Hypothesis 1 ... Stable Isotope Study Of Hunter-Gatherer-Fisher Diet, Mobility, And Intensification ... Marine and Terrestrial Protein in Australian Aboriginal Diets.
Assessing Dietary Variability and Constraint at Gillman Mound using Stable Carbon and Nitrogen Isotopes Caitlin Bonham Smith*
Current research in South Australia has highlighted the need for further exploration into subsistence patterns of Australian Aboriginal people (Pate, 1997; Pate 1998; Owen, 2004; Pate and Owen, 2014; Littleton et al., 2013a,b). Dental microwear analysis has indicated that additional investigation into variation and constraint in these populations is necessary in order to create a more nuanced picture of gender divisions (Littleton et al., 2013a). Gillman Mound, a sand dune located in Adelaide, was used as a burial place by the Kaurna from 1050-400 BP. There are two testable hypotheses regarding the diet of the individuals from Gillman Mound. Were the people buried at Gillman Mound using a variety of local resources, or were they using primarily marine resources? Does stable isotope analysis reflect the same pattern of male variation and female constraint as dental microwear? This poster shows a model of how to analyze stable isotopes in relation to gender and diet among Australian hunter-gatherers.
The people buried at Gillman Mound were eating a variety of local resources, including plant and animal material from the coast and inland.
How can this be tested? The landscape surrounding Gillman Mound is highly varied (Figure 1). There are numerous inland, riverine, and coastal plant and animal food resources. Here are some ways dietary source can be tested: •
Marine versus terrestrial/riverine based diet can be established from the relatively enriched nitrogen and carbon of marine foods. More positive δ15N and δ13C values would indicate the consumption of marine resources (Ambrose, 1993; Hobson and Collier, 1984).
Consumption of plant versus animal food can be tested with ∆δ13CaCo, which is derived from the analysis of bone collagen and apatite in reference to carbon (Katzenberg et al., 2009). This value should be lower in organisms that consume primarily animal foods compared to plant. This provides a direct measure of the importance of plant versus animal foods in diet.
Differentiation between terrestrial and riverine foods requires the most detailed sampling. Terrestrial based isotopes have a significant input to riverine systems. However, seasonal variation is more extreme in riverine systems, and this variation can be detected with stable isotopes (Bunn et al., 2013; Hard and Katzenberg, 2011).
Figure 1 – A map showing the local ecology surrounding Gillman Mound (created by Graig Westell)
Increasing need for specificity in background values
Hypothesis 2 Women buried at Gillman Mound had less variable and more constrained diets.
How can this be tested? Variability in this context can be defined by the types of foods consumed, where a highly variable diet would include eating (or having access to) many different foods and/or eating different types of foods seasonally. In contrast, constraint is a measure of the amount of certain foods consumed, where the social restriction placed on a specific resource (e.g. fish roe) limits the consumption of that resource to a particular gender or age group. Therefore, a constrained diet would be a diet without certain valued foods. Variability and constraint may also be reflected in the extent of differences between individuals. Variability and constraint are not easy to quantify archaeologically, but stable isotope analysis is one way that these measures can be directly observed. •
The consumption of different kinds of animals at different trophic levels, where high trophic level foods are more valuable. This can be measured by δ15N, were a larger value represents a diet composed of food at a high trophic level (Katzenberg et al., 2009).
Different isotope signatures by burial position and location, or a clustering of values from people buried in a similar positions or locations within the mound (Ambrose et al., 2003).
Consumption of different tissues by humans, for example lipids versus protein in animal foods (Katzenberg et al., 2009). This can be observed by using mixing models, but requires extensive background sampling, including at different seasons.
Figure 2 - A Map of Adelaide broken into different environmental provinces established by Laut et al. (1977) and used by Owen (2004).
Conclusions Diet reconstruction using stable isotopes is reliant on an understanding of the stable isotope ecology of the specific environment under observation (Hard and Katzenberg, 2011). Careful tracing of the isotopic signatures through the food web is particularly crucial in investigations of diet in South Australia. This region has complex and varied local environments that were exploited for resources by hunter-gatherers. A detailed comparison of the isotopic ratios of individuals to a variety of local resources will allow for a clearer analysis of variability and constraint in this population. This comparison is made possible by using the tools listed above within the pre-established environmental zones (Figure 2).
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