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.     

Human and animal diet at Conchopata, Peru: stable isotope evidence for maize agriculture and animal management practices during the Middle Horizon

This paper reports δ¹³C and δ¹⁵N values for human and animal skeletal remains from the Middle Horizon (AD 550–1000) site of Conchopata in the Peruvian highlands. The data indicate that maize was the dietary staple for both humans and the majority of animals at this urban site. Camelids at the site segregated into two groups according to δ¹³C values, reflecting two distinct animal management strategies. Human infants were found to have elevated δ¹⁵N values, reflecting the trophic level effect of breastfeeding. No sex based differences in diet were observed.     

Mummies, maize, and manure: multi-tissue stable isotope analysis of late prehistoric human remains from the Ayacucho Valley, Perú

This paper reports the δ¹³C and δ¹⁵N values of bone collagen, muscle and skin from several late prehistoric–early colonial (AD 1490–1640) mummies from Perú's Ayacucho Valley. The mean of the δ¹³C and δ¹⁵N values of bone collagen are −11.5 ± 1.4 and 11.1 ± 0.7‰, respectively. The mean of the δ¹³C values for Vinchos skin is −11.8 ± 1.2‰ and the mean of δ¹⁵N values is 13.2 ± 0.5‰. The samples of muscle tissue have a δ¹³C mean of −11.9 ± 0.9‰ and a δ¹⁵N mean of 12.7 ± 0.3‰. The data from bone collagen indicate maize was the basis of the region's subsistence economy. A significant correlation between δ¹³C and δ¹⁵N values of bone collagen (R² = 0.75) is consistent with the preferential fertilization of maize with composted manure. Both skin and muscle samples are consistently enriched in δ¹⁵N relative to paired samples of bone (2.1 ± 0.5 and 1.6 ± 0.7‰, respectively), possibly as a result of short term physiological stress or differential decomposition.     

Sensitivity of bulk sedimentary stable carbon isotopes to prehistoric forest clearance and maize agriculture

The stable carbon isotope compositions (δ¹³C) of tropical lake sediments and soils have been used to reconstruct the occurrence of prehistoric maize cultivation and its relative importance through time. This study assesses some of the possible variables affecting the response of lake sediment bulk organic carbon isotope (δ¹³C_TOC) values to variations in the scale of prehistoric maize cultivation and the potential of this proxy to yield quantitative estimates of the scale of prehistoric maize agriculture in small tropical watersheds. High resolution analyses of δ¹³C_TOC values, maize pollen concentrations, and mineral influx were conducted on sediments deposited during a ∼220 year period of prehistoric maize agriculture in the watershed of Laguna Castilla, a small lake in the mid-elevations of the Cordillera Central, Dominican Republic. Close correspondence between δ¹³C_TOC values and maize pollen concentrations in the Laguna Castilla sediment record indicates a close relationship between the isotopic values and the scale of prehistoric maize cultivation. Correlations between the δ¹³C_TOC signature and mineral influx indicate that the isotope record is also sensitive to variations in allochthonous carbon delivery. This study establishes that sedimentary δ¹³C_TOC values can provide a highly sensitive proxy of the spatial scale of prehistoric maize agriculture in small tropical watersheds, but emphasizes the need for a better understanding of sediment dynamics and carbon cycling in anthropogenically modified landscapes before this proxy can be widely employed in diverse archaeological settings.     

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.     

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.     

Determining Olmec maize use through bulk stable carbon isotope analysis

Bulk stable carbon isotope analysis on absorbed organic residues in ceramics can be an effective method for discerning patterns of maize use when the ceramics come from relatively uniform archaeological contexts. The bulk stable carbon isotope method is faster and less costly than the more commonly used compound-specific stable carbon isotope analysis. Moreover, the bulk stable carbon isotope method can determine the presence of C4 plant carbon in samples in which organic compounds have degraded. Bulk stable carbon isotope analysis was used to discern patterns of maize (Zea mays mays) use among a sample of 24 ceramic sherds from an Early Franco Period feasting deposit (ca. cal 650 B.C.) at the Olmec site of San Andrés, La Venta, Tabasco, Mexico. A comparison of the δ 13C results of different categories of ceramics showed that proportionally more maize was used in luxury beverage service wares than in utilitarian vessels, suggesting that maize-based beverages were prominent in this probable elite feasting episode.     

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.     

