What at first seemed highly improbable – even ludicrous – is now closer to becoming a reality: The evidence in favor of a second, older Mona Lisa by Leonardo is growing.
New tests and scholarly attributions are moving in favor of attributing a recently re-discovered painting to Leonardo da Vinci. Advocates of the “Isleworth Mona Lisa” claim this to be the original, painted when the sitter, Lisa del Giocondo, was in her youth.
Since the painting’s revelation in Geneva in September 2012, the Zurich-based Mona Lisa foundation has spear-headed efforts to demonstrate the painting’s authenticity (though it claims to have no financial interest in the work).
One strong piece of evidence came from a carbon-dating test performed by The Swiss Federal Institute of Technology (ETH). The test results directly refute arguments that the “Isleworth Mona Lisa” is a later, 16th-century copy of the Louvre’s painting. ETH determined that the painting was almost certainly created between 1410 and 1455 (95.4% probability), and most likely between 1425 and 1450 (68.2% probability).
A second argument was made by Professor John Asmus, a nuclear physicist who conducted four tests on the “Isleworth Mona Lisa” and the Louvre’s “Gioconda.” By digitizing the brushstrokes of both paintings, Asmus determined that they would have been painted by the same artist.

Alfonso Rubino’s application of Vitruvian geometry to the “Isleworth Mona Lisa”
Further support has come from Italian geometrist Alfonso Rubino, who, after studying Leonardo’s “Vitruvian Man” in relation to the artist’s paintings, determined that Leonardo incorporated Vitruvian geometry into his other artwork. Rubino has studied the “Isleworth Mona Lisa” and concluded that its similar proportions and structure serve as incontrovertible evidence of Leonardo’s authorship.
The Isleworth Mona Lisa still has notable detractors in the world of art history. British Leonardo specialist Martin Kemp has argued vehemently against the painting’s acceptance, as has U.S. scholar Richard Spear.