Research reveals freshwater mussel shells were material of choice for prehistoric craftsmen

An international team of researchers, including academics from the Universities of York and Bradford, extracted ancient proteins from prehistoric shell ornaments - which look remarkably similar despite being found at distant locations in Denmark, Romania and Germany - and discovered they were all made using the mother-of-pearl of freshwater mussels.

The ornaments were made between 4200 and 3800 BC and were even found in areas on the coast where plenty of other shells would have been available.

Archaeological evidence suggests the ornaments, known as "double buttons", may have been pressed into leather to decorate armbands or belts.

Dr Hannah Koon, Director of the Light Stable Isotope facility at Bradford and co-author on the paper said: "Tracing the geographical origin of the raw material used to make archaeological shell ornaments is challenging; however, stable isotopes can be used to provide important palaeoenvironmental information. This is because the isotopic composition of the mineral component of shells records the environmental conditions, including temperature and salinity, at the time when the organisms were growing. The stable isotope values of carbon and oxygen, indicated that the shells analysed in this study were formed in freshwater environments, and δ18O values in the shell mineral yielded the average annual δ18O values typical of local precipitations indicating the shells were locally sourced."

Senior author of the study, Dr Beatrice Demarchi, the Department of Archaeology at the University of York and the University of Turin (Italy), said: "We were surprised to discover that the ornaments were all made from freshwater mussels because it implies that this material was highly regarded by prehistoric craftsmen, wherever they were in Europe and whatever cultural group they belonged to. Our study suggests the existence of a European-wide cross-cultural tradition for the manufacture of these double-buttons".

Freshwater molluscs have often been overlooked as a source of raw material in prehistory (despite the strength and resilience of mother-of-pearl) because many archaeologists believed that their local origin made them less "prestigious" than exotic marine shells.

"Palaeoshellomics" reveals the use of freshwater mother-of-pearl in prehistory is published in the journal eLife.

The School of Archaeological and Forensic Sciences has dedicated Light Stable Isotope laboratory facilities to accommodate staff, student and external projects. They specialise in the application of isotopic tools to address questions in archaeological, anthropological, environmental, palaeodietary, climate and forensic research. Housed in the Norcroft Building the facility recently received a large investment award from the University to update its instrumentation.

The research was carried out by researchers at the University of York, University of Turin and Ca' Foscari University (Italy), Universities of Burgundy-Franche-Comté and Lille (France), the University of Bradford (UK), the Moesgaard Museum (Denmark), the Landesamt für Denkmalpflege im Regierungspräsidium Stuttgart and the Niedersächsisches Landesamt für Denkmalpflege (Germany).