A visitor looks at a copy of Leonardo da Vinci's Mona Lisa. (Reuters)

New research revealed that Leonardo da Vinci, the painter of the "Mona Lisa" and a symbol of the Renaissance, was only half-Italian, as his mother was a "slave" from the Caucasus.

Da Vinci's mother was long assumed to be a Tuscan peasant, but Carlo Vecce, a specialist in the Old Master, feels the truth is more convoluted.

"Leonardo's mother was a Circassian slave... taken from her home in the Caucasus Mountains, sold and resold several times in Constantinople, then Venice, before arriving in Florence," he said, as quoted by AFP at the launch of a new book.

In the Italian city, she met a young notary, Piero (Peter) da Vinci, "and their son was called Leonardo."

The findings of Vecce, who has spent decades studying da Vinci and curating his artwork, are based on Florence city archives.

They have formed the basis of a new novel -- "The Smile of Caterina, the mother of Leonardo" -- while also shedding new light on the artist himself.

Any new da Vinci discovery is vigorously debated by the small community of scholars who study him, but Vecce maintains the proof is there.

Among the documents he unearthed is one written by da Vinci's father himself, a legal document of emancipation for Caterina "to restore her freedom and recover her human dignity."

This document is dated 1452 and was revealed Tuesday at a press conference at the headquarters of the publishing house Giunti in Florence.

It was written by "the man who loved Caterina when she was still a slave, who gave her this child named Leonardo and (was) also the person who helped to free her," Vecce said.

His claim is a major shift in perception of da Vinci, who was previously thought to be the result of an affair between Peter da Vinci and a different lady, young Tuscan peasant Caterina di Meo Lippi.

Born in 1452 in the countryside outside Florence, da Vinci spent his life traveling around Italy before dying in Amboise, France in 1519, at the court of King Francis 1.

Vecce argues that the difficult life of his "migrant" mother had an impact on the work of her brilliant son.

"Caterina left Leonardo a great legacy, certainly, the spirit of freedom," he said, "which inspires all of his intellectual scientific work."

It is worth noting that da Vinci was a polymath, an artist who mastered several disciplines, including sculpture, drawing, music, and painting, but also engineering, anatomy, botany, and architecture.