According to the study, published in the journal Nature Communications, the "chewing gum" was found during archaeological excavations at Syltholm in southern Denmark.
For the first time, researchers have extracted an entire ancient human genome from a sample other than bones, in a gum chewed by a 5,700-year-old female, unearthing details about the diet and oral microbes of stone age people. The researchers, including those from the University of Copenhagen in Denmark, extracted the complete ancient human genome from a sample of birch pitch — a gummy substance derived from the distillation of the birch tree’s bark.
According to the study, published in the journal Nature Communications, the “chewing gum” was found during archaeological excavations at Syltholm in southern Denmark. “It is amazing to have gotten a complete ancient human genome from anything other than bone,” said study co-author Hannes Schroeder from the University of Copenhagen.
Based on the analysis of the genome, the researchers could tell that the birch pitch was chewed by a female. “The individual who chewed the pitch was female and that she was genetically more closely related to western hunter-gatherers from mainland Europe than hunter-gatherers from central Scandinavia,” the researchers wrote in the study. The archeologists also found that she probably had dark skin, dark hair, and blue eyes.
Additionally, the scientists could also extract DNA of oral bacteria and infectious microbes from the pitch sample, proving that these kinds of gums can be a very valuable source of ancient DNA, especially for time periods which have no human remains. According to the researchers, the environmental conditions at the site where the birch pitch was found contributed to preserving the sample. “Syltholm is completely unique. Almost everything is sealed in mud, which means that the preservation of organic remains is absolutely phenomenal,” said Theis Jensen, a study co-author from the University of Copenhagen. The study noted that Stylholm is one of the biggest Stone Age sites in Denmark.
According to the findings, the people who occupied the region were heavily exploiting wild resources well into the Neolithic — the final division of the Stone Age, which began about 12,000 years ago. During this period farming and domesticated animals were first introduced into southern Scandinavia, the researchers added. According to them, this is reflected in the DNA results, as they also identified traces of plant and animal DNA in the pitch — specifically hazelnuts and duck.
The archeologists speculate these may have been part of the ancient female’s diet. “The results highlight the potential of chewed birch pitch as a source of ancient human and non-human DNA, which can be used to shed light on the population history, health status, and even subsistence strategies of ancient populations,” the researchers wrote in the study.
The oral microbial DNA from the sample revealed the presence of several bacteria including many harmless species, and also some opportunistic pathogens. One of the pathogens, the researchers mentioned is the Epstein-Barr Virus, which is known to cause infectious mononucleosis, or glandular fever. “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,” said Schroeder.
He said ancient “chewing gums” hold great potential in studying the composition of microorganisms that lived in and on our human ancestors, and also in understanding the evolution of important infectious, pathogenic microbes. “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,” said Schroeder.