The proper choice of proxies for relevant strontium isotope baselines used for provenance and mobility studies in glaciated terranes - Important messages from Denmark.

Strontium (Sr) isotope based provenance and mobility studies of ancient humans and animals necessitate representative isoscapes/baselines. However, regions/terranes that were shaped and affected by glaciers during the last Ice Ages and are covered by glaciogenic sediments present a challenge with regards to the choice of suitable surface proxy archives. Recent studies proposed that only 87Sr/86Sr signatures from pristine areas are relevant for this purpose. To test this theory, 160 new Sr concentrations [Sr] and 87Sr/86Sr signatures composed from ~960 subsamples of soil leachates and plants, complemented with 55 surface waters from agriculturally unaffected pristine forest sites from all over Denmark (island of Bornholm excluded) were analyzed. The results reveal that average 87Sr/86Sr signatures of all three proxies (plants: 0.7115 ± 0.0025; 2σ, n = 162; soil leachates: 0.7118 ± 0.0037; 2σ; n = 161, surface waters: 0.7104 ± 0.0030; 2σ, n = 55) are elevated compared to larger water bodies (creeks, rivers, lakes). In mixing diagrams, the data converge in a shared high [Sr] low 87Sr/86Sr endmember, which points to either remnant natural carbonates and/or organic components retaining carbonate Sr in the studied Podzols/Luvisols. The indications for more abundant carbonates in the past, compared to today's acid leached soils, implies that 87Sr/86Sr values measured from pristine forest locations and heathlands do not adequately reflect the biosphere compositions that prevailed ~12,000-2000 thousand years ago. Consequently, pristine forests in Denmark seem to be unsuitable proxy archive environments for constructing Sr isotope baselines for determining the provenance and mobility of ancient humans and animals. Hence, 87Sr/86Sr values measured in these pristine areas are non-representative and inadequate, and their use will lead to wrong interpretations. Finally, our study sheds light on the complexity of defining relevant and representative isoscapes/baselines in significantly changing environments and areas where the surface biosphere conditions do not necessary reflect the underlying geology.

The geographic distribution of bioavailable strontium isotopes in Greece - A base for provenance studies in archaeology.

Sr isotopes are a powerful tool used to reconstruct human mobility in archaeology. This requires extensive bioavailable 87Sr/86Sr baselines used as reference for deciphering potential areas of origin. We define the first extensive bioavailable Sr isotope baselines for the different geographical regions and surface lithologies of Greece by combining new Sr data with previously published bioavailable 87Sr/86Sr data. We present 82 new Sr concentrations and 87Sr/86Sr signatures of plants, soil leachates, surface waters and spring waters from Central Greece and combine these with published baseline values from all over Greece. We define individual baselines for ten of the thirteen geographical regions of Greece. We also provide soil leachate 87Sr/86Sr ratios from the two archaeological Bronze Age sites of Kirrha and Ayios Vasileios in Central and Southern Greece and demonstrate the validity and applicability of the new baselines for these sites. The bioavailable 87Sr/86Sr compositions of Central Greece define a narrow range of 87Sr/86Sr values between 0.70768 - 0.71021, with the widest range observed for the soil leachates. Sr derived from carbonate weathering appears to be the most important Sr source sampled by the proxies. There is an overall larger variability in baseline ranges of the different geographical regions, the narrowest is that for West Greece and the widest that for West Macedonia. In addition, we computed statistical Sr isotope ranges for the five main surface lithological groups characterising the sampling sites of the various proxies. Narrowly ranged, unradiogenic bioavailable Sr isotope signatures are typical of areas characterised by igneous outcrops as well as by Cenozoic and Mesozoic sediments. Areas, where Palaeozoic and Precambrian bedrock outcrops dominate, produce significantly wider ranges. Our study promotes the usefulness of multi-proxy baselines for geographical reference purposes and thus their promising applicability for future human mobility studies.

Into the fire: Investigating the introduction of cremation to Nordic Bronze Age Denmark: A comparative study between different regions applying strontium isotope analyses and archaeological methods.

