Over the ensuing years, the perplexing presence of “oysters and corals and various other shells and sea snails” on “the high summits of mountains”, far from the sea, worried away at the artist’s imagination. For Leonardo, the accepted explanation by ecclesiastical scholars of a great flood, such as that described in the Old Testament, for the relocation of these shells, didn’t wash. These creatures weren’t thrown there. They were born there.

Seashells in mountains were proof, Leonardo came to believe and confided to his journal, that Alpine peaks were once the floors of seas. And the Earth was therefore much older and far more haphazardly fashioned by violent cataclysms and seismic upheavals over a vast stretch of time (not the smooth hand of God in a handful of days) than the Church was willing to admit.

Fossils and flora

We know from a remark Leonardo makes in his notebooks that the riddle of seashells cropping up incongruously on mountaintops was fresh in his mind just prior to his undertaking work on the first version of the Virgin of the Rocks in 1483. Recalling an incident from the year before, when the artist was designing a never-completed equestrian statue for the Duke of Milan Ludovico il Moro, he writes: “When I was making the great horse for Milan, a large sack full [of shells] was brought to me in my workshop by certain peasants; these were found in [the mountains of Parma and Piacenza] and among them were many preserved in their first freshness.”

The fact that Leonardo was preoccupied with the puzzle of seashells on mountains at the very moment that he began to conceive the Virgin of the Rocks is crucial to our interpretation of his paintings. His fascination with the shells’ displacement sheds intriguing light on how his mercurial imagination might craft the double entendre of a scallop-shaped palm tree, like the one that bristles to the left of Mary, just above John’s head.