Nitrogen isotopes and the trophic level of humans in archaeology

Human and domesticate animal bone collagen δ¹⁵N values in prehistory differ generally by 3‰ or more from Neolithic to post- Roman times in Northwest Europe, leading to an assumed dietary animal protein fraction of 60–80% using a standard interpretation of δ¹⁵N values. We examine the assumptions on which this model rests and the limitations of our knowledge in the analysis of δ¹⁵N values in archaeology. We have developed a set of models which, with small changes made in assumptions (on the order of 1‰), can produce substantially lower estimates of the dietary animal protein fraction for given δ¹⁵N values. We consider the implications of various dietary animal protein fractions on agricultural carrying capacities and human population densities in prehistory.     

Stable isotopes and diet at Ancient Kerma,Upper Nubia (Sudan)

Carbon and nitrogen stable isotope values were measured from bone collagen extracted from archaeological Nubian human (n = 54) and faunal (n = 61) populations from the site of Kerma, Sudan. Collagen suitable for isotopic analysis was extracted from 22 faunal and 48 human samples from the Eastern cemetery site, dated to the Middle Kerma (c. 2050–1750 BC) and Classic Kerma (c. 1750–1500 BC) periods respectively. The isotopic data indicate that the human dietary regimen included a mix of C₃ and C₄ plant-derived components, with a larger C₄ component than previously reported in archaeological Egyptian Nile Valley populations. Elevated δ¹⁵N values are attributed to consumption of dietary resources from a ¹⁵N-enriched terrestrial ecosystem. The faunal isotope data also indicate the consumption of C₃ and C₄ plants. The large range of δ¹³C values measured in both the human and faunal samples supports previous work suggesting that a significant portion of the populations buried at Kerma may have originated elsewhere, further confirming the Nile Valley as a major corridor for population movement in the region.     

Taxonomic, anatomical, and spatio-temporal variations in the stable carbon and nitrogen isotopic compositions of plants from an African savanna

Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios are commonly used to reconstruct palaeodiets and palaeoenvironments. The method is based on our knowledge of isotopic patterns in plants, which are subject to taxonomic and environmental variability. While previous researchers have addressed isotopic variability amongst plants, no studies have looked extensively at a broad suite of taxa over multiple temporal scales from within the savanna biome so as to provide baseline data for palaeodietary and palaeoenvironmental studies. Here we document variations in the isotopic compositions of plants collected over two years from the Kruger National Park, South Africa, with respect to species and anatomical differences, and the influences of geological substrate and spatio-temporal shifts in climate. Results show that environmentally-induced carbon isotopic variations in plants within this region are generally smaller than 2‰, which is lower than what has been previously reported for plants compared across multiple habitat-types. These data suggest that δ¹³C differences of 2‰ or more (or 1‰ if the diet is predominantly C₄) between animals from a given area reliably indicate real dietary differences. Plant δ¹⁵N values vary greatly between different microhabitats (by up to 4‰), responding to a range of environmental influences that may, in turn, significantly influence variation in animal δ¹⁵N values.     

Stable carbon and nitrogen isotope variations in tooth dentine serial sections from Wharram Percy

Here we report δ¹³C and δ¹⁵N measurements of serial sections of human deciduous and permanent tooth dentine from archaeological samples taken from the medieval village site of Wharram Percy, Yorkshire, UK. We found a pattern of enrichment, for both δ¹³C and δ¹⁵N, where the tooth crown was greater than the cervical part of the root, which in turn was greater than the apical portion of the root and the associated rib collagen values. This pattern reflects a decrease in the consumption of isotopically enriched breast milk and the introduction of less enriched weaning foods in the diet. The (mean±SD) difference between the deciduous second molar crowns and corresponding rib samples from the same individuals after 2 years of age was 1.2±0.4‰ for δ¹³C and 3.2±0.8‰ for δ¹⁵N. The δ¹⁵N values are as predicted, but as there were no C₄plants at Wharram Percy, this 1.2‰ enrichment in δ¹³C represents clear evidence of a carbon trophic level effect in collagen from breastfeeding infants. Carbon and nitrogen results also show that the infant diet among those who died in infancy did not differ from those who survived into childhood. This study demonstrates the promise of using dentine serial sections to study the temporal relationships of breastfeeding, weaning, and dietary patterns of single individuals.     

Subsistence and mobility strategies in the Epipalaeolithic: a stable isotope analysis of human and faunal remains at 'Uyun al-Hammam,northern Jordan

This paper investigates evidence for subsistence and settlement activities in the Levantine Middle Epipalaeolithic through the application of stable isotope analysis to human and non-human remains from the site of 'Uyun al-Hammam, northern Jordan. In general, bone from the site suffers a high degree of diagenesis and collagen could not be extracted for analysis here. Carbon and oxygen isotopic values from human tooth enamel samples were variable, but within expected values for the Middle Epipalaeolithic, whereas animal carbon and oxygen isotopic values varied widely, most likely due to hydrological and climatological factors. Carbon and isotopic values for the human samples indicated a predominantly C₃ plant dietary input, while animal samples appeared to have varying amounts of C₄ inputs into their diet. This is the first isotopic analysis conducted on material from the Middle Epipalaeolithic of the southern Levant and, as such, even results constrained by temporal and climatological variants within the region contribute to the overall knowledge of settlement and subsistence strategies during this cultural period.     

