This little lump of birch pitch was used as chewing gum by someone in southern Sweden about 10 000 years ago. (Image: Natalija Kashuba / Stockholm University)
This little lump of birch pitch was used as chewing gum by someone in southern Sweden about 10 000 years ago. (Image: Natalija Kashuba / Stockholm University)

Scientists have found 10 000-year-old Scandinavian genes in prehistoric gum

These small lumps of pitch were chewed 10 000 years ago by people living in what is now Sweden. But who were these people?

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Who were the people that migrated to and settled in Scandinavia after the ice began to melt, more than 11 500 years ago?

DNA analysis technology has become good enough for genetic material to be extracted from the material remnants of humans who lived thousands of years ago. Researchers have recently been able to extract DNA from birch pitch used as chewing gum.

Pitch is a sticky material that is made by warming up birch bark, and was used for various purposes such as gluing together stone tools and weapons. It was also chewed like chewing gum.

“We’ve found over one hundred of these lumps of pitch,” said Per Persson, an archaeologist and researcher at the Museum of Cultural History in Oslo. He has led the pitch project in conjunction with archaeologists and geneticists from Norway and Sweden.

Excavations of an archaeological site from the 1990s. Technology has only recently become good enough for these pieces of pitch to be analysed. (Photo: Per Persson / Stockholm University)
Excavations of an archaeological site from the 1990s. Technology has only recently become good enough for these pieces of pitch to be analysed. (Photo: Per Persson / Stockholm University)

Persson was at the archaeological dig where the pitch lumps were found, at the Huseby Klev site in western Sweden.

“They would mould warm pitch with their hands, but it could also be chewed,” Persson said.

Some of the pitch had tooth marks in it, meaning that it had been chewed. Based on the tooth marks, the researchers estimate that the chewers were between five and eighteen years old. That meant it was also possible that some spit or genetic material from the gum chewers was stored in the pitch.

In fact, researchers were able to find bits of human DNA in several of the pitch lumps. After analysing the results, researchers think they have found the genetic profile of three different people who lived almost 10 000 years ago.

Carbon dating shows that the pitch was about 9880-9540 years old.

But who were these people?

The current theory regarding the origins of people who eventually inhabited Scandinavia is that hunters and gatherers migrated from western Europe more than 11 000 years ago, travelling up the coast of Norway. About 1000 years later, more people came from the northeast, through today’s northern Russia and Finland.

These groups of people met and mingled in Scandinavia. There are few human material remnants that can be DNA tested, but some tests have been conducted on finds discovered in today’s Sweden and Norway. The people that owned these remnants represent a unique genetic group, called Scandinavian hunter-gatherers, who were a genetic combination of Western and Eastern hunter-gatherers from that time.

“These people no longer exist. Although parts of their DNA can be found in modern humans, nobody has the same unique genetic composition,” Persson explains. The recently discovered genes from the pitch match other samples of Scandinavian hunter-gatherer genes. The results show that they have a little bit more in common with Western genes, but not significantly, according to a research paper published in Communications Biology.

However, it isn’t only these genes that show that people from different places ended up in Scandinavia.

Tools

Stone tools were made using several different techniques, which archaeologists assume were developed by different groups of people, and then taught to others as they migrated. Several different tool techniques have been found in Scandinavia, some of which can be traced east, and some of which come from the south.

The remains of tool production found at the dig site in Sweden indicate techniques similar to those used by Eastern hunter-gatherers. However, the researchers emphasize that these different techniques were found close to each other, and that the knowledge a certain group of people had doesn’t necessarily correlate to their genetics.

More pitch might contain DNA

Persson explains that pitch lumps aren’t a particularly common find at an archaeological dig from this period, but that there also hasn’t been that much interest in them.

“I’ve never found anything like this in Norway,” he says.

Persson and the other researchers behind the recent article have been able to show that it is possible to extract DNA from pitch, which means there is a new possible source of knowledge about groups of humans such as those that inhabited Scandinavia almost 10 000 years ago.

“Until now, the most common source of DNA has been bones, but those aren’t found everywhere,” he said.

Only a few individuals from this period of Scandinavian history have been DNA tested previously, including some from Søgne in southern Norway, Steigen in northern Norway, and southern Sweden.

“We’ll see if more resin containing DNA shows up in the future,”  Persson said.

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Read the Norwegian version of this article at forskning.no