Dental study of ancient chewing gum informs about oral microbiomes of the past
COPENHAGEN, Denmark: Though its popularity and constituent ingredients have changed over time, chewing gum has been used by humans for thousands of years. A new study out of Denmark that analysed a 5,700-year-old piece of chewing gum made from birch bark pitch has succeeded in extracting a complete human genome from the pitch, demonstrating its potential as a new source of ancient DNA.
The pitch was found during archaeological excavations carried out by the Museum Lolland-Falster at Syltholm in southern Denmark, and subsequent analysis was conducted by researchers at the University of Copenhagen. Radiocarbon dating of the pitch helped to place it as a specimen from the early Neolithic period in Denmark, while DNA sequencing revealed that it was chewed by a female who was more closely genetically related to the hunter-gatherers of mainland Europe than to those who populated central Scandinavia at the time. It was found that she probably possessed dark skin, dark hair and blue eyes.
Traces of hazelnut and duck DNA were also identified in the pitch, suggesting that these may have formed part of the individual’s diet. The researchers also successfully identified DNA fragments from several bacterial and viral taxa, including the Epstein–Barr virus, which can cause glandular fever.
“[Syltholm] 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,” said Dr Theis Jensen, a postdoctoral student at the University of Copenhagen’s Globe Institute and a co-author of the study.
“We managed to extract many different bacterial species that are characteristic of an oral microbiome,” added Dr Hannes Schroeder, associate professor at the Globe Institute.
“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,” he continued.
Though still a relatively new form of analysis, DNA sequencing from birch bark pitch is growing in popularity, in part owing to its potential to be a good proxy for human bones in archaeogenetic studies. As reported by Dental Tribune International last year, Scandinavian researchers have previously used pitch to sequence DNA from the first humans who settled in the region some 10,000 years ago.
Though a considerable amount of information can be uncovered through the DNA sequencing of pitch, several questions still remain—including the question of what the purpose of chewing it was. Some researchers have suggested that it may have been a method for making the pitch more pliable for further toolmaking purposes, while medicinal and hunger-suppressing uses have also been put forward for consideration.
The study, titled “A 5700 year-old human genome and oral microbiome from chewed birch pitch”, was published on 17 December 2019 in Nature Communications.