Red deer bone and antler collagen are not isotopically equivalent in carbon and nitrogen.

RATIONALE: Bone and antler collagen δ(13) C and δ(15) N values are often assumed to be equivalent when measured in palaeodietary, palaeoclimate and palaeocological studies. Although compositionally similar, bone grows slowly and is remodelled whereas antler growth is rapid and remodelling does not occur. These different patterns of growth could result in isotopic difference within antler and between the two tissue types. Here we test whether red deer (Cervus elaphus) bone and antler δ(13) C and δ(15) N values are equivalent, and whether intra-antler isotopic values are uniform. METHODS: Bone and antler were isotopically analysed from six stags that lived in a temperate maritime climate on the Isle of Rum, Scotland. Multiple antlers from different years were sampled per individual, together with a single bone sample per individual. Up to 12 samples were taken along the length of each antler (total of 25 antlers, 259 samples) so that a chronological record of the isotopic composition during antler growth could be obtained. Collagen was extracted and its δ(13) C and δ(15) N values were measured by continuous-flow isotope ratio mass spectrometry. RESULTS: Intra-antler collagen isotope signatures vary, and show that not all antlers from an individual or a growth year are equivalent in carbon and nitrogen isotopic ratios. δ(15) N values typically increase with distance along antler length, but no overall trend is observed in δ(13) C values. An isotopic offset is visible between bone and antler, with bone δ(13) C and δ(15) N values being higher in most cases. CONCLUSIONS: Bone and antler collagen δ(13) C and δ(15) N values are not isotopically equivalent and are therefore not directly comparable in palaeodietary, palaeoclimate and palaeocological studies. Bone and antler collagen isotopic differences probably relate to differential metabolic processes during the formation of the two tissues. Intra- and inter-antler isotopic variations probably reflect the isotopic composition of an individual's diet rather than physiological parameters, and may have the potential to provide high-resolution individual-specific information in modern and ancient cervid populations

‘Trophic’ and ‘source’ amino acids in trophic estimation: a likely metabolic explanation

Amino acid nitrogen isotopic analysis is a relatively new method for estimating trophic position. It uses the isotopic difference between an individual’s ‘trophic’ and ‘source’ amino acids to determine its trophic position. So far, there is no accepted explanation for the mechanism by which the isotopic signals in ‘trophic’ and ‘source’ amino acids arise. Yet without a metabolic understanding, the utility of nitrogen isotopic analyses as a method for probing trophic relations, at either bulk tissue or amino acid level, is limited. I draw on isotopic tracer studies of protein metabolism, together with a consideration of amino acid metabolic pathways, to suggest that the ‘trophic’/ ‘source’ groupings have a fundamental metabolic origin, to do with the cycling of amino-nitrogen between amino acids. ‘Trophic’ amino acids are those whose amino-nitrogens are interchangeable, part of a metabolic amino-nitrogen pool, and ‘source’ amino acids are those whose amino-nitrogens are not interchangeable with the metabolic pool. Nitrogen isotopic values of ‘trophic’ amino acids will reflect an averaged isotopic signal of all such dietary amino acids, offset by the integrated effect of isotopic fractionation from nitrogen cycling, and modulated by metabolic and physiological effects. Isotopic values of ‘source’ amino acids will be more closely linked to those of equivalent dietary amino acids, but also modulated by metabolism and physiology. The complexity of nitrogen cycling suggests that a single identifiable value for ‘trophic discrimination factors’ is unlikely to exist. Greater consideration of physiology and metabolism should help in better understanding observed patterns in nitrogen isotopic values

Quantification and propagation of errors when converting vertebrate biomineral oxygen isotope data to temperature for palaeoclimate reconstruction

