5,700-Year-Old "Chewing Gum" Reveals An Entire Human Genome

Spit it out: Close­up photograph of the Syltholm birch pitch. Theis Jensen

Scientists have got their hands on the entire genome of a person who lived 5,700 years ago by using a piece of ancient “chewing gum” as a source of DNA. Despite the passing millennia, this chomped-on piece of resin can tell us a lot about its ancient owner. 

While excavating an Early Neolithic site in southern Denmark, archaeologists came across an ancient chewed piece of birch pitch, a substance created by heating the bark of a birch tree, that was widely used as an adhesive and disinfectant. This piece of birch pitch is covered in well-defined human bite marks, suggesting it had been chewed like gum, most likely to remedy toothache or infection. 

The team of bioarchaeologists led by the University of Copenhagen managed to extract ancient DNA from this birch pitch and to sequence the entire genome of the person who once chewed it. It is the first time a complete human genome has been extracted from something other than bones. Their findings are published in the journal Nature Communications today. 

“It is amazing to have gotten a complete ancient human genome from anything other than bone,’’ lead author Hannes Schroeder, an associate professor from the Globe Institute at the University of Copenhagen, said in a statement.

Artistic reconstruction of "Lola", as they has been named. Tom Björklund

Sniffing around the genome revealed some stunningly acute insights into the person who chewed this birch pitch nearly 6,000 years ago. For starters, the person was biologically female, and they were genetically more closely related to hunter-gatherers from mainland Europe, compared to those who lived in central Scandinavia at the time. They most likely had dark skin, dark hair, and blue eyes, similar to many other European hunter-gathers around this time, most famously “Cheddar Man,” one of the earliest inhabitants of what is now the UK. 

But it wasn’t just her DNA that got picked up by the sequencing. DNA fragments of plant and animal DNA were also found in the pitch, specifically hazelnuts and duck, which may have been part of the individual’s diet. 

The researchers also picked up flecks of DNA belonging to different bacteria and viruses, which were most likely from her oral microbiota. One of these bacteria was Porphyromonas gingivalis, the pathogen associated with gum disease. They also found DNA believed to belong to the Epstein-Barr Virus, the pathogen responsible for glandular fever.

"Our ancestors lived in a different environment and had a different lifestyle and diet, and it is therefore interesting to find out how this is reflected in their microbiome," said Schroeder.

"It can help us understand how pathogens have evolved and spread over time, and what makes them particularly virulent in a given environment. At the same time, it may help predict how a pathogen will behave in the future, and how it might be contained or eradicated."

Close up of the chewed birch pitch from Syltholm, southern Denmark. Theis Jensen

 

 

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