Fingerprint of ancient seafarer found on Scandinavia’s oldest plank boat
image:
The Hjortspring boat as currently displayed at the National Museum of Denmark.
view moreCredit: Boel Bengtsson
A fingerprint has been found in the tars used to build the oldest known wooden plank boat in Scandinavia, which provides a direct link to the seaborne raiders who used the boat over 2,000 years ago. By analysing the tar itself, Lund University researchers are closer to solving the long-standing mystery of where the attackers in the boat came from.
WATCH VIDEO: Archaeologist describes moment he discovered ancient fingerprint
In the 4th century BC, an armada of boats attacked the island of Als off the coast of Denmark. Traveling in up to four boats, the unknown attackers were defeated, with the defenders sinking the weapons of their foes into the bog in one of the boats, most likely to give thanks for their victory.
“Where these sea raiders might have come from, and why they attacked the island of Als has long been a mystery,” says Mikael Fauvelle, archaeologist at Lund University.
The boat was discovered in the 1880s in the bog of Hjortspring Mose, excavated in the 1920s, and is now known as the Hjortspring boat. It is the only example of a prehistoric plank boat that has ever been found in Scandinavia. The finding is unique – since it was sunk in a bog as an offering, it was exceptionally well preserved. To this day, the Hjortspring boat has been on display at the National Museum of Denmark.
When the researchers unexpectedly located parts of the boat that had not been chemically preserved, they were able to study these using modern scientific methods.
“The boat was waterproofed with pine pitch, which was surprising. This suggests the boat was built somewhere with abundant pine forests,” says Mikael Fauvelle.
Several scholars had previously suggested that the boat and its crew came from the region around modern-day Hamburg in Germany. Instead, the researchers now believe they came from the Baltic Sea region.
“If the boat came from the pine forest-rich coastal regions of the Baltic Sea, it means that the warriors who attacked the island of Als chose to launch a maritime raid over hundreds of kilometers of open sea,” says Mikael Fauvelle.
So, exactly where did someone unknowingly leave their fingerprint in the tar, as a silent message to future generations? The best way to conclusively address the mystery of the boat’s origins would be through tree year ring counting which could match the planks on the boat to the area where the trees they came from were cut down.
“We are also hoping to be able to extract ancient DNA from the caulking tar on the boat, which could give us more detailed information on the ancient people who used this boat,” concludes Mikael Fauvelle.
DETECTIVE WORK LED TO DISCOVERY:
The latest findings are the result of careful detective work by the researchers.
The team wanted to find material from the boat that had not yet been subjected to conservation. This involved going through the archive at the National Museum and reading old correspondence, detailing when and where materials had been shipped between different storage areas and museums in Denmark.
“When we located some of the boxes of materials, we were very excited to find that they contained samples from the original excavation that had not been studied in over 100 years,” says Mikael Fauvelle.
HOW THE RESEARCHERS EXAMINED THEIR FINDS:
The team used a wide range of modern scientific methods to study the Hjortspring material. They were able to carbon date some of the lime bast cordage used on the boat, giving them the first absolute date from the original excavation material and confirming its pre-Roman Iron Age dating.
They also used x-ray tomography to make high resolution scans of the caulking and cordage material found on the boat. This included making a digital 3D model of the fingerprint found in some of the caulking tar.
They used gas chromatography and mass spectrometry to study the caulking material and to see how it was produced. In addition, they worked with modern rope makers to create replicas of the ships cordage to study the rope-making process used in the boat’s construction.
The research was carried out in collaboration with the research program Maritime Encounters at the University of Gothenburg.
Journal
PLOS One
Article Title
New investigations of the Hjortspring boat: Dating and analysis of the cordage and caulking materials used in a pre-Roman iron age plank boat
Cordage fragments from the Hjortspring boat.
Credit
Mikael Fauvette
Photo of caulking fragment showing fingerprint on the left and high-resolution x-ray tomography scan of fingerprint region on the right.
Credit
Photography by Erik Johansson, 3D model by Sahel Ganji.
Depiction of our experimental reconstruction of lime bast cordage and hitch knot. This reconstruction was made by Mikkel Hollmann and Olof Pipping using a spinning hook. Note that some sections are two ply while others are four ply.
Credit
Mikael Fauvette
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Researchers uncover clues to mysterious origin of famous Hjortspring boat
Partial human fingerprint also discovered in material excavated with ancient boat
image:
The Hjortspring boat as currently displayed at the National Museum of Denmark. Photo by Boel Bengtsson.
view moreCredit: Fauvelle et al., 2025, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)A new analysis of the Hjortspring boat, an ancient wooden plank boat now on display in the National Museum of Denmark, has yielded clues to its potential origin — which has long been considered a mystery, according to a study published December 10, 2025 in the open-access journal PLOS One by Mikael Fauvelle from Lund University, Sweden, and colleagues.
