Assessing natural variation and the effects of charring,burial and pre-treatment on the stable carbon and nitrogen isotope values of archaeobotanical cereals and pulses

The aim of this study is to assess the potential of charred archaeobotanical cereal grain and pulse seed δ¹³C and δ¹⁵N values to provide evidence of crop growing conditions and as a potential component of palaeodietary studies. In order to reliably interpret archaeobotanical δ¹³C and δ¹⁵N values it is necessary to take into account the impact of charring, burial and laboratory pre-treatment procedures. We examine the effects of charring and burial on bulk δ¹³C, δ¹⁵N, %C, %N and C:N ratios in modern cereal and pulse material, and of cleaning by acid–base–acid (ABA) pre-treatment on modern and archaeobotanical charred material. Our study utilised bulk grain and seed samples to help account for within-ear/pod and between-plant variability in δ¹³C and δ¹⁵N values. Heating at relatively low temperatures and for prolonged times (230 °C for up to 24 h) is conducive to the formation of well preserved, undistorted charred cereal grain and pulse seed. Heating for 24 h has a systematic and predictable effect on δ¹⁵N values, with increases of around 1‰ on average in cereal grains and pulse seeds, and no consistent impact on δ¹³C values. Increases in δ¹⁵N are likely due to the loss of lighter ¹⁴N via N-containing volatiles. Burial (for up to 2 years) and ABA pre-treatment have no significant effects on δ¹³C or δ¹⁵N values. After pre-treatment, however, the %C and %N contents of the archaeobotanical material more closely resembles that of the modern charred grains and seeds, suggesting that archaeobotanical remains accumulate non-structural material during burial but retain their original carbon and nitrogen content. Therefore %C, %N contents and C:N ratios can provide useful criteria for assessing archaeobotanical preservation.     

From Traditional Farming in Morocco to Early Urban Agroecology in Northern Mesopotamia: Combining Present-day Arable Weed Surveys and Crop Isotope Analysis to Reconstruct Past Agrosystems in (Semi-)arid Regions

ABSTRACT

We integrate functional weed ecology with crop stable carbon and nitrogen isotope analysis to assess their combined potential for inferring arable land management practices in (semi-)arid regions from archaeobotanical assemblages. Weed and GIS survey of 60 cereal and pulse fields in Morocco are combined with crop sampling for stable isotope analysis to frame assessment of agricultural labour intensity in terms of manuring, irrigation, tillage and hand-weeding. Under low management intensity weed variation primarily reflects geographical differences, whereas under high management intensity fields in disparate regions have similar weed flora. Manured and irrigated oasis barley fields are clearly discriminated from less intensively manured rain-fed barley terraces in southern Morocco; when fields in northern and southern Morocco are considered together, climatic differences are superimposed on the agronomic intensity gradient. Barley δ¹³C and δ¹⁵N values clearly distinguish among the Moroccan regimes. An integrated approach combines crop isotope values with weed ecological discrimination of low- and high-intensity regimes across multiple studies (in southern Morocco and southern Europe). Analysis of archaeobotanical samples from EBA Tell Brak, Syria suggests that this early city was sustained through extensive (low-intensity, large-scale) cereal farming.     

Impact of charring on cereal grain characteristics: linking prehistoric manuring practice to δN signatures in archaeobotanical material

Systematic use of animal manure has been demonstrated to be detectable in the plant δ¹⁵N value but evidence of manure affecting isotopic composition is mainly based on studies of fresh plant material. These findings can potentially be applied to archaeobotanical assemblages and thus provide information about prehistoric manuring practice. Prehistoric grains are generally found in a charred state of which the exact charring conditions are unknown but most likely often multifarious. In this study we examined the influence of grain weight and a range of charring conditions with regards duration, temperature, oxygen availability, and manuring. The charring was applied to emmer, spelt and naked barley with assessment of weight loss, N concentration and δ¹⁵N. There were only small and non-systematic variations in δ¹⁵N in relation to grain weight class. We also found that charring did not distort δ¹⁵N in either a systematic or substantial way and conclude that manuring most likely will be detectable in archaeobotanical charred grains. As certain within-grain variability in δ¹⁵N existed, especially in the intensively manured grains, the resolution of this kind of information should be carefully considered. However, despite attempts to deliberately tamper and distort the grain δ¹⁵N signature, the changes observed in this study were too small to be of any consequences for the archaeobotanical applicability of the method. Thus the isotope method offers unique evidence about prehistoric manuring practice.     

