In recent years, it has become evident that limitations exist in our ability to meaningfully assess
palaeodiet using stable isotope compositions. These limitations in part arise because many of
the fundamental assumptions about tissue-diet relationships are poorly understood. In order
to redress this deficiency, a controlled feeding experiment was undertaken to define the
impact of terrestrial- vs. marine-derived dietary protein consumption on consumer tissue
carbon isotopic compositions (δ13C). Two generations of pigs were raised on one of five
feeds with varying proportions of terrestrial (soy) and marine (fish meal) protein. A
comprehensive range of tissues and fluids from 49 pigs was submitted for δ13C analysis.
The observed tissue–whole diet and tissue–dietary protein carbon isotopic offsets were
found to be highly dependent on the percentage of marine protein in diet. We suggest that
the trend in δ13C offsets most likely derives from the increased routing of non-essential
amino acids, especially glycine, with the increasing proportion of marine protein in the diet.
These findings demonstrate that solely using bulk δ13C compositions not only masks
considerable information about diet, but may also lead to erroneous representations of
marine and terrestrial resource consumption in the past.
- carbon isotopes
- palaeodietary reconstruction
- dietary routing
- Amino acids