Complete DNA extract from a 5700 year old chewing gum

A team of researchers at the University of Copenhagen succeeded in what might have seemed like an impossible feat: they extracted an almost complete human genome from a chewing gum dating back thousands of years. The remains in this gum, in fact, proved to be an excellent source, and never exploited in any other previous study, of a DNA thousands of years old.

It all began when a 5,700-year-old “chewing gum” was found during archaeological excavations on the island of Lolland, Denmark. It is a gummy substance obtained after heating the birch bark, a substance that a local population evidently used to chew. Researchers have extracted a complete human genome; it is the first time that such a thing has been possible without using bones.

In the study, published in Nature Communications, the researchers describe the methods they used and how they came to the conclusion that the substance taken from the birch tree had been chewed by a female genetically linked to hunter-gatherers in continental Europe to a greater extent than the populations living in central Scandinavia at the time. They also discovered that this woman had dark skin, dark hair and blue eyes.

The researchers also found traces of hazelnut and duck DNA, foods that were probably part of the diet of the person who chewed the gum. And, not content, the researchers were also able to extract DNA from several microbes that were part of the woman’s oral microbiome, including some pathogens including the Epstein-Barr virus. This shows how good the level of DNA preservation in this “chewing gum” was.

The excavations took place at Syltholm, considered the largest Stone Age site in Denmark, and were carried out under the patronage of the Lolland-Falster Museum in connection with the excavations carried out for the construction of the Fehmarn tunnel. The main feature of this site is that “everything is sealed in mud, which means that the preservation of the organic remains is absolutely phenomenal,” explains Theis Jensen, a researcher at the Globe Institute who participated in the excavations and study.

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