Using stable isotope analysis to obtain dietary profiles from old hair: A case study from Plains Indians

Stable isotope composition of human tis- sue reflects that of foods consumed, and can provide information about diet independent of artifactual remains. Here we refine and test this method by analyz- ing nitrogen (d 15 N) and carbon (d 13 C) isotope ratios in historic North American Plains Indians hair. Gas-source isotope-ratio mass spectrometry provides high-precision data for both d 15 N and d 13 C( 60.2% ,1 s) in single hair strands as short as 2 cm (100-150 mg). Because hair con- tains more carbon than nitrogen, if only d 13 C data are needed, shorter strands (<1 cm) can be analyzed. This reduction in sample size opens new opportunities for analysis of small hair fragments found in archaeological excavations, as well as for analysis of seasonal variations in long hair strands. We find distinct isotope profiles (d 15 N vs. d 13 C) for two cultural groups, the Lower Brule reservation Sioux of 1892 and the reservation Blackfoot of 1892 and 1935. The resultant dietary profiles indicate a higher consumption of meat by the Blackfoot and a higher consumption of maize (or of animals that had fed on maize or other C4 plants) by the Lower Brule. The two groups of Blackfoot yield similar isotopic profiles despite the passage of four decades, suggesting a strong role for cultural preference even as food sources change. Such stable isotope profiles can be used to link samples from the same cultural tradition based on their similar diets. Am J Phys Anthropol 128:444-452, 2005. ' 2005 Wiley-Liss, Inc.