Palaeodietary implications from stable isotopic analysis of residues on prehistoric Ontario ceramics

Stable isotopic analyses of charred residues encrusted on the interiors of ceramics can be used to infer the nature of the foods that were prepared in the ceramics. We have analysed residues from archaeological sites in Northern and Southern Ontario, from both before and after AD 600, the time of the introduction of agriculture to this region which was largely based on maize. The residues appear to be mainly composed of mixtures of C3 plants, and the flesh of herbivores and fish. δ13C values show that only minor amounts of maize are present after AD 600, sufficient to produce a general increase in the average δ13C value with time. Earlier isotopic studies of human bone collagen from this region show consumption of maize rising from zero to about 50 to 60% of the diet from AD 600 to 1200; much smaller proportions of maize than this are seen in the charred residues. A significant fraction of the 13C-enriched carbon that is present in the residues may represent meat from animals (such as dog or bear) that have fed on maize, rather than the result of cooking maize itself. The large amounts of dietary maize consumed cannot have been included in the stewed meals described by the Jesuits but other prepared foods such as bread must have been consumed as well. The absence of a post-agricultural shift in δ15N shows that beans did not become an important food, and this is consistent with the evidence from the bone collagen analyses. Fish were a significant source of protein at all times.