Birch tar

Birch (bark) tar or birch pitch is a substance (liquid when heated) derived from the dry distillation of the bark of the birch tree. Birch tar/pitch is mainly composed of triterpenoid compounds of the lupane and oleanane family, which can be used as biomarkers to identify birch tar in the archaeological record. The most characteristic molecules are betulin and lupeol which are also present in birch bark. Some of these molecules degrade into other lupane and oleanane skeleton triperpenes. The most commonly found additional molecules are lupenone, betulone, lupa-2,20(29)-dien-28-ol, lupa-2,20(29)-diene and allobetulin. Birch tar was used widely as an adhesive as early as the Middle Paleolithic to early Mesolithic era. Neanderthals produced tar through the dry distillation of birch bark as early as 200,000 years ago. A study from 2019 showed that birch tar production can be a very simple process, merely involving the burning of birch bark near smooth vertical surfaces in open air conditions. However, at Königsaue (Germany), Neanderthals did not make tar with this method but rather employed a technically more demanding underground production method. A find from the Dutch North Sea and two tools from the Italian site Campitello show that Neanderthals used birch tar as a backing on small 'domestic' stone tools. Birch tar also has been used as a disinfectant, in leather dressing, and in medicine. A piece of 5,000-year-old chewing gum made from birch bark tar and still bearing tooth imprints, has been found in Kierikki in Finland. Genetic material retained in the gum has enabled novel research regarding population movements, the types of foods consumed, and the types of bacteria found on their teeth. A different chewing gum sample, dated to 5,700 years old, was found in southern Denmark. A complete human genome and oral microbiome was sequenced from the chewed birch pitch. Researchers identified that the individual who chewed the pitch was a female closely related genetically to hunter-gatherers from mainland Europe.