Organic grave good-related soil microorganisms: Read-out of soil biological memory for archaeological research

Abstract

Soil biological memory is information about soil forming conditions in the past, “recorded” in the form of living, dead and mineralized organisms, traces of their functioning in the soil, and products of their postmortem transformations. The most sensory part of soil biological memory is the microbial memory of soils. Under this term, we propose to understand the ability of various groups soil microbiota to change their structure, functional diversity and activity as a result of impact of natural or anthropogenic factors, and to preserve these changes indefinitely long time. The time frame for the functioning of the soil biological memory is several thousand years. This feature of the microbial memory of soils can be used for archaeological reconstructions. The aim of the study is to reveal specific groups of microorganisms and particularities of soil enzyme activity to reconstruct funeral rite of ancient populations (food in ceramic vessels, clothing of the deceased and decorations of the funeral bed). Soils of archaeological sites of different ages (3200 BCE – 600 CE), located in the Dry steppe zone of the East European Plain (Russia) and in Ararat Plain (Armenia) were investigated.

It has been shown that the high number of lipolytic microorganisms and high level of lipase activity are in soil inside the funeral pots are reliable indicators of the presence of fat food. In the burials of the Bronze Age and the Early Medieval time fatty foods were found in 10% of pots. The high number of keratinophilic fungi is an indicator of the entry of large volumes of keratin-containing substrates (wool, feathers) into the soil and allowed us to reconstruct the clothing of the deceased and decorations of the funeral bed. The abundance of keratinophilic fungi in soil under the feet of the skeleton in Bronze Age burials may indicate the use of wool felted shoes.