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Bayesian analyses of radiocarbon time-frequency data before and after the Kikai-Akahoya volcanic eruption (ca. 7250 BP). Top-left: estimated population growth rates before the eruption (8000-7250 BP), top-right (estimated growth rate after the eruption (7250-6500 BP), bottom-left: difference between the two growth rates; bottom right: estimated log ratio of the proportion of dates 750 years before and after the eruption.
Demography
Reconstructing population dynamics from prehistoric datasets requires us to consider different kinds of proxy variables, from counts of archaeologically dated houses and settlements to radiocarbon dates associated with human activities, or even the age-at-death distribution of skeletal assemblages. This endeavour becomes even more challenging if we consider the indirect nature of these proxies, the size of the sample available, and the chronological uncertainty associated with each of our observation points.
FORAGER will develop and apply a suite of statistical methods that will allow us to make the best of the information we have while accounting for all sources of uncertainties. This will enable us to identify when and where we observe signals suggesting the presence of population booms and busts, and the extent to which these episodes are associated with ecological and cultural factors.
Settlement
FORAGER will examine settlement variation across multiple scales to address a variety of core research questions associated with cycles of demographic growth and decline. Models in demographic ecology predict that under conditions of productive seasonal resource concentrations, forager groups will often (all things equal) aggregate and grow their populations.
During periods of high-density aggregation, foragers may develop complex social structures and associated cultural traditions manifested geographically in geometric arrangements of houses, establishment of extramural activity areas (feasting ovens and communal storage facilities, for example), and satellite communities attached to core villages. In some regions, houses may grow in size and accommodate multiple domestic units acting as collective socio-political units.
Break-down in access to concentrated resources (whether under regional climate/ecological change, human-induced resource depression, competitive exclusion, or other factors) will often favor more dispersed settlement with more frequent residential moves by foraging families. Under these conditions, many elements of social complexity evident in aggregated settlements will decline or at least become largely invisible from an archaeological standpoint. Recognizing that settlement can change dramatically on multiple scales across demographic cycles, FORAGER will apply a variety of models and methods across all study areas for predicting variation in settlement and testing for patterns on scales spanning sub-regions, village settlements, and domestic arrangements within houses.
An artist’s (Eric Carlson) recreation of Housepit 54 at Bridge River, BC, during the IIb floor generation
Climate reconstruction
We will combine globally distributed proxy records with climate model simulations using paleoclimate data assimilation to produce dynamically consistent, spatially complete reconstructions of Holocene climate at decadal to centennial resolution. We’ll use proxy types and proxy-system models to extend the range of climatic variables and seasons represented, and explore use of statistical downscaling techniques to translate the reconstructions to the finer spatial and temporal scales across the four study regions. The reconstructions will provide uncertainty-inclusive, seasonally resolved maps of temperature, rainfall, and other relevant environmental variables, which will be used as inputs for later ecological, archaeological, and demographic analyses.
Human isotopic analysis
FORAGER will investigate dietary variation and long-term dietary transitions using stable isotope analysis of human, animal and plant remains. Stable isotope analysis of ancient human bones and teeth relies on the principle that body tissues preserve the isotopic signatures of foods consumed during life. Carbon, nitrogen and sulphur isotope ratios in bone collagen and tooth dentine provide direct evidence of diet, revealing resource use and dietary change through time.
Existing bulk collagen carbon, nitrogen and sulphur isotope data will be integrated with Bayesian dietary modelling and time-series approaches to reconstruct dietary composition and rates of change through time. To overcome the limitations of bulk collagen analyses, compound-specific isotope analysis (CSIA) of amino acids, enabling more precise reconstruction of dietary practices, including non-protein food resources will be applied. High-resolution dietary histories and incremental dentine isotope analyses will provide insights into lifetime dietary change, seasonal resource use, and inequalities in access to food. Together, these approaches will provide unprecedented insight into the evolution of forager diets and foodways under changing ecological conditions.
