Approximately 10,000 Years Ago, Teenagers in What Is Now Western Sweden Chewed Wads of Birch Bark Pitch and Spat Them Out, and the Saliva Preserved in the Wads Contained Enough Human and Microbial DNA that Scientists Have Since Sequenced the Chewers’ Complete Genomes, Identified the Food They Had Eaten that Day, and Detected the Bacterial Signature of Their Gum Disease.

Why It Matters

The research opens a new, reliable avenue for retrieving ancient DNA where skeletal remains are scarce, reshaping our understanding of Mesolithic populations and their health. It also provides unprecedented, individual‑level insight into diet and disease that traditional archaeology cannot achieve.

Key Takeaways

• Birch bark pitch preserved saliva DNA for 10,000 years
• Genomes link chewers to Western Hunter‑Gatherer ancestry
• DNA reveals diet of deer, trout, duck, hazelnuts, crab apples
• Oral microbiome shows >70% chance of periodontitis
• Pitch offers new source for ancient DNA beyond bones

Pulse Analysis

The discovery that chewed birch bark pitch can act as a time‑capsule for ancient DNA marks a paradigm shift in archaeogenetics. While bone and tooth fragments have long been the primary reservoirs for genetic material, they survive only under specific preservation conditions. Pitch, by contrast, benefits from its intrinsic antimicrobial compounds and anaerobic burial in marine clay, allowing saliva, cells and oral microbes to remain intact for ten millennia. This unique preservation chemistry expands the geographic and chronological reach of DNA studies, especially in regions like Scandinavia where skeletal remains are often poorly conserved.

The 2019 and 2024 investigations of the Huseby Klev wads delivered a multidimensional portrait of three Mesolithic youngsters. Genome‑wide analysis placed them firmly within the Western Hunter‑Gatherer gene pool, confirming continuity with other Scandinavian foragers. Simultaneously, plant and animal DNA traced a diet of red deer, brown trout, duck, hazelnuts and crab apples, while the presence of mistletoe hints at the use of toxic compounds for hunting. Perhaps most striking, the oral microbiome data indicated a greater than 70 % probability of periodontitis, reflecting the harsh dental wear and lack of oral care typical of hunter‑gatherer societies.

Beyond the immediate findings, the study underscores the untapped potential of ancient chewing gum as a genetic archive. Subsequent work on a 5,700‑year‑old Danish pitch sample has already demonstrated similar success, suggesting a broader applicability across Europe and possibly other continents. As sequencing technologies become more sensitive and cost‑effective, researchers can systematically screen existing pitch collections, unlocking personal-level data for populations previously invisible to the genetic record. This could revolutionize reconstructions of migration, diet, health and cultural practices, offering a richer, more nuanced narrative of human prehistory.