Leonardo Che Ritrae la Gioconda (Leonardo Painting the Mona Lisa), by Cesare MaccariCorbis Historical / Getty

Leonardo da Vinci died at the age of 67 on May 2, 1519, at the small manor house in the Loire Valley given to him by King Francis I of France. He was buried nearby in the church of the Château d’Amboise, which was demolished in the early 19th century. An excavation decades later turned up bones that were believed to be Leonardo’s. An inscription notes carefully that the site holds the artist’s “presumed remains.” The acknowledgment of uncertainty is a mark of quiet candor, and unusual in this case: Leonardo enthusiasts are not famous for their restraint. Give them a small mystery and a bit of wiggle room, and the theories come quickly.

We will be hearing a lot about Leonardo this year, the 500th anniversary of his death. Exhibits are being readied in the United States, the United Kingdom, and France. In May, the Queen’s Gallery, at Buckingham Palace, will display Leonardo drawings from the Royal Collection (which owns about 500 of them). A major exhibition at the Louvre, which is home to five Leonardo paintings, including the Mona Lisa, will open in October.

So a wealth of Leonardo will be on display. Also on display—it never really stops—will be the musings of those who believe that they have finally solved some urgent Leonardo mystery, a mystery that might exist, like beauty, only in the mind of the beholder.

After half a millennium, the scholarship on Leonardo is immense, and continuing. Noteworthy developments include the rediscovery of Leonardo’s Salvator Mundi, the restoration of his Adoration of the Magi, and the discovery of a document that clears up uncertainties about the Mona Lisa. But Leonardo’s life and work have long been the stuff of speculation—“wild theories and untrammeled fantasy,” as Martin Kemp, a professor emeritus of art history at Oxford and one of the world’s foremost Leonardo scholars, describes them.

“I get bombarded with things about Leonardo on a regular basis that range from laughable to insane,” Kemp told me recently. The bombardiers include neuroscientists, dentists, ophthalmologists, psychologists, pathologists, geomorphologists, artists, photographers, and even some art historians.

Kemp has devised a taxonomy of disinformed or eccentric ideas about Leonardo. There are the mystic theorists (who believe that secret messages about the nature of the cosmos are concealed in Leonardo’s work); heresy theorists (who believe that Leonardo was involved in some sort of religious cabal); geo theorists (who fall over themselves trying to identify the background landscape in the Mona Lisa and other paintings); attribution theorists (who keep wanting to put Leonardo’s name on work that isn’t his); drag theorists (who believe that the Mona Lisa depicts either Leonardo or one of his pupils dressed as a woman); and sci-fi theorists (pretty much exactly what you’d imagine).

Kemp calls Dan Brown, the author of The Da Vinci Code, the “godfather” of some of these speculations. “He is responsible for the idea that there are hidden codes, messages, mystic geometries, disguised words, and esoteric numbers in Renaissance paintings,” he said. Carmen C. Bambach, a curator in the department of drawings and prints at the Metropolitan Museum of Art and the author of an upcoming four-volume study, Leonardo da Vinci Rediscovered, hears from Leonardo disciples on the fringe at least once a week. A recent example: “Two men said that in Leonardo’s earliest dated drawing, The Arno Valley, from 1473, they saw elephants, camels, and birds in what is essentially a landscape. I commended them for their love of Leonardo, but said there are no elephants or other animals in the drawing.”

One of the more widespread Leonardo theories involves the figure of the apostle John, with his vaguely feminine features, in The Last Supper. The idea here—which parallels the findings of Brown’s Robert Langdon, a fictional “professor of symbology” at Harvard—is that Leonardo was depicting not John but Mary Magdalene, and that Church authorities through the centuries have waged a campaign to cover up an intimate relationship between Jesus and Mary. As far as I’m aware, no reputable scholar supports this interpretation of The Last Supper. Of course, the art establishment might just be part of the cover-up.

Not surprisingly, the Mona Lisa has come in for the closest scrutiny by nonexpert experts. Hidden images in the painting have been found by many. Ron Piccirillo, an artist in Rochester, New York, has claimed on his website that when he looked at the painting upside down and followed “the highlights of her portrait,” he was able to spot “what turned out to be a lion’s head, an ape head and a buffalo head.” He added that “for me, it helps to only use one eye,” and that the viewer should be “extremely close to the left edge of the painting.”

Silvano Vinceti, an art-history sleuth who runs something in Italy called the National Committee for the Promotion of Historical and Cultural Heritage, claims that he can discern minute letters painted in Mona Lisa’s eyes. In the right eye, for instance, he detects the letters L and V. The Louvre says that it has examined the painting with “every possible laboratory test” and has found no letters. This might have been a disappointment—the letters would have made Louis Vuitton a perfect corporate sponsor.

Claims about the background landscape in the Mona Lisa have become something of a growth industry. A paleontologist at the University of Florence, Carlo Starnazzi, argued in the mid-1990s that the lake on the left side of the painting is Lake Chiana and that the bridge on the right is the Burgiano Bridge, both near Arezzo. An art historian, Carla Glori, wrote in her 2010 book, The Leonardo Enigma, that the bridge in the painting can be found in Bobbio, a village south of Piacenza. An artist-photographer, Rosetta Borchia, and a geomorphologist from the University of Urbino, Olivia Nesci, believe the location is the Montefeltro region of northern Italy, and that the bridge can be seen from the heights of Valmarecchia.

