Diversity in foddering strategy and herd management in late Bronze Age Britain: An isotopic investigation of pigs and other fauna from two midden sites

Abstract

Middens of the southern British late Bronze and Iron Age are vast accumulations of cultural debris that can be explained as refuse dumps linked with large periodic feasting events. A distinctive feature of these sites is that their faunal assemblages invariably comprise a considerably higher proportion of pig remains than contemporaneous settlement sites. This paper presents results from a programme of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope analysis of fauna from two major midden sites, Llanmaes in South Wales and Potterne in Wiltshire. The research aim is to reconstruct husbandry strategies and foddering regimes, particularly concerning pigs, to better understand how the challenges of raising large herds were met. Analysis produced exceptionally wide-ranging results for pigs and other domesticates at both sites, particularly in terms of δ¹⁵N values, demonstrating that diverse foddering strategies were employed. Diversity in the late Bronze Age pig foddering regimes indicates that the Neolithic husbandry practices (focusing on woodland fodder) had not been abandoned, but that new husbandry methods (consumption of household waste) were also being practised, which subsequently became more widely established in the Iron Age. The heterogeneity of signatures suggests that animals may have been husbanded in a piecemeal fashion at a local, household level. This in turn hints that fauna may have been brought to these sites from households across the surrounding landscape, rather than being husbanded by specialist producers in the vicinity of the middens.     

An investigation of diet in early Anglo-Saxon England using carbon and nitrogen stable isotope analysis of human bone collagen

The principal aim of this work is to investigate whether protein sources in human diets in early Anglo-Saxon (5th-7th century AD) England varied with geographic location, or with respect to age or sex. The methodology used was analysis of δ¹⁵N and δ¹³C in human bone collagen from 76 adult skeletons from a total of 18 different cemeteries located in inland, riverine and coastal environments. In order to control for the possible effects of socio-economic status on diet, only high status individuals, as identified by grave goods, were studied. Data were analysed using statistical manipulation of the raw results and using IsoSource (Phillips and Gregg, 2003), a mathematical treatment which models the composition of the protein part of human diets using bone stable isotope ratios when the isotopic values for potential protein sources are known or can reasonably be inferred. The results suggest that protein sources varied little according to geographic location and that terrestrial foods dominated at all locations. However there were some subtle patterns. Slightly elevated δ¹³C in skeletons from coastal locations, and δ¹⁵N in those from riverine sites may indicate that communities in these locations made greater use of marine and freshwater resources respectively. If this is correct then it demonstrates that 5th-7th century communities made some use of wild resources even within a predominantly agrarian economy. In general the analysis of the raw data and the IsoSource results were mutually supportive, and this work demonstrates the value of this twin-pronged approach to analysis of human bone stable isotope data.     

Stable isotope analysis of 14 individuals from the Mesolithic cemetery of Vasilyevka II,Dnieper Rapids region,Ukraine

Bone collagen extracted from 14 humans from the Mesolithic cemetery of Vasilyevka II was analysed for their δ¹³C and δ¹⁵N ratios. This cemetery is one of only two later Mesolithic cemeteries from the Dnieper Rapids region, being dated to 7300–6220 cal BC on the basis of three radiocarbon determinations. This analysis provides insights into the nature of the diet of the Dnieper populations at the very end of the Mesolithic period, prior to the adoption of pottery in the region, and the assumed shift towards the exploitation of domesticates in the economies of the populations of the Dnieper region, and considers these in relation to broader temporal indicators of diet in the region.     

Stable isotope palaeodietary study of humans and fauna from the multi-period (Iron Age,Viking and Late Medieval) site of Newark Bay,Orkney

We report here on stable carbon and nitrogen isotope measurements of human and faunal bone collagen from the Iron Age, Viking Age, and Late Medieval site of Newark Bay, Orkney, Scotland. We found a wide range of results for humans in both δ¹³C (−15.4‰ to −20.3‰) and δ¹⁵N (8.6‰–15.6‰) values. The enriched carbon and nitrogen values indicate the consumption of significant amounts of marine protein, which is very unusual for post-Mesolithic (e.g. 4000 cal BC) UK and European populations. Also of interest is a statistically significant difference in δ¹³C (t = −2.48, p = 0.011) and δ¹⁵N (t = −2.44, p = 0.011) values, and therefore diets, between adult males and females at this site, with males (δ¹³C = −17.8 ± 1.2‰, δ¹⁵N = 13.2 ± 1.6‰) having, on average, a higher proportion of marine protein than females (δ¹³C = −18.9 ± 1.1‰, δ¹⁵N = 11.8 ± 1.8‰). The weaning age of the sub-adults was difficult to interpret due to the large isotopic variation in the adult females, but nearly all individuals between birth and 1.25 years have elevated δ¹⁵N values indicating that they were breastfed to some extent.     

