Diet at the medieval stronghold of Kalisz-Zawodzie (Poland): Carbon and nitrogen stable isotope analysis of bone collagen

The Early Middle Ages saw a rise in social stratification within the early Polish state, with various symbols used by different social groups to signal their status. One potential symbol of status was diet. However, previous studies have been inconclusive in determining the role of diet as a marker of social status. This study aims to examine dietary variations in an elite, medieval (12th-13th c.) cemetery at St. Paul's Church in Kalisz-Zawodzie. For this purpose, 40 samples of human and animal remains underwent analysis of stable carbon and nitrogen isotope ratios in bone collagen. Sufficient collagen was found in 34 samples (27 human and 7 animal samples). A comparison between adults (n = 17; delta 13 C:-20.6 to-18.7%o; delta 15 N: 8.7 to 12.6%o) and post-weaning children (n = 10; delta 13 C:-20.7 to-19.1%o; delta 15 N: 8.4 to 10.2%o) revealed a significant difference in delta 15 N values (p = 0.021), indicating distinct diets between these groups. The differences between subadults and adults appear to be an effect of dietary variation among adults. Some adults consumed significant amounts of food items of high delta 15 N (proteins of omnivores or fish). Among those food items, larger fish, characterized by higher delta 15 N values, were previously indicated as a luxury good. In this context, the role of diet in expressing social status is discussed.