In the eyes of some, the Mona Lisa raises medical issues and questions of physiological identity. Vito Franco, a professor of pathology at the University of Palermo, maintained in 2010 that Mona Lisa—the woman herself, Lisa Gherardini, the wife of Francesco del Giocondo, the Florentine silk merchant who commissioned Leonardo to paint the portrait—likely suffered from a cholesterol problem. Franco noted a yellowish accumulation of what he interpreted to be fatty acids under the skin. Kemp, at Oxford, checked the area under magnification and arrived at a different diagnosis: Residue from restoration efforts had “bleached.” One art historian, Angelo Paratico, in 2014 argued (in the same breath) that Mona Lisa might have been a Chinese slave and Leonardo’s mother.

Another theory: The Mona Lisa is a portrait of a man—either Leonardo himself or his pupil and possible lover, Salaì—dressed as a woman. The self-portrait theory found expression in a 1987 Art & Antiques article by Lillian Schwartz, an artist and computer technician who used digital tools to superimpose an image of a Leonardo self-portrait onto an image of the woman in the painting. No question, Schwartz concluded: Leonardo used himself as a model. A similar conclusion is reached in a video now on YouTube titled “Mona Lisa IS Leonardo da Vinci.” The viewer is urged to watch the overlay of a Leonardo self-portrait onto an image of the Mona Lisa in order to see “how amazingly they line up.” The notion that the Mona Lisa is a Leonardo self-portrait is not one that experts have rushed to embrace.

Other investigators have speculated that Mona Lisa’s expression suggests compulsive grinding of her teeth, poor diet, a dysfunctional marriage, deafness, or facial paralysis; that the look of contentment on her face and the coy placement of her hands indicate that she was pregnant; that she was a prostitute; that she is smiling with her mouth closed because her teeth had been blackened by mercury treatments for syphilis; or that she suffered from strabismus (crossed eyes). The Mona Lisa’s famous smile was analyzed in 2005 by researchers at the University of Amsterdam (with technical assistance from the University of Illinois at Urbana-Champaign), using what they called “emotion recognition” software. The researchers determined that the woman in the portrait was 83 percent happy, 9 percent disgusted, 6 percent fearful, and 2 percent angry.

My own study, conducted without the benefit of emotion-recognition software, suggests that experts such as Kemp and Bambach are 100 percent amused by analyses of this kind.

Fanciful rumination about Leonardo will never cease. But, as noted, there’s actual recent news. “One of the many important discoveries,” Bambach says, “was the firming up of what had been questioned about the Mona Lisa. Many historians had gone off on a tangent as to when it was painted, or that the portrait was not of Lisa del Giaconda but of Isabella d’Este and others. The painting had been dated by some as 1500 or 1512.” But in 2005, Armin Schlechter, a manuscript expert in the Heidelberg University library, came across a note, dated 1503, in which Agostino Vespucci, a Florentine official who knew Leonardo, indicated that the artist was working at that very moment on a portrait of Gherardini. That settled that.

The rediscovery of Salvator Mundi was a major event. A painting of that name by Leonardo was known to have existed, but accidents of history (and layers of “restoration”) had concealed its identity. At one point, in 1958, it was sold in Britain for £45 as a painting by someone else. In 2017, Salvator Mundi was auctioned at Christie’s for $450.3 million—this despite lingering questions about attribution among a few connoisseurs. Abu Dhabi’s Department of Culture and Tourism said that it was the buyer of Salvator Mundi and that the painting would be displayed at the Louvre Abu Dhabi; then, in September, the department announced that the unveiling had been postponed. It did not give any reason. In February, the Louvre confirmed that it hopes to display Salvator Mundi in its October show. The phrasing of the Louvre’s statement, according to The Art Newspaper, “suggests that the painting is still owned by a single individual, who is widely believed to be Mohammed bin Salman, the Crown Prince of Saudi Arabia.”

Also in 2017: Leonardo’s Adoration of the Magi, its restoration complete, was returned to public display at the Uffizi Gallery, in Florence. According to Frank Zöllner, an art historian at Leipzig University and the author of a catalogue raisonné of Leonardo, “Infrared and digital imaging has shown how he drew the 70 or so figures of the composition directly onto the prepared panel in freehand, without the means of transferring preliminary sketches onto the wood panel. The painting has sketchy elements because it was unfinished. It shows the artistic spontaneity of Leonardo.”

Kemp brought up another discovery: “Scientific examination of all his paintings has shed enormous light on how incredibly varied his technique was. Leonardo was always striving for something new. Every conception triggered new experimentation. For example, he used powdered glass mixed with gesso, instead of just gesso, in priming a painting to give it, presumably, a kind of radiance.”

As hundreds of Leonardo’s works travel around the globe, people will have more chances than ever before to see his technique firsthand. What would Leonardo have made of all the fuss over his quincentennial—and, for that matter, all the wild theorizing on the margins? I put the question to Kemp, anticipating the sort of censorious observation you’d expect from an Oxford don at a high table. I got something else.

“He would have loved it,” Kemp said. “He was interested in fame and immortality. He would have been pleased that his name is still on people’s lips.”

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