Figured Stones or Lithified Body Parts?

The curious stones at the bottom of the illustration look very much like shark’s teeth ... strange coincidence?  From Canis carchariæ dissectum caput by N. Steno (1667).

Nicolas Steno (Niels Stensen) was born in Denmark in 1638 during the Thirty Years War, lived through a major plague epidemic, pursued studies in medicine and anatomy, and by the time he was in his late 20s was recognized as one of the greatest anatomists of the day.  In 1666 he went to Italy, converted to Catholicism, settled in Tuscany, was accepted into the Accademia del Cimento (Academy of Experiment), and gave up anatomy.  His interests had turned to what we today call geology or earth science, piqued by curious forms in the Tuscan rocks that resembled sharks’ teeth and seashells. Steno's studies soon expanded far beyond these odd rocks, tackling basic problems of stratigraphy.  He came up with three of the basic tenets of geology taught today: the law of superposition, the principle of original horizontality, and the principle of cross-cutting relationships.

Then Steno abandoned earth science.  By 1678 he had devoted his life to Catholicism, though he grew disillusioned with the religious establishment, not surprising given his genius.  He spent more and more time in contemplation, living as an emaciated ascetic until he died in 1686.

A young Nicolas Steno.  Source.

This amazing man is the subject of Alan Cutler’s The Seashell on the Mountaintop, a book about Nicholas Steno’s contributions to earth science, especially his studies of the puzzling forms in rock that looked so much like living organisms but couldn’t possibly be.  After all, how could seashells have gotten inside hard rock thousands of feet above sea level?

Perhaps they were transported by the Great Flood, but wouldn’t that require God to have created the  mountains after the flood?  There was the additional problem that some of the forms didn’t resemble any living organisms.  Of course they could be creatures that had gone extinct, but that would be counter to the widespread “knowledge” that God didn’t create things to have them go extinct.  Most likely these figured stones were created in the beginning as part of the rocks, or generated from the rocks.  After all, different forms were found in different rock types.

Steno, though a devout man, disagreed.  He maintained that the tongue stones had once been sharks' teeth and the figured stones seashells.  A great debate ensued.

Martin Lister pointed out that many figured stones bore no resemblance to living creatures, for example this one, an ammonite.  From Historiae animalium angliae (1678).  Source.

Like Steno, Agostino Scilla concluded that figured stones looked like seashells because ... they had been seashells.  Collecting lithified shells far from the sea, from Vain Speculation Undeceived by Sense (1670).

In the end Steno convincingly argued that these oddities, which we now call fossils, must have been living creatures in the past.  The implications were huge.  It meant that landscapes undergo immense change, and that the Earth has a history on a scale much greater than our own.  Thus was the science of geology born.  Steno remained a religious man through it all, considering geologic processes  to be part of the wondrous work of God.

The Seashell on the Mountaintop is great reading.  Steno the man and the birth of geology are interesting stories in and of themselves of course, but Cutler’s talent as a writer makes them even more fascinating.  I highly recommend this book (and thanks to Lockwood of Outside the Interzone for suggesting it).