Tag: Strontium isotopes

Caprine husbandry practices at the prehistoric site of Monjukli Depe in southern Turkmenistan: A Multi-Isotope Perspective

On By Roz GillisIn News, Projects, Research

Jana Eger (j.eger@fu-berlin.de)

Department of History and Cultural Studies at the Free University of Berlin

Sheep and goat predominate in the Neolithic and Aneolithic/Chalcolithic faunal assemblages in southern Central Asia and adjacent microregions, yet their husbandry is still incompletely understood. Some aspects of caprine herding practices, such as the annual timing/seasons of birth and feeding in the context of local conditions, have received little attention so far. This case study addresses these aspects by using an integrated approach combining a multi-isotope analysis (nitrogen, carbon, oxygen, and strontium) mainly on caprine teeth/bones with zooarchaeological results and archaeobotanical data from Monjukli Depe in order to explore the life histories of animals herded at the site. Monjukli Depe is in southern Turkmenistan and inhabited in the late Neolithic (ca. 6200-5650 BCE) and again in the early Aeneolithic (ca. 4800-4350 BCE). Excavations at this site have yielded a large, well-preserved animal bone assemblage.

Passing herd along the Kopet Dag behind the yurt during excavation. Photo: Monjukli Depe Project.

In the first step of the research, bone collagen was extracted from mandibles of sheep and goat and analysed for carbon and nitrogen isotopes (FIG 1). A total of 23 caprine individuals were sampled in the study. From this we can detect past environmental conditions and the range of vegetation to which the animals had continuous access during their lives, including their reliance on C3 and C4 plants. While both plant groups occur in southern Turkmenistan today, the preliminary archaeobotanical data from Monjukli Depe point to a predominance of C3 plants.

Jana sampling material for stable isotope analysis at the chemical lab of the Curt-Engelhorn–Center for Archaeometry GmbH, Mannheim (Germany). Credit: Martin Riesenberg.

The next step, was to sequentially sample lower 3rd molars from the sampled mandibles and analysed for carbon and oxygen isotopes. The δ18O and δ13C values provide insights into seasonal changes in diet and fodder composition over the annual cycle. Several second molars were sampled in addition, so that ca. 11 to 12 months of the first year of the animals’ lives were included in the analyses.

δ18O (white circles) and δ13C (black circles) values, and 87Sr/86Sr ratios (black dashes) for two sheep individuals of Monjukli Depe with both second and third molar sampled (Credit: Jana Eger)

In a third step, the δ18O sequences obtained from the teeth were used to assess strontium isotope analysis. From each tooth two sample positions of the highest and lowest δ18O values were selected to measure the strontium ratios (87Sr/86Sr) to investigate the possibility of different grazing locations on a seasonal scale. The δ18O sequences were further used to provide information about the birth seasonality in the Monjukli herd population.

The analysis reveals that a large proportion of caprine individuals received a more diverse vegetation than others with possible contribution of C4 plants in diet – both on a seasonal and long-term basis. Furthermore, the results support a scenario in which sheep and goats were kept in small flocks at ecologically different locations close to the settlement. Herding practices in the Monjukli case seemed to focus on landscape micro-variability rather than exploiting advantages of altitude differences. The study further indicates that sheep and goat were born across multiple seasons within the annual cycle, and they were raised to maintain a continuous supply of fresh milk along with tender meat, consistent with previous suggestions that husbandry was both meat- and milk-oriented.

Overall, the information gained from the investigation helps to draw a more detailed picture of sheep and goat husbandry, including a better understanding of breeding practices and controlled herd security by the people who tended the animals. The data provide evidence of a wide zootechnical knowledge in this early village society.

The results of the multi-isotope investigation, recently published and online accessible here: https://www.sidestone.com/books/mensch-tier-verhaeltnisse-in-monjukli-depe, were viewed through the lens of the interdisciplinary field of Human-Animal Studies, which direct their focus to complex and multidimensional interspecies relations . The interpretation included zooarchaeological study of over 50,000 animal remains and the analyses of zoomorphic representations in the form of miniaturized clay objects. Thus, the stable isotopic results are considered within the wider socio-cultural practices and conceptions of relations between humans and (other) animals at the settlement of Monjukli Depe.

This research derives from the Monjukli Depe Project at the Free University of Berlin (FUB) under the direction of Prof. Dr. Susan Pollock and Prof. Dr. Reinhard Bernbeck, and was undertaken as part of my PhD (2014-2020) within the frame of the Berlin Graduate School of Ancient Studies. The financial support for this study was provided by the German Research Foundation, and Frauenfördermittel of the Department of History and Cultural Studies at FUB.

Current Methods and Best Practices in Strontium Isotope Mapping

On By Roz GillisIn Projects, Research

Emily Holt, Jane A. Evans, and Richard Madgwick

Drawing on variations in bioavailable strontium in different environments to provenance biological materials has become increasingly common since its first application in archaeology almost four decades ago, and it is frequently applied to zooarchaeological materials. Provenancing biological materials, including faunal remains, using strontium isotope ratios generally requires a map of bioavailable strontium, commonly known as an isoscape, to compare results with. However, both producing the isoscape and using it to interpret results present methodological challenges that researchers must carefully consider.

To help researchers understand the complexities of strontium analysis, we reviewed current research to produce a critical synthesis and recommend best practices. We addressed sampling the archives needed to build an isoscape, applying the different mapping and modeling methods currently available, and interpreting the results of archaeological analyses against isoscapes. Our critical review is freely available to read and download from Earth-Science Reviews until May 8, 2021

Sampling

Current research indicates that, while many archives can be analyzed to produce isoscapes, modern plant materials usually provide the best approximation of bioavailable strontium. Modern plants can be used alone or combined with other archives if applying a machine learning approach to mapping. In areas where erosion has significantly shifted the location of surface sediments, modern plants may not provide an appropriate archive for building an isoscape that is applicable to archaeological materials. In these areas, alternative archives such as archaeological rodent remains may be preferable. Archaeologists should also be aware that contemporary soil treatments like fertilizers may affect the bioavailable strontium in soils. Areas used for agriculture should be avoided when sampling.

Strontium pathways (adapted from Bataille et al. 2020, Fig. 1)

It is essential to collect appropriate metadata when sampling. Collecting metadata improves the legacy benefits of strontium data by making them more broadly applicable. These metadata and the results of the analyses should be archived in one of several online databases to maximize their usefulness.

Mapping and modeling

We found that domain mapping currently produces the most accurate, most interpretable isoscapes for most research questions. However, machine learning approaches are also powerful and promise to provide more accurate and geographically wide-ranging isoscapes over time. Machine learning is computationally intensive and may not currently be an option for many researchers, but will be more widely available in the future.

Strontium isoscapes that are both appropriate and sufficiently high resolution to answer specific research questions do not exist for most parts of the world. Researchers intending to incorporate strontium analysis into their research designs should expect to conduct primary sampling and analysis to create appropriate isoscapes or refine existing ones, which should themselves not be utilized uncritically.

Interpretation

Strontium isotope analysis is currently the best developed and understood provenance tool. However, because isotope data can only exclude options of possible origin, the development of multi-isotope methods provides the route to a more powerful future approach. Using strontium isotope analysis for provenancing is most successful when combined with other isotopes and/or trace elements as part of a likelihood approach.

Future directions

In the future, we expect that increasing amounts of primary data and the increasing application of machine learning approaches to mapping will mean that strontium analysis continues to improve as a method of provenancing.

This research was apart of the ZANBA – Zooarchaeology of the Nuragic Bronze Age, a Marie Sklodowska Curie fellowship awarded to Emily Holt.