Isotope Diet Reconstruction
Also known as: stable isotope analysis, carbon-nitrogen isotope analysis, diet isotope analysis
Isotope diet reconstruction uses the stable isotope ratios of carbon (C13/C12) and nitrogen (N15/N14) in human bone collagen to infer the composition of past diets. Pioneered by Margaret Schoeninger and Michael DeNiro in the 1980s, this method reveals long-term dietary patterns by analyzing the chemical signature of food absorbed into skeletal tissues. Stable isotopes provide quantitative information about the relative contributions of terrestrial versus marine foods, and between plant and animal sources, making it a powerful tool for understanding past subsistence practices.
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When to use it
Apply isotope diet reconstruction when seeking quantitative dietary information from skeletal remains. Most informative in contexts where faunal or botanical remains are sparse or where dietary diversity is high. Particularly valuable for distinguishing marine versus terrestrial foods, or for tracking the adoption of agricultural crops like maize. Works best with well-preserved collagen in bone or tooth. Most reliable when the isotopic baseline of available foods in the region is well-characterized through faunal and botanical studies.
Strengths & limitations
- Provides quantitative, long-term dietary information integrated over years to decades of life
- Distinguishes marine versus terrestrial food sources with high reliability
- Capable of detecting the adoption of new crops (especially C4 plants like maize) in the diet
- Works well in assemblages lacking well-preserved faunal remains
- Non-destructive sampling possible from small bone or tooth fragments
- Heavily dependent on the local isotopic baseline; poorly characterized food sources limit interpretation
- Cannot distinguish between isotopically similar food sources without additional information
- Assumes collagen preservation is good; diagenetically altered collagen yields unreliable results
- Reflects only protein sources; carbohydrate and fat contributions are not directly measurable
- Requires larger bone samples than some other isotope analyses, which may be problematic for fragile remains
Frequently asked
What does a carbon-13 enriched value indicate about diet?
Enriched carbon-13 (higher delta-13C values) can indicate consumption of C4 plants like maize, sorghum, or millet, or it can indicate marine resources (which are also enriched in C13). To distinguish between these sources, nitrogen-15 values are examined: marine diets show high nitrogen-15, while diets dominated by C4 plants show intermediate nitrogen-15. Regional context and auxiliary data help clarify which source is responsible for carbon-13 enrichment.
How does collagen preservation quality affect isotope results?
Diagenetic alteration can modify isotope ratios in bone collagen over time. Indicators of collagen quality include the carbon-to-nitrogen atomic ratio (should be 2.9-3.6) and amino acid composition. Poorly preserved samples with unusual C:N ratios or evidence of microbial colonization should be excluded from analyses. Modern mass spectrometry facilities routinely assess collagen quality before reporting isotope results.
Can isotope diet reconstruction distinguish between different animal protein sources?
Isotope analysis alone cannot reliably distinguish between herbivore (like deer) and carnivore (like bear) protein without additional information. Both are enriched in nitrogen-15 relative to plants, but the magnitude of enrichment differs slightly. Coupling isotope results with zooarchaeological evidence (faunal remains and bone surface modifications) provides the best approach to identifying protein sources.
How is the isotopic baseline established for interpretation?
The baseline is constructed by measuring isotope ratios from faunal remains (herbivores, carnivores, marine fish) and botanical remains from the same region and time period as the human remains. This establishes the range of isotope values for potential foods. If baselines are unavailable, published values from ecologically similar regions can be used, though this introduces uncertainty. Detailed faunal and botanical studies are ideally conducted alongside dietary isotope analysis.
What does high nitrogen-15 enrichment indicate?
High nitrogen-15 (high delta-15N values) indicates a diet rich in animal protein, particularly from marine sources or predatory animals. Marine diets consistently show the highest nitrogen-15 enrichment because marine food webs are longer (more trophic levels) than terrestrial systems, amplifying nitrogen-15 enrichment. Terrestrial carnivores and freshwater fish-eating populations also show elevated nitrogen-15. Vegetarian diets show low nitrogen-15 values.
Sources
- Schoeninger, M. J., & DeNiro, M. J. (1983). Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals. Geochimica et Cosmochimica Acta, 47(4), 625-639. DOI: 10.1016/0016-7037(84)90091-7 ↗
- Ambrose, S. H. (1990). Preparation and characterization of bone and tooth collagen for isotopic analysis. Journal of Archaeological Science, 17(4), 431-451. DOI: 10.1016/0305-4403(90)90007-R ↗
- Katzenberg, M. A. (2008). Stable isotope analysis: a tool for studying past diet, demography, and life history. In M. A. Katzenberg & S. R. Saunders (Eds.), Biological Anthropology of the Human Skeleton (pp. 413-441). Wiley-Liss. link ↗
How to cite this page
ScholarGate. (2026, June 3). Isotope Diet Reconstruction. ScholarGate. https://scholargate.app/en/archaeology/isotope-diet-reconstruction
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