Investigation of the ‘canopy effect’ in the isotope ecology of temperate woodlands

Anomalously ¹³C-depleted carbon stable isotope values from closed forest ecosystems have been termed the ‘canopy effect’. Originally this was ascribed to recycling of depleted carbon from forest floor decomposition of organic material, although others have suggested that it is equally likely to be due to variations in leaf-level processes in response to increased shade. This depletion in the heavier carbon isotope is passed on to woodland herbivores feeding within the forest environments. A similar isotopic depletion has also been reported in the archaeological literature from more open temperate woodland settings, but no measurements have been made on the plants at the base of the food chain in order to quantify the effect. In this study we attempt this by examining the carbon and nitrogen stable isotopic values of different species of grasses from a range of open to closed habitat settings within Wytham Wood, Oxfordshire, UK. We find a strong relationship between carbon isotopic depletion of plant tissue and lowered light intensity with an up to 5‰ shift between grass grown in open and closed locations. In order to follow this up the food chain, we also report data on wool from sheep grazing in open pastures near the Wood, and on fallow deer living within the woodland, but which turn out not to show a strong canopy effect, probably related to their feeding strategies. We conclude that there is indeed a strong ‘canopy effect’ in temperate woodland, probably related to differential light levels, but that not all apparently woodland-dwelling mammals show such an effect. We also show considerable isotopic variation at the base of the food chain, which should counsel caution when attempting to interpret dietary isotopes using mixing models.     

Stable isotope evidence for palaeodiets in southern Turkmenistan during Historical period and Iron Age

The subsistence patterns of Iron Age and Historical period humans from south-western Turkmenistan have been reconstructed using the carbon and nitrogen isotopic compositions of archaeological faunal and human bones. A qualitative comparison of the isotopic signatures points to a small proportion of ruminant meat and dairy in human diet for both periods. The ranges of proportions of dietary items yielded by a quantitative approach based on concentration dependent mixing models confirm the high proportions of plant food in the average diet, and show little change in the reconstructed diet for both periods. A comparison of results from zooarchaeological and isotopic approaches illustrates their complementarity in subsistence patterns reconstruction.     

Chemical,elemental, and isotopic effects of acid concentration and treatment duration on ancient bone collagen: an exploratory study

Demineralization of bone for collagen extraction is most commonly performed using dilute hydrochloric acid (HCl) despite the fact that little data exists on the effects of differing acid concentration or treatment time on the quantity and quality of collagen extracts and that hydrochloric acid is extremely effective at hydrolyzing peptide bonds. Data on yield, elemental composition, and isotopic signature from bone collagen obtained from multiple extractions performed on two large ancient human bone samples from prehistoric Puerto Rico indicate that there is no meaningful difference between acid treatments ranging from 0.05 to 0.2 M concentration and 24–120 h of treatment. As such, a shorter course of demineralization using more concentrated acid would appear to produce quality results in a shorter time.     

Stable isotope analysis of prehistoric populations from the cemeteries of the Middle and Lower Dnieper Basin,Ukraine

This paper presents the results of new stable isotopes (carbon and nitrogen) analysis of human, faunal and fish remains from thirteen cemeteries from the Middle and Lower Dnieper Basin, Ukraine. The results are integrated with earlier analyses, undertaken solely on human samples, in order to provide a comprehensive overview of subsistence across the Upper Palaeolithic through to Eneolithic periods in this region. This is the first time that a combined sample of human, faunal and fish remains has been studied in order to interpret subsistence strategies across these periods in Ukraine. The total dataset comprises 113 samples of human, faunal and fish remains, 59 of which include new analyses of faunal and fish remains that have not previously been made available for study (Table 1). The analysis of the faunal and fish remains allows for a consideration of trophic levels which indicates that the consumption of freshwater fish occurs from the Epipalaeolithic period onwards. Whilst the majority of the cemeteries and the individuals therein cluster in relatively tight groups, there is a significant offset between the human and faunal samples due to the consumption of freshwater resources. The fish samples analysed in the study appear to exhibit a relatively random distribution when compared to the other samples analysed. In general, freshwater resources remain significant through until the end of the Neolithic period and into the Eneolithic period at the sites investigated.     

