Multivariate carbon and nitrogen stable isotope model for the reconstruction of prehistoric human diet

Using a sample of published archaeological data, we expand on an earlier bivariate carbon model for diet reconstruction by adding bone collagen nitrogen stable isotope values (δ¹⁵N), which provide information on trophic level and consumption of terrestrial vs. marine protein. The bivariate carbon model (δ¹³C_apatite vs. δ ¹³C_collagen) provides detailed information on the isotopic signatures of whole diet and dietary protein, but is limited in its ability to distinguish between C₄ and marine protein. Here, using cluster analysis and discriminant function analysis, we generate a multivariate diet reconstruction model that incorporates δ¹³C_apatite, δ¹³C_collagen, and δ¹⁵N holistically. Inclusion of the δ¹⁵N data proves useful in resolving protein-related limitations of the bivariate carbon model, and splits the sample into five distinct dietary clusters. Two significant discriminant functions account for 98.8% of the sample variance, providing a multivariate model for diet reconstruction. Both carbon variables dominate the first function, while δ¹⁵N most strongly influences the second. Independent support for the functions' ability to accurately classify individuals according to diet comes from a small sample of experimental rats, which cluster as expected from their diets. The new model also provides a statistical basis for distinguishing between food sources with similar isotopic signatures, as in a previously analyzed archaeological population from Saipan (see Ambrose et al.: AJPA 104(1997) 343-361). Our model suggests that the Saipan islanders' ¹³C-enriched signal derives mainly from sugarcane, not seaweed. Further development and application of this model can similarly improve dietary reconstructions in archaeological, paleontological, and primatological contexts. Am J Phys Anthropol, 2012. © 2011 Wiley Periodicals, Inc.