Here’s what you’ll learn when you read this story:Researchers discovered a fingerprint on Scandinavia’s oldest plank boat, used by seaborne raiders over 2,000 years ago. The print was left in the caulking tar by one of the boat’s makers. Experts still hope the fingerprint can point to clues about who the raiders were and why they attacked the island of Als. Researchers scoured Scandinavia’s oldest plank boat (likely used by the raiders), and discovered a fingerprint pressed into the tar caulking material. They also used X-ray tomography for high-resolution scans, created a 3D model of the fingerprint, and employed chromatography and mass spectrometry to help see how the caulking tar was produced.