Soil biochemical inticators of initial presence of fat in different archaeological contexts

Abstract

The article proposes a new biochemical approach for the reconstruction of the initial presence of fat-containing products in different archaeological contexts (ceramic vessels from burials, soil samples in different parts of the skeleton and cultural layers of archaeological sites) based on the study of qualitative and quantitative changes in the parameters of the soil microbial community, namely, specific groups of microorganisms (lipolytics), a number of lipolytic enzymes, as well as the utilization spectrum of readily available low molecular weight sub-strates. Ground samples of the studied objects were collected in the following regions: ceramic vessels — the Republic of North Ossetia-Alania and the Chechen Republic; burials — Krasnodar Krai; the cultural layer of the settlement — Lipetsk region. The number of lipolytic microorganisms and the level of enzymatic activity in the soil directly depend on the amount of the incoming substrate, in the decomposition of which they participate. After the decomposition of organic residues in the soil, a microbial and enzyme pools are formed, which can persist for a long period. The obtained preliminary data on the study of the decomposition dynamics of fatty substrates give us possibility for the reconstruction of the initial presence of fat in different archaeological contexts using the methods of soil microbiology and biochemistry. But, for a more accurate extrapolation of the results of a model experiment to archaeological objects, more points of observation in time are needed, since the introduction of substrates with different properties and composition can provoke microbial community succession in different ways. Hence, the equilibrium state of the microbial community in each variant of the experiment will be reached at different times. However, the results of the study of soils and cultural layers of archaeological sites of Bronze Age and early me-dieval time have convincingly shown the possibility of applying our approach. As we assumed, the maximum li-pase activity was found in the soil samples under the skull, chest and pelvis, i.e. in areas of human body with the highest content of fat tissues. This showed the possibility for reconstruction the original contents of the vessels from burials using the methods of soil microbiology and biochemistry. A high number of lipolytic microorganisms and lipase activity were detected only in 15–20 % of the vessels. We suggest that fat food may not have been as widely used in the funeral rite as ritual food. The study of lipase activity made it possible to clarify the features of the economic usage of the territory of archaeological site, to identify possible places for cooking.