Ancient Fingerprint on Scandinavia's Oldest Plank Boat Points to Baltic Raiders

A tiny fingerprint pressed into preserved caulking has given researchers a rare, human connection to the Hjortspring boat — the oldest wooden plank vessel known from Scandinavia — and fresh clues about where a band of sea raiders came from more than 2,400 years ago.

A Vessel Frozen in Time

Discovered in the 1880s and excavated from the Hjortspring Mose bog in the 1920s, the Hjortspring boat was remarkably preserved by low-oxygen peat. The craft is on display at the National Museum of Denmark, but its geographic origins have long been debated.

Fingerprint, Tar and Rope Yield New Evidence

Researchers who reexamined fragments of the boat located several pieces of caulking tar and lime-bast cordage that had escaped earlier conservation treatments. One chunk of tar bears an impressed human fingerprint, likely left by someone who repaired or handled the vessel — a direct physical link to an individual who touched the boat more than two millennia ago.

A caulking fragment (left) from Hjortspring boat that shows a fingerprint, and the high-resolution x-ray tomography scan (right) of the fingerprint region. | Credit: Photography by Erik Johansson; 3D model by Sahel Ganji;CC BY 4.0

Using gas chromatography and mass spectrometry (GC-MS), the team identified the caulking as a mixture of animal fat (probably tallow) and pine pitch (resin). That blend indicates access to pine resources and suggests construction or repair in a pine-rich landscape. According to Mikael Fauvelle of Lund University, who led the analysis, the chemical signature points away from previous ideas tying the boat to the Hamburg region and instead toward Baltic coasts east of the modern island of Rügen.

Dating, Scans and Experimental Work

Radiocarbon dating of lime-bast rope from the vessel provides the first direct dates from the boat's organic material: calibrated results place the material between about 381 and 161 B.C., consistent with a pre-Roman Iron Age context (the broader event is placed roughly between 400 B.C. and 101 B.C.).

The team also used X-ray tomography to create detailed 3D models of the caulking and cordage sections, allowing close study of the fingerprint's ridge patterns. While the print is readable, ridge analysis could not determine the individual's sex or identity. To better understand ancient technology, researchers collaborated with modern rope makers to recreate lime-bast cordage and study period rope-making techniques.

Cordage, or rope fragments from the Hjortspring boat. | Credit: Mikael Fauvelle;CC BY 4.0

Historical Context and Implications

About 2,400 years ago an armada of roughly 80 raiders in this boat and three others attacked the island of Als (off modern Denmark). The attackers were defeated, and the victorious islanders reportedly sank the captured vessel along with weapons and shields as a votive offering — a deposition that helped preserve the craft in the bog.

If the pine-resin signature does indicate an origin along the eastern Baltic coast, these raiders would have crossed considerable open sea to reach Als, offering new insights into the range and organization of Iron Age maritime raids and long-distance seafaring in northern Europe.

Next Steps

The study, published Dec. 10 in PLOS One, notes plans to attempt DNA extraction from the tar, which could provide genetic information about the people who handled the boat. Combined chemical, radiocarbon and imaging evidence is helping archaeologists reconstruct craft technologies, mobility, and the social networks of seafaring communities more than two millennia ago.

Key methods: GC-MS chemical analysis, radiocarbon dating of lime-bast cordage, X-ray tomography for 3D modeling, experimental rope replication.