The entire genome of a female who lived in Denmark 5,700 years ago has been sequenced, from a piece of prehistoric “chewing gum.”
It’s impossible to know whether she was a girl or full-grown woman, but like other early Europeans, as we know now, she likely had dark skin, dark hair and blue eyes, Theis Jensen of the University of Copenhagen and a host of co-authors reported Tuesday in Nature Communications.
The international team also managed to elucidate from the masticated bit of birch pitch found at Syltholm, on the island of Lolland, that the prehistoric lady seems to have hosted the herpes species known as Epstein-Barr, as well as the bacteria that causes gonorrhea. She may have suffered the ravages of gum disease as well, say the scientists based on analyzing nonhuman DNA in the birch tar, which is indicative of her oral microbiome (the bacteria living in her mouth).
The oral microbiome also included – among a riot of germs – Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola, which cause periodontal disease. Another microbe detected in the gum was Pneumococcus, the cause of pneumonia.
Furthermore, the genome analysis indicates that the woman was related to Western hunter-gatherers from mainland Europe and doesn’t evince ancestry from hunter-gatherers closer to home in central Scandinavia, or Neolithic farmers, though they seem to have reached that area when she was alive. Possibly she came from afar or originated in peoples who migrated northward to Scandinavia as the Ice Age waned, but hadn’t mixed with other peoples yet.
The “birch pitch” she was chewing is the same as the birch bark tar that prehistoric peoples (including Neanderthals) were using tens and hundreds of thousands of years earlier to glue stone axes to handles (a technique known as hafting).
There has been quite the debate over how tricky it is to make birch bark glue. Originally, it was thought to require advanced anaerobic firing. More recently, though, science has demonstrated that birch tar can be made by taking the bark, heating on a rock, and scraping off the pitch. That’s it. Scraped off the rock, the tar can be used to glue something – or, we learn, to chew.
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“Small lumps of this material have been found at archaeological sites and have often included tooth imprints, which suggests that they were chewed,” the archaeologists write.
Which begs the question of whether the prehistoric Danes were chewing gum as gum – or whether they were doing that to soften birch tar that had been manufactured and cooled, in order to better haft some tool.
Some even postulate that the prehistoric peoples had realized birch tar had a medicinal property: it contains betulin, a natural antiseptic.
The medicinal theory might sound a tad far-fetched, given that people over the ages have demonstrated fervent faith in the curative properties of categorically poisonous substances, but perhaps the prehistoric peoples of Scandinavia were onto something. In 1999, a paper rebutting an editorial from 1897 (really!) in the British Medical Journal, which mourned the spread of the “disgusting habit” of chewing gum, pointed out that masticants had been found in Scandinavia going back to the Middle Stone Age – and argued that the ancients had realized that chewing the tar helped preserve their teeth.
In any case, while the production of birch glue has provoked heated argument over the smarts of Neanderthals and archaic humans, there is no question that by 5,700 years ago making birch glue was a cinch.
Wondrously, the researchers note that they elucidated all this about her appearance just from the DNA retrieved from the masticated birch tar: no human remains have been recovered from the site. Ergo, now we know that the woman had dark hair, dark skin, blue eyes and herpes, and was lactose intolerant, without ever finding her body.
Duck à la hazelnut
The nonhuman DNA sequences in the bit of tar also turned out to include mallard duck and hazelnut, which leads to the suggestion that bits of those foods were trapped in the lady’s teeth.
Regarding her complexion, recent evidence has suggested that hunter-gatherers in Europe and Britain of the late Stone Age had light-colored eyes and dark skin. The light-colored complexion only developed later in prehistory. It bears noting that Scandinavia was uninhabitable in the Ice Age. It was the last part of Europe to be settled: peoples spread there only as the ice began to retreat.
Separate analysis of Scandinavian hunter-gatherer genomes (done in 2018) detected two routes of inbound migration to the region around 11,000 to 12,000 years ago: One from the south, and another from the northeast along the ice-free Norwegian Atlantic coast. Quickly, though, the people of Scandinavia developed lighter skin tones than either of their forebears, suggesting adaptation to the low light levels: Depigmentation was necessary to absorb as much ultraviolet B as possible in the gray north – so their bodies could synthesize vitamin D. No sun, no vitamin D = brain damage.
The lady of Syltholm still had the dark skin, it seems, which also could suggest she was a fairly recent arrival. Her lactase intolerance, on the other hand, was expected: Separate genetic studies have indicated that “lactase non-persistence” was the human norm until the domestication of the goat and cow in the Neolithic, starting very roughly also around 11,000 years ago. It is still the norm in modern societies that shun dairy products.
What kind of life might she have led, aside from a penchant for duck and hazelnuts? Culturally, this period is marked by the transition from the Late Stone Age Ertebølle culture, beginning about 7,300 years ago and lasting to 5,900 years ago.
They still used tools made of stone, bone and antlers, but had begun to dabble in pottery and to husband domestic animals — though nobody’s guessing whether the local hunter-gatherers developed farming or whether farming folk were among the incoming migrants. But the evidence has begun to suggest that hunting-gathering as a lifestyle didn’t immediately roll over and submit to the wonders of agriculture and that, if anything, pockets of hunter-gatherers clung on. Genetically distinct hunter-gatherer groups may have survived for much longer than previously assumed.
In fact, these “survivors” could have triggered the resurgence of hunter-gatherer ancestry that is proposed to have occurred in central Europe between 7,000 and 5,000 years ago, the authors suggest. The lady of Syltholm may well have been a member of a purely hunting-gathering society that hunted a duck, gathered hazelnuts and scorned the farmers who began to take root in Scandinavia around the time she lived and died.