18 Dec 2019

Ancient Genome Found in Lump of Birch Pitch

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Wired reports the results of an interesting study of ancient human DNA.

Nearly 6,000 years ago, in a seaside marshland in what is now southern Denmark, a woman with blue eyes and dark hair and skin popped a piece of chewing gum in her mouth. Not spearmint gum, mind you, but a decidedly less palatable chunk of black-brown pitch, boiled down from the bark of the birch tree. An indispensable tool in her time, birch pitch would solidify as it cooled, so the woman and her comrades would have had to chew it before using it as a sort of superglue for, say, making tools. Our ancient subject may have even chewed it for its antiseptic properties, perhaps to ease the pain of an infected tooth.

Eventually she spit out the gum, and six millennia later, scientists found it and ran the blob through a battery of genetic tests. They not only found the chewer’s full genome and determined her sex and likely skin and hair and eye color, they also revealed her oral microbiome—the bacteria and viruses that pack the human mouth—as well as finding the DNA of hazelnut and duck she may have recently consumed. All told, from a chunk of birch pitch less than an inch long, the researchers have painted a remarkably detailed portrait of the biology and behavior of an ancient human.

When that birch pitch hit the ground 5,700 years ago, the European continent was playing host to a full-tilt transformation of its human residents. Agriculture was spreading north from the Middle East, and humans were literally and figuratively planting roots—if you’re looking after crops, you’re staying put and building up infrastructure to support your efforts, not following around herds of wild game.

But several converging lines of evidence indicate that this gum-chewing woman actually was a hunter-gatherer, thousands of years after the invention of agriculture. For one, previous analyses have allowed scientists to associate certain genes with either agricultural or hunter-gatherer lifestyles. They did this by matching DNA samples with archaeological evidence for those people—farming tools versus hunting tools, for instance.

The genetics of this ancient woman point to the hunter-gatherer way of life, matched with contemporaneous archeological evidence from the area. “You find lots of fish traps and eel-catching prongs and spears,” says University of Copenhagen geneticist Hannes Schroeder, coauthor on a new paper in Nature Communications describing the findings. Evidence of a more settled lifestyle at the site only came later in history.



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