World in Ruins - The Rocks Don't Lie - page 47

ried him across the Alps and Apennines, where he saw fossils layered in rocks high above
sea level, well beyond the reach of even the largest waves. Some rock layers lay flat, others
were contorted and lay at steep angles. While the fossils in the hills around Florence looked
like seashells, most natural philosophers did not consider them signs of ancient life. The
educated consensus was that they were insignificant mineral oddities, sports of nature that
merely resembled oysters and clams.
Soon after Steno arrived, in October 1666, fishermen on the Tuscan coast hauled in the
body of a monstrous great white shark near the mouth of the Arno River. When word of
the several-ton beast reached the Medici palace, Ferdinand ordered it brought to his court
in Florence for the Accademia to examine. But the shark was too large to transport and
was already starting to rot. So its enormous head, as big as a whole pig, was loaded onto a
horse-drawn cart and sent up the Arno River valley.
Steno, the academy's newest member, considered the honor of dissecting the enormous
shark's head a once-in-a-lifetime opportunity. He cut as the grand duke and a mesmerized
crowd of courtiers watched. The jaws were large enough to swallow a man whole. Yet
its brain was tiny—just three ounces. How could such a diminutive brain control a giant
killing machine?
Steno focused first on its teeth. Each serrated blade was identical to the mysterious
tongue stones. They were as identical “as one egg resembles another.” 1 Seeing that tongue
stones were actually shark's teeth, he wondered how the teeth of giant sharks could end
up enclosed in solid rock. They must have become fossilized after laying in the mud of an
ancient seabed that somehow became stranded high above the sea.
Steno described his findings in a short report to the grand duke, with a digression on
the origin of tongue stones and the implications for understanding other fossils. He poin-
ted out the flaw in the conventional wisdom of the time: that fossils spontaneously grew
within rocks. A growing object would crack the rock, yet one never saw cracks around
fossils found in rocks. Even more telling was that tongue stones were always perfect rep-
licas of their biological counterparts. In contrast, most crystals contained a defect, even
when grown in a lab. Steno argued that fossils resembling broken mussel shells found with