Stable isotope analysis of prehistoric human and commensal diet on Aitutaki, southern Cook Islands

Abstract

This thesis investigates the prehistoric diet of humans and two of their key commensals on Aitutaki using stable carbon and nitrogen isotopes. This technique gives us new insight into the diet of these three groups and results are considered in the context of the development of agricultural systems on Aitutaki, as well as in light of the wider context of cultural developments and environmental change in the Cook Islands and Polynesia as a whole. Ultimately, it allows us to more fully understand the complex interactions between humans and the two largest commensals in order to evaluate the utility of these animals as proxies for humans in dietary analyses. The results indicate that the prehistoric human diet on Aitutaki can be characterised as mixed, dominated by terrestrial plants and marine protein with lesser amounts of terrestrial protein. While the amount of protein eaten by the individuals was very similar, they varied in how much marine or terrestrial protein they ate. The pigs had a slightly more terrestrial diet, with a greater emphasis on plant foods. Their protein intake was more variable and terrestrial in nature than the humans’. Dogs had a higher trophic level, more marine-oriented, diet than either humans or pigs. Like the humans, their diet contained more variation in the source of their protein. Overall, however, the diets of all three groups were very similar. While the overall nature of the human, pig and dog diets, and their relationships to one another, remained relatively constant over time, beginning in the 14th century they show a decline in the amount of fish consumed and had a more terrestrial diet overall. This confirms trends seen in the archaeofaunal assemblages, and throws light on the relationship between environmental change and human subsistence practices in East Polynesia. The similarity of the pig and dog diets to human diet, and the fact that the relationship remained constant over time, demonstrates the usefulness of the Aitutaki commensal animals as proxies for humans in stable isotope analysis. However, the specifics of that relationship vary by species and by place. While the individual dietary variability provides us with new ways of looking at dietary change within populations, it also demonstrates the importance of obtaining as large an assemblage for analysis as possible in order to ensure that samples are representative of the population as a whole.