Birch bark tar

Did You Know?

• Birch bark tar is mainly composed of triterpenoid compounds of the lupane and oleanane family, which serve as biomarkers for its identification in the archaeological record.
• The most characteristic molecules in birch bark tar are betulin and lupeol, also present in birch bark.
• Commonly found additional molecules include lupenone, betulone, lupa-2,20(29)-dien-28-ol, lupa-2,20(29)-diene, and allobetulin.

Ancient and modern uses

Birch bark tar was employed as an adhesive from the Middle Paleolithic onward. Neanderthals at Königsaue in Germany used an underground production method, though a 2019 study showed that simpler open-air production by burning bark under overhanging stone was possible. Finds from the Dutch North Sea and the Italian site Campitello indicate Neanderthals applied birch bark tar as backing on small domestic stone tools. The substance also served as a disinfectant, in leather dressing, and in medicine. A 5,000-year-old piece of chewing gum made from birch bark tar, bearing tooth imprints, was discovered in Kierikki, Finland; genetic material from it allowed research into population movements, diet, and oral bacteria. Another chewing gum sample, 5,700 years old from southern Denmark, yielded a complete human genome and oral microbiome, revealing the chewer was a female closely related to mainland European hunter-gatherers. During the Mesolithic, birch bark tar fastened arrow fletching and, with rawhide lashing, fixed axe blades. From the Neolithic to the Iron Age, it was frequently found in archaeological contexts, used as an adhesive to repair and decorate ceramic vessels and as a sealing or waterproofing agent. Ötzi’s hafted arrow points and copper axe exemplify its use in the Copper Age. Birch bark tar also assembled metal artefacts like pendants and ornaments functionally and decoratively. In the Roman Era, wood tar largely replaced it, but birch bark tar continued to be used, for instance, to decorate hinges and other bone objects.