Changes in funerary practices are key to the understanding of social transformations of past societies. Over the course of the Nordic Bronze Age, funerary practices changed from inhumation to cremation. The aim of this study is to shed light on this fundamental change through a cross-examination of archaeometric provenance data and archaeological discussions of the context and layouts of early cremation graves. To this end, we conducted 19 new provenance analyses of strontium isotopes from Early Nordic Bronze age contexts in Thisted County and Zealand and Late Bronze Age contexts from Thisted County and Vesthimmerland (Denmark). These data are subsequently compared with data from other extant relevant studies, including those from Late Bronze Age Fraugde on the Danish island of Fyn. Overall, the variations within our provenience data suggest that the integration and establishment of cremation may not have had a one-to-one relationship with in-migration to Nordic Bronze Age Denmark. Moreover, there seems to be no single blanket scenario which dictated the uptake of cremation as a practice within this part of Southern Scandinavia. By addressing habitus in relation to the deposition of cremations as juxtaposed with these provenance data¸ we hypothesize several potential pathways for the uptake of cremation as a new cultural practice within the Danish Nordic Bronze Age and suggest that this may have been a highly individual process, whose tempo may have been dictated by the specificities of the region(s) concerned.

Unraveling ancestry, kinship, and violence in a Late Neolithic mass grave.

The third millennium BCE was a period of major cultural and demographic changes in Europe that signaled the beginning of the Bronze Age. People from the Pontic steppe expanded westward, leading to the formation of the Corded Ware complex and transforming the genetic landscape of Europe. At the time, the Globular Amphora culture (3300-2700 BCE) existed over large parts of Central and Eastern Europe, but little is known about their interaction with neighboring Corded Ware groups and steppe societies. Here we present a detailed study of a Late Neolithic mass grave from southern Poland belonging to the Globular Amphora culture and containing the remains of 15 men, women, and children, all killed by blows to the head. We sequenced their genomes to between 1.1- and 3.9-fold coverage and performed kinship analyses that demonstrate that the individuals belonged to a large extended family. The bodies had been carefully laid out according to kin relationships by someone who evidently knew the deceased. From a population genetic viewpoint, the people from Koszyce are clearly distinct from neighboring Corded Ware groups because of their lack of steppe-related ancestry. Although the reason for the massacre is unknown, it is possible that it was connected with the expansion of Corded Ware groups, which may have resulted in competition for resources and violent conflict. Together with the archaeological evidence, these analyses provide an unprecedented level of insight into the kinship structure and social behavior of a Late Neolithic community.

Bioavailable 87Sr/86Sr in European soils: A baseline for provenancing studies.

We present 87Sr/86Sr isotope ratios for ~1200 selected soil samples, collected by the GEMAS consortium from grazing (Gr) and agricultural (Ap) soils in Europe with the aim to better understand the strontium isotope distribution in the bioavailable fraction of the top-soil and its potential for provenancing applications. Spatial analysis shows that there is a clear distinction between coastal (<100 km) and non-coastal (>100 km) samples in their variance and that this variance is mirrored in the sodium concentration, suggesting an important but highly variable contribution from seaspray. We present two 87Sr/86Sr maps at 25 km × 25 km scale: one based solely on the measured data using a classical kriging approach and one based on a Random Forest model using complementary GEMAS data to predict the strontium isotope composition at the remaining 3000+ GEMAS sampling locations, including appropriate uncertainty assessment. Using a forensic Bayesian likelihood ratio approach, a tool was developed in R to create provenancing likelihood ratio maps. The maps delineate areas of high and low likelihood and allow investigators to direct their resources to areas of interest. For actual forensic case work either the measured or the modelled data can be used as reference data for the overall distribution of 87Sr/86Sr values in Europe.

Understanding Final Neolithic communities in south-eastern Poland: New insights on diet and mobility from isotopic data.