Seasonality of human site occupation based on stable oxygen isotope ratios of cod otoliths

Oxygen isotope ratios (δ¹⁸O) were measured in micromilled samples of cod otoliths recovered from two Stone Age sites, one from Skoklefald, southeastern Norway and five from Skipshelleren, southwestern Norway. Discrete samples of otolith material were milled from the edge of the otolith towards the centre, each sample representing 3–4 weeks of growth. The δ¹⁸O values showed seasonal signals, covering a period 1–2 years prior to the time of capture. Isotope ratios at the edge of the otoliths, which is the material deposited at the time of fish capture, corresponded to the coldest seasonal water temperatures, in late winter or early spring. These data provide independent evidence for the season of use of the Skoklefald and Skipshelleren sites.     

Archaeological collagen: Why worry about collagen diagenesis?

DNA appears to decay by random chain scission resulting in a predictable range of fragment lengths. Collagen decay has also been modelled in this same way, although it has become increasingly evident that collagen decay does not follow this same pattern. Radiocarbon and stable isotope analysis now use ultra-filtration to isolate large fragments (>30% of original polymer length) even in Pleistocene bone. How then does collagen decay? This study contrasts experimentally degraded samples with collagen extracted from forensic, archaeological and fossil bone. In experimentally degraded bone, values for amino acid and elemental (C:N) composition, bulk δ ¹³C, δ ¹⁵N, and aspartic acid racemisation (AAR) changed very little until 99% of the collagen was lost, suggesting that the collagen triple helix and polypeptide chains remained remarkably intact. This suggestion was demonstrated directly by examining the integrity of individual polypeptide chains using cyanogen bromide (CNBr) cleavage followed by SDS-PAGE electrophoresis. In ancient samples, AAR values remain remarkably stable and the pattern of CNBr-cleavage was only replaced with a smear of smaller polypeptides in the oldest (Pleistocene) bones investigated. Smearing may reflect both modification of the methionine resides (the sites of CNBr-cleavage) and/or partial hydrolysis of the collagen molecule. The findings reveal why it is not usually necessary to worry about collagen diagenesis; it is mostly intact. However, evidence of partial deterioration of the oldest bone samples suggests that alternative purification strategies may increase yields in some samples.     

Human subsistence strategy at Liuzhuang site,Henan, China during the proto-Shang culture (∼2000–1600 BC) by stable isotopic analysis

Since the discovery of the proto-Shang culture, created mostly by ancestors of the Shang clan from the late Neolithic Age to the early Shang period (∼2000–1600 BC), the subsistence strategy and lifestyle of humans in China during their movement southwards have been a great focus. Chinese literature and archaeological findings suggest that the proto-Shang societies were composed of different cultural groups and had various subsistence strategies. For example, at the Liuzhuang site, three types of burials, i.e., stone coffin, wooden coffin and earthen shaft-pit, are found. The wooden coffin and earthen shaft-pit burials had been adopted locally in the Central Plains since the Neolithic Age while the stone coffin burials were usually used by people living in Northeast China and had never been found in the Central Plains before. In this study, stable carbon and nitrogen isotopic analyses were performed on human bones from the Liuzhuang site and animal bones from Zhangdeng site in Henan province, China to determine whether different social groups had various accesses to food resources and whether their dietary difference was related to inequality in social status. Humans have mean δ¹³C and δ¹⁵N values of −7.6 ± 0.6‰ and 9.6 ± 1.0‰ (n = 19) respectively, which strongly indicates that humans rely primarily on C₄-based food. The main contribution of C₄-based food in their diet is from millet agriculture or animals that consume millet by-products. The isotopic spacing of carbon and nitrogen isotopic values between pigs and humans, between dogs and humans, and between cattle and humans, all imply that these animals were the main meat resources for humans. Surprisingly, the δ¹³C values and δ¹⁵N values of humans with different types of burials are quite close, indicating that they had equal access to food resources. This result suggests that the proto-Shang humans had adapted to the local subsistence strategy, and the local cultural factors in the Central Plains were very well integrated into proto-Shang culture.     

