Scientists in Denmark have squeaked out an entire human genome from a prehistoric piece of “chewing gum.” Made from birch tar, the 5,700-year-old gum also contained evidence of diet and disease and is providing a remarkable snapshot of life during the early Neolithic.
Lola was a Neolithic female who lived in Denmark some 5,700 years ago when the region was slowly transitioning from hunter-gathering to agriculture. She had blue eyes, dark hair, and dark skin and was closely related to foragers and farmers who came from continental Europe. Lola’s diet included duck and hazelnuts, and she may have suffered from gum disease and mononucleosis.
We know this about Lola despite the fact that her bodily remains are completely unknown to archaeologists, and, as this time period dates to prehistory, no written records exist about her life and the community she lived in. Incredibly, these rich details were gleaned from a single piece of birch pitch — a kind of ancient chewing gum that’s produced by heating birch bark.
The birch pitch examined in the study. Image: Theis Jensen
The birch pitch, found at the Syltholm site in southern Denmark, was so well preserved that it yielded an entire human genome. Previously, archaeologists have shown that it’s possible to extract bits and pieces of genetic information from birch pitch, but this is the first time that scientists have managed to pull out a whole human genome. What’s more, the researchers, led by Hannes Schroeder from the University of Copenhagen, also managed to extract nonhuman DNA from the gummy remnant, which provided evidence of Lola’s diet and the microorganisms inhabiting her mouth at the time she chewed on the birch pitch. Details of this work were published today in Nature Communications.
Birch pitch has been used by humans since the Middle Pleistocene. The sticky blackish-brown substance was primarily used as glue, but it likely served other purposes as well. Early humans probably chewed on the substance to restore its malleability prior to hafting stone tools, but they may have also done so just for the pleasure of it. The pitch could’ve been used for medicinal purposes, such as easing toothaches or other maladies, as a kind of toothbrush, or to suppress hunger.
Reconstruction of “Lola,” showing the duck and hazelnuts that constituted her diet. Illustration: Tom Björklund
The birch pitch was found sealed in mud, which contributed to its remarkable preservation. Theis Jensen, a co-author of the study and a postdoc at the University of Copenhagen, said the pitch’s hydrophobic qualities also contributed to the preservation.
“DNA from the environment would have a hard time penetrating the substrate,” explained Jensen in an email to Gizmodo. “In general, [birch pitch specimens] preserve very well—even in areas with very acidic soils.”
Jensen was surprised by the quality of the DNA pulled from the pitch, but he was equally amazed by the story embedded within. Lola, whose age could not be determined, had blue eyes, dark hair, and dark skin. Fascinatingly, her lineage was traced to mainland Europe and not central Scandinavia.
“Lola’s features were common amongst individuals of Western Hunter-Gatherers, who lived in central Europe at that time and beyond,” said Jensen.
As the authors noted in the study, dark skin has been documented before in other European hunter-gathers, “suggesting that this [trait] was widespread in Mesolithic Europe and that the adaptive spread of light skin pigmentation in European populations only occurred later in prehistory.”
Lola was also lactose intolerant, an observation “which fits with the notion that lactase persistence in adults only evolved fairly recently in Europe, after the introduction of dairy farming with the Neolithic revolution,” wrote the authors in the study.
“What is striking is that Lola was basically a hunter-gatherer living in the Neolithic.”
In addition to the human genome, the researchers were able to discern DNA belonging to plants and animals, namely hazelnuts and duck — likely the meal consumed by Lola prior to her chomping away on the birch pitch. These foods are suggestive of a hunter-gatherer diet. What’s more, the archaeologists didn’t find any evidence of domesticated foods at the Syltholm site, which came as a surprise given that it dates to the Early Neolithic and the establishment of agriculture. The new research, therefore, speaks to Denmark’s transition from the Mesolithic to the Neolithic.
“What is striking is that Lola was basically a hunter-gatherer living in the Neolithic,” Jensen told Gizmodo.
Jensen said the genetic data “also fits very well with finds from the site,” which suggests the “population to a large degree continued to hunt, gather, and fish during the Early Neolithic,” he explained. The switch to farming, therefore, was likely “a more ‘collaborative’ effort between the immigrating farmers and the hunter-gatherers already residing” in Denmark, said Jensen.
The microbial DNA extracted from the birch pitch allowed the researchers to reconstruct Lola’s oral microbiome. Though a sample of one, the results are potentially indicative of other Neolithic humans living in Lola’s community. The vast majority of microbes identified were harmless, but the researchers identified Porphyromonas gingivalis, a bacterium linked to gum disease, bacterial DNA associated with pneumonia, and the Epstein-Barr virus, which causes mononucleosis, also known as mono or glandular fever.
“We don’t know whether [these microbes] impacted her in any way,” said Jensen. “Most of the bacteria are commensal species, that under specific circumstances can turn pathogenic. But we don’t know if she had pneumonia or glandular fever the day she chewed the pitch.”
It’s pretty amazing what these scientists were able to get out of a single piece of ancient chewing gum. And indeed, the new research strongly suggests that archaeologists should be on the lookout for similar artefacts. Clues to our ancient past and our biology can be found in the most unexpected places.
Featured image: Tom Björklund