Prehistoric craftsmen sought freshwater mussels for their ornamental shell

May 7 (UPI) -- Some 6,000 years ago, the freshwater mussel served as the ornamental shell of choice for prehistoric craftspeople.

When researchers analyzed ornamental shells from across prehistoric Europe, they found the artifacts were all composed of mother-of-pearl from freshwater mussels.

The so-called double-buttons, which would have been pressed into leather bracelets and belts, were found in Denmark, Germany and Romania. They were made between 4200 and 3800 BC. Some of the ancient ornaments were found among coastal sites, where a variety of shells would have been available.

Archaeologists have previously overlooked freshwater mollusks as a source material for cultural objects. Researchers assumed their ubiquity would have made them less appealing, and thus less valuable and sought after.

"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," Beatrice Demarchi, an archaeologist at the University of York, said in a news release. "Our study suggests the existence of a European-wide cross-cultural tradition for the manufacture of these double-buttons."

The ornaments date to a period of change in continental Europe. Many of the people of Europe were still hunter-gatherers, but in the south, farmers from the Mediterranean were importing news ways of living. Soon, farming and new cultural traditions would transform all of Europe.

Despite the cultural and socioeconomic fragmentation and instability, the latest findings suggest the region's disparate groups shared some cultural and technological traditions.

"The fact that these ornaments look consistently similar and are made from the same material suggests there may have been some kind of interaction between these distinct groups of people at this time," said York archaeologist Andre Colonese. "They may have had a shared knowledge or tradition for how to manufacture these ornaments and clearly had a sophisticated understanding of the natural environment and which resources to use."

The findings -- published this week in the journal eLife -- were made possible by a new method for extracting proteins from mollusk shells.

"This is the first time researchers have been able to retrieve ancient protein sequences from prehistoric shell ornaments in order to identify the type of mollusk they are made from," Demarchi said.