Manuring and stable nitrogen isotope ratios in cereals and pulses: towards a new archaeobotanical approach to the inference of land use and dietary practices

This paper explores the impact of animal manure application on the δ¹⁵N values of a broad range of crops (cereals and pulses), under a range of manuring levels/regimes and at a series of locations extending from northwest Europe to the eastern Mediterranean. We included both agricultural field experiments and areas where ‘traditional’ farming is practised. Our aim is to ground-truth interpretation of δ¹⁵N values in archaeobotanical crop remains as evidence of past growing conditions and husbandry practices. The results confirm the potentially radical impact of manuring on δ¹⁵N values in cereals, depending on manuring level, but indicate only a slight effect on pulses, which can fix atmospheric nitrogen. The expected geographical trend towards greater δ¹⁵N with increasing climatic aridity is not apparent, probably because the growing conditions for crops are ‘buffered’ through crop management. Each of these observations has fundamental implications for archaeobotanical interpretation of δ¹⁵N values as evidence of land use practices and (together with analysis of bone collagen/tooth enamel in potential consumers) palaeodiet.     

The effect of charring and burial on the biochemical composition of cereal grains: investigating the integrity of archaeological plant material

Stable isotope analysis of charred archaeobotanical cereal grains has the potential to provide direct evidence of crop growing conditions in the past and to refine palaeodietary predictions. If isotope values of archaeobotanical material are to be considered robust, it is necessary to characterise the compositional changes associated with their charring and burial. This study used a suite of analytical techniques, including FT-IR and solid state ¹³C NMR, to characterise changes in the biochemical composition of modern einkorn grains with heating at 230 °C for 2 h, 4 h, 8 h and 24 h, encompassing conditions that replicate their undistorted ancient counterparts. The biochemical composition of archaeobotanical charred einkorn grains was also investigated by FT-IR and solid state ¹³C NMR in order to assess the changes in composition which occur during burial. Results of FT-IR and solid-state ¹³C NMR show that heating of modern einkorn grains resulted in Maillard reactions between cereal proteins and starch, forming high molecular weight melanoidins, which contain both alkyl and aromatic carbon. Loss of low molecular weight carbon and nitrogen-containing volatiles resulted in a slight but non-systematic increase in the δ¹³C values and a systematic increase of 0.8‰ in the δ¹⁵N values of the charred einkorn grains. Solid-state ¹³C NMR shows that the ancient charred einkorn grains consisted entirely of aromatic carbon and retained a similar proportion of nitrogen to their modern 24 h charred counterparts, despite a significantly lower concentration of amino acids. This indicates that the amino acid nitrogen in the ancient charred grains was retained in the stable melanoidins whose polymeric structure makes them resistant to subsequent degradation.     

The Preservation and Interpretation of δ34S Values in Charred Archaeobotanical Remains

The measurement of sulphur isotope (δ³⁴S) values in charred plant remains has the potential to inform understanding of the spatial configuration and ecology of crop production. We investigated the effects of charring, manuring, oxidation and anaerobic soil conditions on modern cereal grain/pulse seed δ³⁴S values, and assessed the effect of chemical pre‐treatment on charred modern and archaeobotanical grain/seed δ³⁴S values. We used these results to interpret δ³⁴S values in archaeobotanical material from Neolithic Çatalhöyük. Our results suggest that δ³⁴S values can be reliably preserved in charred grain/seeds but are subject to influence by anaerobic soil conditions, the effect depending on the timing of flooding in relation to S assimilation.     

