Variation in collagen stable nitrogen values in black-tailed jackrabbits (Lepus californicus) in relation to small-scale differences in climate,soil, and topography

Longstanding observations about the relationship between increasing aridity and ¹⁵N enrichment in mammalian collagen values have led to an interest in their use as a paleoclimatic marker. Here we report on variability in collagen nitrogen values from five modern and two archaeological samples of black-tailed jackrabbits (Lepus californicus) from the eastern Great Basin of the United States (N = 178 individuals). Nitrogen δ¹⁵N values were highly variable within all samples. Modern samples showed significant differences despite similarities in average annual precipitation and temperature. Archaeological samples were indistinguishable from each other or from modern samples taken from the same area despite independent evidence for differences in precipitation for the two prehistoric periods considered. Differences between modern samples were most strongly associated with soil characteristics. We discuss these results in light of their relationship with topography and vegetation and highlight their implications for archaeological applications of stable nitrogen analyses in several contexts.     

Estimating weaning and early childhood diet from serial micro-samples of dentin collagen

Age of weaning is an important measure of parental investment, and in various human and non-human primate studies, has been correlated with a range of developmental factors such as stature, cognitive functions, obesity, ability to cope with stress, and rates of disease. Archaeological estimation of the weaning process is generally at the level of an entire burial population, creating some challenges in using such data to test anthropological theory. We describe a method that tracks the weaning process at the individual level, based on the measurement of stable nitrogen and carbon isotope ratios in serial sections of first molar dentin collagen. We apply this micro-sampling technique to a sample of individuals from CA-CCO-548, a well-studied and ancient site on the banks of Marsh Creek in Central California. Results show great variation between individuals in both the length of the weaning process, the age at which breastfeeding stopped, and the source of early complementary childhood foods.     

New Dietary Evidence on Medieval Rural Communities of the Basque Country (Spain) and Its Surroundings from Carbon and Nitrogen Stable Isotope Analyses: Social Insights,Diachronic Changes and Geographic Comparison

This paper presents the results of palaeodietary reconstruction based on stable carbon and nitrogen isotope analysis on bone collagen of five medieval rural populations from the Basque Country (northern Spain) spanning from 5^th to 15^th centuries ad . One hundred forty‐seven human and 47 domestic faunal samples were successfully analysed with the objective of defining agrarian productive strategies and food consumption patterns. The results grouped the five sites in two clusters: on one side Zaballa and Treviño, whose inhabitants followed diets exclusively based on C₃ plants with significant intake of animal protein, and on the other, the populations from Aistra and Zornoztegi, who combined C₃ and C₄ plants and consumed lower amounts of animal protein. The isotopic values from Dulantzi were intermediate to these two groups. No differences were detected when individual status markers, such as grave goods, were available. Conversely, some restrictions on the access to certain food resources based on sex were uncovered. A relevant change in δ¹³C values was identified around 10^th century, a consequence of a shift in the consumption patterns of C₃ and C₄ plants. Finally, these Basque sites were compared with those of the medieval Iberian case studies available in the literature. This comparison made evident the distinctive nature of the diet of the Basque medieval rural contexts. Copyright © 2017 John Wiley & Sons, Ltd.     

Anthropogenic saltpetre: dual (oxygen and nitrogen) isotopic constraints to the biogeochemical processes

Saltpetre constitutes one of the major ingredients of gunpowder, which was a driving force during the political changes in late medieval to early modern times in Japan. Two types of model saltpetre mineralization are studied. One represents efflorescent saltpetre formed as the byproduct of indigo dye manufacture, whereas the second is anthropogenic, derived from relict nitre‐beds. Here, oxygen and nitrogen isotopic analysis, as expressed by δ¹⁸O and δ¹⁵N notations, is applied. The calculated δ¹⁸O values for ambient water, responsible for the microbial‐mediated oxidation of ammonium into oxygen in nitrates, tended to have higher ranges than average local meteoric waters of the relevant regions. An overall trend could be seen, showing the apparent positive nitrogen isotopic fractionation during the microbial transformation from initial organic nitrogen into nitrate product. Dual isotopic analysis for industrial nitrates provides a useful tool for investigation of the provenance of historic gunpowder. Present anthropogenic saltpetre involves positive control over temperature–moisture regimes and oxygen fugacity during formation, the process being distinctive from those prevailed in British India and other European countries.     

