The people who lived at Huseby-Kiev in western Sweden 10,000 years ago made their living by hunting and fishing. That doesn’t sound surprising until you consider that this was a landscape that had, until recently, been covered by ice sheets 4 km (2.5 miles) thick. How they occupied the re-emerging landscape is a bit of a mystery. We don’t 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 from millennia ago. Using this ancient chewing gum, archaeologist Natalija Kashuba of Uppsala University recently recovered DNA from two women and one man who had lived, worked, and apparently chewed gum on the shores of ancient Sweden. That means 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 met 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’s also a handy glue for repairing cracked pottery or gluing bone points onto stone blades to make a vicious-looking composite point (see gallery). That’s how people at Huseby-Kiev seem to have used it.