Birch tar
Birch tar or birch pitch is a substance (liquid when heated) derived from the dry distillation of the bark of the birch tree. Compounds. It is composed of phenols such as guaiacol, cresol, xylenol, and creosol. Ancient and modern uses. 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. A rare find from the Dutch North Sea shows that Neanderthals used birch bark tar as a backing on small 'domestic' stone tools. Birch tar also has been used as a disinfectant, in leather dressing, and in medicine. 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. Ends of fletching of arrows were fastened with birch-tar and birch-tar-and-rawhide lashings were used to fix the blade of axes in the Mesolithic period. Russia leather is a water-resistant leather, oiled with birch oil after tanning. This leather was a major export good from seventeenth and eighteenth century Russia, as the availability  of birch oil limited its geographical production. The oil impregnation also deterred insect attack and gave a distinctive and pleasant aroma that was seen as a mark of quality in leather. Birch tar is also one of the components of Vishnevsky liniment. Birch tar oil is an effective repellent of gastropods. The repellent effect lasts about two weeks. The repellent effect of birch tar oil mixed with petroleum jelly applied to a fence lasts up to several months. Birch tar oil has strong antiseptic properties owing to a large amount of phenol derivatives and terpenoid derivatives. Birch tar oil also  is used in perfumery as a base note to impart leather, tar, smoky, and wintergreen notes. It is used as an ingredient in some soaps, notably being the scent of Imperial Leather.