They actually rowed across open water in small boats two thousand years ago
More than two thousand years ago, a warship and its warriors were swallowed by a Danish bog, preserving not just wood and weapons but the unresolved question of where these raiders had come from. A century after the Hjortspring boat was excavated, researchers at Lund University have returned to forgotten archive fragments — caulking, cordage, and a single human fingerprint pressed in tar — and found in them the first credible answers. The pine pitch used to seal the hull points toward Baltic shores far from Denmark, suggesting a planned, long-distance raid by seafarers who belonged to a maritime tradition far older than the Vikings. In recovering these details, science reminds us that the past is not exhausted — only waiting for the right questions.
- A warship deliberately sunk by Iron Age defenders has held its secrets for over two millennia, frustrating every attempt to identify the raiders who died attacking the Danish island of Als.
- Researchers discovered that the boat's caulking contained pine pitch — a material foreign to Denmark — upending the assumption that the vessel was locally built and pointing instead to the pine-forested Baltic coast.
- Radiocarbon dating of cordage fragments, a technique unavailable to the original 1921 excavators, confirmed the vessel's age with modern precision and validated what had only been estimated for a century.
- A partial human fingerprint preserved in tar on the hull — extraordinarily rare for the period — collapsed the distance between the present and the hands that once built and crewed this ship.
- The team is now pursuing tree-ring analysis of the timber and ancient DNA extraction from the tar, racing to name the raiders before the evidence reaches its limit.
- The findings reframe Scandinavian maritime history, positioning the Hjortspring boat not as an isolated artifact but as the peak of a seafaring culture that predated Viking fame by thousands of years.
In the early 1920s, workers in Scandinavia pulled from a bog the remains of a nearly 66-foot warship, its hull still accompanied by the weapons of men who had failed to conquer the Danish island of Als. The vessel — the Hjortspring boat — had been deliberately sunk by the island's defenders around two thousand years ago and was eventually brought to the National Museum of Denmark in Copenhagen. The broad outline of the story was always legible: raiders came, failed, and were buried with their ship. But who they were and where they had come from remained stubbornly unanswered.
In 2024, a team led by Mikael Fauvelle at Lund University turned to materials that had sat in museum archives since the original excavation — fragments of caulking and cordage that no one had subjected to modern analysis. The caulking told an unexpected story: rather than local Danish materials like linseed oil or animal fat alone, it contained pine pitch, the dried sap of pine trees. Because Denmark's Iron Age landscape held few pine forests, the boat almost certainly was not built there. The Baltic coast, rich in pine, became the leading candidate — implying that the raiders had traveled a significant distance and mounted a deliberate, organized assault.
The cordage fragments enabled radiocarbon dating, confirming the vessel dated to the fourth or third century BC with a precision the original archaeologists could never have achieved. Even more arresting was the discovery of a partial human fingerprint preserved in tar on the hull — a direct, tactile trace of the person who built or handled the boat, rare anywhere in the ancient world and never before found in quite this context.
For researchers like Ole Kastholm at the Roskilde Museum, the pine pitch discovery illuminated something larger: a level of technical knowledge and long-distance coordination that modern observers have consistently underestimated in ancient peoples. The Hjortspring boat, he and Fauvelle argue, represents the culmination of a Scandinavian maritime tradition stretching back through the Bronze Age, when Nordic peoples had to cross open water to trade for copper and tin unavailable in their own region.
The work is not finished. Fauvelle's team is analyzing X-ray scans of the wood for tree rings that might identify the timber's origin, and attempting to extract ancient DNA from the tar to genetically trace the raiders themselves. Each new technique reopens questions that once seemed permanently closed, sketching a world where the sea was a highway rather than a boundary, and where a fingerprint pressed into tar can still carry meaning two thousand years later.
In the early 1920s, workers in Scandinavia pulled something extraordinary from a bog: the remains of an ancient warship, its hull still holding the weapons of men who had died trying to conquer a Danish island. The vessel, which came to be known as the Hjortspring boat, was nearly 66 feet long and built to carry roughly two dozen warriors. It had been deliberately sunk by the island's defenders around two thousand years ago, and there it stayed, preserved in the waterlogged earth, until archaeologists excavated it and brought it to the National Museum of Denmark in Copenhagen.
For more than a century, the boat's basic story was clear enough: raiders had attacked the island of Als, failed, and paid with their lives. But the deeper questions lingered. Who were these men? Where had they come from? When exactly did the attack happen? The wooden hull offered few answers, and for decades the mystery seemed to have reached its limit. Then, in 2024, a team of researchers led by Mikael Fauvelle at Lund University in Sweden decided to examine materials that had been sitting in museum archives since the original dig—fragments of caulking, the sealant that made the boat watertight, and pieces of cordage that had survived the centuries.
