Researchers at the University of Copenhagen have extracted a complete human genome from a chewed piece of birch pitch from the Stone Age.
A team of archaeologists found this form of "chewing gum" during an excavation on Lolland, an island in Denmark. The DNA within it has lasted more than 5,700 years, and researchers are calling it an untapped source of ancient DNA.
This is the first time an entire ancient human genome has been extracted from anything other than bones. The research results were recently published in Nature Communications.
"It is amazing to have gotten a complete ancient human genome from anything other than bone," said Hannes Schroeder, associate professor at the Globe Institute, University of Copenhagen, 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."
Based on the genome, researchers determined that the "gum chewer" was a female with dark skin, dark hair and blue eyes.
They nicknamed her "Lola" and could tell she was closely related to hunter-gatherers from the mainland Europe rather than those who lived in central Scandinavia.
The discovery of the birch pitch occurred at an excavation in Syltholm, carried out by the Museum Lolland-Falster in relation to the construction of the Fehmarn tunnel.
"Syltholm is completely unique. Almost everything is sealed in mud, which means that the preservation of organic remains is absolutely phenomenal," said Theis Jensen, who worked on the study and participated in the excavations. He is doing postdoctoral research at the Globe Institute. "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."
Results from the DNA showed that Lola was likely consuming plants and animals like hazelnut and duck as part of her normal diet.
In the Stone Age, birch pitch was not only used as chewing gum, but also as an all-purpose glue for hafting stone tools, according to the research. It may have even been used to relieve toothaches.
In addition, the researchers were able to extract bacteria from the DNA, which included many commensal species and opportunistic pathogens.
They even found remnants of the Epstein-Barr virus, which is known to cause infectious mononucleosis or glandular fever.
"It can help us understand how pathogens have evolved and spread over time, and what makes them particularly virulent in a given environment," said Schroeder. " At the same time, it may help predict how a pathogen will behave in the future, and how it might be contained or eradicated."