A single human molar can record nearly a decade of dietary shifts, and this project will read those chemical signals to map how prehistoric hunter-gatherers coped with seasonal food shortages. Archaeologists have long known that seasonal resource availability shaped human behaviour—affecting everything from nutrition to settlement patterns and gender roles—but direct evidence has been frustratingly ambiguous. Existing methods rely on plant and animal remains, which are often hard to interpret. This project sidesteps those problems by analysing teeth from human burials at two Mesolithic sites in Sweden and Latvia, plus a few dogs that ate similar food. Because teeth grow in layers and never remodel, they preserve a sub-annual record of diet, mobility, and stress. The team will use stable isotopes to track dietary changes over 7–8 years per tooth, strontium isotopes to trace seasonal movement, and stress markers to identify lean periods like late winter. This is fundamental science with no immediate practical application. But the techniques developed here—especially high-resolution sequential sampling of dentine—could eventually be used to study metabolic stress events in modern human or animal remains, or to refine how we understand human resilience to environmental change in any period or region.
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The changing seasonal availability of resources has long been seen as a structuring principle of human adaptation. Alongside the direct impact on the subsistence economy and nutrition, there are often accompanying, wide-ranging social consequences in terms of the gendered division of labour, mobility and settlement patterns. Seasonal food shortages are also a common occurrence in both hunter-gatherer and agricultural societies. While the importance of seasonality has long been acknowledged, investigating it archaeologically in any detail has proven challenging. Studies have focussed primarily on faunal and floral remains, but their interpretation is often ambiguous. The project offers a new approach centred on human remains themselves. Teeth grow sequentially, providing an archive of an individual's life history from infancy to early adulthood. Unlike bone, teeth do not remodel over time and so retain biochemical signals incorporated during their formation, offering a sub-annual record of changes in diet, mobility and health. We will also analyse a small number of dogs from the same sites as the humans. As canid teeth develop over a shorter time period, they will offer an even higher-resolution view of any seasonal dietary changes. Since- prior to recent times -?dogs often ate much of same food as their human companions, we expect that human and dog diets will track seasonal changes in food availability in similar ways. We will use sequential stable carbon and nitrogen isotope analysis on tooth dentine to track changes in diets over the formation period of the tooth, on the order of 7-8 years for a human molar. We will then compare the results against modelled diets based on what is already known about the foods that would be available in the selected study areas and their stable isotope values. The models will explore different possible combinations of seasonally available foods, to see which provides the best fit with the observed human (and dog) results. The question of storage is an important one that will also be considered, as it extends the availability of foods over a longer part of the year. A second part of the study uses strontium isotopes in tooth enamel to investigate mobility over the period of crown formation, ca. 3 years for the first molar crown. A third part of the study will look for stress markers in the teeth, as these might be expected to show seasonal trends (e.g., late winter is usually a period of resource shortage in north temperate environments). The selected study sites are Skateholm in southern Sweden and Zvejnieki in northern Latvia. Both are the burial places for hunter-gatherer communities dating to the Mesolithic period. Skateholm has access to the marine/estuarine resources of the Baltic, while Zvejnieki is beside a freshwater lake. Previous results on human bone - representing a long-term average diet -?demonstrate the importance of both terrestrial and aquatic resources at both sites. Some sequential dentine data are available, and suggest variation in diets at sub-annual and inter-annual scales, but these are at too low resolution for our purposes. We will therefore develop higher-resolution sampling methods focussed on intra-annual variation in diets. The project will investigate past human adaptations to seasonal climates in a more direct way than has been previously possible. This in turn will enable a much more nuanced understanding of past lifeways, addressing the inter-connected themes of food and health, mobility and settlement patterns, gender, inequality and resilience. The results will be of interest to archaeologists world-wide, providing worked-through case studies illustrating the benefits of higher-resolution sequential sampling methods to address questions of seasonality that are fundamental to human adaptations. Also of interest will be the demonstration of the ability to identify metabolic stress events in ancient (and modern) human and faunal remains.
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