New radiocarbon dating of organic materials found with the mysterious Hjortspring boat, discovered in 1920 on Denmark’s island of Als, suggests the mysterious craft’s makers may have been distant invaders who traveled from across the Baltic Sea to attack the island’s inhabitants.
Led by Mikael Fauvelle from Lund University, Sweden, and colleagues, the new analysis, which dated the boat’s original construction to sometime between the 4th and 3rd century BCE, is consistent with previous dating of the wood recovered at the same site.
The research team also found a human fingerprint in the boat’s mortar, providing what the researchers called a “human link” between scientists in the 21st century and the craft’s ancient builders almost 2,400 years earlier.
A Discovery Leaving More Questions Than Answers
When scientists first discovered the Hjortspring boat in 1920, they couldn’t immediately determine its origins. Some weapons were also found, but they offered little insight into the boat’s makers.
“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 researchers write in a new study detailing their work. “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.”
Unfortunately, because early twentieth-century archaeologists used preservation materials on the boat and on related artifacts also uncovered at the site, nearly all of them were unable to be carbon-dated.
“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,” the study authors explained.
Still, modern technologies ultimately enabled dating some of the wood from the boat’s site to around 300 BCE. Although not conclusive, the ancient date offered some potential context for its original construction.
For their new analysis, the Lund University team gained access to some previously unstudied cord and caulking samples collected from the boat’s site. Unlike the samples treated in 1920, these untreated organic cords and caulking proved viable for modern carbon dating techniques.
“Going through the archives, however, we were able to find some original cordage that had not been conserved,” they explained.
After selecting and testing the samples, the team obtained a radiocarbon date for the cordage of 381-161 BCE. The team said this result confirms the boat’s “pre-Roman Iron Age” date of manufacture. Still, this date did not offer any insight into the boat’s origins.
Next, the team used a gas chromatography-mass spectrometer to determine the chemical composition of the caulk. According to the team’s analysis, the ancient material was a combination of animal fat and pine pitch. Denmark had very few pine forests during this period, making the use of local pine pitch extremely unlikely.
Although they concede the pitch could represent some ancient trade with distant visitors, they believe the most likely explanation involves distant invaders from across the Baltic, where pine forests were much more abundant.
“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.”
The team believes the possibility of a long, successful sea voyage suggests the attack on Al’s Island may have been organized, planned, and premeditated. They also suggest its location at the bottom of the lagoon has symbolic meaning for the island’s ancient inhabitants.
“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 researchers explain. “The invaders were defeated, and the local defenders sunk (sic) the boat into a bog as an offering to give thanks for their victory.”
When analyzing the caulking material, they found an unexpected remnant of one of the boat’s ancient owners: a partial fingerprint. The team said that finding an ancient fingerprint from this distant time period is “extremely unusual.”
Although there is no ancient fingerprint database to compare the newly discovered fingerprint against, the team said its presence in the caulking may indicate that it was left by someone repairing the craft while it was still in use. If true, the team suggests finding it during this study provides a “direct link to the seafarers of the ancient vessel.”
“Finding a fingerprint on the tar fragments from the boat was a big surprise for us,” they write. “It is great to have found a direct connection with one of the people who used this ancient boat.”
“[This] 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,” the researchers added.
The study “New investigations of the Hjortspring boat: Dating and analysis of the cordage and caulking materials used in a pre-Roman Iron Age plank boat” was published in PLOS One.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.