About 3,500 years ago, a woman, likely a dancer or priestess of some god now lost to history, was laid to rest in an log casket and buried under a small mound of earth in what is now Sweden. Underneath a wrap of bearskin, the woman wore a tasseled woolen dress, cinched with a belt bearing a large bronze buckle shaped like the sun. At her feet, the woman’s caretakers had placed a birchbark container holding an ancient brew, which lingered in the vessel thousands of years later.
The exact significance of the drink—was it served at her funeral? Was it left as an offering, or to sustain her in her next life?—remains unknown. But thanks to the combined efforts of University of Pennsylvania biomolecular archaeologist Patrick McGovern and Sam Calagione, founder and president of Dogfish Head Brewery, it’s possible for us to get a taste of the past.
In October 2013, McGovern and Calagione added Kvasir, their reconstruction of the drink from the dancer’s tomb, to their lineup of Ancient Ales. Previous entries in the series include Midas Touch, reconstructed from 2,700-year-old drinking vessels found in a tomb in central Turkey, and Chateau Jiahu, based on preserved 9,000-year-old pottery found in a Neolithic-era Chinese village.
In order to resurrect the recipe from traces left on the birchbark container, McGovern used two chemical analysis techniques: gas chromatography, which uses heat to separate the elements of a substance based on their boiling points, and mass spectrography, which determines the masses of atoms or molecules in a sample by deflecting them with a magnetic field. Luckily, the tomb’s environment had kept what remains of the mixture fairly fresh.
With these techniques, McGovern can detect the signature of chemical compounds that are unique to specific plants or other ingredients in the brew. In the Scandinavian drink, for example, McGovern found beeswax compounds indicating the presence of honey, and triturpenoids, indicating birch resin. He also looks for traces of botanical evidence: filaments of wheat or barley, fragments of herbs, and pollen grains.
To start building the recipe, “we triangulate between all the chemical and botanical pollen evidence,” Calagione says. “But all Dr. Pat can tell from that is the laundry list of ingredients.” (In this case: lingonberries, cranberries, barley, birch resin, bog myrtle, yarrow, juniper, and honey, among other things). “We still have to figure out other stuff: what ratio of ingredients do we use? What color was the beer? Was it carbonated? We have a lot of creative input.”
It took about a full year’s worth of work, and three to four test batches, for Dogfish Head to refine their modern kvasir into something that satisfied both Calagione and McGovern. The result is a drink that’s more notably tart than modern beers. But the taste is also complex, sweet in the middle from birch syrup and honey, along with herbal notes in the nose, and with a dry finish thanks to the lingonberries. Calagione recommends pairing Dogfish Head’s Kvasir with sweet and sour pork, beef tacos, smoked fish, gingerbread or apple pie.
Could the same techniques that McGovern and Calagione use be employed by future archaeologists looking to reconstruct the stuff we quaff today?
It might be a bit harder for them to do so; while pottery and other ancient materials are porous enough to provide a good ground to hold onto residue, the glass and plastic of our era provides much less purchase. 3,500 years from now, brewers will probably be stumped by just how we crafted the mysterious ritual beverage known as Bud Light Lime.
Thirsty for something historical? Calagione and McGovern hosted a tasting of Dogfish Head Kvasir—including an all-new variant made with wild yeast—and other ancient ales at Cheers to Science! Nordic Grog: Brewing On The Wild Side, a program at the 2014 World Science Festival.