Three 10,000-year-old pieces of chewing gum have been found to contain the oldest examples of human DNA from Scandinavia. The Stone Age DNA has confirmed a theory that humans colonised the peninsula on two separate occasions.
The chewing gum, made of a tar-like substance extracted from the bark of a birch tree, was excavated in the early 1990s from a site called Huseby Klev in western Sweden. Huseby Klev was the home to a group of hunter-fishers who lived in the Mesolithic (middle Stone Age) period.
The saliva these Mesolithic humans left in the chewing gum they spat onto the ground allowed them to be identified as two females and one male. As well as that, the team based at Stockholm University identified that they were most genetically similar to Scandinavian hunter-gatherers, the first human settlers on the peninsula. This group migrated from the south of Scandinavia around 11,500 years ago.
Remarkably, however, tools also found at the site did not match up to the technology developed by Scandinavian hunter-gatherers, but rather with tools made by Mesolithic humans from eastern Europe, in what is now Russia. The blades were shaped by a technique known as “pressure-knapping”, which produces a sharpened stone blade with a conical core. The Mesolithic humans then used the tar-like chewing gum to glue the blade to a handle made from an animal bone.
The presence of this eastern technique provides proof of the theory that Scandinavia was colonised by two separate groups: the Scandinavian hunter-gatherers from the south, and the eastern hunter-gatherers from Russia. Evidence supporting this theory was hard to come by, since few human bones have been preserved from that era, and even fewer preserved in the right conditions for the DNA to be analysed.
“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,” said Natalija Kashuba, lead author of the study.
Per Persson, of the Museum of Cultural History in Oslo, believes that analysing preserved chewing gums is a promising archaeological technique for a variety of reasons. “DNA from these ancient chewing gums have an enormous potential not only for tracing the origin and movement of peoples long time ago, but also for providing insights in their social relations, diseases and food,” Persson said.
Co-author of the study, Anders Götherström of the Archaeological Research Laboratory at Stockholm University, believes that our ancestors’ DNA tells us much more than simply their genes. “Much of our history is visible in the DNA we carry with us, so we try to look for DNA where ever we believe we can find it,” said Götherström.