Dietary changes and millet consumption in northern France at the end of Prehistory: Evidence from archaeobotanical and stable isotope data

Diachronic changes of dietary human habits between the Neolithic and the Bronze Age are mainly identified through archaeological artefacts and archaeozoological and archaeobotanical studies. This paper aims to demonstrate the importance of a multi-disciplinary approach for palaeodietary studies and to identify the food changes between Neolithic and Bronze Age human groups in northern France. These changes are probably linked to the introduction of new crops, such as millet, and the use of stable isotope analysis on bones and teeth proves to be an effective method for assessing the role of this specific cereal in the diet and the economy. Stable isotope analyses were performed on bone and tooth collagen and apatite from eight humans and five domestic animals from a Late Bronze Age site (LBA; Barbuise; 15th–13th c. BC; Aube). The studied corpus is compared with isotopic data from human and animal bones from a nearby Neolithic site (Gurgy; 5th mill. BC; Yonne) and regional Neolithic to Iron sites located in northern France. Moreover, Barbuise data are supplemented by information from an important archaeobotanical study carried out on 21 LBA and Early Iron Age sites in the region. Neolithic and LBA human collagen isotopic ratios (δ¹³C, δ¹⁵N) differ statistically, as do those of some animals. Carbon isotopic ratios of human apatite corroborate collagen results indicating the consumption of ¹³C enriched food by LBA humans and animals compared to Neolithic samples. The high number of occurrences of plant remains in the Bronze Age settlements near the site points to the consumption of C₄ plants, such as millet, and would account for these results.     

Finding millet in the Roman world

Examining the evidence for millet in the Roman empire, during the period, circa 753 bc–610 ad, presents a number of challenges: a handful of scant mentions in the ancient surviving agrarian texts, only a few fortuitous preserved archaeological finds and limited archaeobotanical and isotopic evidence. Ancient agrarian texts note millet’s ecological preferences and multiple uses. Recent archaeobotanical and isotopic evidence has shown that millet was being used throughout the Roman period. The compiled data suggests that millet consumption was a more complex issue than the ancient sources alone would lead one to believe. Using the recent archaeobotanical study of Insula VI.I from the city of Pompeii, as a case study, the status and role of millet in the Roman world is examined and placed within its economic, cultural and social background across time and space in the Roman world.     

Iron Age Diet at Sisak,Croatia: Archaeobotanical Evidence of Foxtail Millet (Setaria Italica [L.] P. Beauv.)

Recent excavations at Sisak, Croatia, unearthed an Early Iron Age pot filled with archaeobotanical remains within the floor of a structure dating to between the sixth and fourth centuries BC. Burnt in situ the archaeobotanical remains provide unique evidence for diet and agriculture in a region where archaeobotanical evidence is rare. The preliminary results from this analysis are outlined here, with a focus on the discovery of foxtail millet (Setaria italica [L.] P. Beauv.) and its contribution to the diet of the Early Iron Age population at Sisak.     

Finger millet: the contribution of vernacular names towards its prehistory

Finger millet, Eleusine coracana (Linn.) Gaertn. is usually considered to have been domesticated in tropical Africa. Nonetheless, it diffused across much of the Old World in prehistory, reaching Taiwan, the Himalayas, and Sumatra. The archaeobotanical record remains extremely patchy and the routes and dates of its arrival in many locations remain unknown. The paper makes use of comparative linguistics to begin the resolution of some of these issues. It reviews the archaeobotanical data which exists and then compiles tables of African and Asian names for finger millet. The paper identifies locally common linguistic roots, but there are no very widespread terms, suggesting there may a constant reborrowing of names with its near relative, goosegrass, Eleusine indica. A synthesis of the diffusion of finger millet is given at the end of the paper.     

Hatching seeds before they’re counted

Like other analytic aspects of archaeology, archaeobotany has been growing progressively more quantitative in the past few decades. This may be a sign of the proliferation of increasingly mature and sophisticated methodologies for analyzing botanical data, but associated with the sophistication of quantitative methods is their inherent opacity: the value and applicability of anthropological conclusions drawn from quantitative archaeobotanical data are not only limited by the amount of information that can be extracted from data by sophisticated statistical tools, but also by our ability to draw reasonable anthropological—as opposed to merely statistical—conclusions. Even the words “classification” and “significance” have different meanings in statistics and in anthropology. In this paper, I propose the use of graphical analysis for archaeobotanical data in addition to, or instead of, typical statistical tools like significance tests, variable reduction, and clustering. Applied to data from charred seed assemblages from the ancient Near East, the visual representation of quantitative data has the advantage of handling semiquantitative data better and being interpretable without reliance on the paradigm of a formal statistical test.     

