Neanderthals may have used birch tar as a medical tool to ward off infections and insect bites. A recent study found that distilled birchtar could have been used as a medicine for frequent injuries. The study also revealed that Neanderthals also knew how to extract birch bark and used it as an adhesive to haul weapons. The most efficient method involves burning a roll of bark in a clay vessel, heating it to create a tarry resin, and using a tin can instead of a clay bowl. The researchers tested the tar against cultures of Staphylococcus aureus and E. coli.