Could Leonardo da Vinci's mother, Caterina, have been a slave kidnapped from the mountainous Caucasus region of Central Asia? That's the latest hypothesis re-igniting a long-running debate about the identity of this mysterious woman largely lost to history. Historian Carlo Vecce of the University of Naples told reporters at a Tuesday press conference that he discovered a previously unknown document supporting the claim. He's also written a historical novel about Caterina's life (Il Sorriso di Caterina or Caterina's Smile) based on his research.

It's well-established that Leonardo was born in 1452, the illegitimate son of a Florentine notary named Ser Piero d’Antonio and a woman named Caterina. Ser Piero went on to marry a woman named Albiera Amadori, followed by three subsequent marriages after her 1464 death. His various unions produced 16 children (11 of whom survived their early years), in addition to Leonardo, who grew up in his father’s household and received a solid education.

As for Caterina, many historians have identified her as a local peasant girl and eventual wife of a kiln worker named Antonio di Piero del Vacca (nicknamed "L'Accattabriga" or "the quarrelsome one"). But that's all we know of her. So naturally, over the years, various alternative identifications have been suggested. Perhaps the most controversial, proposed in 2014 by Italian historian Angelo Paratico, is that Caterina had been a Chinese domestic slave imported from Crimea by Venetian traders and sold to a Florentine banker.

Paratico's book, Leonardo da Vinci: A Chinese Scholar Lost in Renaissance Italy, was published the following year. His theory was based in part on research by Renzo Cianchi of the Leonardo Library in Vinci, who proposed that Caterina had been a slave belonging to one of Ser Piero's wealthy friends. According to the New York Times, that is also the hypothesis of a forthcoming book about Leonardo's genealogy by Alessandro Vezzosi, director of Leonardo da Vinci Heritage.

Noted Leonardo scholar Martin Kemp of Oxford University took a different tack, arguing in his 2017 book, Mona Lisa: The People and the Painting (co-authored by Giuseppe Pallanti), that Caterina had been a 15-year-old orphan girl. Kemp unearthed documentary evidence that a young girl of that age named Caterina di Meo Lippi had lived less than a mile from Vinci with her baby brother Papo. She could have become pregnant by Ser Piero during one of his hometown visits. Among the evidence: Antonio da Vinci's 1458 tax return, confirming that five-year-old Leonardo was then living in his household.

As for Vecce, he acknowledged that his own research had been "guided" by the slave hypotheses put forth by Paratico and Vezzosi, although he initially resisted the idea. But then he discovered a document dated November 2, 1452, six months after Leonardo had been born, emancipating an enslaved Circassian woman named Caterina on behalf of her mistress, the wife of Donato di Felippo di Salvestro Nati. The notary who signed the document was none other than Ser Piero, Leonardo's father.

“When I saw that document I couldn’t believe my eyes,” Vecce told NBC News. “I never gave much credit to the theory that she was a slave from abroad. So, I spent months trying to prove that the Caterina in that notary act was not Leonardo’s mother, but in the end all the documents I found went into that direction, and I surrendered to the evidence. At the time, many slaves were named Caterina, but this was the only liberation act of a slave named Caterina [that] Ser Piero wrote in all his long career. Moreover, the document is full of small mistakes and oversights, a sign that perhaps he was nervous when he drafted it, because getting someone else’s slave pregnant was a crime.”

A healthy bit of skepticism is warranted here, and Vecce has yet to publish a scholarly paper carefully detailing his findings. (It's apparently in progress.)

“Carlo Vecce is a fine scholar," Kemp told NBC News. "His ‘fictionalized’ account needs the sensation of a slave mother. I still favor our ‘rural’ mother, who is a better fit, not least as the future wife of a local ‘farmer.' But an unremarkable story does not match the popular need for a sensational story in tune with the current obsession with slavery.” At the end of the day, Kemp added, “none of the stories are demonstrably proven.”