Alkaline cooking and stable isotope tissue-diet spacing in swine: archaeological implications

In this study we examine the effects of alkaline cooking on carbon and oxygen stable isotopic ratios of mineralized tissues from nine pigs raised on monotonous mixed C3/C4 vegetarian diets. Two sources of collagen (humerus and mandible) and two sources of apatite (humerus and enamel) were analyzed. Within each diet group, humerus and mandible collagens were found to record equivalent δ¹³C and δ¹⁸O ratios; however, enamel apatite was found to be enriched over bone apatite by 2.3‰ in carbon and 1.7‰ in oxygen. Alkaline cooking was found to slightly, but significantly increase the Δ¹³C_{collagen-diet} and Δ¹⁸O_{collagen-diet} of bone collagen. A similar trend towards enrichment was observed in bone and enamel Δ¹³C_apatite-diet and Δ¹⁸O _apatite-diet, but the differences were not significant. Observed isotopic shifts were consistent with increased nutrient utilization of the alkaline-cooked maize as compared to raw maize. In addition, a reexamination of the relationship between diet and tissue carbon isotopic values suggests that species and alimentary type should be considered when interpreting ancient diets.     

Variations in the C/C ratios of modern wheat grain, and implications for interpreting data from Bronze Age Assiros Toumba, Greece

Variations in the ¹³C/¹²C ratios of wheat grain at different spatial and temporal scales are examined by analysis of modern samples, including harvests of einkorn and durum wheat from Greece, and serve as a guide to interpreting data for Bronze Age grains from Assiros Toumba. The normal distribution and low variability of δ¹³C values of einkorn from 24 containers in the Assiros storerooms are consistent with pooling of local harvests, but less likely to represent the harvest of several years or include grain imported from further afield. Correlation between emmer and spelt δ¹³C values provides strong support for other evidence that these were grown together as a maslin crop. ¹³C discrimination (Δ) for the Bronze Age samples is estimated to be 2.5‰ larger than at present, and would be consistent with an intensive, horticultural regime of cereal cultivation, possibly involving some watering.     

Dietary patterns and social structures in medieval Sigtuna, Sweden, as reflected in stable isotope values in human skeletal remains

Stable isotopes (δ¹³C, δ¹⁵N) have been studied in human burials from the medieval town Sigtuna in Sweden. Dietary patterns of 80 adult individuals were analyzed on three cemeteries representing the phases of establishment, prosperity and decline of the town. All analyzed individuals were radiocarbon dated. One of the cemeteries, Church 1, represents a population of higher social status than those at the other two cemeteries.The δ¹³C values are homogenous and showed that the protein intake was mainly of terrestrial origin in the whole population. δ¹⁵N values varies more and they may indicate a higher input of vegetables in the diet at one of the cemeteries, the Nunnan block.Already in the initial phases of Sigtuna a social hierarchy had been established which is reflected in dietary patterns. Apparently more animal protein was consumed among the high status population of the town. Furthermore, differences in dietary patterns between the sexes were noted. In all phases the females show more clustered values indicating a more homogeneous diet than that of the males.     

Patterns of Resource Use and Isotopic Niche Overlap Among Guanaco (Lama guanicoe), Pampas Deer (Ozotoceros bezoarticus) and Marsh Deer (Blastocerus dichotomus) in the Pampas. Ecological,Paleoenvironmental and Archaeological Implications

