or been pastured on salt marshes, resulting in elevated δ15N and δ13C values.86 The pigs from the Anglo-Saxon site at Bloodmoor Hill have similar δ13C values to those at Dudley Castle, but lower δ15N values; however, the cattle at Bloodmoor Hill also have relatively low δ15N values, so this may reflect local environmental conditions (and perhaps the temporal difference) rather than different management. This may also apply to the single pig value from the other Anglo-Saxon site, Berinsfield. The broad dating and small sample sizes for these sites hinders the detailed examination of temporal variation across the medieval period:87 it is certainly not possible to identify an overall trend.

The site of Dryslwyn Castle in Carmarthenshire, Wales,88 is a particularly interesting comparison, with isotopic results from good numbers of both pigs and cattle (Tab 2). In all phases, cattle δ13C values were lower than those at Dudley Castle and the northern English medieval sites. This could reflect greater use of wooded environments, but could also reflect a wide-scale geographical difference in plant δ13C values,89 or pasture and/or fodder derived from wet habitats, which tend to have lower δ13C values. Pig δ13C values were also lower than at the English medieval sites throughout, significantly so in the ‘Welsh’ phase (1220s to 1287) and the ‘Decline’ phase (c 1407 to c 1450), which might well reflect greater use of wooded habitats, but not in the ‘English’ phase (1287 to c 1407), when they were significantly higher than in the Welsh phase. As at Dudley Castle, cattle isotope values did not change significantly between the earlier (Welsh) phase and the subsequent (English) phase, so the change in pig isotope values probably reflects a change in the pig husbandry regime, rather than a general climatic or environmental change. Pig δ15N values were higher than those of cattle in both phases, interpreted as reflecting a more omnivorous diet. Further, in the Welsh phase, there was a negative correlation between pig δ13C and δ15N values, interpreted by Millard et al as possibly indicating a diet obtained in woodland that included both fungi and invertebrates in varying amounts. In fact, both pig δ13C and δ15N values were significantly higher than those of cattle in the English phase but not the Welsh phase (our analysis; Mann-Whitney U-test, P<0.02), and

85 Eg van Klinken et al 1994; Stevens et al 2006.86 Richards et al 2006, 125; Müldner et al 2009, 1124.87 A consequence of the fact that isotopic values for animals have primarily been used as a baseline for exploring

human diet.88 Millard et al 2012.89 van Klinken et al 1994.


this could reflect a somewhat higher trophic level for the pigs, perhaps a different feeding regime that included more waste from human food preparation and processing. Another alternative suggested by Millard et al is a shift in procurement of pork from markets rather than local sources, so that pig isotopes reflect non-local environments; however, the variability in isotope values does not change, and there is no evidence that the same applies to cattle. Whatever the explanation, there is good isotopic evidence at Dryslwyn Castle for a change in the husbandry regime of pigs between the Welsh phase (1220s to 1287) and the English phase (1287 to c 1407; in the Decline phase (c 1407 to c 1450), pig isotope values fell back towards those seen in the Welsh phase).

However, at Dryslwyn Castle, unlike at Dudley Castle, there is no evidence from the δ15N values that the change in pig management included feeding them on large amounts of legumes; on the contrary, it seems more likely that they received more household or food-processing waste that would raise their trophic level compared to cattle. The pigs at the two Anglo-Saxon sites (Fig 11) have low δ15N values, but so do the cattle, and at all of the sites except for Dudley Castle in phase 6 (1321–97), whatever the absolute value of δ15N, pigs have higher δ15N values than cattle. This may reflect the greater omnivory of extensively managed pigs in this period: their diet could have included animal protein

fig 11Inter-site comparison of pig stable-isotope values from medieval sites in Britain. © J Hamilton and R Thomas.


derived from worms and insects obtained by rootling, possibly human waste and rubbish, and they may also have been allowed to feed on manured areas after harvest, all of which would have raised pig δ15N relative to cattle. Alternatively, in some cases it may reflect deliberate feeding of anthropogenic wastes to pigs (eg at St Giles where one individual had a noticeably higher δ15N). It is not clear how the proportion of these foods in pig diets might have changed at Dudley Castle between phases 5 (1262–1321) and 6 (1321–97), so it is hard to make a clear calculation of their (positive) contribution to δ15N relative to legumes (negative). It is clear, though, that the intensively managed pigs supplied to Dudley Castle in the later 14th century were consuming at least enough legumes to offset the difference from cattle due to omnivory.

As Fig 11 shows, there are clear differences between pig isotope values at different medieval sites and periods. At two sites where there are sufficient temporally resolved data these can be interpreted in terms of changes in pig management, though we are far from having a general picture — indeed, to obtain this, many more such studies at individual sites are needed. It is illuminating to consider the zooarchaeological and isotopic evidence for the change in pig husbandry regimes at Dudley Castle in the light of historical and environmental evidence, and shows the potential of this kind of analysis for the detailed understanding of animal husbandry.

