Old DNA has been recovered from rudimentary chewing gum emitted by a man from the Stone Age who lived in Sweden some 10,000 years ago.
The chewing gum – which still bears the mark of the teeth of its chewers – is made of tar made from the bark of birch trees.
The DNA that people left in their gums is the oldest known human DNA from Scandinavia, a region that has so far produced few human skeletal remains.
Analysis suggests that, despite the use of tools originating from the east of hunter-gatherers, the chewing gum-chewers were related to more Western populations.
& # 39; This supports the theory that culture and genetic imports in Scandinavia came from two different routes – one from Western Europe and the other from the east, in what is today Russia.
Old DNA has been recovered from rudimentary chewing gum (pictured) spit out by people from the Stone Age who lived in Sweden about 10,000 years ago
The chunks of age-old chewing gum were excavated from an archaeological site called Huseby-Klev, located on the west coast of Sweden, dating back to around 10,000 years ago.
The early Mesolithic hunter-fishermen who lived in Huseby-Klev made the chewing gum from berkeberteer.
Along with chewing, this material was also used by people from the Stone Age as an adhesive for the production of tools and other technologies.
Researchers from the University of Oslo and the University of Stockholm found that the DNA in the chewing gum was left by three people, in particular two women and one man.
Imprints of the teeth of the three chewers can still be seen in some parts of the gums.
The researchers were & # 39; overwhelmed & # 39; by the results they got from the lumps of gums, said the first author, Natalija Kashuba, who is now based at the University of Uppsala.
& # 39; We almost came across this & # 39; forensic investigation & # 39; against, where DNA was requested from these mastic clogs, which were spit out at the site some 10,000 years ago, & # 39; she said.
It is only thanks to recent advances in DNA sequencing technology that such studies are now feasible.
The Huseby Klev site was dug up in the 1990s, when it was not possible to sequence human DNA – let alone keep it outside of human remains.
The team had initially been hesitant about the prospect of studying the old gum, Mrs. Kashuba added.
But, she said, they were & # 39; really impressed that archaeologists took care of the excavations and preserved such fragile material & # 39 ;.
Researchers discovered that the DNA in the gums came from two women and one man. Imprints of the teeth of the three chewers can still be seen in some of the old pieces of chewing gum (pictured, a piece of chewing gum, in the middle, with two casts on each side.) Text prints can be seen on all three)
& # 39; Demography analysis suggests that the genetic composition of Huseby Klev individuals is more similar to western hunter-gatherer populations than eastern hunter-gatherers & # 39 ;, said Emrah Kirdök, University of Stockholm, who carried out the computer-based analysis of undertook the old DNA.
These western hunter-gatherers were among other population groups in Sweden and early Mesolithic people groups of Ice Age Europe.
But the tools that archaeologists have found on the Huseby Klev site were based on a type of stone-based technology known to have been brought into Scandinavia from the Eastern European plain, in what is today Russia.
These findings support earlier suggestions that migrations of culture and genetics to Scandinavia came in two different ways.
The Huseby Klev site was dug up in the 1990s (photo). At this time it was not possible at all to sequence human DNA – let alone keep it outside of human remains
Few human bones from this time have been dug up in Scandinavia and many of them have not been preserved well enough to provide DNA for analysis.
The successful sequencing of DNA from these pieces of old chewing gum reveals a second source of human genetic information that can also serve as a good proxy for old human bones in the field.
"DNA from this ancient chewing gum has enormous potential," said author and archaeologist Per Persson of the Oslo Museum of Cultural History.
& # 39; Not only for tracing the origins and movement of people long ago, but also for providing insights into their social relationships, diseases and food, & # 39; he added.
& # 39; Much of our history is visible in the DNA that we carry with us & # 39 ;, adds fellow author Anders Götherström, who is an archaeologist at the University of Stockholm.
& # 39; So we try to find DNA wherever we believe we can find it. & # 39;
The full findings of the study were published in the journal Communication Biology.
The chunks of age-old chewing gum were dug up from an archaeological site called Huseby-Klev, located on the west coast of Sweden, which dates back to about 10,000 years ago
HOW did PEOPLE LEARN DURING THE MESOLITHIC PERIOD?
The Mesolithic period, also called Middle stone age, is an old time period (8000 BC to 2700 AD) that took place between the paleolithic period (old stone age) with its broken stone tools and the neolithic period (new stone age) with its polished stone tools.
The material culture of the mesolithic period is characterized by a greater innovation than the paleolithic.
Among the new types of chipped stone tools were microliths: very small stone tools that were intended to be mounted together on a shaft to produce a serrated edge. Polished stone was another innovation that originated in some Mesolithic groups.
Northern European Mesolithic People (called Maglemosian & # 39; s), which flourished around 6000 BC, left traces of primitive huts with bark-covered floors and wood-based adzes.
At Starr Carr in Yorkshire there are signs that there were four or five cabins, with a population of around 25 people. There are indications that these sites may only be 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 from antlers or bone, as well as needles and pins, fish hooks, harpoons and fish spears with different teeth. Some larger tools made from crushed stone, such as club heads, have also been found.
Wooden structures have also been found and have been well preserved thanks to the preservative properties of marshes. Some of the constructions discovered included ax handles, paddles and an excavated canoe, and fishing nets were made using bark fiber.
Deer were hunted, as well as fish and water birds, and some species of marsh plants may have been used.
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