So, has the world found Mona Lisa's first smile?

A younger and happier version of Leonardo Da Vinci's masterpiece has been presented today in Geneva with the suggestion that the painting was executed by the Renaissance master approximately a decade earlier than the iconic picture that hangs in the Louvre.

Known as the Isleworth Mona Lisa, the artwork has been the focus of a 35 years of research, which has been summarized in a 320-page book published by The Mona Lisa Foundation, a non-profit organization based in Zurich, Switzerland, and a video.

Listing historical and archival records, scientific and experimental data, the book aims to support the theory that the painting is the original portrait of Lisa Gherardini del Giocondo, while the Louvre masterpiece is a later version, completed in Rome around 1516 at the encouragement of Lorenzo de' Medici's brother Giuliano.

"Historical evidence suggests that Leonardo da Vinci left unfinished an earlier portrait of Mona Lisa in which she is flanked by side columns," the Mona Lisa Foundation said in a statement.

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Slightly larger in size than the Louvre portrait, the Isleworth painting indeed shows an unfinished background framed by two columns. It features a darker tonality while depicting a younger lady with a less enigmatic smile.

Although it has been hailed as a new finding, the Isleworth Mona Lisa is not unknown to art historians. Its authenticity has been the subject of debate ever since the canvas was discovered in 1913 by English art collector Hugh Blaker. He bought it from a noble family‭ who had owned it for 150 years ‬and took it to his studio in Isleworth, London –- hence the name.

In‭ ‬1915 his stepfather John R. Eyre, an art historian, published a book suggesting that Leonardo painted two versions of the Mona Lisa and claiming that at least the bust, the face and the hands of the Isleworth lady were a genuine work by Leonardo Da Vinci –- basically, a prequel to his famous portrait.

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The story of the painting continues with the American collector Henry F. Pulitzer. He bought the artwork in 1962, then brought it to Switzerlawly and left it secured in a bank vault. It remained there for 40 years.

The artwork is now owned by an international consortium that remains anonymous. The consortium acquired

the canvas from the estate of Pulitzer’s late partner in 2008 and entrusted it to

The Mona Lisa Foundation for deeper research.

According to the foundation's experts, four  historical accounts strongly point to existence of two Mona Lisa portaits.

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In his work‭ "‬Lives of the Artists," 16th century painter and art historian Giorgio Vasari(1511–1574) named Lisa Gherardini, the wife of the wealthy Florentine silk merchant Francesco del Giocondo as the subject of the portrait. He dated the painting shortly after Leonardo’s return to Florence in 1500, and stated that it was left unfinished after four years.

Vasari's version is confirmed by an acquaintance of Leonardo da Vinci, Florentine city official Agostino Vespucci, a relative of the explorer, navigator and cartographer Amerigo Vespucci.

Perhaps the earliest witness of the masterpiece, Agostino Vespucci wrote in October 1503 that Leonardo was working on three paintings at the time, including a portrait of Lisa del Giocondo. Vespucci's annotations were found in 2005 at the Heidelberg University's library.

Another account can be found in the travel journal of Antonio De Beatis, the secretary of the cardinal Louis d'Aragona. Written between 1517and 1518, the diary reported that Leonardo had finished the Mona Lisa by 1517, and that it was completed for Giuliano de’ Medici.

To add to the contradiction, the account of the Renaissance historian Gian Paolo Lomazzo (1538 – 1592) referred in his‭ ‬1584 Treatise on Painting, to "a Gioconda and a Mona Lisa."

"The accounts are totally different from each other, and were written decades apart. Taken together, they point to two distinct and different portraits, one being of the young Mona Lisa, and the second to a 'Florentine woman,' or 'La Gioconda,'" the Mona Lisa Foundation said.

La Gioconda is the Italian alternative name for the Mona Lisa hanging in the Louvre.

"The historical evidence suggests that the earlier version of Mona Lisa, the portrait of Lisa del Giocondo, was probably delivered unfinished into the hands of her husband Francesco before Leonardo departed Florence for Milan in 1506," the Mona Lisa Foundation wrote.

Further historical evidence would come from a drawing by Raphael of the Mona Lisa.‭ ‬Now in the Louvre, the drawing was probably done from memory from Leonardo's original after Raphael visited the master's studio in 1504.

Featuring two columns, the sketch mirrors that of the Isleworth painting.

"The artwork indeed reminds Raffaello's drawing and raises many questions," Alessandro Vezzosi, the director of the‭ ‬Museo Ideale in the Tuscan town of Vinci, where Leonardo was born in 1452, said.

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Along with leading Da Vinci expert Carlo Pedretti of the Armand Hammer Center for Leonardo Studies at the University of California, Vezzosi is carrying an independent research on the puzzling Isleworth painting.

He suggested that most likely several hands worked on the canvas.

"Just compare the face with its quality and intensity with the cluster of trees in the backdrop. The trees reveal a different technique and problems of perspective. Most likely, they were painted by someone else," Vezzosi said.

In the past twelve years, the painting underwent any possible test, from gamma rays and infrared reflectography to forensic age regression to determine what the Louvre Mona Lisa would have looked like 11 to 12 years earlier.

But it was mathematics that helped the foundation's experts to discover what they called "Leonardo's hidden technique."

Simple horizontal lines drawn across both the Louvre and the Isleworth paintings — previously brought to the same ratio — show exact proportional similarities despite the fact that, in reality, the figures within them were not painted to the same size.

"The eyes, the nose, the distance between the mouth and the chin, are exactly in the same location. Only the same artist could have known how to do that without the benefit of modern technological aids," art historian Stanley Feldman, principal author of the 320 page book, said.

As expected, the claim is raising a controversy in the art world.

Vezzosi called the suggestion that Da Vinci portrayed Lisa del Giocondo at two different moments of her life "a fascinating possibility," but according to Oxford professor Martin Kemp "there is no basis for thinking that there was an earlier portrait."

"The Isleworth Mona Lisa mistranslates subtle details of the original, including the sitter's veil, her hair, the translucent layer of her dress, the structure of the hands. The landscape is devoid of atmospheric subtlety," he said in a statement.

Kemp also pointed out that the Isleworth piece is painted on canvas.

Like the majority of‭ ‬Leonardo's works, the Mona Lisa in the Louvre is painted on wood.

Photos: Detail of the Isleworth Mona Lisa. Credit: The Mona Lisa Foundation.

– The Isleworth Mona Lisa. Credit: The Mona Lisa Foundation.

– A graphic experiment, comparing the earlier and Louvre Mona Lisas, shows exact proportional similarities. Credit: The Mona Lisa Foundation.