Ancient DNA has been recovered from rudimentary chewing gum spat out by a Stone Age human who lived in Sweden around 10,000 years ago.
The gum — which still bears the mark of its chewers’ teeth – was made from tar created from the bark of birch trees.
The DNA the people left behind in their gum is the oldest known human DNA from Scandinavia, a region that has produced few human skeletal remains so far.
Analysis suggests that, despite using tools of eastern hunter-gatherer origin, the gum chewers were related to more western populations.
‘This supports the theory that culture and genetic imports into Scandinavia came from two distinct routes — one from western Europe and the other from the east, in what is today Russia.
Ancient DNA has been recovered from rudimentary chewing gum (pictured) spat out by Stone Age humans who lived in Sweden around 10,000 years ago
The lumps of ancient chewing gum were unearthed from an archaeological site called Huseby-Klev, located on the west coast of Sweden, which has been dated back to around 10,000 years ago.
The early Mesolithic hunter-fisher peoples that lived at Huseby-Klev made the chewing gum from birch bar tar.
Along with being chewed, this material was also used by Stone Age peoples as a glue for the production of tools and other technologies.
Researchers from the University of Oslo and Stockholm University found that the DNA in the gum had been left behind by three individuals, specifically two women and a man.
Imprints of the three chewers’ teeth can still be seen in some of the gum pieces.
The researchers were ‘overwhelmed’ by the results they got from the lumps of gum, said paper first author Natalija Kashuba, who is now based at Uppsala University.
‘We stumbled into this almost “forensic research”, sequencing DNA from these mastic lumps, which were spat out at the site some 10 000 years ago,’ she said.
It is only thanks to recent advances in DNA sequencing technology that this studies like this are now achievable.
The Huseby Klev site was excavated in the 1990s, when it was not possible to sequence human DNA at all — let alone that preserved outside of human remains.
The team had been initially hesitant about the prospect of studying the ancient gum, Ms Kashuba added.
However, she said, they were ‘really impressed that the archaeologists took care during the excavations and preserved such fragile material.’
Researchers found that the DNA in the gum had come from two women and a man. Imprints of the three chewers’ teeth can still be seen in some of the ancient pieces of gum (pictured, a piece of gum, centre, with two casts on either side. Teeth imprints can be seen on all three)
‘Demography analysis suggests that the genetic composition of Huseby Klev individuals show more similarity to western hunter-gatherer populations than eastern hunter-gatherers’, said Stockholm University’s Emrah Kirdök, who undertook the computer-based analysis of the ancient DNA.
These western hunter-gatherers included other populations in Sweden and early Mesolithic populations from Ice Age Europe.
But the tools archaeologists have found at the Huseby Klev site were based on a type of stone-based technology known to have been brought into Scandinavia from the East European Plain, in what today is Russia.
These findings support previous suggestions that migrations of culture and genetics into Scandinavia came along two different routes.
The Huseby Klev site was excavated in the 1990s (pictured). At this time, it was not possible to sequence human DNA at all — let alone that preserved outside of human remains
Few human bones from this time have been unearthed in Scandinavia and many of them have not being preserved well enough to yield DNA for analysis.
The successful sequencing of DNA from these pieces of ancient chewing gum reveals a second source of human genetic information that may also serve as a good proxy for ancient human bones in the field.
‘DNA from these ancient chewing gums have an enormous potential,’ said paper author and archaeologist Per Persson, of Oslo’s Museum of Cultural History.
‘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,’ he added.
‘Much of our history is visible in the DNA we carry with us,’ added fellow paper author Anders Götherström, who is an archaeologist at Stockholm University.
‘So we try to look for DNA where ever we believe we can find it.’
The full findings of the study were published in the journal Communications Biology.
The lumps of ancient chewing gum were unearthed from an archaeological site called Huseby-Klev, located on the west coast of Sweden, which dates back to around 10,000 years ago
HOW DID PEOPLE LIVE DURING THE MESOLITHIC PERIOD?
The Mesolithic period, also called Middle Stone Age, is an ancient time period (8000 BC to AD 2700) that took place between the Paleolithic Period (Old Stone Age) with its chipped stone tools, and the Neolithic Period (New Stone Age) with its polished stone tools.
The Mesolithic period’s material culture is characterized by greater innovation than the Paleolithic.
Among the new types of chipped stone tools were microliths: very small stone tools intended for mounting together on a shaft in order to produce a serrated edge. Polished stone was another innovation that arose in some Mesolithic groups.
Northern European Mesolithic people (called Maglemosian’s), who flourished at about 6000 BC, left behind traces of primitive huts with bark-covered floors and adzes for working wood.
At Starr Carr in Yorkshire, there are signs that four or five huts existed there, with a population of around 25 people. There is evidence that these sites may only have been occupied on a seasonal basis.
An artist’s impression of tribes fishing during the Mesolithic period
Aracheologists have also found smaller flint tools from this group. These were mounted as points or barbs for arrows and harpoons and were also used in other composite tools.
They used adzes and chisels made of antler or bone, as well as needles and pins, fish-hooks, harpoons and fish spears with several prongs. Some larger tools made of ground stone, such as club heads, have also been found.
Wooden structures have also been found and have remained well-preserved due to the preservative qualities of bogs. Some of the structures discovered include ax handles, paddles and a dugout canoe, and fishnets were made using bark fibre.
Deer were hunted as well as fish and waterfowl, and some varieties of marsh plants may have been used.
