Strontium isotope tracing of prehistoric human mobility in France

Human mobility in recent history is well documented and often related to drastic external changes, including war, famine, and the discovery and exploration of new geographic regions and resources. Reconstruction of mobility patterns in prehistory is thus a crucial part of understanding the forces that drove our ancestors, but it is complicated by the fact that the archaeological evidence becomes scarce as we go back in time. The application of stable isotopes in archaeological research has revolutionised palaeomobility studies by providing independent data, which can be used to evaluate models of migration, trade, and cultural change. This research project explores the use of strontium isotope ratios (87Sr/86Sr) to trace prehistoric human mobility patterns. Strontium isotope ratios vary across the landscape based on the age and composition of the underlying geology. Through diet humans incorporate strontium into their skeletal tissues such as bones and teeth. Teeth form during childhood and are resistant to weathering and geochemical alteration, often preserving the original isotope values. By comparing the strontium isotope ratios in teeth to the variations of strontium isotopes in the landscape it becomes possible to investigate mobility across geologically different areas between childhood and death. This study establishes the Isotopic Reconstruction of Human Migration (IRHUM) reference database and provides the first dataset of 87Sr/86Sr isotope ratios of plant and soil samples, covering all major geologic units of France. This provides a new powerful tool for the archaeological science community as it allows the mapping of the variations of bioavailable 87Sr/86Sr isotope across the landscape. Utilizing this dataset, a bioavailable 87Sr/86Sr isotope map for archaeological provenance studies in France is created. For the application of this method to human fossil teeth new analytical methods to detect diagenetic overprint were tested. These now allow for rapid scanning to investigate the suitability of samples, minimising the damage to fossil remains. Least destructive analytical techniques for strontium isotope analysis, such as micro drilling thermal ionisation mass spectrometry and in situ laser-ablation MC-ICPMS, were further developed and applied to a range of materials of known composition, including shark and dugong teeth, modern and archaeological fauna samples, and fossil and modern human teeth. Finally, strontium isotope tracing was applied to three key archaeological sites in France, including the Neanderthal sites of Moula-Guercy, and the Neolithic sites of Le Tumulus des Sables and La Grotte des Perrats. Strontium isotope tracing proved to be a valuable technique and in combination with additional strings of evidence from archaeological material and other isotopic tracers, such as oxygen, improved our understanding of prehistoric human mobility at these sites. By covering different geographic locations and different time periods this study tests geochemical fingerprinting and offers new insights into these renowned archaeological sites

Las Lunas, Yuncler (Toledo). Un depósito de materiales metálicos del Bronce Final en la Submeseta Sur de la Península Ibérica

Se exponen los resultados del primer estudio realizado sobre un nuevo conjunto de materiales metálicos del Bronce Final recuperado a finales de 2008 en las excavaciones arqueológicas del yacimiento de Las Lunas (Yuncler, Toledo, España). La localización geográfica del hallazgo, lejos de las principales zonas de dispersión conocidas para este tipo de conjuntos, la singularidad de los objetos que integra, y las relaciones atlánticas y mediterráneas que evidencian sus materiales, lo convierten en un ejemplo destacado para el estudio de este período en el centro de la Península Ibérica.Peer reviewe

A needle in a haystack: Strontium isotopes (87Sr/86Sr) in otoliths identify origin of Largemouth Bass from a large Southwest reservoir

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Laser ablation strontium isotopes and spatial assignment show seasonal mobility in red deer (Cervus elaphus) at Lazaret Cave, France (MIS 6)

Zooarchaeological analysis is a useful means of exploring faunal palaeoecology, paleoclimate and past human behaviours. The Middle Pleistocene archaeological site Lazaret Cave, located in modern-day Nice, France, features a vast assemblage of faunal remains pertinent to the understanding of early Neanderthal subsistence behaviours as well as red deer (Cervus elaphus) ecology during MIS 6. This pilot study examines materials from archaeological layer UA25, a short-term occupation layer at Lazaret dating to ~150,000 years ka, which has revealed 28 early Neanderthal remains as well as thousands of faunal bones, of which red deer and ibex (Capra ibex) are most abundant. Molars from three red deer mandibles and a single ibex were analysed for strontium (87Sr/86Sr) isotopic analysis using laser ablation mass spectrometry to determine animal movements during tooth formation, combined with intra-tooth oxygen (δ18O) isotope analysis to determine seasonality. The isotope data was modelled within a local 87Sr/86Sr isoscape and computational spatial assignment was undertaken to reconstruct potential summer and winter ranges of red deer. Results from this pilot study show seasonal mobility within 20 km of Lazaret, identifying two possible summer and winter ranges for the red deer excavated from UA25. Both possible summer ranges are located at higher elevations further from Lazaret while winter ranges have been assigned to lower elevations closer to the coastline and closer to Lazaret. The ibex shows no 87Sr/86Sr variation throughout the first, second and third molar and the spatial assignment indicates it lived proximal to the site during the period of tooth formation. In addition to providing the first evidence of red deer spatial ecology in southern France during MIS 6, we also infer from the faunal isotope data that hominins at Lazaret Cave were likely hunting red deer in autumn and winter when they were closer to the cave site, while hunting in summer would have required up to 20 km of travel

