Paris (AFP)

The analysis of a "chewing gum", more than 5,000 years old, reveals not only the origins of its chewing machine but also the color of its eyes, the germs that its mouth hosted and the composition of its meals.

"For the first time, an ancient and complete human genome has been recovered from something other than bones or teeth," Hannes Schroeder of the University of Copenhagen, co-author of the study published in the journal, told AFP. Nature Communications.

This "very precious source of ancient DNA", especially for periods when human remains are scarce, is nothing but a paste, blackish, obtained from heated birch bark, "more common than we don’t think so because it keeps well enough. "

Its asset: having, in prehistoric times, been widely chewed. Evidence of tooth imprints often found on the birch pitch.

The paste studied by researchers from the University of Copenhagen was discovered during archaeological excavations carried out by the Lolland-Falster Museum in Syltholm in the south of Denmark.

"Syltholm is truly a unique site. Almost everything is sealed in mud, suddenly, the preservation of organic remains is phenomenal," said in a statement another study co-author, Theis Jensen, also from the University of Copenhagen. .

- Duck and hazelnuts -

By studying the human DNA that the birch pitch contained, the researchers were able to establish that the person who had chewed it was a woman, probably with blue eyes and dark skin and hair.

According to the study, the machouilleuse was genetically closer to the hunter-gatherers of continental Europe than those of central Scandinavia.

However, the researchers admit that they do not know exactly why, 5,700 years ago, this woman kneaded the dough between her teeth.

If sometimes it served as glue (chewing it made it malleable before use), the paste could also be used to relieve toothache (it has antiseptic properties), serve as a toothbrush, appetite suppressant or simply chewing gum.

Researchers have also extracted DNA from oral microbes and several human pathogens. Mainly harmless species, "but also some which are potentially very pathogenic like Streptococcus pneumoniae which is the main cause of pneumonia. We have also recovered the DNA of the Epstein-Barr virus responsible for infectious mononucleosis".

"This can help us understand how pathogens have evolved and spread over time, and what makes them particularly virulent in a given environment," says Hannes Schroeder.

The "chewing gum" also contained DNA from plant and animal species such as hazelnut or duck, suggesting that they were eaten shortly before chewing.

© 2019 AFP