The ancient Hjortspring boat was discovered on the Danish island of Als and first excavated in the early 20th century. Researchers believe it belonged to a group of warriors who attacked the island and were defeated, but archaeologists have not previously determined precisely where these warriors came from and when.
For this paper, the researchers carbon-dated and analyzed some previously unstudied caulking and cord materials found with the boat. Using gas chromatography - mass spectrometry, they determined that the caulk was likely made up of animal fat and pine pitch.
At this point in history, Denmark itself had few pine forests. The researchers note that it is possible that pine pitch somehow reached Denmark via trade. However, other coastal areas along the Baltic Sea, east of Denmark, did have pine forests, leading the researchers to believe that the boat may have been built in these regions, and it and its warriors may have come from this direction. If true, the boat would likely have traveled a long distance over the open ocean to reach Als, potentially indicating a notably organized and premeditated attack.
Carbon-dating of the cords and caulk found that the boat was likely built somewhere in the 4th or 3rd century BCE, which lines up with previous datings of wood from the Hjortspring site.
In addition, the team found a partial human fingerprint in part of the caulking material during their study. While they were unable to determine exactly where this fingerprint may have come from, the researchers suggest that it could have been left by one of the crew members during a repair of the boat, “providing a direct link to the seafarers of the ancient vessel.”
The authors add: “New analysis of Scandinavia’s oldest plank boat brings us a step closer to solving the 100-year-old mystery of the ancient boat’s origins. Using cutting-edge scientific methods, researchers have zeroed in on the Baltic Sea Region as the most likely source for the circa 2,400-year-old boat, while also discovering a fingerprint left by an ancient seafarer in the tar used to waterproof the vessel.”
“Finding a fingerprint on the tar fragments from the boat was a big surprise for us. Fingerprints like this one are extremely unusual for this time period. It is great to have found a direct connection with one of the people who used this ancient boat.”
“The boat was used by a small army of invaders who attacked the island of Als in southern Denmark over 2,000 years ago. The invaders were defeated and the local defenders sunk the boat into a bog as an offering to give thanks for their victory. Ever since the boat was excavated from the bog in the early 1920s, the question of where the invaders came from has been an open mystery. The weapons they used which were found in the boat were quite common for the time and were used throughout Northern Europe, giving us few instructions as to their origins. Several different theories for the boat’s origins have been proposed over the past 100 years, with some scholars suggesting the boat’s crew came from somewhere in northern Germany or perhaps a different part of modern-day Denmark. Now our scientific analysis of the boat’s caulking material gives us the first major new clue in over a century. The boat was waterproofed with pitch from pine trees, which were rare in both Denmark and northern Germany during the first millennium BCE. We argue that this means the boat and its crew most likely came from further east along the shores of the Baltic Sea where pine forests were more abundant.”
“The boat was excavated before modern dating methods were available and most of the material from the boat was immediately conserved using chemicals that make radiocarbon dating impossible. Going through the archives, however, we were able to find some original cordage that had not been conserved. We obtained a radiocarbon date from the cordage that returned a date range of between 381 and 161 BCE, confirming the pre-Roman Iron Age date of the boat.”
Comparison of Hjortspring boat (Above, 3D model by Richard Potter) with securely dated Bronze Age art (Rørby sword and Sagaholm rock art) as well as an example of early Iron Age art from Brastad. Thousands of other examples of Bronze Age boat depictions exist. Note the continuity in form and design evident in these different boat depictions.
Credit
Fauvelle et al., 2025, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
Photo of caulking fragment showing fingerprint on the left and high-resolution x-ray tomography scan of fingerprint region on the right. Photography by Erik Johansson, 3D model by Sahel Ganji.
Credit
Fauvelle et al., 2025, PLOS One, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
In your coverage, please use this URL to provide access to the freely available article in PLOS One: https://plos.io/44sjLHv
Video caption: Archaeologist Mikael Fauvelle talks about the findings at the National Museum of Denmark, where the Hjortspring boat is on display.
Video credit: Lund University, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
Video link: https://plos.io/4p8Dt3f
Citation: Fauvelle M, Bengtsson B, Pipping O, Hollmann M, Mortensen MN, Toft P, et al. (2025) New investigations of the Hjortspring boat: Dating and analysis of the cordage and caulking materials used in a pre-Roman iron age plank boat. PLoS One 20(12): e0336965. https://doi.org/10.1371/journal.pone.0336965
Author countries: Sweden, Denmark
Funding: This research was supported by grants from the following funders: Marcus and Amalia Wallenberg Foundation grant awarded to M.F. for Complex Canoes project (grant number: 2022.0108) Riksbankens Jubileumsfond grant awarded to J.L. for Maritime Encounters program (grant number: M21-0018). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Journal
PLOS One
Method of Research
Observational study
Subject of Research
People
Article Title
New investigations of the Hjortspring boat: Dating and analysis of the cordage and caulking materials used in a pre-Roman iron age plank boat
Article Publication Date
10-Dec-2025
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