Organic Residue Analysis
During processing, cooking, or storage, organic molecules—notably lipids—from food products are absorbed and protected within the porous matrix of artefacts, or form amorphous carbonised deposits on their surface. By extracting and analyzing these trapped compounds, we can characterize their molecular and isotopic compositions. This identifies unique chemical fingerprints that reveal the original contents and functions of the artefacts, providing clear evidence of ancient diets, processing technologies, and resource exploitation.
As part of the FORAGER project, this method will be used to analyze hundreds of pottery fragments and fire-cracked rocks. This approach allows us to quantify regional culinary shifts and track how food processing evolved alongside changing diets and resource availability.
Strontium isotopic analysis
Sequential strontium isotopes ratios (87Sr/86Sr) in the tooth enamel will be measured in medium-sized game species, primarily deer species and wild boar, to track their movements across different landscapes, allowing estimations of hunting territory in relation to the settlement location. Measurement of carbon, nitrogen and sulphur isotopes in plant and animal remains will provide additional variables, as these two partly reflect local environmental conditions. We will also use proteomic based sexing of enamel proteins to examine the sexual composition of deer species to inform on hunting and animal management strategies. These proxy datasets will be used to examine spatiotemporal patterning in the geographic range of hunting activities across major demographic transitions.
Species Distribution Modelling
Drawing upon open-access published datasets of fauna and flora and site reports we will model the temporal density of different taxonomic groups and, where available, specific food related technologies (grinding stones, fishing implements etc.). Seasonality indicators will be developed from these inventories and integrated with settlement archaeology contributing to our contextual understanding of relevant degrees of seasonal occupation, storage and sedentism.
Modelling Cultural Inheritance
This method investigates patterns of diversification, transformation, and loss in the technologies, toolkits and strategies used by Holocene foragers across different regions. These inherited cultural traditions exhibit heritable continuity because they are reproduced within social-learning networks. The principle of descent with modification will be used to frame the analysis of inheritance, innovation and diversification processes. The approach aims to clarify the extent to which regional-scale cultural turnover and loss is driven by major demographic transitions, and the degree to which these processes intersect with climatic fluctuations, subsistence change, shifts in settlement and mobility, plus the possible role of ecosystem management and ecological inheritance in mitigating change and disruption.
House styles in the Plains Village Traditions in USA showing increasing uniformity in styles after a demographic surge.
Sample variance for wealth and subsistence measures across 12 occupation floors from Housepit 54 at the Bridge River Village site (K’etxelknáz) in British Columbia (Prentiss et al. 2023: 7). Wealth proxies include prestige objects such as beads, pendants, stone bowls, nephrite jade and other non-local raw materials, among others. Subsistence proxies include various faunal remains such as those of dog, deer, and sockeye salmon, as well as presence of hunting-related artifacts, etc. (Prentiss et al. 2023)
Measuring Inequality
WP 6 focuses on the emergence and persistence (or not) of inequality. Bringing together data from several WPs, it explores the potential relationships between demographic change and fluctuations in social- and wealth inequality at different scales. This approach hypothesises that population growth and density may trigger incipient inequality, while population declines may have inverse effects, leading to more cooperative, communal, and generally more egalitarian systems.
In regions where relevant data are available (Japan and Pacific Northwest), size and spatial organization of eg settlements, houses, and house floors and features will be examined for markers of material wealth-based inequality. This will be explored at regional, local, village, and domestic group/household scales where possible. A second proxy for wealth- and status-based inequality will be developed based on mortuary contexts. This will include looking at presence and nature of grave goods, burial attributes/features, evidence of funerary rites/rituals, etc. These will be collated from published sites across all four regions investigated by FORAGER, providing two different lenses through which to observe conditions and circumstances related to inequality. Other proxies will also be explored: for example, where possible, stable isotope analyses will be used to inform on patterns of resource access, dietary breadth, and subsistence well-being. Overall, WP6 will attempt to better understand inequality and its implications as holistically as possible.
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