The Hjortspring boat, unearthed on the Danish island of Als, was first excavated in the early 20th century. Archaeologists theorize it was utilized by a group of warriors who attempted an invasion of the island but ultimately faced defeat. While the weaponry associated with the vessel was common across Northern Europe during that era, the precise origins of these warriors and the timeline of the boat's construction have remained elusive.
Carbon Dating and Chemical Analysis of Ancient Caulking
To shed light on these mysteries, researchers analyzed previously unexamined materials found alongside the boat, including cordage and waterproofing caulk. They employed radiocarbon dating to ascertain the age and utilized gas chromatography-mass spectrometry to analyze the chemical composition of the caulking. Their findings revealed that the waterproofing substance was a mixture of animal fat and pine pitch.
During the first millennium BCE, Denmark had limited pine forests. While it's conceivable that pine pitch was acquired through trade, substantial pine forests existed along parts of the Baltic Sea coast to the east of Denmark. This evidence implies that the vessel may have been built in one of those eastern areas. If validated, this indicates that the boat and its crew likely navigated a considerable expanse of open water to reach Als, suggesting a meticulously organized military operation.
Radiocarbon analysis of the cordage and caulk indicates the boat was constructed between the 4th and 3rd centuries BCE, aligning with earlier estimates of wooden remains from the Hjortspring site.
A Rare Fingerprint From the Iron Age
A particularly remarkable finding was a partial human fingerprint preserved within the caulking. While researchers cannot definitively identify the individual, it is believed to have been imprinted in the tar during a repair by a crew member. The team noted that this mark could provide a direct connection to the ancient seafarers of the vessel.
The authors stated, "Our new analysis of Scandinavia's oldest plank boat brings us closer to unraveling the century-old enigma surrounding its origins. By employing advanced scientific techniques, we have identified the Baltic Sea Region as the most probable source of the approximately 2,400-year-old boat, while also uncovering a fingerprint left by an ancient mariner in the tar used for waterproofing."
They added, "Discovering a fingerprint on the tar fragments was a surprising revelation for us. Such fingerprints are exceptionally rare from this historical period, making it thrilling to have established a direct link to one of the individuals who operated this ancient vessel."
Solving a Century-Old Scandinavian Mystery
Researchers explain, "This boat was employed by a small contingent of invaders who assaulted the island of Als over 2,000 years ago. After being defeated, the local defenders submerged the boat in a bog as a tribute for their victory. Since the boat's excavation in the early 1920s, the question of the invaders' origins has remained open. The weapons discovered with the boat were widespread at the time, providing little insight into their provenance. Various theories have emerged over the last century, with some suggesting the crew hailed from northern Germany or other regions of modern Denmark. Our scientific examination of the caulking now offers the first significant new clue in over a hundred years. The use of pitch from pine trees, which were scarce in Denmark and northern Germany during the first millennium BCE, suggests the boat and its crew likely originated from further east along the Baltic Sea, where pine forests were more prevalent."
The researchers also elaborated on the challenges of dating the boat. "Excavated before modern dating techniques were available, much of the boat's material was immediately treated with chemicals that hinder radiocarbon dating. However, we discovered original cordage that had not undergone conservation, allowing us to obtain a radiocarbon date ranging from 381 to 161 BCE, which confirms the pre-Roman Iron Age timeline for the boat."
This study received funding from the Marcus and Amalia Wallenberg Foundation grant for the Complex Canoes project and the Riksbankens Jubileumsfond grant for the Maritime Encounters program. The funders had no involvement in the study's design, data collection, analysis, publication decisions, or manuscript preparation.