Soil analyses at Ukrainian archaeological site
They are small, inconspicuous and quite important: earthworms are thought to have been more significantly involved in the establishment of modern civilisation than previously assumed. This is suggested by findings from a study by the Collaborative Research Centre (CRC) 1266 “Scales of Transformation - Human-Environmental Interaction in Prehistoric and Archaic Societies” at Kiel University (CAU). A research team from Kiel analysed the soils at an archaeological site in the Ukraine and determined that deep-digging earthworms benefited from prehistoric farming and created fertile soils in return. This has considerable effects on the reconstruction of the “Agricultural Revolution”, which was so important for humanity and spread agriculture and livestock farming across the globe.
Soil profile analysis supports Darwin's theory
Charles Darwin dedicated a book to the earthworm in 1881. Observations and experiments led him to conclude that the worms were extremely beneficial for arable farming – in contrast to their then social condemnation as pests. Darwin also focused on the formation of arable soils. According to his theory, the earthworm played a decisive part in its formation.
The archaeological-paleoecological research team from Kiel examined the most fertile arable soils, the humus-rich black earth of Central and Eastern Europe. “The natural occurrence of this soil type is normally concentrated in the Eurasian Steppes between the Ukraine and China, which are characterised by their continental climate. Its occurrence and formation in the temperate climate zones of Central and Eastern Europe had been a puzzle for a long time,” said PD Dr Stefan Dreibrodt as the team's geoarchaeologist and soil scientist. Bearing Charles Darwin’s assumption in mind, he researched soil formation across archaeological sites in Central Ukraine where black earth occurred.
Investigations focused on the Copper Age mega-settlement of Maidanets’ke (3990–3640 BCE). It is one of the early prehistoric major settlements in which tens of thousands of people lived together. For the study, 34 soil profiles were taken from different places and were later examined in the laboratory. This revealed that all of the surrounding landscape was changed to provide food for the large population. The people who lived there cleared forests and created areas to be cultivated. “The open agricultural land now available abruptly changed conditions for all living beings. Including the earthworms. From then on, the soils were exposed to distinct heat and aridity in the summer and severe frost in the winter,” explained Dreibrodt. At the same time, the open landscape provided more food for the earthworms all year round. Deep-digging earthworms benefited from this combination as they could survive periods of heat and frost by withdrawing deep into the earth. These types of deep-digging species constantly transport material to the surface in order to keep their vertical tunnels open. By doing so, they pile organic material up on the surface of the soil – as Charles Darwin had described. This is how the humus-rich black earth was formed, layer by layer, over 5,000 years.
Earthworms as part of the Neolithic Agricultural Revolution
Around 12,000 years ago in the Fertile Crescent of the Near East – as the region between Turkey and the Arabian Peninsula is also known – people switched from using hunter-gatherer strategies to feed themselves to a settled lifestyle based on agricultural food production. This historically important step is called the Agricultural Revolution. From then on, people lived in the same place, bred cattle, cultivated crops and produced ceramics (for processing and storing the harvest, among other things). Over many centuries, these activities associated with the new Neolithic lifestyle, of which there is archaeological evidence, are spread from Anatolia through South-Eastern Europe to Central Europe in what is known as the “Neolithic package”. Although climate conditions along this route are very variable, the fertile black earth in key Neolithic zones form the dominant soils, explained Prof. Dr Eileen Eckmeier, Professor of Geoarchaeology and Environmental Risks at Kiel University.
According to her research results from the Ukraine, team leader Dreibrodt and other members of the team regard the Neolithic transformation of the landscape as the trigger for the advancement of the deep-digging earthworms. “Earthworms need to be counted as part of the Neolithic package,” said Professor Johannes Müller, spokesperson of the Collaborative Research Centre 1266. “As an element of the Neolithic package, deep-digging earthworms are the missing link between people and the soil that we have not known about until now. A milestone for archaeological research. And an innovation without which our modern civilisation would never have been established.”
Dreibrodt, S., Hofmann, R., Dal Corso, M., Bork, H.-R., Duttmann, R., Martini, S., Saggau, P., Schwark, L., Shatlio, L., Videiko, M., Nadeau, M.-J., Meiert Grootes, P., Kirleis, W., Müller, J. (2022). Earthworms, Darwin and prehistoric agriculture-Chernozem genesis reconsidered. GeodermaVolume 409, 2022. DOI: https://doi.org/10.1016/j.geoderma.2021.115607