Quirks & Quarks

Ancient chewing gum reveals reveals identity of chewer and what she ate

5,700 year-old gum preserved the genome of a dark-haired, blue-eyed woman who'd eaten duck for dinner.

5,700 year-old gum preserved the genome of a dark-haired, blue-eyed woman who'd eaten duck for dinner

5700 year old gum discovered in a stone age archeological site in southern Denmark contained an entire human genome and microbial DNA. (Theis Jensen)
Listen8:43

Discovering old, used chewing gum is rarely a cause for celebration. It's a little different, though, when that gum is found in a nearly 6,000-year-old archeological site and preserves the genome of the Neolithic woman who was chewing it.  

The gum was found on an island in southern Denmark. The researchers who analyzed it were able to extract DNA from the chewer that had been trapped in the gum 5,700 years ago. The DNA revealed the sex of the chewer, and also some of her physical attributes.  

"She had this really striking combination of dark skin and dark hair and blue eyes. And of course, we also recovered the microbial DNA which added a whole lot more," said archeologist Hannes Schroeder, in conversation with Quirks & Quarks host Bob McDonald.  Schroeder is an assistant professor of archeology at the University of Copenhagen,

This is the first time ever scientists have extracted an entire ancient genome from anything other than bone or teeth, giving insight into some of Europe's early inhabitants and their lifestyle. 

"It is quite amazing — 10 to 15 years ago, nobody thought we would get an ancient genome, full stop. And now we're able to recover ancient genomes from something like an ancient piece of chewing gum," said Schroeder about his findings. The team's work was published in the journal Nature Communications

This is interesting because it tells us something about the evolution of lighter skin tones in this part of the world as a way of adapting to these light poor environments.- Hannes Schroeder

This DNA recovered in the gum is just the latest genetic evidence of dark skinned individuals living in Europe thousands of years ago. 

"This is interesting because it tells us something about the evolution of lighter skin tones in this part of the world as a way of adapting to these light-poor environments," said Schroeder.

DNA reveals hunter gatherer ancestry

When Schroeder and his colleagues analyzed this Stone Age woman's DNA, they found it very closely resembled the genomes of hunter gatherers who lived in Europe 6,000 to 10,000 years ago.

"And that fit also with the fact that we recovered plant and animal DNA from the gum as well, which we found to be hazelnuts and duck DNA. And these are obviously wild resources," added Schroeder

He said this is interesting because at the time this female was eating wild duck and hazelnuts in what is now Denmark, there were already farming communities present just a hundred kilometres away in Germany.

"But it looks like she and her community were still genetically hunter gatherers and also living still a hunter gatherer lifestyle."

An artist's illustration of what the ancient gum chewer who lived in Scandinavia would have looked like. (Tom Björklund)

Ancient uses for chewing gum

Scientists had previously discovered this gum-like substance on tools from similar Stone Age archeological sites where the gum was used as a glue to help hold the parts of the tools together.

The gum was derived from birch pitch. Schroeder said it was made by boiling birch bark to extract the pitch. The gooey substance solidifies when cooled. 

"Then in order to make it usable, people used to chew it."

We identified a number of bacterial species, for instance, that are involved in different forms of tooth decay.- Hannes Schroeder, University of Copenhagen

Microbial treasure trove

Schroeder said one of the more exciting aspects of their discovery is that they were also able to extract DNA from microbes that would have been in the woman's mouth — her oral microbiome.  

Most of the bacterial species they discovered were harmless and very closely resembled modern oral microbiomes.

"But then there are some that are potentially really pathogenic," he added. 

This suggests another possible reason why the woman would have been chewing the gum. The gum contains antibacterial compounds and might have been used as a way to fight cavities and toothaches.

"We identified a number of bacterial species, for instance, that are involved in different forms of tooth decay," he said. 

They also discovered a streptococcus species responsible for developing pneumonia, as well as viral DNA from the Epstein-Barr virus that causes glandular fever.

"Through that, we can't say whether she had pneumonia or glandular fever, but we know that she was infected with these particular pathogens."

Schroeder said the fact they were able to even recover the microbial DNA from an ancient piece of chewing gum "opens up entirely new avenues of research."

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