The impact of manuring on nitrogen isotope ratios in cereals: archaeological implications for reconstruction of diet and crop management practices

Recent archaeological studies of human diet have used stable nitrogen isotope ratios (δ¹⁵N) from human bone collagen to infer the relative importance of terrestrial plant and animal foods. This approach is based on widely observed enrichment of δ¹⁵N up the food chain, plants having distinctly lower values than the herbivores that consume them. Studies of early farming diets in Britain, Denmark and Germany have tended to detect relatively high δ¹⁵N values (e.g. c. +9‰), interpreted as evidence of a diet largely based on animal products, though archaeobotanical evidence for crop cultivation (e.g. carbonised cereal grain and chaff) is widespread. This paper investigates the impact of manuring on δ¹⁵N values in modern cereals, and of charring on these cereal values. The results from two long-term experiments demonstrate that manuring significantly raises δ¹⁵N in cereal grain and chaff. Depending on manuring levels and frequency, it appears that human diets with a major component of such grain would conventionally be interpreted as indicating a largely animal-based diet or a mixed plant/animal diet. Moreover, preliminary analyses of experimentally charred grain and chaff from manured and unmanured conditions are promising for the extraction of reliable ancient δ¹⁵N values from archaeobotanical cereal remains. The wider implications of these results, and the need for further work, are discussed.     

Small preys and plant exploitation by late pleistocene hunter–gatherers. A case study from the Northeast of the Iberian Peninsula

The aim of this paper is to explain the subsistence strategies of late hunter–gatherers from the Northeast of the Iberian Peninsula on the basis of zooarchaeological and archaeobotanical records. The study is based on the Molí del Salt archaeological site which has yielded an Upper Palaeolithic and Mesolithic sequence. Each of the disciplines shows us a various type of assemblage to approach the same problem. Archaeobotanical materials, including charcoal and seeds provide data on the strategies related to firewood gathering and vegetal food supply, which was a basic subsistence resource for these groups. The archaeobotanical assemblage is mainly formed by conifers, but other species related to edible plants are also important. Bone assemblage, mainly formed by Oryctolagus cuniculus, show how hunting and meat processing is highly related. The environmental constraints as well as mobility are discussed in order to achieve an ampler knowledge on human activities.     

Towards a distinction between digested and undigested glume bases in the archaeobotanical record from Neolithic northern Greece: A preliminary experimental investigation

Abstract

This study investigates the possibility of distinguishing digested from undigested glume wheat chaff in the archaeobotanical record. To this end the contents of dung pellets collected from a goat fed on einkorn spikelet forks and glume bases are analysed and the derived einkorn chaff examined macroscopically with the aid of scanning electron microscopy. The modern dung pellets contained recognisable glume bases which, compared with undigested ones, demonstrated a ‘rugged’ surface. When these dung pellets were charred, glume bases were still preserved in them. The experimental pellets show that dung can contribute glume bases in archaeobotanical assemblages and that these glume bases may be distinguishable from those derived from glume wheat dehusking by-products used as fuel. These results need to be further explored on archaeobotanical materials. Moreover, further experimentation with different charring regimes, as well as the examination of more experimental specimens is needed.     

FROM BRONZE AGE HILLFORT TO CAPITAL CITY NEW RADIOCARBON DATES AND THE FIRST ARCHAEOBOTANICAL INVESTIGATION AT THE VILNIUS CASTLE HILL

The ‘Castle Hill’ represents the core territory of Vilnius, around which gravitated urban development, eventually culminating in the foundation of the capital of Lithuania. However, we know very little about the earliest occupation on Castle Hill - how it developed over time, and what the activities were of the people that inhabited the site. While the study of plant remains can provide a crucial insight into human staple foods, agricultural activities and the palaeoenvironment, previous attempts of archaeobotanical investigations of such an important cultural heritage site was cut short due to the outbreak of World War II. Here is presented the first archaeobotanical analyses from the territory of Castle Hill together with new radiocarbon dates stretching from the 8^th century BC until the 14^th century AD. The primary archaeobotanical analyses in combination with published datasets from adjacent regions around Castle Hill show that the diversification of crops and the introduction of various crop rotation practises during the 8-13^th centuries AD. Here, for the first time, attention is drawn to the agricultural strategies in medieval Vilnius that likely played a pivotal role in the formation and development of the city.     

