As the Neolithic era paves its onset, a young woman threw a lump of ancient chewing gum made from birch tar into a shallow, brackish lagoon that drew fishermen to the coast of southern Denmark.
Nearly 6,000 years later, researchers excavating underneath the site spotted the gum which lied amidst wild animal bones and pieces of wood. From that her complete DNA was reassembled and broadest strokes of her portrait were painted.
The strands of DNA found in the gum point to a hunter-gatherer from continental Europe. She lived near the lagoon, protecting herself from the open sea by shifting sand barriers. The time frame that dates her existence can be traced back to 5,600 years ago, as per the carbon dating results of the birch tar.
Alongside her DNA, some material of hazelnuts consumed by a duck was found. 40 different types of microbes were also found. Hannes Schroeder, a molecular anthropologist at the University of Copenhagen, referred to this occurrence as nothing short of a miracle. It is for the first time that a genome is extracted from a piece of gum, and not from a teeth. We never expected to get the whole genome.
The long lump of ancient gum was about 2 cm long. It was discovered during archaeological excavation that was taking place at Syltholm on Lolland Island, before construction work on the Fehmarn tunnel to connect Denmark to Germany.
The stone age site was not merely a fishing ground, but it had remnants of other animals like piles of bones from cattle, deer, ox, wildcats, dogs, and otters. These items were found near the remnants of wooden fish traps, over hundreds of generations.
Theis Jensen says “This was a place of special significance.” She does research work at the University of Copenhagen and was the first author of the study. She states, “These people didn’t live at the site, but probably on dry land a couple of hundred meters away.”
Birch tar is made by heating the tree’s bark, and it is also used as a natural adhesive. In the stone age, the material was extracted on a mass scale to haft arrowheads and other tools and had some other applications too. Lumps of the tar found at archaeological sites also contain juvenile tooth marks, denoting tooth brushing was done in the period with the help of Birch tar.
Jensen and Schroeder first wondered during the excavations process whether the chewed birch tar from Syltholm will contain any amount of preserved DNA. To find out, they washed pieces of the tar and extracted what DNA they could find. Jensen reiterated It had a tremendous amount of DNA in it.
The scientists found out a way in which their sufficient DNA findings were enough to reconstruct a full human genome. It showed that the person was female and had dark skin, dark hair and blue eyes. She seems more closely related to hunter-gatherers from mainland Europe than those who lived in central Scandinavia at the time, as stated by a report in Nature Communications. It is impossible to predict her age, but given that children seemed to chew birch tar, the scientists predict her to be young.
Further, this particular DNA also helped to find an oral microbiome in the mouth. Some bacterial species were also found which were linked to severe periodontal disease, and Streptococcus pneumonia, a major cause of pneumonia. Scientists spotted the Epstein-Barr virus, which can cause glandular fever. She might be ill, all can be present without causing any disease or illness to her.
Anders Götherström and her team in May at Stockholm University extracted sections of human DNA from older chewed birch tar. The studies as a whole concluded that birch tar can be valuable for recovering ancient human genomes from sites where no bones or teeth can be found.
Jensen says, “How birch is a beautiful substitute for bones.” And It’s beyond incredible how accurately it provides information.”
Götherström said the latest work was exciting, he stated, “that the microbial DNA is an important finding in the process of excavation. It occurs only in the mouth which in turn is an exposed area of the body. It is possible that this type of material will outcompete bones when looking for DNA from ancient pathogens.”