Interpretation of bulk nitrogen and carbon isotopes in archaeological foodcrusts on potsherds

Abstract

Rationale Foodcrust, the charred deposit adhering to the surface of containers, is a possible source of information on the function of ancient vessels and the subsistence of prehistoric humans. While the carbon isotope ratios in those materials are useful in detecting the usage of C4 plants, the reliability of nitrogen isotopic signatures has not been fully investigated. Methods The validity of bulk nitrogen isotope ratios has previously been investigated in coastal or riverine environments, where multiple resources from terrestrial and aquatic ecosystems were available, but not in terrestrial settings which provide a simpler mixing of terrestrial animals and plants. Hence, we conducted an exhaustive study on charred deposits on potsherds at two inland archaeological sites belonging to prehistoric Jomon hunter‐gathers in central Japan, focusing on δ15N values and atomic N/C ratios determined using an isotope ratio mass spectrometer and an elemental analyzer, respectively. Results For both sites, the δ15N values showed significant correlations with the N/C ratios among samples from the inner surface, suggesting that these have recorded animal contribution. Furthermore, previous studies of Neolithic pottery from North Europe and Far East Russia bearing strong marine signatures had shown reasonably higher δ15N values and N/C ratios in comparison with our data from terrestrial settings. On the other hand, some charred materials probably originating from plant starch showed lower values with both parameters. Samples from the outer surface produced less meaningful isotopic and elemental ratios altered by a thermal effect and/or contamination from soot. Conclusions When the samples of foodcrusts were selected carefully from the inner surface, bulk nitrogen isotopes and N/C ratios reflect the composition of what was cooked or processed in containers. This will provide useful information for understanding the human adaptation from the Late Pleistocene to the Holocene in conjunction with residual lipid analyses.

The impact of cooking and burial on proteins: a characterisation of experimental foodcrusts and ceramics

“…Lipid analysis of foodcrusts has considerably improved our understanding of ancient diet and particularly of marine resource utilisation. The method has been applied to detect food in assemblages across a vast geography spanning Europe and Northern Asia [24,[26][27][28][29][30][31][32] East Asia [25,[33][34][35][36][37] and the Americas [22,38], and to select samples that do not contain aquatic resources for use in carbon dating, which are thus unhindered by the reservoir effect [23].…”

Lipids in Archaeological Pottery: A Review on Their Sampling and Extraction Techniques

“…A surface residue on the vessel’s outer walls may derive from soot deposited during cooking activities on the fire. In contrast, visible burnt residues adhering to the inner wall of a container can result from the charring of food [ 6 , 7 , 8 , 9 ]. More commonly, organic residues occur as invisible absorbed material within the porous unglazed vessel wall.…”