Oxygen isotope analysis of bioapatite in vertebrate remains (bones and teeth) is commonly used to address questions on palaeoclimate from the Eocene to the recent past. Researchers currently use a range of methods to calibrate their data, enabling the isotopic composition of precipitation and the air temperature to be estimated. In some situations the regression method used can significantly affect the resulting palaeoclimatic interpretations. Furthermore, to understand the uncertainties in the results, it is necessary to quantify the errors involved in calibration. Studies in which isotopic data are converted rarely address these points, and a better understanding of the calibration process is needed. This paper compares regression methods employed in recent publications to calibrate isotopic data for palaeoclimatic interpretation and determines that least-squares regression inverted to x=(y-b)/a is the most appropriate method to use for calibrating causal isotopic relationships. We also identify the main sources of error introduced at each conversion stage, and investigate ways to minimise this error. We demonstrate that larger sample sizes substantially reduce the uncertainties inherent within the calibration process: typical uncertainty in temperature inferred from a single sample is at least ±4°C, which multiple samples can reduce to ±1-2°C. Moreover, the gain even from one to four samples is greater than the gain from any further increases. We also show that when converting δ18Oprecipitation to temperature, use of annually averaged data can give significantly less uncertainty in inferred temperatures than use of monthly rainfall data. Equations and an online spreadsheet for the quantification of errors are provided for general use, and could be extended to contexts beyond the specific application of this paper.Palaeotemperature estimation from isotopic data can be highly informative for our understanding of past climates and their impact on humans and animals. However, for such estimates to be useful, there must be confidence in their accuracy, and this includes an assessment of calibration error. We give a series of recommendations for assessing uncertainty when making calibrations of δ18Obioapatite-δ18Oprecipitation-Temperature. Use of these guidelines will provide a more solid foundation for palaeoclimate inferences made from vertebrate isotopic data.We are grateful to the University of Cambridge (AJEP) and the Royal Society (RES) for financial support

Late Pleistocene/Early Holocene Migratory Behavior of Ungulates Using Isotopic Analysis of Tooth Enamel and Its Effects on Forager Mobility

Zooarchaeological and paleoecological investigations have traditionally been unable to reconstruct the ethology of herd animals, which likely had a significant influence on the mobility and subsistence strategies of prehistoric humans. In this paper, we reconstruct the migratory behavior of red deer (Cervus elaphus) and caprids at the Pleistocene-Holocene transition in the northeastern Adriatic region using stable oxygen isotope analysis of tooth enamel. The data show a significant change in δ18O values from the Pleistocene into the Holocene, as well as isotopic variation between taxa, the case study sites, and through time. We then discuss the implications of seasonal faunal availability as determining factors in human mobility patterns

Increased climate seasonality during the late glacial in the Gebel Akhdar, Libya

Oxygen isotope analysis (δ18O) of caprine and bovine tooth enamel carbonates from the Haua Fteah cave (Gebel Akhdar massif, northeast Libya) reveals significant differences in palaeoseasonality during the last c. 70 ka. Data indicate different phases of human occupation of the region occurred under notably different climatic conditions. During the last glacial period, prior to the Last Glacial Maximum, a gradual increase in climate aridity occurred. This was followed in the late glacial (c. 16.6–14.7 ka) by considerably more arid conditions and much greater climate seasonality, which was likely produced by changing winter precipitation amounts and a strengthening of arid summer air masses. The high seasonality in the late glacial coincides with a period when human activity at the Haua Fteah greatly intensified. Significant changes in subsistence strategies and the seasonal exploitation of food resources also occurred at this time. The results presented here suggest that changes in the seasonal climate may have affected the seasonal supply of floral and faunal resources available to local human populations at the time, which resulted in changing subsistence practices

Pleistocene and Holocene palaeoclimates in the Gebel Akhdar (Libya) estimated using herbivore tooth enamel oxygen isotope compositions