Geographic variation in bone carbonate and water δO values in Mendoza,Argentina and their relationship to prehistoric economy and settlement

Questions of mobility, settlement pattern, and their relation to economic organization and resource use are central to ongoing work in central-western Argentina. Here we analyze geographic patterns in the distribution of 178 human bone carbonate δ¹⁸O samples, 46 human tooth enamel carbonate δ¹⁸O samples, and 48 water δ¹⁸O samples from throughout the Andean Cordillera and Monte Desert and evaluate their implications for prehistoric mobility and economy. We confirm and refine previous generalizations regarding a highland/lowland dichotomy in water δ¹⁸O values and show that the range of human carbonate δ¹⁸O values generally reflect available water sources. While there is little within-lifetime change in patterns of water use, we show that most individuals have stable isotope signatures consistent with water use from multiple areas or areas other than where they were ultimately interred. These data indicate high levels of residential mobility, and we conclude by discussing their implications for our understanding of regional prehistory.     

Guanaco (Lama guanicoe) isotopic ecology in southern South America: spatial and temporal tendencies, and archaeological implications

We synthesize and discuss available isotopic data on Holocene guanaco samples from southern South America, extending from Tierra del Fuego Island to northern Patagonia and the Pampean region. We evaluate temporal and spatial tendencies on the basis of 91 samples (mainly based on δ¹³C_collagen values), presenting implications for paleodietary research in archaeology. We conclude that there are no strong correlations with latitude in the macro-spatial scale, while there is a set of interesting patterns at smaller regional scales. These patterns lead us to evaluate the role of ecologic and topographic variables (e.g. canopy effect, variations in altitude, ecotones) in structuring isotopic variability. Finally, on the basis of the present analysis we suggest a number of hypotheses and perspectives for the use of stable isotopes as geographic tracers of guanaco distribution in the past, and specific implications for the paleodietary study of human samples.     

Pottery wall thinning as a consequence of increased maize processing: a case study from central New York

The histories of maize in northeastern North America are not well understood at the subregional level. The complexity of formation processes for various lines of evidence for maize use requires the application of many analytical methods and techniques to produce data on subregional maize histories. The present analysis uses bulk δ¹³C values on directly dated charred encrusted cooking residues to provide the first direct correlation of water-based maize cooking to trends in pottery wall thinning. The results add to the growing body of evidence for the history of maize use in central New York.     

Isotopic Determination of Seasonality in Diet and Death from Nubian Mummy Hair

Sections of human hair from naturally desiccated Sudanese Nubian mummies representing X-Group (AD 350-550) and Christian (AD 550-1300) periods in the Wadi Halfa area have been analysed for their isotope ratios. Because the carbon in hair represents food intake over the growth period of this tissue, analysis comparing segments taken next to the scalp with those further along the shaft can indicate diet just prior to death as well as any recent shift in food consumption. Modern populations in this area practise seasonal crop scheduling which involves the cultivation of C₃ plants (wheat, barley and most fruits and vegetables) in the winter and the hardier C₄ plants (sorghum and millet) in the summer. Shifting isotopic values along the length of hair strands of the ancient inhabitants of this area demonstrate that this practice has its roots at least as far back as the Initial Phase of Intensive Agriculture. The most common season of death appears to have been summer, the time of greatest climatic, nutritional and physiological stress for both ancient and modern inhabitants.     

Dating of modified femora of extinct dwarf Hippopotamus from Southern Madagascar: Implications for constraining human colonization and vertebrate extinction events

Two significant events in the late Holocene history of Madagascar were (a) the arrival of people, and (b) the loss of nearly two dozen species of land vertebrates in the socalled “subfossil extinctions”. The consensus is that the faunal losses occurred shortly subsequent to human arrival, but the timing of these events is poorly constrained. The minimum age for initial human presence on the island may now be set at approximately 2000 bp, on the basis of AMS ¹⁴C dates for human-modified femora of extinct dwarf hippos from SW Madagascar. Assuming that this date also marks the beginning of deleterious human interactions with the subfossil fauna, and assuming that this fauna became completely extinct by 900 bp, the width of the anthropogenic “extinction window” may have been as long as c. 1000 a. This estimate, nearly twice the length of previous ones, is close to the unadjusted minimum for the duration of the terminal Pleistocene extinction event in the Americas. Whether or not this length of time comports with theoretical expectations of a “blitzkrieg” pattern of losses is uncertain, but greater refinement in dating the end of the subfossil extinctions is unlikely to produce radically shorter estimates of duration.     

