Some 9,700 years ago, a group of people in Scandinavia lived as hunter-gatherers, fishing, hunting, and gathering resources. Teenagers, both boys and girls, chewed resin to produce glue after consuming trout, deer, and hazelnuts. One of the teenagers, suffering from a severe gum infection, had difficulty eating the chewy deer-meat and preparing the resin. This provides a glimpse of the Mesolithic period just before Europeans began farming, from analysis of DNA in the chewed resin conducted and published in Scientific Reports.
The location, Huseby Klev, is north of Gothenburg (Göteborg), Sweden, and was excavated in the early 1990s. The site, radiocarbon dated to between 10,200 and 9,400 years ago, yielded flint artefacts and resin pieces. Some resin pieces showed teeth imprints, indicating that teenagers had been chewing them. The birch bark pitch resin, used as an adhesive substance in stone tool technology, was also chewed for recreational or medicinal purposes in traditional societies.
Half of the DNA extracted from the resin was of human origin, representing some of the oldest human genomes from Scandinavia with a common ancestry profile. The resin also contained male and female human DNA, indicating teenagers of both sexes were involved in preparing glue for tool making.
The other half of the DNA was non-human, including organisms such as bacteria and fungi living in the discarded mastic. The analysis of the DNA required adapting existing computing tools and developing new analytical strategies, marking the beginning of a new workflow for this type of analysis.
The resin contained bacteria expected in an oral microbiome, as well as traces of bacteria implicated in conditions such as tooth decay or caries, and systemic diseases. It also revealed an abundance of bacteria associated with serious gum disease – periodontitis – suggesting that the girl who chewed the resin likely suffered from periodontitis.
In addition to bacteria, the resin contained DNA from red deer, brown trout, hazelnuts, and foxes. The presence of fox DNA could indicate it was part of the diet or used in textiles. However, more analysis is needed to interpret the findings accurately.
This discovery represents a significant step in understanding human culture from the Stone Age, with the potential for more surprises to emerge as further research is conducted.
