Food is essential to life, and is an important and integral part of the archaeological record. Archaeology facilitates examination of ancient food, using those results to define our understanding of culture and chronology. Radiocarbon dating charred food crust presents challenges. We have mastered issues of recovery and lab treatment, but archaeology retains assumptions about food being a simple representation of the past. Now we ask, are these records all they appear to be and only what they appear to be? How do the principles of cooking chemistry help understand radiocarbon dating charred food in vessels?
From one Oneota (Blood Run) vessel sampled in three locations we obtained three radiocarbon dates including two that are congruent (from the rim and the exterior shoulder) and one discrepant (from the upper interior wall), pointing to the importance of understanding your sample of charred material. It also provides an example of the importance of understanding cooking chemistry. Multiple paired charred food crust and annual samples from southeastern Iowa and other locations show the effectiveness of chemical pretreatment to obtain congruent dates.
Our NSF grant was awarded to develop a chemical pretreatment method that would produce congruent dates on paired charred food crust and annual samples. We are studying dates produced on charred food obtained from rim vs. body sherds from the same vessel. A repeat of the concept of dating multiple samples from different areas of the same vessel should be paired with an annual from the same context allows us to confirm which dates are congruent. We combine our knowledge of archaeology, food chemistry, lab chemistry, and radiocarbon dating with a healthy dose of curiosity to produce recommendations and methods that will yield more accurate dates on charred food crust, as well as identify when the food cooked in the vessel just cannot yield an accurate date. We show the pitfalls of attempting a freshwater reservoir correction factor and discuss radiocarbon dates obtained on reference fish and other reference animal bones.