ROME: It has all the ingredients of a Dan Brown thriller - an ancient crypt, a collection of human bones, a passionate sleuth and a famous Leonardo da Vinci painting.
Italian researchers have edged closer to solving one of the greatest mysteries in art history - the identity of the Renaissance woman who posed for Leonardo's Mona Lisa, the Louvre's greatest treasure and one of the world's most famous paintings.
After four years' spent excavating human remains from beneath a centuries-old convent in Florence, researchers have identified a small collection of bones they believe may belong to Lisa Gherardini, whom many scholars believe was the model for Leonardo's masterpiece.
The team revealed yesterday (Thursday) that carbon dating showed that the bones, which include a femur, dated from around the time that Gherardini died, in July 1542, at the age of 63.
Historical records indicate that Gherardini, who spent her last years in religious seclusion in the Sant'Orsola convent, was laid to rest at the site.
"I'm convinced it is her," Silvano Vinceti, an art historian who led the research team, told The Daily Telegraph. "There is a strong compatibility between the results from our archaeological and historical research and the results from the carbon dating. It is highly probable that the remains belong to Lisa Gherardini."
The next stage in the research would have been to take DNA samples from the bone fragments and compare them with DNA extracted from the remains of two of the five children that Gherardini had with her husband, the wealthy silk merchant Francesco del Giocondo.
But the children's remains, discovered in a tomb in the Basilica of Santissima Annunziata in Florence, have been badly damaged over the years by flooding from the Arno River.
"The dampness has irreparably damaged the remains and they cannot provide enough DNA to make a comparison," said Prof Giorgio Gruppioni, the head of the forensic anthropology laboratory at Bologna University.
"What we hope is that sophisticated techniques will eventually allow us to extract and analyse and compare the DNA to be able to ascertain that genetically these are the remains of Lisa Gherardini."
For now, the research has come to a halt, its results as intriguing and enigmatic as Mona Lisa's famous smile.
Critics have also pointed out that dozens of people were buried beneath the convent and that, even if the remains corresponded roughly to the date of Gherardini's death, they could belong to another woman.
Mr Vinceti, the head of the National Committee for the Promotion of Historic and Cultural Heritage, had hoped to find Gherardini's skull and then use forensic techniques to reconstruct her face, comparing that with the painting. But no skull has yet been found.
Even if the bones could be proven to belong to Gherardini, scholars are divided over whether she was the model for the Mona Lisa. It has been variously suggested that the famous painting is a self-portrait by Leonardo, a painting of a courtesan or a Spanish noblewoman, or even that it was based on Salai, his male apprentice and possible lover.
In 2010 Mr Vinceti claimed to have found the remains of Caravaggio, the famous Renaissance painter, after they had lain in an unmarked grave in Porto Ercole, Tuscany, for four centuries.
He said he was 85 per cent certain that the set of bones, which tests showed belonged to a man who died around 1610, were the artist. But some experts said there was not enough evidence to show definitively that the remains were those of Caravaggio and that the "discovery" had been concocted on the 400th anniversary of the artist's death in order to boost tourism.