5,700-year-old piece of gum reveals the complete DNA of a prehistoric woman

A small lump of chewed birch pitch found on the island of Lolland held an unusually rich record of one person’s life. Scientists recovered human DNA, mouth microbes, and food traces from a single piece of resin that still showed tooth marks.

The find dates to about 5,700 years ago, right as farming was spreading into southern Scandinavia. It offers a rare human snapshot from a site without any buried skeletons.

Precise dating of DNA from gum

The work was led by Theis Z. T. Jensen at the Globe Institute, University of Copenhagen (GIUC).

In this study, the team reconstructed a complete ancient human genome from a chewed birch pitch that calibrates to between 5,858 and 5,661 years before present.

The researchers used radiocarbon dating to fix the age of the gum, then confirmed the material as birch pitch using Fourier transform infrared spectroscopy and gas chromatography mass spectrometry.

Those tests picked out chemical markers typical of pitch, including betulin and related compounds.

Chewing likely softened the resin for toolmaking, since fresh pitch hardens as it cools. Ethnographic records and chemistry also point to mild antiseptic properties, which could have made it a handy mouth cleaner in a pinch.

The Syltholm site preserved organic materials exceptionally well. Even so, the only direct human material from the site is this one chewed piece of pitch.

How they pulled DNA from gum

Sequencing produced roughly 390 million DNA reads, and about one third aligned to the human reference genome.

That volume of authentic ancient DNA made it possible to rebuild the woman’s genome to an average depth of 2.3x.

The researchers were able to build a complete version of her mitochondrial DNA and found that it belonged to a group called K1e, which was one of the maternal lineages present in prehistoric Europe.

“The results highlight the potential of chewed birch pitch as a source of ancient DNA,” wrote Jensen. This line captures why the gum matters for both archaeology and genetics.

Ancient DNA studies often rely on teeth or dense bone. This result shows that masticated pitch can sometimes match those tissues in how much human DNA it can hold.

What her DNA reveals

The sex determination analysis showed the chewer was female, based on how the reads mapped to the X and Y chromosomes.

Her genomic profile clusters with Western hunter gatherers rather than early farmers or eastern hunter gatherers.

“We also find that she likely had dark skin, dark brown hair and blue eyes,” wrote Jensen. Trait predictions using the HIrisPlex S system point to dark skin, dark brown hair, and blue eyes. 

The genome lacks the key European variants for lactase persistence, so she was likely lactose intolerant as an adult. That fits a period before dairy tolerance rose to high frequencies in Europe.

Where she fits in prehistory

Genetic affinity tests show no detectable influx from eastern hunter gatherers or Anatolian farmers.

In southern Denmark around 3700 BC, at least some people still carried a largely hunter gatherer gene pool despite visible shifts in tools and pottery.

Later research documents strong natural selection on several pigmentation genes during the last few thousand years in Europe.

That helps explain why light skin spread later, while blue eyes appear in some earlier hunter gatherers.

These patterns suggest culture and genes do not always move in lockstep. Farming practices may arrive through contact and learning before ancestry profiles change.

The mouth microbes

Beyond human DNA on the gum, the pitch held a detailed oral microbiome profile. The mix of bacteria matched what is typical for the human mouth, including commensal species common today.

The team detected members of the red complex associated with periodontal disease, such as Porphyromonas gingivalis and Treponema denticola.

Those organisms are opportunists that can flourish under certain conditions and contribute to gum disease.

They also recovered sequences from Streptococcus pneumoniae and Epstein Barr virus. Streptococcus pneumoniae is a major cause of invasive disease in people today.

Finding ancient pathogen DNA does not prove active illness in this woman. It does show that many familiar microbes already shared our mouths thousands of years ago.

What she ate that day

Plant and animal DNA in the pitch point to hazelnut, Corylus avellana, and mallard, Anas platyrhynchos. These foods were common in coastal and woodland diets across Mesolithic and early Neolithic Scandinavia.

Those reads probably reflect a recent meal before the chewing session. The presence of birch DNA, unsurprisingly, comes from the pitch itself.

Ancient gum, DNA, and modern science

Chewed pitch opens doors at sites where human bones are missing or too fragile. It can capture ancestry, traits, oral ecology, and even dietary hints from a few mouthfuls of resin.

New work extends the approach to other places and periods. A 2024 paper from Sweden reports that Mesolithic chewers had signs consistent with poor oral health, and shows that ancient pitch can track diet and microbial imbalance.

These studies turn everyday actions into scientific evidence. A brief chew can preserve a trove of information about bodies, habits, and environments long after bones have vanished.

The study is published in Nature Communications.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates. 

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–