Laser ablation strontium isotopes and spatial assignment show seasonal mobility in red deer (Cervus elaphus) at Lazaret Cave, France (MIS 6)

Funding statement This research is part of the collective research project named “Paleoecology of the Lazaret cave: human-environment interactions on the coast of the meridional Alps during the late Middle Pleistocene (MIS6)”, granted by the DRAC PACA (French Ministry of Culture). SB thanks QUADRAT DTP NERC (NE/S007377/1) studentship for stipend support. KB and MLC thank the Leverhulme Trust (RPG-2017-410 and PLP-2019-284) for support during the production of this paper.Peer reviewedPublisher PD

Sampling Plants and Malacofauna in 87Sr/86Sr Bioavailability Studies : implications for isoscape mapping and reconstructing of past mobility patterns

Acknowledgments: We thank Annabell Reiner and Sven Steinbrenner (MPI-EVA) for technical and practical support with preparation and analysis of samples. We thank the La Ferrassie Team for support during field sampling and project development, especially Harold Dibble, Shannon McPherron (MPI-EVA), Teresa Steele (UC Davies), Vera Aldeias (MPI-EVA, University of Algarve), Paul Goldberg (University of Wollongong, University Tübingen), Dennis Sandgathe (Simon Fraser University, University of Pennsylvania), Alain Turq (Musée national de Préhistoire, CNRS), and Jean-Jacques Hublin (MPI-EVA), as well as Mike Richards (SFU). Special thanks to Daphne Katranides and Aaron Katranides. We also thank the editor (TP) and two reviewers whose constructive comments greatly improved this manuscript. Funding: This research was funded by the Max Planck Society and a Leverhulme Trust grant to KB (RPG-2017-410), with additional support from Australian Research Council Discovery grants DP0664144 and DP110101417 to RG. KJ thanks the ERC ARCHEIS 803676, and IM thanks Australian Research Council Discovery Early Career Award (DE160100703), for salary support during production of this manuscript.Peer reviewedPublisher PD

Mapping of bioavailable strontium isotope ratios in France for archaeological provenance studies

Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) of archaeological samples (teeth and bones) can be used to track mobility and migration across geologically distinct landscapes. However, traditional interpolation algorithms and classification approaches used to generate Sr isoscapes are often limited in predicting multiscale ⁸⁷Sr/⁸⁶Sr patterning. Here we investigate the suitability of plant samples and soil leachates from the IRHUM database (www.irhumdatabase.com) to create a bioavailable ⁸⁷Sr/⁸⁶Sr map using a novel geostatistical framework. First, we generated an ⁸⁷Sr/⁸⁶Sr map by classifying ⁸⁷Sr/⁸⁶Sr values into five geologically-representative isotope groups using cluster analysis. The isotope groups were then used as a covariate in kriging to integrate prior geological knowledge of Sr cycling with the information contained in the bioavailable dataset and enhance ⁸⁷Sr/⁸⁶Sr predictions. Our approach couples the strengths of classification and geostatistical methods to generate more accurate ⁸⁷Sr/⁸⁶Sr predictions (Root Mean Squared Error = 0.0029) with an estimate of spatial uncertainty based on lithology and sample density. This bioavailable Sr isoscape is applicable for provenance studies in France, and the method is transferable to other areas with high sampling density. While our method is a step forward in generating accurate ⁸⁷Sr/⁸⁶Sr isoscapes, the remaining uncertainty also demonstrates that fine-modelling of ⁸⁷Sr/⁸⁶Sr variability is challenging and requires more than geological maps for accurately predicting ⁸⁷Sr/⁸⁶Sr variations across the landscape. Future efforts should focus on increasing sampling density and developing predictive models to further quantify and predict the processes that lead to ⁸⁷Sr/⁸⁶Sr variability.Funding was provided by ARC DP110101415 (Grün, Spriggs, Armstrong, Maureille and Falguères) Understanding the migrations of prehistoric populations through direct dating and isotopic tracking of their mobility patterns. Part of this research was supported by the Australian French Association for Science & Technology through the ACT Science Fellowship program (2013) to M. Willme

Fishery collapse, recovery, and the cryptic decline of wild salmon on a major California river

