There's only one Mona Lisa! Why a 10-year study got it all wrong

Who is the Mona Lisa, really? There are two answers – and French scientist Pascal Cotte has got both of them wrong.

Cotte has told a BBC documentary about his 10-year study of Leonardo da Vinci’s most famous painting using the Layer Amplification Method (LAM). When you look down through the layers of Leonardo’s painting, you see the fossils of his changing conception of the Mona Lisa. The first image he set down, Cotte says, was far less harmonious than the woman we see today – and she did not smile.

It’s fascinating stuff, and a real contribution – but Cotte has leapt to a totally false conclusion. He claims that Leonardo started out painting a “different” woman and that the Mona Lisa we see today therefore does not portray Lisa Gherardini, the wife of a Florentine merchant, at all.

In other words, Leonardo originally painted a woman called Lisa Gherardini – then painted a new portrait on top.

Cotte is not the first scholar to doubt the Mona Lisa’s identity. The reason we know her name at all is because the great art chronicler Giorgio Vasari provides it, in his Life of Leonardo da Vinci, published in 1550. Vasari says Leonardo was commissioned by a silk merchant called Francesco del Giocondo to portray his wife Lisa. Vasari definitely means the painting that is now in the Louvre – he describes it precisely. But historians used to reckon it was really a painting of a Medici mistress. Much more exciting!

Then, just as Cotte was starting his research a decade ago, an amazing discovery was made in Heidelberg University Library. An art historian spotted a marginal note written by the Florentine civil servant Agostino Vespucci in 1503, in a book he owned. In the note, Vespucci (an eyewitness who was right there in 1503) says Leonardo is working on a portrait of “Lisa del Giocondo”. This contemporary source vindicates Vasari. Leonardo’s Mona Lisa is indeed a painting of a Florentine merchant’s wife.

So why did the painting change so much as it was worked on? Did Leonardo in fact reuse his picture and paint someone new on top?

No. There’s no reason to think that. Cotte is not looking at the kind of man Leonardo was.

No artist has ever been so complex, so subtle, so many-sided. Of course the Mona Lisa has layers. That smile? It’s not just a random whim. Leonardo’s anatomical notes include a study of “the muscles called lips” and how they move. Behind every detail – her eyes, hair, the river in the background – are notes and sketches in which Leonardo analyses anatomy, the forces of nature and the shadows and perspectives that reveal bodies in space.

The Mona Lisa is not a portrait of “another woman” – but it is no longer a simple portrait of Lisa Gherardini del Giocondo either. As Leonardo worked on this painting over the years – from 1503 until about 1506, although he kept it with him all his life – his knowledge of science and art was distilled in it. This is a philosophical painting, a deliberately enigmatic essay on painting and truth.

To imitate life, Leonardo betrayed his model. Instead of simply showing a real woman called Lisa, it became a painting whose ethereal beauty and powerful presence is the sum of Leonardo’s understanding. And even more elusive ideas crept in. When Marcel Duchamp drew a moustache on a postcard of the Mona Lisa he showed that “she” has a male component: that makes this charismatic image even more universal, an embodiment of the mystery of existence.

Cotte has forgotten that Leonardo was a genius. Of course he did not do anything so banal as paint someone else on top of his portrait of a Florentine woman. What he did was so much more fascinating. He worked on this portrait until the face of a real person was transformed into a myth.