Persistent deathplaces and mobile landmarks: The Holocene mortuary and isotopic record from Wadi Takarkori (SW Libya)

Recently, a new program of territorial study was launched in the area of Wadi Takarkori (Wadi Takarkori Project, hereafter WTP), located in south-western Libya at the border with Algeria in a strategic position between the Tassili and Acacus Mountains. The core of this program was the excavation of a rock shelter together with the systematic mapping and selected excavations of stone structures in the wadi area, mainly tumuli, a typical Saharan feature.     

Paleodietary analysis of the prehistoric population of the Canary Islands inferred from stable isotopes (carbon,nitrogen and hydrogen) in bone collagen

Nitrogen and carbon isotope compositions were measured in the bone collagen from a total of 86 prehispanic samples of the Canary Islands, and hydrogen in 70, all of them with enough amount of bone collagen, and adequate N and C content. These samples belong to prehistoric population of El Hierro (n = 27), Tenerife (n = 18), and Gran Canaria (n = 41). Isotope compositions were also obtained for prehistoric and modern food resources that were likely consumed by these people. Marked differences were observed among the three islands regarding the three isotopes analyzed: the δ¹⁵N values were highest among the population of Gran Canaria (10.8‰ ± 0.9‰), who also showed the highest δD values (7 ± 8‰). The population of El Hierro showed the highest δ¹³C values (−18.6‰ ± 0.7‰). These data suggest a high consumption of marine products by the population from El Hierro, and also an important consumption of terrestrial meat or marine, piscivore fish, by the population from Gran Canaria, together with domesticated C₃ plants (barley and/or wheat), fruits of Ficus carica and other wild species, and goat products. Additionally, marked differences were observed between men and women, which suggest that women consumed a more vegetal-based diet, a finding which is in agreement with the higher proportion of teeth with carious lesions among women.     

A meal on the hoof or wealth in the kraal? Stable isotopes at Kgaswe and Taukome in eastern Botswana

Iron Age sites associated with the Toutswe tradition in Eastern Botswana date between CE 700–1300 and share a variety of settlement patterns, economic features and material culture. The presence of domestic fauna, settlement structures and concentrations of vitrified dung provide archaeological evidence for herding economies. However, due to factors of preservation and past retrieval techniques, evidence for plant remains is still somewhat limited for the Toutswe sites in Botswana. Additionally, archaeological remains such as flora, fauna and material culture often provide only indirect evidence for their contributions to diet. This study provides new evidence for the diet of individuals from the Toutswe tradition. Given the large numbers of animal remains and residues at Toutswe sites, the expectation is that animal domesticates were also an integral part of the diet. Stable isotopic analysis of human remains indicates that even though domestic cattle and sheep occur in great abundance at Toutswe sites, their contribution to the diet may be minimal. The main source of protein for individuals at Kgaswe and Taukome comes from C4 plants such as sorghum and millet and to a lesser extent, animal products. The practice of maintaining large domestic herds for economic and social reasons rather than for primary subsistence in southern Africa today may have its roots in the Iron Age populations of the region. Copyright © 2010 John Wiley & Sons, Ltd.     

A re-assessment of Basketmaker II cave 7: massacre site or cemetery context

Our ongoing investigation of early maize farming in the American Southwest has entailed stable isotope analysis and accelerator radiocarbon dating of Basketmaker II remains from sites in the Four Corners region. Here we report radiocarbon dates on a large mortuary assemblage excavated by Richard Wetherill in 1893 from a burial cave in southeastern Utah. It has long been thought that all individuals interred in Cave 7 were massacred in a single violent attack given embedded projectiles and evidence for blunt force trauma. However, accelerator radiocarbon dates on purified bone collagen (n = 96) do not lend strong support to this argument, even among the subset of individuals with clear evidence for violent injuries. Moreover, nearly 80% of Cave 7 burials examined in the study show no evidence of perimortem trauma and no adult females or subadults under the age of 12 appear to have suffered violent deaths. Rather than an anomalous single-event massacre, the Cave 7 radiocarbon dataset suggests that raiding and intra-group, male/male violence was episodic among Basketmaker groups in southeastern Utah. Population densities were relatively high and individuals interred in Cave 7 and elsewhere in the region were heavily dependent on maize agriculture, a prehistoric economic strategy typically characterized by high amplitude fluctuations in productivity. Variability in the array of grave goods accompanying Cave 7 male burials and elsewhere suggests competitive social differentiation likely heightened during periods of resource shortfall leading to intra-group conflict, raiding and perhaps ritualized acts of violence.     

