SCIENCE has been unable to resolve a long-running dispute over the authenticity of a medieval map showing Greenland and North America. Two new studies have produced contrasting results 鈥� one dating the map鈥檚 parchment to the early 15th century, the other dating the ink as modern.
The Vinland Map appears to be a German 15th-century copy of a 13th-century original. It claims to show 鈥渢he Island of Vinland, discovered by Bjarni and Leif in company鈥�. If genuine, central Europeans must have known of visits to the New World made by Norse explorers half a century before Columbus set sail, raising questions about whether he also knew of its existence.
The map surfaced in 1957, when it was offered for sale bound with an authentic 15th-century manuscript called the Tartar Relation. The British Museum declined to bid after its keeper of manuscripts, Bertram Schofield, concluded it was a fake. But philanthropist Paul Mellon bought it for $300,000 and donated it to Yale University.
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In 1995, scientists cut a sliver of parchment from the edge of the map for carbon dating. After a lengthy analysis, Jacqueline Olin of the Smithsonian Institution in Washington DC, and her colleagues concluded that the parchment probably dates from within 11 years of 1434 (Radiocarbon, vol 44, p 45).
In 1973, Chicago-based microscopist Walter McCrone found signs of anatase, a form of titanium dioxide first produced in the 1920s, in ink residues on the map. In a second study released last week, Robin Clark of University College London and colleagues confirmed the finding. They found the ink also contains carbon black, which was used in medieval times. Most of the black has flaked off, leaving yellow lines containing anatase. Clark suggests a modern forger drew the yellow lines to simulate ageing, then added the carbon black (Analytical Chemistry, vol 74, p 3658).
The age of the parchment doesn鈥檛 impress Clark. 鈥淎ny possible forger would have to be nuts not to use an old parchment,鈥� he says. Nor is Olin persuaded by the ink evidence. She thinks deterioration of a medieval ink made from iron gallotannate could have left a titanium residue. Few inks from the period have been analysed, she points out, and iron inks are known to leave yellow residues.
In the absence of clear scientific evidence, historians are relying on other clues. Paul Saenger of the Newberry Library in Chicago thinks the map is fake because there are mistakes in the Latin, and because it鈥檚 oriented to the north. Other medieval maps are oriented toward the east.
Californian historian Kirsten Seaver is finishing a book on the subject. She suspects Joseph Fisher, an elderly Jesuit priest and map scholar who lived in Austria, drew the map on a blank flyleaf from the Tartar Relation in the 1930s, 鈥渕ostly as a private doodle, but with the knowledge that if found it could cause a Nazi scholar no end of pain鈥�. The Norse explorers hailed by the map were in fact Catholic, so it would have affirmed Nazi claims of Norse achievements but also challenged their hatred of Catholics. If a Nazi wanted to believe the Norse discovered America, 鈥渉e would have found the Roman Church was there first,鈥� she says.