Once they finished, the ancient humans spat out the lumps. The tar retained some of their DNA, which helped modern-day researchers identify their genetic origin.
The researchers released the details of their discovery in the scientific journal Communications Biology.
Their findings proved incredibly fortunate. Few human bones from that age in Scandinavia made it to modern times and not all of the bones retained enough DNA for genetic analysis.
The ancient chewing gum not only kept more than enough genetic data, but it also held the oldest human DNA sequenced from Scandinavia so far.
The DNA from the chewing gum came from three individuals, a male and two females. They established an incredible connection between human genetics and the material belongings of their culture. (Related: Natural methods to treat sensitive teeth.)
Chewing gum from ancient times served as an alternative source of human genetic data. It may even substitute for human bones.
The birch bark tar came from Huseby-Klev, an archaeological site on the western coast of Sweden. Dating back to the early Mesolithic period, it once served as home to a small group of hunter-gatherers.
Researchers began excavating Huseby-Klev during the early 1990s. However, it took a while for them to develop technology to study the genetic data of ancient humans, much less extract human DNA trapped within plant tissue.
The ancient Scandinavians used birch bark tar in many ways. Not only did the material serve as chewing gum, but it also acted as an adhesive for Stone Age tools and items.
“When Per Persson and Mikael Maininen proposed to look for hunter-gatherer DNA in these chewing gums from Huseby Klev we were hesitant but really impressed that archaeologists took care during the excavations and preserved such fragile material,” remarked researcher Natalija Kashuba.
Kashuba was with the Museum of Cultural History (KHM) when she ran the experiments alongside her Stockholm and UiO counterparts. Her team ended up doing the equivalent of "forensic research" as they sequenced ancient human DNA from 10,000-year-old chewing gum.
Kashuba and her teammates found that the ancient humans in Huseby-Klev displayed close genetic affinity to other hunter-gatherer groups in what became modern-day Sweden. They were also closely related to early Mesolithic people from Europe during the Ice Age.
Meanwhile, analysis of the tools found at the same site identified the artifacts as stone-based technology that came from the East European Plain. The plain belongs to Russia today.
Researchers earlier developed a theory that Scandinavia received cultural and genetic influences from two different directions. The ancient artifacts at Huseby-Klev supported the connection between human genes and material belongings.
“Demography analysis suggests that the genetic composition of Huseby Klev individuals show more similarity to western hunter-gatherer populations than eastern hunter-gatherers,” explained Stockholm researcher Emrah Kirdök, who ran the computer analyses of the genetic data.
KHM researcher Per Persson said that the genetic data in the ancient chewing gum showed the origin and movement of ancient humans during the Stone Age. It also shed light on their diet, diseases, and social relations.
Stockholm researcher Anders Götherström added that human DNA showed much of their history. Therefore, they look for genetic data wherever it might appear – such as ancient chewing gum.