Researchers uncover clues to mysterious origin of ancient ship unearthed over 100 years ago

The ship is thought to be the oldest preserved plank-built boat of Northern Europe. (Sahel Ganji/Lund University via CNN Newsource)

When an ancient ship was unearthed in Scandinavia over 100 years ago, archeologists started to uncover bits and pieces of its history.

On board the plank-built vessel was a hoard of weapons — swords, spears, shields and more — revealing a tale of warriors who attempted to attack the Danish island of Als and were ultimately defeated. The island’s defenders sank the ship in a bog, where it remained until its discovery and excavation over two millennia later.

But there were still lingering questions, such as where the invaders came from and when. Now, a new study may bring scientists one step closer to uncovering the mysterious origin of the famous vessel known as the Hjortspring boat.

The findings, which were published Wednesday in the journal PLOS One, provide radiocarbon dating data as well as an analysis of building material, suggesting the boat traveled farther than previously thought.

“Our work has provided an important new clue for the mystery of where the raiders in the boat came from,” said lead author Mikael Fauvelle, an associate professor and researcher in the department of archeology and ancient history at Lund University in Sweden.

“During the Bronze Age, Scandinavians needed to travel by sea to trade for copper and tin, which were needed to make bronze and were not mined in the Nordic region at the time,” Fauvelle said in an email. “The Hjortspring boat, therefore, represents the end result of one of Scandinavia’s early maritime cultures.

“Studying the boat gives us critical information not only about early Iron Age seafaring, but also information about seafaring in the preceding Bronze Age.”

The researchers also uncovered something unexpected: a partial human fingerprint found on tar fragments on the boat, which one of the original seafarers may have made. According to Fauvelle, the fingerprint was a rare find that could provide a direct link to someone who had used the ancient boat.

Uncovering the boat’s past

Before its sinking, the Hjortspring boat was nearly 20 meters (about 66 feet) long and could hold up to 24 men. The boat, which is currently on display at the National Museum of Denmark in Copenhagen, is made up of a bottom plank sewn together with two side planks, and a curved extension at each end.

The ship is thought to be the oldest preserved plank-built boat of Northern Europe and is evidence of the advanced shipbuilding technology of Scandinavia’s early Iron Age, said study coauthor Flemming Kaul, a senior researcher and curator of the prehistory collections at the National Museum of Denmark.

Shortly after the boat’s excavation in the early 1920s, extensive studies were carried out to determine where the invaders came from. It wasn’t until 2024, when the authors of the new study analyzed previously unexamined caulking — a sealant material that makes a boat watertight — and cordage (rope and twine) found with the boat, that the first new major clue in over a century was uncovered.

It was previously assumed that the caulking was made from local materials such as linseed oil or tallow (cow fat), but the researchers found that the material instead to consist of a mixture of animal fat and pine pitch, or dried sap from pine trees.

During this period, Denmark had few pine forests, suggesting that the boat may have been built in a different region, such as the coastal areas along the Baltic Sea that did have pine forests. If the warriors came from that direction, it would suggest they traveled a long distance and could indicate that the attack was organized and premeditated, according to the study.

The new clue “shows that the Scandinavian seafaring tradition of raiding and trading, most famously associated with the Viking age, has very deep roots that go back thousands of years to the early Iron and Bronze Ages,” Fauvelle said. “It also shows that ancient Scandinavia was a very interconnected region. Much like today, political conflicts and alliances transcended regional boundaries and people must have had both contacts with each other over considerable distances.”

Ole Kastholm, a specialist in ancient Scandinavian seafaring and a senior researcher at the Roskilde Museum in Denmark, found the unexpected use of pine pitch for caulking to be exciting. Kastholm, who was not involved with the new study, agrees with the authors’ suggestion that the Hjortspring boat could have come from around the Baltic Sea.

“We have a modern tendency to underestimate the people of the past and their achievements — but they actually rowed and paddled in small, open vessels across the North Sea, Skagerrak and the Baltic Sea. This could have been in logboats, and in smaller plank-built boats such as the Hjortspring Boat,” Kastholm said in an email.

“The study also shows how important it is that we in our museum-collections take care of old artefacts,” he added. “When the Hjortspring Boat was excavated in 1921, one could not have known that 100 years later there would be a number of highly specialized methods that would be able to extract knowledge from even the most insignificant pieces from the excavation. Hopefully one day we are able to pin down the exact geographical origin of this unique vessel.”

Unexpected finds in the archive

When the study authors pulled the caulking fragments from the archive, they also came across some intact cordage, an unexpected find that allowed for radiocarbon dating to be performed.

This modern dating method did not exist at the time of the boat’s excavation, and even after the technique was developed it could not be applied to the vessel’s wood planks due to the chemicals used to preserve them for museum display. But from the cordage, it was determined that the vessel was from the fourth or third century BC, which lines up with previous datings, the authors noted.

And then there was the partial fingerprint from the boat, which was the icing on the cake, as “fingerprints are very rare for this time period and area,” Fauvelle said. A few other fingerprints have been found in tar, “but they all come from different time periods and very different contexts. To find one on such a unique boat is extremely special,” he added.

While the new clues may provide important background about the warriors, the authors hope further research can one day solve the mystery of the ship’s origin. In pursuit of answers, they are studying X-ray scans of the wood that might reveal tree rings, Fauvelle said. He also said the team hopes to extract ancient DNA from the tars, which could help pinpoint the origin of the raiders.

“The Hjortspring boat and the Hjortspring find (with its many weapons) gives evidence as to conflict and strategy during the Early Iron Age of Northern Europe,” Kaul said in an email.

“It is important to continue such studies in order to understand how maritime history is a crucial part of the history (prehistory) of South Scandinavia, where the sea, the fjords, connect the lands. And in the case of Hjortspring, it could be underlined that maritime history is also naval history,” Kaul added. “The control of the Baltic Sea, and the (trade) routes, was as important in the Early Iron Age as it is today.”