Beyond the grave: variability in Neolithic diets in Southern Germany?

Carbon and nitrogen stable isotope analyses were undertaken on human and faunal remains from two Neolithic sites in Southern Germany; the LBK settlement at Herxheim and the middle Neolithic cemetery at Trebur. Stable isotope data were used to reconstruct the diets of individuals buried at these sites and to look at dietary variation between groups classified by their sex, age, grave goods and cultural affiliation. Overall there was surprisingly little variation in the diet between the groups, as described by the stable isotope analysis, despite significant differences in the composition of grave goods. Also surprising, considering the archaeological evidence for extensive grain cultivation in this region during the Neolithic, was that the majority of individuals had δ¹⁵N values consistent with the consumption of significant amounts of animal protein.     

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.     

Subsistence and the isotopic signature of herding in the Bronze Age Hexi Corridor,NW Gansu,China

Dietary patterns at two Bronze Age sites in the Hexi Corridor are investigated by the analysis of stable carbon and nitrogen isotopes in faunal bone collagen. The findings are compared with archaeobotanical remains from one of the sites which include high proportions of millet (Panicum miliaceum and Setaria italica) as well as the western derived cereals wheat (Triticum aestivum), barley (Hordeum vulgare) and oat (Avena sativa). The isotopic data indicate domestic omnivores (Canis and Sus) had diets dominated by millet. Minimally offset δ¹⁵N values between herbivore and omnivore fauna suggest low consumption of animal protein by omnivores. Diets of herded animal (Bos and Caprinae) included only low proportions of C4 foods, suggesting that these animals were not regularly foddered with millet plants, and that their grazing areas were mostly beyond the agricultural zone. The wide range in δ¹⁵N values amongst herbivore fauna (4.1‰–11.8‰) suggests grazing occurred in a variety of ecological zones, and this would be consistent with the occurrence of long-distance transport of livestock in the region.     

Trace element concentrations in teeth – a modern Idaho baseline with implications for archeometry,forensics, and palaeontology

Concentrations of 69 minor and trace elements were measured in situ using laser ablation inductively-coupled plasma mass spectrometry in multiple teeth of modern herbivores (Cervus elaphus, Odocoileus hemionus, Odocoileus virginianus; n = 52), omnivores (Ursus americanus; n = 56), and carnivores (Felis concolor; n = 33; Canis lupus; n = 4) from Idaho, USA. On each tooth, two to five analyses were collected on enamel, primary dentine, and secondary dentine with spot diameters of 30–100 μm. Continuous 30-μm-wide line traverses were collected across deer, elk, and wolf teeth. Results confirm trace element concentrations below 1 ppm for many elements, including Li, Be, transition metals (excepting Mn, Fe and Zn), heavy metals (excepting Hg and Pb), the rare earths, and actinides. Strontium and Ba generally biopurify with increasing trophic level, but Ba shows decreasing discrimination with tissue type in the order secondary dentine – primary dentine – enamel. Most elements show strong zoning within tissues and variable trophic level behavior, so concentrations in omnivores rarely fall between herbivores and carnivores. Trace element mass balance suggests that soil and dust, not food, commonly deliver the largest trace element load in terrestrial carnivores and omnivores, even for elements that biopurify, like Ba. Use of trace elements for inferring past diets are likely compromised by unknown rates of dust and soil ingestion rather than indicating the degree of herbivory and carnivory. The low concentrations of many elements provide multiple sensitive markers of post-burial overprinting that can be used to discriminate altered vs. original biogenic compositions. REE and actinide trends do not directly follow bedrock compositions.     

Stable isotope investigations of charred barley (Hordeum vulgare) and wheat (Triticum spelta) grains from Danebury Hillfort: implications for palaeodietary reconstructions

Palaeodietary studies typically focus on the analysis of bone collagen due to the limited availability of plant remains. Isotopic analysis of plant remains, however, allow for a more extensive consideration of the contribution of plants to the human diet and can potentially provide information about the environment in which the crops were grown. This paper reports the results of carbon and nitrogen isotope analyses performed on charred barley and wheat grains recovered from pits within Danebury Iron Age hillfort. To the best of our knowledge, this is the first Iron Age site in Britain from which charred grains have been isotopically analysed. Our results suggest that cereals found at the hillfort were grown in several different environmental contexts. The isotope data demonstrate that the herbivores were not consuming a diet primarily based on grains as the δ¹⁵N values of the grains are very similar to those of the herbivores. Palaeodietary investigations typically assume that humans eating plant protein only would have the same δ¹⁵N value as the local herbivores. This assumption is clearly invalid at Danebury, where the humans and animals appear to have consumed either different parts of the same plants or different plants. Researchers typically interpret high differences between human and animal δ¹⁵N values as indicative of diets high in animal protein, however where major plant resources have δ¹⁵N values similar to those of the herbivores our ability to distinguish between plant and animal sources of protein in the diet is limited. Our research has demonstrated that whenever possible it is desirable to measure the isotopic signatures of potential major plant resources in order to understand past subsistence strategies.