What they found changed the picture. The caulking was not made from local Danish materials like linseed oil or animal tallow, as earlier archaeologists had assumed. Instead, it was a mixture of animal fat and pine pitch—the dried sap of pine trees. This detail mattered because Denmark in the Iron Age had few pine forests. The boat, it seemed, had been built somewhere else entirely, likely along the Baltic coast where pine grew in abundance. If the raiders came from that direction, they had traveled a considerable distance, suggesting their attack was organized and deliberate rather than opportunistic. The findings, published in PLOS One in December 2024, offered the first major breakthrough in understanding the boat's origins in over a hundred years.
The cordage fragments also allowed researchers to perform radiocarbon dating—a technique that did not exist when the boat was first excavated. The analysis confirmed that the vessel dated to the fourth or third century BC, aligning with earlier estimates but now supported by modern scientific precision. Even more striking was an unexpected discovery: a partial human fingerprint, preserved in tar on the boat's surface. Fauvelle described it as extraordinarily rare for the period and region. A few other ancient fingerprints have been found in tar, but never in a context quite like this—never on such a significant vessel, never with such a direct connection to the hands that built and used it.
The implications reach far beyond a single boat. Fauvelle and his colleagues argue that the Hjortspring vessel is evidence of a maritime tradition in Scandinavia that stretched back thousands of years before the Vikings became famous for their seafaring. During the Bronze Age, Scandinavians had to travel by sea to trade for copper and tin, metals not found in the Nordic region but essential for making bronze. The Hjortspring boat represents the culmination of that early maritime culture—a sophisticated, seaworthy vessel built by people who understood how to construct ships capable of crossing open water.
Ole Kastholm, a specialist in ancient Scandinavian seafaring at the Roskilde Museum who was not involved in the study, emphasized that modern observers often underestimate the achievements of ancient peoples. Those early mariners, he noted, regularly rowed and paddled across the North Sea, the Skagerrak strait, and the Baltic in small open boats. The pine pitch discovery was particularly exciting to him because it suggested a level of technical knowledge and long-distance coordination that scholars are only now beginning to appreciate. He also stressed the importance of careful museum stewardship—the fact that fragments from a 1921 excavation could yield new insights a century later depended entirely on their preservation and accessibility.
The researchers are not finished. Fauvelle's team is examining X-ray scans of the wood to look for tree rings that might reveal where the timber came from. They are also attempting to extract ancient DNA from the tar, hoping that genetic analysis might pinpoint the geographic origin of the raiders themselves. Each new technique applied to the boat's remains has the potential to answer questions that seemed permanently closed. What emerges from this work is a picture of an interconnected ancient world, where political conflicts and trade networks spanned considerable distances, where the sea was not a barrier but a highway, and where control of maritime routes mattered as much then as it does today.
Notable Quotes
The Hjortspring boat represents the end result of one of Scandinavia's early maritime cultures, showing that the seafaring tradition most famously associated with the Viking age has very deep roots going back thousands of years.— Mikael Fauvelle, lead researcher, Lund University
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.— Ole Kastholm, specialist in ancient Scandinavian seafaring, Roskilde Museum
The Hearth Conversation Another angle on the story
Why does it matter where this boat came from? It sank two thousand years ago.
Because it tells us something about how people organized themselves. If these raiders came from the Baltic, they traveled hundreds of miles to attack one island. That suggests coordination, planning, resources. It's not a random raid—it's a military operation.
And the pine pitch is the clue that proves this?
It's one piece. The boat was built with materials from a region that had pine forests. Denmark didn't. So either the boat was built elsewhere and brought there, or the builders came from elsewhere. Either way, it points to the Baltic.
What about the fingerprint? That seems almost too intimate.
It is. It's someone's actual hand, pressed into tar while the boat was being built or used. We don't have names, we don't have records, but we have that. For a period where we have almost no individual traces, it's extraordinary.
Can they actually figure out who these raiders were?
They're trying. DNA from the tar, tree ring analysis, more radiocarbon dating. Each technique that didn't exist in 1921 is another chance to learn something new. But the honest answer is we may never know exactly who they were. We'll just know more about how they lived and traveled.
So this is really about understanding early maritime culture?
Exactly. It pushes back the story of Scandinavian seafaring centuries before the Vikings. It shows that people were already crossing open water, organizing raids, trading across regions. The Vikings didn't invent that tradition—they inherited it.