CONCLUSIONS

Analysis of carbon and nitrogen stable isotopes of pig mandibles from Dudley Castle between the mid-13th century and late 14th century reveals a statistically significant reduc-tion in δ15N values, decreased dietary diversity, consistency in δ13C values and higher δ15N and δ13C values in young pigs indicative of the suckling effect. What is clear is that along with changes in pig numbers, size and age profiles there were distinct changes in isotope values, strengthening the case for a major change in pig management at some sites in 14th-century England. This study also demonstrates the value of conducting fine-grained isotopic analyses and integrating sources regarding animal and plant management strate-gies to develop further our understanding of past animal husbandry regimes in the later medieval period.

acknowledgementsWe are very grateful to Dudley Metropolitan Borough Council, and to John Hemingway in

particular, for granting permission to sample the pig mandibles from Dudley Castle, and to Richard Jones, Naomi Sykes and the two referees for helping us to clarify our arguments.

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Résumé

Glandée, légumineuses et cochons: témoins isotopiques et zooarchéologi-ques de l’évolution des pratiques d’élevage du cochon dans l’Angleterre de la fin du Moyen-Âge par Julie Hamilton et Richard Thomas

L’analyse zooarchéologique d’un assemblage substantiel d’os d’animaux découverts lors de fouilles à Dudley Castle, dans la région Ouest-Midlands, suggère qu’une évolution significa-tive est intervenue dans l’élevage des cochons au cours du 14e siècle. Une diminution marquée de l’abondance relative des cochons, associée à la taille croissante des os post-crâniens et de la dentition, ainsi qu’une proportion plus importante d’individus au stade néonatal, laissent envisager la possibilité d’un contrôle renforcé de la reproduction et de l’alimentation intervenant à cette époque, avec l’émergence de pratiques d’élevage clos. L’analyse des iso-topes stables du carbone et de l’azote d’un échantillon de 41 mandibules de cochons appartenant à deux phases d’occupation bien datées permet d’appuyer cette interprétation. Entre la fin du 13e siècle et la fin du 14e siècle, on assiste à une diminution statistiquement sig-nificative de δ15N, mais pas de δ13C, parallèle-ment à une diminution probable de la diversité du régime diététique du cochon. Ce papier passe en revue plusieurs explications possibles, qui confirment toutes qu’une évolution majeure est intervenue dans l’élevage des cochons à cette époque.

Zusammenfassung

Eichelmast, Hülsenfrüchte und Schwe-ine: isotopische und zooarchäologische Beweise für veränderte Praktiken in

der Schweinehaltung im spätmittelal-terlichen England von Julie Hamilton und Richard Thomas

Zooarchäologische Analyse eines bedeutenden Fundes von Tierknochen, die in Dudley Castle, West Midlands, ausgegraben wurden, legt nahe, dass im 14. Jh. eine wesentliche Verän-derung in der Schweinehaltung zu verzeichnen war. Eine dramatische Abnahme in der relative Häufigkeit an Schweinen, kombiniert mit einer Zunahme in der Größe der postcranialen Knochen und Zähne, sowie ein höher Anteil von neugeborenen Tieren erhöht die Wahrs-cheinlichkeit, dass während dieser Zeit eine größere Kontrolle bei der Zucht und beim Füttern der Tiere ausgeübt wurde, weil die Tiere zunehmend in umzäunten Bereichen gehalten wurden. Die Analyse mit Hilfe von stabilen Kohlenstoff- und Stickstoffisotopen von 41 Schweineunterkiefern aus zwei eng datierten Siedlungsphasen stützt diese Interpre-tation. Zwischen dem späten 13. und späteren 14. Jh. war eine statistisch signifikante Abnahme von δ15N, aber nicht von δ13C zu verzeichnen, und die Ernährung der Schweine wurde wahrs-cheinlich auch weniger vielseitig. Der Artikel diskutiert mehrere Erklärungen für dieses Muster, die alle mit einer größeren Veränderung in der Schweinehaltung in dieser Zeit kompat-ibel sind.

Riassunto

Pascoli boschivi, legumi e suini: reperti isotopici e zooarcheologici comprovanti il cambiamento nell’allevamento dei suini nell’Inghilterra tardomedievale di Julie Hamilton e Richard Thomas

L’analisi zooarcheologica di una cospicua quantità di ossa animali provenienti dagli scavi del castello di Dudley nella regione delle


Midlands Occidentali indica che durante il XIV secolo avvenne un cambiamento impor-tante nell’allevamento dei suini. Lo spettaco-lare calo dell’abbondanza relativa dei suini abbinato all’aumento delle dimensioni delle ossa postcraniali e dei denti e all’elevata per-centuale di ossa neonatali, indica la possibilità che in questo periodo, grazie all’introduzione degli allevamenti entro recinti, si esercitasse un maggiore controllo sulla riproduzione e sull’alimentazione. L’analisi degli isotopi stabili

del carbonio e dell’azoto su un campione di 41 mandibole di suini relative e due fasi di occu-pazione rigorosamente datate corrobora questa interpretazione. Tra il tardo XIII e il tardo XIV secolo si riscontra una rilevante diminuzi-one di δ15N, ma non di δ13C, e probabilmente anche la dieta dei suini divenne meno varia. L’articolo adduce varie spiegazioni per questi andamenti, tutti compatibili con un cambia-mento importante nelle pratiche di allevamento dei suini avvenuto in questi tempi.

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