A new study suggests that Bronze Age Scandinavians crossed open seas 3,000 years before the Vikings, showing they were skilled seafarers who regularly traveled between present-day Denmark and Norway. These long-distance voyages likely took place centuries before the well-known Viking Age began, challenging earlier beliefs about the limits of prehistoric navigation in the region.
Published in the journal PLOS ONE, the research challenges long-standing beliefs that Bronze Age communities stuck to coastal waters. Led by Boel Bengtsson of the University of Gothenburg, the study presents evidence that early mariners may have routinely completed open-water voyages across the Skagerrak Strait, covering distances where no land was visible for nearly 50 kilometers.
To investigate this possibility, researchers used a simulation program known as the “Voyage Optimization Tool.” They compared two potential routes: a longer, safer 700-kilometer coastal path and a direct 110-kilometer crossing over open water. The goal was to determine whether ancient crews had the necessary skill and equipment to navigate far from shore.
The team combined archaeological findings, environmental data, and boat performance tests. Central to the study were replicas of ancient sewn-plank boats, including designs based on the Hjortspring and Ullerslev vessels. These boats, crafted from stitched wooden planks and powered by paddles, were tested under different wind and wave conditions.
Results showed that in calm summer weather—with waves under one meter and winds below 10 knots—the shorter, open-sea route was not only possible but more efficient. Travel time could be cut by up to 25 percent compared to the coastal route, making it more suitable for urgent or priority journeys.
Seafaring and navigation in the Nordic Bronze Age: The application of an ocean voyage tool and boat performance data for comparing direct open water crossings with sheltered coastal routes – @PLOSONE https://t.co/DAtyzapRNe pic.twitter.com/HIep45qTQ4
— Jerome OLLIER https://jeromeollier.bsky.social/ (@JeromeOLLIER) April 2, 2025
Researchers estimate that such crossings may have begun as early as 2300 B.C. Successful voyages would have required not only seaworthy boats but also experienced crews. Navigation was likely guided by natural cues such as the sun’s position, nearby landmarks, and possibly even animal behavior—techniques still used in some traditional seafaring cultures today.
While the coastal route offered safety and opportunities to restock supplies, it posed its own challenges. The longer distance and slower pace may have made it less practical for regular trade or time-sensitive travel.
Beyond navigation, the study also helps explain cultural similarities between northern Denmark and southwest Norway. Artifacts, burial styles, and building methods found in both regions suggest frequent contact. Researchers argue these connections are better explained by direct open-sea travel than by gradual coastal movement.
The study not only reshapes our understanding of Bronze Age maritime culture but also introduces a flexible research tool. Long-held views about early Nordic travel are now being reconsidered, as researchers show that Scandinavians crossed seas centuries before Vikings set sail.