We present the first comprehensive multi-isotopic data on human and animal remains from the Final Neolithic Corded Ware culture (ca. 2900-2300 cal. BC) in south-eastern Poland. The study focused on communities of two settlement areas located in the Malopolska Upland and in the Subcarpathian region. Carbon and nitrogen isotopes of bone collagen were investigated to obtain insights into human dietary preferences, whereas the strontium isotope composition of human tooth enamel was used to trace the mobility and provenance of individuals. Sr isotope data point to a non-local origin of at least one-quarter of the investigated individuals in the Subcarpathian region, consistent with associated allochthonous grave inventories of eastern or western origins. In contrast, all investigated individuals in the Malopolska Upland were of local origin. Furthermore, our study shows an example that the use of fauna for the assessment of the local 87Sr/86Sr range of an archaeological site can lead to incorrect conclusions and suggests that a detailed Sr isotopic survey of the geological background and its hydrologic elements is necessary to provide conclusive constraints for the identification of local and non-local individuals in prehistoric communities. Carbon and nitrogen isotope composition of bone collagen indicate an omnivorous diet that included C3-based terrestrial plant and animal resources, in which plant food dominated. In both regions, there were no significant sex differences in dietary intakes. Higher δ15Ncoll values of younger infants presumably reflect the effect of weaning.

Isotope values of the bioavailable strontium in inland southwestern Sweden-A baseline for mobility studies.

The inland area of southwestern Sweden is well known for its well-preserved archaeological animal and human remains dating back to the Mesolithic and Neolithic (10000-4000 and 4000-1700 BC). They allow application of multiple bioarchaeological methods, giving insights into various and complementary aspects of prehistoric human life, as well as economic and social structures. One important aspect concerns human mobility and its relation to social networks and to circulation of objects. Here, strontium isotope analysis plays a crucial role. The present study aims to construct a strontium isotope baseline of southwestern Sweden with considerably greater coverage and higher resolution than previously published data. As the region has been affected by glacial events, the relation between bedrock geology and isotope signals of the bioavailable strontium in such areas is given special attention. We determined strontium isotope ratios for 61 water and five archaeological animal samples, and combined the data with previous measurements of two water and 21 non-domestic faunal samples. The results reveal a complex pattern. Several areas with distinct baseline ranges can be distinguished, although with overlaps between some of them. Overall, the bioavailable strontium isotope signals mirror the basement geology of the region. The highest ratios occur in the geologically oldest eastern parts of the Precambrian terrain, while lower ratios are found in the western part, and the lowest ratios occur in the youngest Paleozoic areas. At the same time, there are minor deviations compared to the underlying bedrock, due to glacial transport, overlying sediments, and local intrusions of younger rocks. The background data set now available allows for more nuanced and detailed interpretations of human and animal mobility in the region, in particular by identification of subregions with differing strontium isotope ratios within the Precambrian province. Also, we can now identify long distance mobility with greater confidence.

Author Correction: 137 ancient human genomes from across the Eurasian steppes.

with In this Article, Angela M. Taravella and Melissa A. Wilson Sayres have been added to the author list (associated with: School of Life Sciences, Center for Evolution and Medicine, The Biodesign Institute, Arizona State University, Tempe, AZ, USA). The author list and Author Information section have been corrected online.

137 ancient human genomes from across the Eurasian steppes.

For thousands of years the Eurasian steppes have been a centre of human migrations and cultural change. Here we sequence the genomes of 137 ancient humans (about 1× average coverage), covering a period of 4,000 years, to understand the population history of the Eurasian steppes after the Bronze Age migrations. We find that the genetics of the Scythian groups that dominated the Eurasian steppes throughout the Iron Age were highly structured, with diverse origins comprising Late Bronze Age herders, European farmers and southern Siberian hunter-gatherers. Later, Scythians admixed with the eastern steppe nomads who formed the Xiongnu confederations, and moved westward in about the second or third century BC, forming the Hun traditions in the fourth-fifth century AD, and carrying with them plague that was basal to the Justinian plague. These nomads were further admixed with East Asian groups during several short-term khanates in the Medieval period. These historical events transformed the Eurasian steppes from being inhabited by Indo-European speakers of largely West Eurasian ancestry to the mostly Turkic-speaking groups of the present day, who are primarily of East Asian ancestry.