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Archaeologists find DNA in a 10,000-year-old piece of chewing gum

Archaeologists find DNA in a 10,000-year-old piece of chewing gum

Kashuba et al. 2019

The people who lived in Huseby-Kiev in western Sweden 10,000 years ago earned their money by hunting and fishing. That does not sound surprising until you realize that this was a landscape that until recently was covered by 4 km thick ice sheets. How they occupy the re-emerging landscape is a bit of a mystery. we don't know much about who they were, where they came from, or how they found their way to Sweden when the ice receded.

In the 1990s, archaeologists recovered a few chewed birch bark chunks, some of which still contained fingerprints and tooth stains left thousands of years ago. With the help of this old chewing gum, archaeologist Natalija Kashuba from the University of Uppsala has recently recovered DNA from two women and a man who lived, worked and apparently chewed gum on the banks of old Sweden. That means we can link DNA from old people to their artifacts, and that's a big indication of how people migrated to Scandinavia after the ice age.

Two groups of hunter-gatherers met in Sweden

Birch bark height, like other juices and resins from different trees around the world, makes a decent chewing gum. When chewed and softened, it is also a handy glue for repairing cracked earthenware or gluing bone points on stone trays to make a vicious-looking composite (see gallery). That's how people at Huseby-Kiev seem to have used it.

Based on the tools and other hints that these people also left behind, it seems that people in Scandinavia came together from two directions when the ice caps withdrew. One group migrated northwards from Western Europe, while the other migrated from the southwest of modern Russia to the southwest. These two groups of people each had their own unique ways of making stone tools, and that is how archaeologists have succeeded in distinguishing their sites and tracing their migration paths.

The people from Russia, for example, brought a technology called pressure flaking, where a pointed stick or bone is used to break off small flakes off the edge of a stone tool, creating a sharp knife. Over time this new Eastern pressure-flaking technology eventually replaced the older Western European techniques.

When these two populations of hunter-gatherers met in Scandinavia, they seem to be married. Through the mixing of their gene pools, a new population emerged over time, which anthropologists call Scandinavian Hunter-Gatherers (anthropologists are not generally known for creative naming schemes). We know this from DNA from human remains that are several centuries younger than the site in Huseby-Kiev.

The gums in Huseby-Kiev are the oldest human DNA ever recovered from Scandinavia and it sheds some light on the time these population groups first met.

Under the gums

When Kashuba and her colleagues compared the DNA of all three pieces of chewing gum with old DNA databases from other sites, it turned out that the two women and the man from Huseby-Kiev were closely related to the Scandinavian hunter-gatherer group, but their names looked more like Mesolithic people from Western Europe than Russia. It is the first time that archaeologists have found Scandinavian hunter-gatherer DNA that is clearly linked to stone tools, and it shows that people in Scandinavia already used the newer Eastern European method of pressure flaking 10,000 years ago.

It also shows that the spread of the new technology was not only supported by people from Eastern Europe. The two groups acted on ideas, not just genes.

On a smaller scale, the DNA samples in the three inconspicuous pieces of grass sand reveal something about people's lives and culture 10,000 years ago. The tooth stripes in the chewing gum came from milk teeth (which most people call milk teeth), suggesting that making stone tools was not a strictly mature work. And two out of three genes were genetically feminine, suggesting that tool making was not a gender-specific task either.

As DNA sequence technology improves, archaeologists find old DNA in surprising places. Earlier this year, the stem of a clay pipe revealed the genome of a enslaved woman who once lived in Maryland. Kashuba and her colleagues say that gums, resins and similar materials from around the world can also be good sources of old DNA, even in places where few human bones have been able to preserve DNA from the distant past. They also suggest that these materials contain proteins and other molecules that can provide clues about the dietary patterns and microbiomes of the elderly.

Communication Biology, 2018. DOI: 10,138 / s42003-019-0399-1 (About DOI & # 39; s).

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