Scientists extract complete human genome from a thousands-of-years old “chewing gum”

By Dr. Ananya Mandal, MDDec 18 2019

It seems that chewing gum is not a new trend! Researchers have found chewing gum that is 5,700 years old and it has provided clues regarding ancient DNA. A study with the findings was published in the journal Nature Communications. It is titled, “A 5,700-year-old human genome and oral microbiome from chewed birch pitch.”

A team from the University of Copenhagen used an excavated piece of gum that was chewed and extracted human genome from it. The gum was prepared from birch pitch and was used to chew at leisure, they speculated. According to experts, this is the first time that whole of the ancient genome has been extracted from an excavated artefact other than bones.

Artistic reconstruction of the woman who chewed the birch pitch. She has been named Lola. Illustration by Tom Björklund.

There have been reports that birch pitch was used in the Palaeolithic times as glue. It is a brownish black gummy substance made by heating the bark of the birch tree. Once it cools, it needs to be chewed to make it usable in daily use as glue. It may also have been used as a toothache remedy or an antiseptic, say some experts. It may have also been used as chewing gum at leisure, they add. They wrote, “The oldest examples of chewed pitch found in Europe date back to the Mesolithic period and chemical analysis by Gas Chromatography-Mass Spectrometry (GC-MS) has shown that many of them were made from birch (Betula pendula)”.

The excavation at Syltholm, east of Rødbyhavn in southern Denmark was carried out by the Museum Lolland-Falster during their work on the Fehmarn tunnel. Theis Jensen, a post doctorate student at the Globe Institute was working on his PhD and was part of the Syltholm excavations. Jensen said, “Syltholm is completely unique. Almost everything is sealed in mud, which means that the preservation of organic remains is absolutely phenomenal.” He added, “It is the biggest Stone Age site in Denmark and the archaeological finds suggest that the people who occupied the site were heavily exploiting wild resources well into the Neolithic, which is the period when farming and domesticated animals were first introduced into southern Scandinavia.”

Lead researcher, Associate Professor Hannes Schroeder from the Globe Institute, University of Copenhagen, said in a statement, “It is amazing to have gotten a complete ancient human genome from anything other than bone. What is more, we also retrieved DNA from oral microbes and several important human pathogens, which makes this a very valuable source of ancient DNA, especially for time periods where we have no human remains.”

On detailed look at the genome they figured out that the user of the gum was a female and she was more related to the hunter-gatherers who lived in central Europe compared to those who lived in central Scandinavian regions. They speculated from the genome that she most likely had blue eyes, dark hair and dark skin. From the chewing gum the team also isolated DNA of the plant and animals that may have come in contact with it. They specifically found duck and hazelnuts that the female could have consumed before or around the time of chewing the gum, they speculated.

Next the researchers looked at the genome of the microbes that were found in the chewing gum. These were probably the genome of the microbiota, commensal organisms and opportunistic bacteria of the mouth and gastrointestinal tract of the female who was chewing it. Schroeder explained, “The preservation is incredibly good, and we managed to extract many different bacterial species that are characteristic of an oral microbiome. Our ancestors lived in a different environment and had a different lifestyle and diet, and it is therefore interesting to find out how this is reflected in their microbiome.” One of the microbial genome found was said to be of Epstein-Barr Virus, he added. They also write that they foud, “Neisseria subflava and Rothia mucilaginosa, as well as several bacteria included in the red complex (i.e. Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola)”. Schroeder also said, “It can help us understand how pathogens have evolved and spread over time, and what makes them particularly virulent in a given environment. At the same time, it may help predict how a pathogen will behave in the future, and how it might be contained or eradicated.”

The team concluded that “pieces of chewed birch pitch are an excellent source of ancient human and non-human DNA. In the process of chewing, the DNA becomes trapped in the pitch where it is preserved due to the aseptic and hydrophobic properties of the pitch which both inhibits microbial and chemical decay.” They further wrote, “The genomic information preserved in chewed pieces of birch pitch offers a snapshot of people's lives, providing information on genetic ancestry, phenotype, health status, and even subsistence. In addition, the microbial DNA provides information on the composition of our ancestral oral microbiome and the evolution of specific oral microbes and important human pathogens.”

This study was funded by the Villum Foundation and the EU's research programme Horizon 2020 through the Marie Curie Actions.