Fall-run Chinook salmon (Oncorhynchus tshawytscha) from the Sacramento–San Joaquin River system form the backbone of California’s salmon fishery and are heavily subsidized through hatchery production. Identifying temporal trends in the relative contribution of hatchery- versus wild-spawned salmon is vital for assessing the status and resiliency of wild salmon populations. Here, we reconstructed the proportion of hatchery fish on natural spawning grounds in the Feather River, a major tributary to the Sacramento River, using strontium isotope (87Sr/86Sr) ratios of otoliths collected during carcass surveys from 2002 to 2010. Our results show that prior to the 2007–2008 salmon stock collapse, 55%–67% of in-river spawners were of hatchery origin; however, hatchery contributions increased drastically (89%) in 2010 following the collapse. Data from a recent hatchery marking program corroborate our results, showing that hatchery fish continued to dominate (∼90%) in 2011–2012. Though the rebound in abundance of salmon in the Feather River suggests recovery of the stock postcollapse, our otolith chemistry data document a persistent decline of wild spawners, likely leading to the erosion of locally adapted Feather River salmon populations

Bioavailable soil and rock strontium isotope data from Israel

Strontium isotope ratios (87Sr / 86Sr) of biogenic material such as bones and teeth reflect the local sources of strontium ingested as food and drink during their formation. This has led to the use of strontium isotope ratios as a geochemical tracer in a wide range of fields including archaeology, ecology, food studies and forensic sciences. In order to utilise strontium as a geochemical tracer, baseline data of bioavailable 87Sr / 86Sr in the region of interest are required, and a growing number of studies have developed reference maps for this purpose in various geographic regions, and over varying scales. This study presents a new data set of bioavailable strontium isotope ratios from rock and soil samples across Israel, as well as from sediment layers from seven key archaeological sites. This data set may be viewed and accessed both in an Open Science Framework repository (https://doi.org/10.17605/OSF.IO/XKJ5Y, Moffat et al., 2020) or via the IRHUM (Isotopic Reconstruction of Human Migration) database.This research has been supported by the Australian Research Council (grant nos. DP0664144, DP110101417, and DE160100703) and the Flinders University (Research Investment Fund Grant)

Sampling Plants and Malacofauna in 87Sr/86Sr Bioavailability Studies: Implications for Isoscape Mapping and Reconstructing of Past Mobility Patterns

Establishing strontium isotope (87Sr/86Sr) geographical variability is a key component of any study that seeks to utilize strontium isotopes as tracers of provenance or mobility. Although lithological maps can provide a guideline, estimations of bioavailable 87Sr/86Sr are often necessary, both in qualitative estimates of local strontium isotope "catchments" and for informing/refining isoscape models. Local soils, plants and/or animal remains are commonly included in bioavailability studies, although consensus on what (and how extensively) to sample is lacking. In this study, 96 biological samples (plants and snails) were collected at 17 locations spanning 6 lithological units, within a region of south-west France and an area with a high concentration of Paleolithic archaeological sites. Sampling sites aligned with those from a previous study on soil bioavailable strontium, and comparison with these values, and the influence of environmental and anthropogenic variables, was explored. Data confirm a broad correspondence of plant and snail 87Sr/86Sr values with lithological unit/soil values, although the correlation between expected 87Sr/86Sr values from lithology and bioavailable 87Sr/86Sr ratios from biological samples was higher for plants than for snails. Grass, shrub and tree 87Sr/86Sr values were similar but grasses had a stronger relationship with topsoil values than trees, reflecting differences in root architecture. Variability in 87Sr/86Sr ratios from all plant samples was lower for sites located on homogeneous geological substrates than for those on heterogeneous substrates, such as granite. Among environmental and anthropogenic variables, only an effect of proximity to water was detected, with increased 87Sr/86Sr values in plants from sites close to rivers originating from radiogenic bedrock. The results highlight the importance of analyzing biological samples to complement, inform and refine strontium isoscape models. The sampling of plants rather than snails is recommended, including plants of varying root depth, and (if sample size is a limitation) to collect a greater number of samples from areas with heterogeneous geological substrates to improve the characterizations of those regions. Finally, we call for new experimental studies on the mineralized tissues of grazers, browsers, frugivores and/or tree leaf feeders to explore the influence of 87Sr/86Sr variability with soil profile/root architecture on 87Sr/86Sr values of locally-feeding fauna.This research was funded by the Max Planck Society and a Leverhulme Trust grant to KB (RPG-2017-410), with additional support from Australian Research Council Discovery grants DP0664144 and DP110101417 to RG. KJ thanks the ERC ARCHEIS 803676, and IM thanks Australian Research Council Discovery Early Career Award (DE160100703), for salary support during production of this manuscript