A new study explores whether birch tar, long associated with Neanderthal toolmaking, may have served another purpose as well.
In a new study from the University of Cologne, the University of Oxford, the University of Liège, and Cape Breton University in Canada, researchers recreated birch tar using techniques associated with Neanderthals and tested whether it could slow bacterial growth.
Their results suggest the material may have done double duty in prehistoric life, helping attach stone tools while also offering a way to treat wounds. The study was published in PLOS One.
That possibility makes birch tar more than a technical material. It raises the question of whether Neanderthals recognized useful healing properties in natural substances and applied them deliberately.
More Than an Adhesive
Birch tar is a thick substance made from birch bark and is commonly found at Neanderthal archaeological sites in Europe. Because traces of it are often attached directly to stone artifacts, archaeologists have long thought its main use was as an adhesive for hafting. Hafting is the process of joining separate parts together, such as when making tools.
“However, new studies suggest that birch tar may also have been used for other purposes,” says Tjaark Siemssen of the University of Cologne and Oxford University, who is leading the current study.
Ethnographic evidence from many parts of the world shows that birch tar has also been used for medicinal purposes, among other uses.
“Alongside these findings, there is also growing evidence of medicinal practices and the use of plants among Neanderthals, which is why we were interested in the use of birch tar in this context,” says Siemssen.
Recreating Neanderthal Production Methods
The researchers experimentally produced tar from birch species that already existed during the Neanderthal era. They used extraction methods reconstructed from Neanderthal contexts.
In one method, birch bark was burned underground in a sealed pit. Without oxygen, dry distillation occurs, releasing birch tar from the bark. In another method, birch bark was burned next to a hard surface, such as a stone, so the tar condensed on the stone.
Testing Its Antibacterial Effects
The researchers then tested the birch tar samples to examine their antimicrobial properties. Every sample was able to hinder the growth of Staphylococcus aureus bacteria. S. aureus is a major cause of wound infections and is now classified as a multidrug-resistant hospital-acquired pathogen.
The antibacterial effect appeared in tar produced by all of the extraction methods. “The findings suggest that antimicrobial properties played a role as far back as the time of the early Neanderthals and could have been used in a targeted manner,” explains Siemssen.
Relevance for the Present
Along with offering new insight into Neanderthal culture, the findings may also matter today because of the global rise in bacterial resistance to common antibiotics.
“Our findings show that it might be worthwhile to examine targeted antibiotics from ethnographic contexts – or, as in this case, from prehistoric contexts – in greater depth,” concludes Siemssen.
Reference: “Antibacterial properties of experimentally produced birch tar and its medicinal affordances in the Pleistocene” by Tjaark Siemssen, Aderonke Oludare, Marcel Schemmel, Janos Puschmann and Matthias Bierenstiel, 18 March 2026, PLOS ONE.
DOI: 10.1371/journal.pone.0343618
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