Research claims that da Vinci was only half-Italian.

Renaissance genius Leonardo da Vinci was the son of a slave who was trafficked to Italy from her home in the Caucasus, according to new research presented in Florence on Tuesday.

The claim was made by historian Carlo Vecce, a professor at the University of Naples L'Orientale, during the presentation of his new book, an historical novel called Il Sorriso di Caterina or Caterina's Smile.

There has long been mystery surrounding the identify of da Vinci's mother Caterina who gave birth out of wedlock on 15 April 1452 to a son, baptised Leonardo, after a relationship with prominent notary Piero da Vinci.

In the past scholars have speculated that Caterina might have been a local peasant girl, an orphan or even a slave. A discovery by Vecce in the state archives in Florence appears to confirm the latter theory.

Vecce came across a legal document written in Latin on 2 November 1452 - around six months after Leonardo was born in the Tuscan town of Vinci - signed by none other than Piero da Vinci.

The certificate, which refers to Caterina as a "slave" from "Circassia", grants her emancipation "to recover her freedom and recover her human dignity".

Vecce believes that Caterina was abducted, possibly by Tartars, from the mountainous Caucasus area of central Asia.

She was then taken across the Black Sea to Costantinople, where she was likely bought as a slave by Venetian merchants, before arriving in Florence in 1442.

During her time working as a wet nurse for a family in Florence Caterina met Piero da Vinci who - a year after Leonardo was born - arranged a marriage between her and a local man. Caterina went on to have five children with her husband.

“The notary who freed Caterina was the same person who loved her when she was still a slave and with whom he had this child,” Vecce told reporters in Florence.