Fruits and seeds from Roman cremations in Limagne (Massif Central) and the spatial variability of plant offerings in France

During Roman times plant products were frequently used as offerings in graves. The cremation ritual, dominant during the two first centuries AD in Gaul, allowed the preservation of some of these plant remains by carbonization. Up to now in Grande Limagne (Auvergne, Massif Central) only one cremation burial had given rise to archaeobotanical study. Five new sites are analysed in the Clermont Ferrand area. Vegetal offerings are largely dominated by cereals (Triticum aestivum/turgidum and Hordeum vulgare principally but also Panicum miliaceum and possibly a hulled wheat species) and pulses (Lens culinaris, Lupinus albus, Pisum sativum and Vicia faba). Grande Limagne results are compared to archaeobotanical data from other parts of France. Auvergne sites are close to those from central France and differ from Mediterranean and Rhône valley sites. This group is characterized by a greater part of Mediterranean or exotic fruits, newly introduced or developed by the Romans, and bread or pastry. This reflect the strongest Romanization of the Mediterranean–Rhône–Rhine axis. On the other hand cereal- and pulse-offerings dominating in central France could be more affected by Iron age traditions. This last hypothesis has to be confirmed by new studies on Iron age cremation burials.     

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.     

Persistence of the cultural landscape in Campania (Southern Italy) before the AD 472 Vesuvius eruption: archaeoenvironmental data

Cultural landscapes were prominent during the Early Roman period when agronomic knowledge allowed the spread of intensive land exploitation in most of the available land. The aim of this contribution is to explore whether for the Campania region (Southern Italy) archaeoenvironmental data would support continuity or change in the cultural landscape of Roman tradition in the 4th and 5th centuries. To do so, new data from two sites located on the northern slopes of the Vesuvius, both buried by the AD 472 eruption have been investigated. Charcoal analysis, ¹⁴C dating, and chemical analysis of organic residues were carried out in order to study the landscape and the food production at these sites. The results suggest the persistence of the Roman cultural landscape until the 4th and 5th centuries in this area. The landscape is in fact strongly marked both in agriculture and woodland exploitation and management, being characterized by managed chestnut forests as well as valuable cultivations of walnut, large vineyards, olive groves, and probably orchards and crops. The integrated approach with archaeobotanical and archaeometric analyses proves to be a powerful method for the study of the past landscapes, providing a good insight into the environment. Furthermore, this study provided the most ancient evidence of chestnut silviculture for wood.     

Paleoenvironment and plant cultivation on terraces at La Quemada,Zacatecas, Mexico: the pollen,phytolith and diatom evidence

This paper reports the results of pollen, phytolith and diatom analyses conducted on a series of soil samples collected from a large, possibly communal, system of terraces associated with La Quemada in the Malpaso Valley, Zacatecas, Mexico. These analyses rendered data related to both paleoenvironmental and plant cultivation in the area. Preliminary pollen analyses of soil sediments suggest Agave sp. and Opuntia spp. cultivation played an important role on the terraces. The phytolith analyses recovered abundant, well preserved grass phytoliths, including Zea mays. The composition of the grass community suggests that paleoenvironmental conditions in this area were warm and dry, similar to those of today. The presence of three fresh water diatom taxa and sponge spicules in several archaeological soil samples suggests the possibility that water was carried to the terraces for irrigation from the nearby Rio Malpaso on a regular basis.     

The influence of manuring on stable isotopes (δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N) in Celtic bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.): archaeobotanical and palaeodietary implications

This paper examines the impact of animal manure on δ¹⁵N and δ¹³C values in a legume, Celtic Black broad bean (Vicia faba). In a field experiment, V. faba was cultivated in plots treated with farmyard manure and pure sheep manure. The results indicate that highly intensive manuring can increase δ¹⁵N values in beans, stems, leaves and pods. In comparison, manuring had a relatively small impact on δ¹³C values. In terms of palaeodietary reconstructions, the high δ¹⁵N values in very intensively manured beans (+3?‰) are equivalent to the trophic-level effect. Based on the experimental results, it is suggested that high δ¹⁵N values in archaeobotanical remains of V. faba may be attributable to small-scale cultivation with intensive manuring.