Mass spectrometric analysis of the stable carbon isotope composition (13C/12C or 
delta 13C) of bone collagen from human remains recovered at archaeological sites 
provides a direct chemical method for investigating dietary patterns of 
prehistoric human populations. This methodology is based on the facts that (1) 
different food items within the human diet have distinct delta 13C values, and 
(2) the delta 13C value of human bone collagen is determined by the delta 13C 
value of the diet. Studies of the development of subsistence patterns based on 
corn agriculture, one of the most significant developments in North American 
prehistory, can benefit from the use of stable carbon isotope techniques because 
corn has a high delta 13C value relative to other components of the human diet. 
Measurements of delta 13C of bone collagen from prehistoric human skeletal 
remains from southeastern Missouri and northeastern Arkansas indicate that 
intensive corn agriculture began in this region around A.D. 1000, that the 
incorporation of corn into the human diet was a rapid phenomenon, and that 35 to 
77% of the human diet from A.D. 1000 to A.D. 1600 consisted of corn. Results 
from an isochronous population in southeastern South Dakota (A.D. 1400) suggest 
that 78 to 90% of the diet of this group consisted of corn, with no difference 
between males and females. Coupled with more traditional archaeological methods, 
stable carbon isotope analysis of bone collagen can significantly enhance 
reconstruction of dietary patterns of prehistoric humans.