For centuries, scholars have analyzed Leonardo da Vinci’s Vitruvian Man, searching for the hidden principle behind its flawless geometric structure. Now, more than 500 years later, a possible answer has emerged—and the surprising part is that it didn’t come from an art historian or a mathematician, but from a dentist.

Even those with little interest in art are likely familiar with the Vitruvian Man—it’s featured on the one-euro coin and is one of Leonardo’s most iconic works. The drawing illustrates the ideal human proportions by placing the figure inside two perfect shapes: a circle and a square. Da Vinci based the image on the writings of ancient Roman architect Marcus Vitruvius Pollio, for whom the drawing is named.