5,700 year old 'chewing gum' reveals entire genetic code of stone age woman
The complete genetic code of a stone age woman has been recovered from a piece of ancient chewing gum, the first time such a feat has been achieved without any human body parts.
Archaeologists have known for some time that people as far back as the Neanderthals used tar from birch trees to make sticky adhesive for mounting tools. And tooth marks found in discarded pieces suggested they had also chewed the tacky substance, possibly to soften it to make it more malleable for working.
Researchers at the University of Copenhagen found a 5,700 year old piece of ancient gum during excavations at Syltholm, east of Rodbyhavn in southern Denmark, ahead of the building of a new tunnel.
When they analysed the pitch they found the complete genome of a late Mesolithic or early Neolithic female. The DNA showed she had dark hair, dark skin and blue eyes. And her last meal before she spat out the gum had been duck and hazelnuts.
It is the first time that a full genetic sequence from an ancient site has been recovered without the need for bones and represents a new untapped resource for archaeologists looking for clues about past populations.
“It is amazing to have gotten a complete ancient human genome from anything other than bone,’’ said Associate Professor Hannes Schroeder, who led the research.
“What is more, we also retrieved DNA from oral microbes and several important human pathogens, which makes this a very valuable source of ancient DNA, especially for time periods where we have no human remains.”
Some archaeologists believe that birch tar was chewed to relieve toothache because it is mildly antiseptic, or may have acted as a prehistoric toothbrush. The Syltholm gum was found entirely encased in mud, which preserved genetic information from the saliva.
The DNA showed that the female - named Lola by the team - was more closely related to hunter-gatherers from mainland Europe, which fits well with archaeological evidence showing central European farmers moved north at this time, bringing agriculture to traditional hunter-gatherer communities.
“Syltholm is completely unique,” said Dr Theis Jensen, one of the excavators.
“Almost everything is sealed in mud, which means that the preservation of organic remains is absolutely phenomenal.
“It is the biggest Stone Age site in Denmark and the archaeological finds suggest that the people who occupied the site were heavily exploiting wild resources well into the Neolithic, which is the period when farming and domesticated animals were first introduced into southern Scandinavia.”
The researchers also succeeded in extracting DNA from bacteria and viruses in the pitch, showing the kinds of diseases that the ancient female may have suffered from, including Epstein-Barr Virus, which causes 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,’ added Prof Schroeder.
“The preservation is incredibly good, and we managed to extract many different bacterial species that are characteristic of an oral microbiome.
“At the same time, it may help predict how a pathogen will behave in the future, and how it might be contained or eradicated.”
The research was published in the journal Nature Communications.
