Down To The Bone: Transforming Isotope Analysis Through The Temporal Investigation Of Human And Animal Bone

Stable isotope analysis is a ubiquitous research application in archaeology with stable carbon and nitrogen isotopes being routinely used to reveal the dietary ecology of past human societies. However, surprisingly little is known of the temporal resolution surrounding it and, over time, pitfalls have appeared in the traditional bulk method currently utilised. This project will address the issue of temporality through empirical evidence of metabolic sequencing within a single section of bone to eliminate the use of multiple elements, reducing the destruction of finite archaeological material. This will provide guidance for sampling strategies and archaeological interpretations globally, and substantially improve ethical considerations and data yield when sampling skeletal material. Current methods used to elucidate dietary biographies in past civilisations require several skeletal elements per individual to capture dietary signals for different time periods due to our understanding of bone metabolism and its variation between elements. However, this results in multiple elements being partially destroyed and the validity of comparing different bones of differing functions has been scrutinised (e.g., Fahy et al. 2017). Meanwhile, research suggests that temporal variability exists within the same skeletal element (e.g., Matsubayashi and Tayasu 2019; Matsuo et al. 2019). Thus, this project will explore the potential for a new single-element method, where multiple successive samples are taken along the growth axis of one bone (following Matsubayashi and Tayasu 2019), multiplying archaeological information whilst minimising destruction.
The humerus and the femur are the two elements under investigation, due to their robust nature and cortical thickness. Adjacent to human remains, large domestic fauna will be similarly studied, to explore husbandry practices at a higher temporal resolution. The effect of mechanical loading will also be examined by observing and comparing trends in metabolism in the upper limb bones between bipeds (humans) and quadrupeds (fauna). Biochemical variation will be examined by carbon and nitrogen isotope values between multiple successive segments. Paired with histomorphometric applications including osteon population density, this will establish a temporal resolution across the sampled transect. Statistical analyses will reveal the relationships between the different lines of evidence, predominantly the relationship between remodelling rates, isotope values and respective bone segments. The potential for advancement in the research using other scientific applications will also be assessed (e.g, proteomics, compound-specific isotope analysis).
Objectives
- To better understand intra-element variation in cortical bone remodeling and how this impacts isotope values.
- To create a holistic study of bone remodelling variation within human cortical bone using histomorphometric techniques to establish a metabolic chronology.
- To revisit assemblages where multiple-element isotope analysis was carried out to compare the lines of evidence.
- Examine the validity of using segmental bone collagen analysis on faunal remains to make inferences on husbandry techniques.
- To provide guidance for new sampling strategies to address specific archaeological questions on life histories, cultural or social shifts, and interpretations of past diets and reduce the destructive impact on archaeological remains.
Establishing the metabolic chronology of cortical bone has the potential to reform how isotope analysis of archaeological remains is carried out. With the ever-increasing amount of analyses being undertaken, it is vital that our sampling is better informed and that we can understand the timescale that we are analysing. In introducing a novel sampling strategy where multiple time averages can be collected from just a single element, I hope to refine both our technical and ethical standards for archaeological science