Ancient Chewing Gum DNA

Discovering how humans lived 10,000 years ago often relies on analyzing dry bones or stone tools. However, a recent breakthrough in paleogenetics has come from a much humbler source: ancient chewing gum. Researchers have extracted DNA from birch bark pitch found at a site in Sweden, unlocking a treasure trove of information about the diet, oral health, and genetics of Mesolithic hunter-gatherers.

The Time Capsule in the Pitch

The artifacts in question are lumps of masticated birch bark pitch (or tar), dating back approximately 9,700 to 10,000 years. These were originally excavated in the early 1990s at Huseby Klev, a Mesolithic site north of Gothenburg in western Sweden. While archaeologists knew these lumps were human-made, the technology to fully analyze them did not exist at the time of their discovery.

Recently, a team led by Anders Götherström at Stockholm University re-examined these ancient “chewing gums.” Birch pitch was a common substance in the ancient world. It was produced by heating birch bark to create a sticky, black glue used for hafting tools, such as attaching stone arrowheads to wooden shafts. However, the presence of tooth marks suggests that teenagers and children frequently chewed the pitch. Whether they did this to make the substance pliable for work, to clean their teeth, or simply for enjoyment remains a topic of discussion among anthropologists.

Because birch pitch is water-resistant (hydrophobic), it acts as an incredible preservative. It protects the DNA trapped inside from degrading as quickly as it would in bone or soil. This allowed researchers to sequence the genomes of three specific individuals who chewed the gum: two females and one male.

A Menu from the Mesolithic Era

One of the most remarkable aspects of this study is the ability to reconstruct exactly what these individuals had been eating. The pitch trapped DNA fragments of plants and animals that were present in the mouth at the time of chewing. This provides a snapshot of a specific meal rather than a general diet inferred from bone isotopes.

The genomic analysis revealed a diverse hunter-gatherer menu including:

• Hazelnuts: A staple high-energy food source for early Europeans.
• Trout: Indicating fishing was a primary survival strategy.
• Red Deer: A common game animal in the region.
• Mallard Duck: Showing the consumption of waterfowl.
• Fox: Evidence suggests they may have processed foxes for fur or food.

This list confirms that the people of Huseby Klev utilized a broad spectrum of resources available in their Scandinavian environment. The presence of hazelnut DNA is particularly common in Mesolithic finds, suggesting these nuts were a critical calorie source that could be stored for winter.

Bacterial Fingerprints and Oral Health

Beyond diet and human genetics, the chewing gum provided a detailed look at the microbiome of these ancient people. The researchers successfully identified several species of oral bacteria that still affect humans today.

The analysis showed a microbiome distinct from modern populations but with recognizable pathogens. The team found significant traces of:

• Porphyromonas gingivalis: A primary bacterium associated with severe gum disease (periodontitis).
• Treponema denticola: Another contributor to periodontal disease.
• Streptococcus pneumoniae: A pathogen linked to pneumonia.

Perhaps most interestingly, the gum contained traces of Streptococcus mutans, the main culprit behind tooth decay and cavities. Historically, it was believed that cavities became common only after the Neolithic transition to farming, when diets shifted toward carbohydrate-rich grains. Finding cavity-causing bacteria in hunter-gatherers suggests that their consumption of starchy plants (like hazelnuts) or perhaps honey was sufficient to cause dental issues long before agriculture took hold.

The Technology Behind the Discovery

The method used to extract this information is known as metagenomics. Instead of looking for a specific gene, scientists sequence all the DNA found in a sample and then use powerful computers to sort the fragments. They compare these fragments against massive databases of known genomes to identify which pieces belong to humans, which belong to animals, and which belong to bacteria.

This approach is revolutionizing archaeology. In the past, determining the sex of a skeleton required a well-preserved pelvis or skull. Now, a chewed piece of birch tar can reveal that a specific individual was female, had dark skin and blue eyes (a common combination for European hunter-gatherers of that era), and had recently eaten duck.

This study aligns with similar findings, such as the “Lola” specimen found in Denmark. In that case, a 5,700-year-old piece of pitch revealed a complete human genome plus evidence of the Epstein-Barr virus. The Huseby Klev study pushes this timeline back significantly further, proving that DNA can survive in these resinous materials for ten millennia.

Implications for History

The Huseby Klev findings paint a vivid picture of life in Scandinavia 10,000 years ago. We now see these individuals not as primitive stereotypes but as people with complex diets and health struggles similar to our own. They hunted deer, fished for trout, and snacked on hazelnuts. They sat together, perhaps repairing tools with sticky pitch, and suffered from gum disease and toothaches.

This research validates birch pitch as a premier source of ancient DNA. As archaeologists revisit collections in museums around the world, many more overlooked lumps of black tar may turn out to be biological time capsules waiting to be read.

Frequently Asked Questions

What is the ancient chewing gum made of? The “gum” is actually birch bark pitch. It is a tar-like substance created by heating the bark of birch trees. Ancient humans used it primarily as a glue for making tools, but they also chewed it.

Why did ancient people chew birch pitch? There are three main theories. First, chewing the pitch made it warm and pliable, which was necessary for using it as glue. Second, birch bark contains betulin, which has antiseptic properties, so it may have been used to treat gum pain or clean teeth. Third, it may have simply been a way to suppress hunger or pass the time.

How does the DNA survive for 10,000 years? Birch pitch is hydrophobic, meaning it repels water. Water is one of the main agents that breaks down DNA over time. The resin acts as a sealed protective casing, preserving the genetic material much better than porous bone or soil.

What did the researchers find in the gum? They found human DNA (determining the sex and genetic ancestry of the chewers), DNA from food (hazelnuts, trout, deer, duck), and DNA from oral bacteria (including those that cause gum disease and pneumonia).

Where is Huseby Klev located? Huseby Klev is an archaeological site located on the island of Orust, north of Gothenburg on the western coast of Sweden. It dates back to the Mesolithic period.