ABSTRACT

In this paper, we analyze the isotopic niche and resource use of the guanaco (Lama guanicoe), pampas deer (Ozotoceros bezoarticus) and marsh deer (Blastocerus dichotomus) on the temperate plain of the northern Pampa region in the southeast of South America. The measured stable isotope compositions in bone tissue are δ¹³C, δ¹⁵N and δ¹⁸O. All the analyzed samples were recovered from different archaeological sites from the late Holocene. According to the results, the guanaco was strictly confined to the Pampa plain environment, developing a broad niche based on C₃ plants and a variable contribution of C₄ grasses within a grazing trend. The pampas deer preferentially used the Pampa plain, but also the prairies on the borders of the wetland, showing eurioic characteristics and a narrower niche based on C₃ plants. In turn, the marsh deer was strictly confined to wetland environments, developing a C₃ diet–base, within a narrow isotopic niche and stenoic characteristics. The three mammals showed a wide range of intraspecific variability, which was a key factor in their adaptability to spatial and temporal changes in the vegetation coverage. In fact, the temporal trends of their isotopic values were concurrent with the major climatic variations of the Holocene. Differences in the correlations between the values of both carbon sources in both deer species compared with the guanaco suggest a distinct chemical composition of their diet and/or differences in the allocation of nutrients. The isotopic values of nitrogen and spacing of the carbon sources in guanaco (pseudoruminant) and both deer species (ruminants) show no significant differences between them, thus establishing the values for local large herbivores. Significant correlations between δ¹³C and δ¹⁵N were found in the guanaco and marsh deer. The regional and extra–regional variability in the guanaco's δ¹³C_collagen and δ¹⁵N probably reflect the clinal variations in the vegetation coverage and the amount of rainfall. The collagen isotope values in the guanaco throughout the entire Holocene show that the humid Pampa would have shifted between being a more recurrent mesic and temperate plain with minor phases of dry–mesic conditions like during the Little Ice Age, and a humid and warm one at the peaks of the Holocene Thermal Maximum and the Medieval Climatic Anomaly. The guanaco and the pampas deer adapted to all the climatic changes that happened on the humid Pampa until the biological invasions of large European mammals changed the herbivores’ guild composition of this vast plain, pushing them into peripheral habitats due to competition. The within–species variability in isotopic signals through time and space make it necessary to carry out adequate sampling before reconstructing the diets of local past populations.     

Fisherfolk and farmers: Carbon and nitrogen isotope evidence from Middle Horizon Ancón,Peru

This study investigates human dietary patterns and economic trends at the coastal site of Ancón, Peru during the Andean Middle Horizon (550AD –1000AD ) using stable isotopic data from 32 individuals buried at the site. δ¹³C and δ¹⁵N results from human bone collagen and δ¹³C from human tooth enamel and bone carbonate indicate that inhabitants consumed a mixed diet composed primarily of marine protein and C₄ resources, with only marginal reliance on C₃ foods. Over time, Ancóneros appear to have relied more heavily on C₄ resources, particularly maize, despite the fact that the crop could not have been grown locally. These results are notable given that C₃ rather than C₄ or marine foods dominate the site's archaeological record. These data suggest that Ancón's inhabitants either had access to more fertile land up‐valley where maize could be cultivated successfully or that they engaged in trade relationships with their valley neighbours. A third possibility is that increased maize consumption at Ancón during the Middle Horizon resulted from Wari imperial influence and interregional exchange. Comparisons of δ¹³C values in enamel and bone carbonate from Ancón individuals indicate that δ¹³C_{carb_enamel} values are significantly more positive than δ¹³C_{carb_bone} values. This suggests that the diets of young children were systematically enriched in ¹³C compared to that of adults, perhaps as a result of nursing activity and/or differential dietary practices among various age groups at the site. Copyright © 2009 John Wiley & Sons, Ltd.     

The Seaweed FlyThoracochaeta zosterae(Hal.) (Diptera: Sphaerocidae) in Inland Archaeological Contexts: δC and δN Solves the Puzzle

The presence of the flyThoracochaeta zosteraein cesspits had led to the unlikely interpretation that seaweed had been present in Mediaeval cesspitis. Archaeological and modern pupae fromT. zosteraewere sampled along with their probable larval diets (extracted plant material from cesspit and seaweed, respectively). The spacing between pupae and food for δ¹³C and δ¹⁵N was similar for both modern and archaeological samples. Modern pupae had isotopic ratios typical for marine invertebrates for δ¹³C. Archaeological puparia had isotopic values typical for terrestrial grazers (i.e., non-marine), indicating that there was no marine inclusion in the cesspits.     

Shell-gathering from mangroves and the seasonality of the Southeast Asian Monsoon using high-resolution stable isotopic analysis of the tropical estuarine bivalve (Geloina erosa) from the Great Cave of Niah, Sarawak: methods and reconnaissance of molluscs of early Holocene and modern times

