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

The people who lived at Huseby-Kiev in western Sweden 10,000 years ago made their living by hunting and fishing. 4 km (2.5 miles) thick, which is not surprising enough. How they occupied the re-emerging landscape is a bit of a mystery. WThey do not know much about who they actually were, where they came from, or how they made their way into Sweden as the ice receded.

In the 1990s, archaeologists recovered a few chewed-up lumps of birch bark pitch, some of which still held fingerprints and tooth marks left behind millennia ago. Using this ancient chewing gum, the archaeologist Natalija Kashuba of Uppsala University has recently been recovered from the past, worked, and apparently chewed on the shores of ancient Sweden. This is how we can now link DNA from ancient people to their artifacts, and that's a big clue about how people migrated into Scandinavia after the Ice Age.

Two groups of hunter-gatherers in Sweden

Birch bark pitch, like other saps and resins from various trees around the world, makes a decent chewing gum. When chewed and softened, it is also a handy glue for gluing bone points to a composite vicious-looking composite point (see gallery). That's how people at Huseby-Kiev seem to have used it.

Based on the tools and other hints of these people, it seems that people converge on Scandinavia from two directions. One group migrated northward from western Europe, while another migrated southwest from the plains of modern-day Russia. These two groups of people have their own unique ways of making stone tools, which is how to manage their pathways.

The people who came from Russia, for example, brought a technology called pressure flaking, which involves using a pointed stick or bone to break off small flakes from the edge of a stone tool, creating a sharp blade. Over time, this new eastern pressure-flaking technology will be replaced by the older Western European techniques.

When these two populations of hunter-gatherers put in Scandinavia, they seem to have intermarried. Over time, the mix of their gene pools created a new population, which Anthropologists call Scandinavian Hunter-Gatherers (anthropologists are known for creative naming schemes). We know this from Husseby-Kiev.

The gum at Huseby-Kiev is the oldest human DNA ever recovered from Scandinavia, and it was known when these populations were first encountering each other.

Under the gum

When Kashuba and her colleagues compare the DNA of the world to the databases of ancient DNA, Huseby-Kiev was closely related to the Scandinavian hunter-gatherer group-goal their genomes looked more like Mesolithic people from western Europe than from Russia. It's the first time archaeologists have found Scandinavian hunter-gatherer DNA is linked to it, and it shows that people in Scandinavia 10,000 years ago were already using the newer European method of pressure-flaking.

It also shows that the spread of the new technology has been made by people from Eastern Europe. The two groups were trading ideas, not just genes.

We have smaller scale, the DNA samples in the three unassuming lumps of pitch revealing something about the lives and culture of people 10,000 years ago. The tooth marks in the gum came from deciduous teeth, suggesting that making stone tools was not strictly adulterated. And two of the three genomes were genetically female, which suggests that tool-making also was not a gender-specific job.

As DNA sequencing technology improves, archaeologists are finding ancient DNA in surprising places. Earlier this year, the stem of a clay pipe revealed the genome of an enslaved woman who once lived in Maryland. Kashuba and her colleagues say that gums, resins, and similar materials from around the world may also be good sources of ancient DNA, even in places where few human beings have managed to preserve DNA from the distant past. They also suggest that these materials may contain proteins and other molecules that could offer clues about ancient people's diets and microbiomes.

Biology Communications, 2018. DOI: 10.1038 / s42003-019-0399-1 (About DOIs).