There’s a reason you’ve heard of a “Mona Lisa” smile but not “Mona Lisa” eyebrows: She doesn’t have any. The world’s most famous painting was created by Leonardo da Vinci at the beginning of the 16th century. That was, to put it mildly, a long time ago — long enough for the eyebrows that Leonardo originally painted to have faded, according to at least one expert. French engineer Pascal Cotte made a 250-megapixel scan of the portrait in 2007 and spent an estimated 3,000 hours analyzing his data after being allowed to use the Louvre’s laboratory, concluding that the painting originally included both brows and lashes.

People (especially women) have been plucking and shaving their eyebrows for thousands of years based on fashion trends, but that doesn’t appear to be the reason that the subject of the “Mona Lisa” — widely thought to be Lisa del Giocondo — is sans eyebrows in her portrait. Her husband is believed to have commissioned the painting, which Leonardo ultimately kept; some historians have speculated that he was simply never paid for his work, while others believe he became personally attached to it. In any case, Cotte also concluded that the woman’s face initially appeared wider, and her smile more expressive, in the drafting stages, with her famously sedate, evocative look coming later.