This paper describes a reconnaissance, high-resolution, study of stable isotopes (δ¹⁸O and δ¹³C) from modern shells of the estuarine bivalve Geloina erosa, and those dated to the early Holocene that were harvested by people from mangroves near the Great Cave of Niah on the north coast of Borneo. This reconnaissance study provides high-resolution palaeoclimatic-palaeohydrological information concerning early human activity in the region and the past character of the Southeast Asian Monsoon. Laser ablation continuous flow isotope ratio mass spectrometry (LA-CF-IRMS) on modern shells of Geloina erosa revealed ‘saw-tooth’ stable isotopic profiles that bear a close resemblance to peaks and troughs of trends in recent local rainfall, including the 1998 El Niño drought, highlighting the potential of Geloina erosa for reconstructing seasonality of the Southeast Asian Palaeomonsoon. LA-CF-IRMS analysis of prehistoric shells of Geloina erosa held in the Harrisson Archives of the Sarawak Museum revealed cyclical shifts in δ¹⁸O with similar amplitudes of variation as found in modern shells of Geloina erosa. As at the present day, this probably reflects the changing seasonality of the monsoon rains with shifts to negative δ¹⁸O values during periods of high runoff. Lighter mean δ¹⁸O values of the prehistoric shells, however, may indicate a greater annual surplus of rainfall and possibly consistent with the early Holocene strengthening of the summer monsoon at that time. The similarity of the last growth increment δ¹⁸O of the prehistoric shells to their mean δ¹⁸O profile values suggests that gathering took place during times of moderate runoff.     

Coast–inland mobility and diet in the Danish Mesolithic and Neolithic: evidence from stable isotope values of humans and dogs

Here we present the stable isotope ratios of carbon and nitrogen measured in bone collagen extracted from humans, dogs, herbivores and fish from Mesolithic and Neolithic coastal and inland sites in Denmark. Bones of freshwater fish from several Early Mesolithic lake-side sites have δ¹³C values surprisingly similar to those seen in marine fish. We propose a model, based on δ¹³C and δ¹⁵N, for the correction for both marine and hard water reservoir effect in radiocarbon dates. A strong reliance on aquatic protein is demonstrated for the Mesolithic inhabitants of the region from the middle of the Early Mesolithic onwards. A significant part of the protein in the diets of the dogs and humans from the Middle and Late Mesolithic was of marine origin, even at inland sites. This observation points to a high degree of (seasonal) coast-inland mobility. The isotopic evidence indicates that during the Neolithic small quantities of aquatic foods were still common sources of dietary protein.     

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.     

Investigating foetal and perinatal mortality in prehistoric skeletal samples: a case study from a 3000-year-old Pacific Island cemetery site

The Teouma skeletal sample from Vanuatu represents one of the few truly colonising populations in the Pacific Islands. Therefore, investigating the factors that may have affected foetal/infant mortality in this population is potentially important for understanding the success of settlement in this region of the world. We investigate whether stable isotope analyses of carbon and nitrogen in conjunction with skeletal ageing techniques, can aid in identifying whether the subadults from Teouma died before or after birth in an attempt to understand the potential threats to foetal and infant survival. Multiple skeletal ageing methods using diaphyseal lengths were used to age the young subadults (n = 7). Using regression-based skeletal ageing methods, four of the individuals were aged at around full-term gestation (37–42 weeks gestation), while the remaining three individuals died preterm. The isotope analyses did not assist in identifying the individuals that survived post-birth because none of the subadults displayed the 2–3‰ trophic increase in δ¹⁵N values expected for a breastfed infant, probably as a result of their young age. However, all of the foetal/perinatal individuals exhibited higher δ¹⁵N values in their bone collagen compared with the adult females of the sample, with two of the individuals demonstrating unusually high δ¹⁵N values. The δ¹³C values of the foetuses/perinates did not exhibit the same variation. We explore a number of possible explanations for this elevation of perinatal/foetal δ¹⁵N values and tentatively suggest that this is a result of in utero stress as a consequence of chronic maternal ill-health. The osteological and palaeodemographic evidence supports the assertion that females, foetuses and perinates were susceptible to environmental stress within this colonising population, resulting in early death of the perinatal individuals in addition to early terminations of pregnancy or premature birth possibly caused by infectious and/or metabolic diseases.     

Stable carbon isotope analysis of human tooth enamel from the Bronze Age cemetery of Ya'amoun in Northern Jordan

Seventy-five teeth from the Bronze Age cemetery of Ya'amoun were sampled for carbon isotope analysis. The sampled teeth represented the transitional period of the Middle/Late Bronze Age. The results showed that the components of the diet that are reflected in the carbon isotope data remained the same during this period with an average δ¹³C of about −11.87‰. This value reflects more C₃ plant consumption.     

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.