Doubts crept in around Greenland, which looked so good it was frankly suspicious, and questions soon spread all over the map: about the wormholes, the handwriting and, most important, the weirdly crumbling ink.

For over half a century, scholars have fought over the authenticity of the Vinland Map, which Yale University unveiled to the world in 1965; at the time, calling it evidence of Viking explorations in the western Atlantic, the first European depiction of North America and a precious medieval treasure.

Yale now says someone duped a lot of people.

“The Vinland Map is a fake,” Raymond Clemens, the curator of early books and manuscripts at the Beinecke Rare Book and Manuscript Library at Yale, said in a statement this month. “There is no reasonable doubt here. This new analysis should put the matter to rest.”

The university said that a team of conservators and scientists, analyzing the elements in the map’s lines and text, found high levels of a titanium compound used in inks that were first produced in the 1920s. Mr. Clemens said the team hoped to publish an article in a scientific journal. Ars Technica, Smithsonian Magazine and Gizmodo, among other news outlets, reported the conclusion this month.