The palaeoclimate of the Gebel Akhdar massif, in Cyrenaica, northeast Libya, is investigated using the stable oxygen isotope ratio (δ18O) of herbivore tooth enamel from the archaeological faunal assemblages of the Haua Fteah and Hagfet ed Dabba caves. Samples accumulated through human activity at the sites, thus climatic interpretations are in direct chronological association with periods of human presence in the local landscape. Wild Ammotragus lervia (Barbary sheep) and Bos sp. (auroch), and domestic Ovis sp. and Capra sp. from the Levalloiso-Mousterian (≥73.3–43.5 ka) to the Neolithic (∼9.3–5.4 ka) cultural phases are analysed. Results indicate that the most arid environment represented by the samples occurred at ∼32 ka, when populations associated with Dabban lithic assemblages were present within the region. Climatic instability increased during oxygen isotope stage 2. Consistent with other palaeoenvironmental investigations in the Gebel Akhdar, there is no evidence for hyper-arid events during the last glacial and surface water, most probably in the form of local springs, was available throughout the time periods considered. Overall, results indicate that different cultural groups occupied the Gebel Akhdar landscape under different climatic conditions, but that climate variations appear to have been of lower magnitude than those that occurred at inland North African locations. These reconstructions provide further support to the theory that the Gebel Akhdar may have served as a refugium for human populations in North Africa during times of global climatic extremes

The Signs of Maize? A Reconsideration of What δ¹³C Values Say about Palaeodiet in the Andean Region

Palaeodietary isotope studies have long assumed C_4 signals in South American archaeological populations to be due to the consumption of maize (Zea mays), which in turn, underlie interpretations important social processes. We presents δ¹³C data from wild plants (n=89) from the south coast of Peru, which may have been significant in the diets of humans and animals in the past. A combination of these with previously published results from domesticates of the Andean region (n=144) brings the proportion of C_4 species likely to have contributed to the human dietary isotopic signal, whether directly or indirectly, to almost one third. This undermines the widespread assumption that maize is the only plant to contribute a C_4 signal to diets. By considering both direct and indirect routes whereby C_4 plants may have contributed to the human isotopic signal we show the need for a reassessment of how palaeodietary studies are interpreted in the Andes, and perhaps elsewhere in the Americas.LC would like to thank the AHRC, the Anthony Wilkins Fund and the Santander Universities Grant for Travel to Latin America for enabling this research. TCO would like to thank the Wellcome Trust.This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s10745-012-9509-0

Comment on “Ecological niche of Neanderthals from Spy Cave revealed by nitrogen isotopes of individual amino acids in collagen.”

We welcome Naito et al.'s recent efforts to gain greater information about the diet and ecological niche of Neanderthals, through compound-specific amino acid nitrogen isotopic analysis of bone collagen from Neanderthal remains from Spy Cave in Belgium as well as of specimens of contemporary animal species (Naito et al., 2016a). The application of a relatively novel technique (see: Styring et al., 2010, Chikaraishi et al., 2014, McMahon and McCarthy, 2016) is not without its problems, and we would like to provide a critical comment on the implications of uncertainties for the interpretation and application of this method, and on analytical aspects of this technique.Non

Ecological globalisation, serial depletion and the medieval trade of walrus rostra

The impacts of early ecological globalisation may have had profound economic and environmental consequences for human settlements and animal populations. Here, we review the extent of such historical impacts by investigating the medieval trade of walrus (Odobenus rosmarus rosmarus) ivory. We use an interdisciplinary approach including chaîne opératoire, ancient DNA (aDNA), stable isotope and zooarchaeological analysis of walrus rostra (skull sections) to identify their biological source and subsequent trade through Indigenous and urban networks. This approach complements and improves the spatial resolution of earlier aDNA observations, and we conclude that almost all medieval European finds of walrus rostra likely derived from Greenland. We further find that shifting urban nodes redistributed the traded ivory and that the latest medieval rostra finds were from smaller, often female, walruses of a distinctive DNA clade, which is especially prevalent in northern Greenland. Our results suggest that more and smaller animals were targeted at increasingly untenable distances, which reflects a classic pattern of resource depletion. We consider how the trade of walrus and elephant ivory intersected, and evaluate the extent to which emergent globalisation and the “resource curse” contributed to the abandonment of Norse Greenland

Living and Dying at the Portus Romae

This paper presents the first results of research into plant, animal, and human remains from Portus, the maritime port of Imperial Rome, in order to examine the diet and geographical origins of its inhabitants between the second and sixth century AD. Comparisons with evidence from the excavation and ceramic analysis show clear changes throughout the period, with shifts in diet and patterns of foods import that can be related to the commercial and political changes following the breakdown of Roman of the Mediterranean