The Mona Lisa is two-faced. At least that's what a self-proclaimed Italian art detective says. Silvani Vinceti says his research shows that Leonardo da Vinci used two models—one female and one male—to create the famous 16th-century portrait that hangs at the Louvre, the Guardian reports.

"I believe that this goes with a long-time fascination of Leonardo’s, that is, the subject of androgyny," he says, adding that, for da Vinci, the "perfect person was a combination of a man and a woman." Vinceti says he examined the painting—"arguably the world's most famous," per the Telegraph—using infrared technology.

In the first layer, he says, the Mona Lisa's face looks "melancholic and sad," with no trace of a smile. So who were the models? The female, many historians agree, was Lisa Gherardini, the wife of a Florentine silk merchant.

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The male, according to Vinceti, is likely da Vinci's longtime assistant Gian Giacomo Caprotti (aka Salai, or Little Devil), who was da Vinci's "supposed main male squeeze," per the New York Post.

His conclusion is based on comparisons of the Mona Lisa's face with other paintings for which Caprotti served as the model, including St. John the Baptist.

Caprotti is discernible, "particularly in Mona Lisa’s nose, her forehead, and her smile," Vinceti tells the Telegraph. Not everyone is convinced. "The infra-red images do nothing to support the idea," says art historian Martin Kemp, adding that Vinceti's theory is "a mish-mash of known things, semi-known things, and complete fantasy." The Mona Lisa has long been the subject of various theories, including, per the Telegraph, that a lost original depicted her naked.

(Two historians think they have IDed da Vinci's living relatives.)

This article originally appeared on Newser: Da Vinci May Have Used Male Model for Mona Lisa