Molecular transport of methane, ethane and nitrogen and the influence of diffusion on the chemical and isotopic composition of natural gas accumulations

Laboratory experiments have been performed to determine diffusion coefficients of natural gas components (methane, ethane and nitrogen) and isotope fractionation effects under simulated in situ pressure (up to 45 MPa effective stress) and temperature conditions (50–200°C) in water‐saturated pelitic and coarse‐grained rocks. Effective diffusion coefficients of molecular nitrogen (0.39 × 10^?11 to 21.6 × 10^?11 m² sec^?1 at 90°C) are higher than those for methane (0.18 × 10^?11 to 18.2 × 10^?11 m² sec^?1 at 90°C). Diffusive flux rates expressed in mass units are generally higher for N₂ than for CH₄. Both methane and (to a lesser extent) nitrogen diffusion coefficients decrease with increasing total organic carbon (TOC) content of the rock samples because of sorption processes on the organic matter. This effect decreases with increasing temperature. Effective diffusion coefficients increase upon a temperature increase from 50 to 200°C by a factor of four. Effective diffusion coefficients and steady‐state diffusive flux decrease with effective stress. Stationary diffusive fluxes drop by 50–70% for methane and 45–62% for nitrogen while effective diffusion coefficients are reduced by 38% (CH₄) and 32–48% (N₂), respectively. Isotope fractionation coefficients of diffusive transport are higher for methane (?1.56 and ?2.77‰) than for ethane (?0.84 and ?1.62‰). Application of the experimental results to geological systems show that diffusive transport has only a low transport efficiency. Significant depletion of natural gas reservoirs by molecular diffusion is only expected in cases of very poor caprock qualities (in terms of thickness and/or porosity) and over extended periods of geological time. Under these circumstances, the chemical and isotopic composition of a gas reservoir will change and maturity estimates based on these parameters may be deceptive. To account for these potential effects, nomograms have been developed to estimate diffusive losses and apply maturity corrections.     

Isotopic evidence for Middle Horizon to 16th century camelid herding in the Osmore Valley,Peru

Archaeological and zooarchaeological data indicate that camelid pastoralism was a subsistence and economic mainstay of Middle Horizon and more recent cultures in the Osmore region of southern Peru. However, it is not known whether camelids were primarily herded in highland puna pastures or near lower elevation sites in the middle valley or along the coast. This research examines the elevation of archaeological camelid herding in the Osmore Valley using stable isotope analysis. Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios were measured on 28 archaeological camelid bone samples from the Middle Horizon sites of Cerro Baúl and Cerro Mejía, the Late Intermediate site of Yaral and the late pre‐Hispanic to Colonial period site of Torata Alta. Twenty‐three archaeological camelids have δ¹³C and δ¹⁵N values similar to five modern camelids maintained in highland puna pastures. In contrast, three camelids from the high status Wari site of Cerro Baúl, and two from Yaral have unexpectedly high δ¹³C and/or δ¹⁵N values outside the expected range for camelids pastured in highland puna habitats. The results may be explained by differences in foddering practices, altitudinal herding range or climatic conditions. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) were also assessed to infer pasture elevation using the camelid remains from Cerro Baúl (n = 11). One individual in this sub‐sample exhibits a non‐local ⁸⁷Sr/⁸⁶Sr value indicative of an origin in the highland puna region east or south of Lake Titicaca. It was not possible to further distinguish between camelids herded in lower to middle elevation habitats outside the Lake Titicaca basin using ⁸⁷Sr/⁸⁶Sr values. This study suggests that multiple isotope proxies may be used to identify animals primarily pastured in lowland coastal versus highland puna (> 4000 masl (meters above sea level)) habitats, but are less useful at distinguishing between animals pastured in lower to middle elevation settings. Copyright © 2010 John Wiley & Sons, Ltd.