Abstract
OBJECTIVE: This doctoral research has multiple aims: 1) to establish an isoscape that depicts 87Sr/86Sr variation for Aotearoa New Zealand (Aotearoa) using previously established machine-learning methods, 2) to use the constructed 87Sr/86Sr isoscape and a probabilistic assignment model to predict provenance for a prehistoric sample of dogs (kurī) that lived among early Māori populations at the NRD site on the North Island of Aotearoa, 3) to re-evaluate published 87Sr/86Sr data for archaeological human remains (kōiwi tangata) from Wairau Bar using the new 87Sr/86Sr model, and 4) to show the applicability of 87Sr/86Sr analysis for studying past populations in geologically under-sampled islands in the South Pacific, specifically on the Polynesian Outlier, Taumako, southeastern Solomon Islands. All projects seek to use 87Sr/86Sr analysis as a tool to understand migration in the South Pacific, with their primary focus on Aotearoa.
METHODS/MATERIALS: This research utilizes human dental enamel, kurī (Canis familiaris) dental enamel, plant, and soil samples to explore migration using strontium isotope analysis. Preparation and 87Sr/86Sr analysis of all samples, except the Taumako human dental enamel, were completed at the Otago Community Trust Centre for Trace Element Analysis in Dunedin, New Zealand. The Taumako samples were analyzed at the Max Planck Institute of Evolutionary Anthropology in Leipzig, Germany.
RESULTS: This doctoral research produced a 87Sr/86Sr isoscape (R2=0.53, RMSE=0.001) and validated its use for region-of-origin predictions using cow milk samples (n=33) obtained from farms throughout Aotearoa. Predictions for cow milk highlighted all potential origin locations that share similar 87Sr/86Sr values, with the closest predictions averaging 7.05 km away from their true place of origin. These results of this study, published in PLOS ONE (Kramer et al. 2022), demonstrate that this bioavailable strontium isoscape is effective for tracing locally produced agricultural products in Aotearoa.
Furthermore, two archaeological case studies were investigated using the 87Sr/86Sr isoscape. The first re-evaluates the kōiwi isotope data from Wairau Bar and suggests that the inhabitants of the early period settlement originate from various regions within Aotearoa and may have used Wairau Bar as a central meeting locale. The second case study integrates 87Sr/86Sr isoscape predictions for kurī with additional lines of evidence (aDNA, dietary isotopes, dental analysis) to create an “osteo-history” for the North Runway Development (Auckland) site to better understand 1) human-dog interactions; 2)the role kurī played in early Māori societies; and 3) to potentially use kurī as a proxyfor human behavior at the site. The fourth article shows the applicability of performing87Sr/86Sr analysis even in regions of the world where constructing a 87Sr/86Sr isoscapemay not be feasible, like Taumako island, in the eastern Solomon Islands chain. Thisstudy, published in American Journal of Physical Anthropology (Kramer et al. 2020)shows that 87Sr/86Sr analysis can help uncover societal structures and interactionspheres through the analysis of 87Sr/86Sr data.
DISCUSSION/CONCLUSION: The ultimate objective of this doctoral research (four related articles) was to illustrate that using machine learning techniques to construct 87Sr/86Sr isoscapes and perform assignment predictions can improve our understanding of interaction spheres among and within past populations. With the availability of the 87Sr/86Sr model produced in this thesis and the case studies illustrating its worth, this study aims to promote and contribute to future 87Sr/86Sr-focused research in Aotearoa and the South Pacific. Furthermore, this study demonstrates that 87Sr/86Sr analysis contributes to our understanding of population variation and structure even in regions where 87Sr/86Sr isoscapes cannot be constructed due to paucity of existing data needed to perform machine learning approaches.
BROADER IMPACTS: This research matters because it will: 1) improve our understanding of early migration, settlement strategies, and interaction spheres in Aotearoa, 2) provide a cost-effective reference 87Sr/86Sr isoscape for Aotearoa that will aid future provenance research, and 3) engage the public using archaeological case studies to illustrate how 87Sr/86Sr can help researchers better understand our ancestors.