Ancient Baltic warriors sailed to Denmark 2,400 years ago, study finds

New analysis of ancient boat points to Baltic origin

A new scientific study of the Hjortspring boat, a 2,400-year-old wooden vessel, suggests its warrior crew sailed from the eastern Baltic Sea to attack Denmark. The findings, published in PLOS One, use chemical analysis and radiocarbon dating to solve a century-old archaeological mystery.

The boat was discovered in a bog on the Danish island of Als and first excavated in the 1920s. Archaeologists believe it belonged to a raiding party that was defeated, after which the boat was sunk as a ritual offering.

Chemical fingerprint of pine pitch provides a clue

Researchers led by Mikael Fauvelle of Lund University analyzed previously unstudied cordage and waterproofing caulk from the boat. Using gas chromatography-mass spectrometry, they found the caulk was made from animal fat mixed with pine pitch.

This is a critical detail. During the first millennium BCE, pine forests were scarce in Denmark and northern Germany. Extensive pine forests, however, grew along the Baltic Sea coast to the east.

"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 authors stated.

A human fingerprint preserved in ancient tar

One of the most surprising discoveries was a partial human fingerprint preserved in the caulking material. The researchers believe it was likely pressed into the tar during a repair by a crew member.

"Finding a fingerprint on the tar fragments from the boat was a big surprise for us," the team said. "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 mark provides a rare, tangible link to the individuals who built, maintained, or sailed the vessel over two millennia ago.

Dating confirms a pre-Roman Iron Age attack

Dating the boat had been difficult because most of its materials were treated with conservation chemicals that ruin radiocarbon dating. The team found untreated cordage in museum archives and performed new tests.

The radiocarbon dating placed the boat's construction between 381 and 161 BCE, confirming it is from the pre-Roman Iron Age. This aligns with earlier dating of wooden remains from the site.

The new evidence paints a clearer picture of a long-distance, organized military expedition. The warriors would have had to cross a significant stretch of open sea to reach Als from the eastern Baltic.

Solving a 100-year-old mystery

For over a century, historians debated where the Hjortspring warriors originated. The weapons found with the boat were common across Northern Europe, offering no clear clues.

• Previous theories suggested origins in northern Germany or other parts of Denmark.
• The new chemical analysis of the pine pitch is the first major clue in over 100 years pointing eastward.
• The study was funded by grants from the Marcus and Amalia Wallenberg Foundation and Riksbankens Jubileumsfond.

"New analysis of Scandinavia's oldest plank boat brings us a step closer to solving the 100-year-old mystery," the authors concluded. The boat remains on display at the National Museum of Denmark.