Adipocere withstands 1600 years of fluctuating groundwater levels in soil

An extraordinarily well-preserved skeleton of a child, interred in a stone sarcophagus in the Late-Roman era, was discovered in the city of Mainz (Germany) in 1998, covered with a puff pastry-like substance assumed to be adipocere. It is the first time that this substance, which is derived from fat under oxygen-deficient conditions and prevents corpses from decaying, has been discovered on corpses buried under conditions described in the present paper.     

Hardwood ash nixtamalization may lead to false negatives for the presence of maize by depleting bulk δC in carbonized residues

Among the multiple proxies for detecting maize in precontact economies is the use of δ¹³C analysis of carbonized residues from ceramic cooking vessels. Although maize horticulture was widely established in Eastern North America (ENA) by A.D. 1000, there are carbonized residues from ceramic assemblages after this date that lack the elevated δ¹³C values indicative of the presence of maize. This may be due to the true absence of maize, or other factors including the masking of maize. Prior experimental research by Hart et al. demonstrated that the addition of C₃ plants or consumers to two part mixes with maize can mask maize presence even when maize is the dominant ingredient. Here we investigate the effect of alkali processing of maize (nixtamalization) on δ¹³C using the widespread ENA process of boiling maize kernels with wood ash, a C₃ product, to create hominy. Our experiments test whether or not the process of hardwood ash nixtamalization can mask the presence of maize in adhering carbonized residues by depleting δ¹³C values, and whether there is a reciprocal δ¹³C enrichment effect on the hardwood ash employed in nixtamalization. Overall, there is substantial δ¹³C depletion of residues when maize is cooked with hardwood ash, and hardwood ash cooked with maize shows the reciprocal enrichment. Therefore, the depleted values after the adoption of maize may be false negatives due to the nixtamalization process.     

Non-linear relationship between bulk δC and percent maize in carbonized cooking residues and the potential of false-negatives in detecting maize

Bulk δ¹³C values on charred cooking residues adhering to pottery sherd interior surfaces have been used as a source of information on the histories of maize in various locations in the western hemisphere. This approach is based on an assumption of a linear relationship between the percent maize in the resource mix cooked in a pot and δ¹³C. Previous experiments suggest that this relationship is non-linear, and maize may not be identified from bulk δ¹³C values even when it contributed substantially to the resource mix. A second round of experiments, presented here, indicates that the mobilization of carbon from maize and C₃ resources over time is the critical variable in residue formation and the resulting bulk δ¹³C value. This is influenced by the form of maize being cooked.     

Changing growing conditions for crops during the Near Eastern Bronze Age (3000–1200 BC): the stable carbon isotope evidence

The analysis of carbon isotope discrimination (Δ¹³C) in crop plant remains from seven Bronze Age sites in northern Mesopotamia and the Levant shows clear differences in water availability between the different geographic areas and throughout the different periods (3000–1200 BC). Amongst the different moisture variables modelled precipitation minus evaporation (P-E—using a macrophysical climate model (MCM)) results in very high correlation (0.74) with Δ¹³C values in barley, supporting the significance of climate parameters (effective moisture) in carbon fixation in this species. The comparison of Δ¹³C values of different crops in different periods confirms increased aridity during the Middle Bronze Age (2000–1600 BC), compared to the later Early Bronze Age (2700–2000 BC) particularly in the north-eastern Syrian territory with generally lower Δ¹³C values during the Middle Bronze Age, as has been documented in palaeoclimate proxies, and in agreement with the MCM. Standard deviation in Δ¹³C values from grains or seeds of one species originating from different samples of an individual site may be understood as variability in moisture conditions during the grain-filling period around the considered location. Large standard deviations occur preferably in sites with low mean annual precipitation (e.g. at Emar) and suggest that in these sites, at least some of the crops were irrigated.