Proceedings of the Royal Society B published a study in which Danish researchers extracted DNA and chemical fingerprints from 30 pieces of birch bark tar recovered at nine Alpine lakeside settlements, some as old as 6,300 years. The work was led by archaeologist Ana White of the University of Copenhagen, and most of the samples came from Neolithic stilt-house communities around the region’s lakes, Science Alert reported.
Birch bark tar, produced by heating bark in low oxygen, is the earliest synthetic material on record. Phys.org noted that Neolithic farmers used it to haft stone blades, seal cracked pottery, and chew it much like modern gum.
White’s team combined gas chromatography–mass spectrometry with ancient DNA sequencing. Twenty-nine samples carried the chemical signature of birch tar, and DNA was retrieved from 28. The sex of 16 individuals was determined—an unusually high rate for material of this age. Twelve pieces were loose wads bearing tooth marks; the rest adhered to flint blades or pottery repairs.
Residues on the tar revealed traces of barley, wheat, peas, beech, and hazel. Repaired pots contained DNA from peas, hazelnuts, and sheep, while tool adhesives carried wild boar and fish. Poppy DNA appeared repeatedly; the authors wrote that “it’s unclear if the poppy seeds were eaten as food or for their opioid effects.”
Female DNA occurred on three tar plugs used to mend pots, whereas male DNA dominated ten tool adhesives. “We must remember that these are extremely small populations we are studying here, over enormous time spans,” said Håkon Glørstad of Oslo’s Museum of Cultural History.
Chemical tests showed that some tar had been blended with conifer resin, a mix that altered its mechanical properties. The researchers also confirmed that saliva softened tar, making it workable until reheated.
“The exact reason for chewing this material is unclear, but it is likely that it was chewed for medicinal purposes, as it contains natural compounds with antimicrobial properties,” said White.
With human bones scarce in Alpine Neolithic sites, tar wads serve as genetic time capsules, preserving human genomes and oral microbiomes. The adhesive itself reaches back nearly 200,000 years to Neanderthals and remained in use into the Roman era; in the Alpine villages under study, people made and chewed birch tar for at least 3,500 years.
The team argued that combining residue chemistry with genomic analysis could unlock information from the many resin lumps stored in European museums. “What was previously just an object, a lump of resin from the Stone Age, has suddenly become something that can give us a lot of new knowledge,” said Glørstad.
The preparation of this article relied on a news-analysis system.