The usefulness of Stable Isotope Analysis in Archaeology (Theme 3-Subsistence and diet)
· Every chemical in nature has isotopes.
· The main difference is their atomic mass.
· Different isotopes have different amounts of protons and neutrons but still remain stable.
· C14 is an unstable isotope due to the radioactive nature of the neutrons and protons.
· This means that whilst C14 decays at the rate of the half life, stable isotopes do not decay so are useful in the archaeological record.
· Key isotopes to analyse: Carbon, Nitrogen and Sulphur-all link to diet.
· Analysis takes place using collagen (bone) or tooth enamel.
How do discuss it within an essay:
1. When food is eaten and digested it already has a carbon and/or nitrogen trace within it.
2. Human bones reflect the amount of plants ingested during the lifetime based on the C13 ratio.
3. The nitrogen ratio can distinguish which plants were or were not eaten at a particular time in prehistory.
4. Analysing the nitrogen ration can distinguish those who eat more meat from those who eat more plants in their diet.
5. Eating of marine food (fish and shell fish) causes a significant change in the isotope ratio of nitrogen (4% higher) than that of normal mammals. This is due to the nitrogen ratio of marine plants being higher and causing an increase in the marine food that has eaten them.
6. A higher proportion of maize in the diet can be identified because this gives rise to skeletal C13 values higher than those who only ate C3 plants.
7. A diet rich in terrestrial meat can be distinguished from a more vegetarian diet because of the differences in the C13 and N15 ratios.
8. Other uses include understanding of animal fats (slight problem as it does not distinguish milk from normal animal fat) to analyse the use of dairy products in prehistory. Uses residue analysis normally found as a trace within a pot sherd.
Key Dietary Trends to Discuss:
· Binford: Nunamiut Eskimo study and the different hunter gatherer camps including kill zones-highlight the ethnographic parallels but also the problems with the use of analogies. Binford discovered that almost 90% of the dietary needs were covered by meat.
· Richard Lee: !Kung tribe-as an anthropological study Lee discovered that this tribe only took 30% of their calorie intake from meat and the rest from plants.
· Mesolithic –Neolithic transition in Britain: stable isotope analysis of the Mesolithic has highlighted that there was increased exploitation of marine resources in the diet…