Fossils and the Birth of Paleontology: Nicholas Steno (1 of 2)

Nicholas Steno

If one day in history had to be picked as the birth of paleontology, it might be the day in 1666 when two fishermen caught a giant shark off the coast of Livorno in Italy. The local duke ordered that this curiosity be sent to Niels Stensen (better known as Steno), a Danish anatomist working at the time in Florence. As Steno dissected the shark, he was struck by how much the shark teeth resembled “tongue stones,” triangular pieces of rock that had been known since ancient times.

Today, most people would instantly wonder whether the tongue stones were giant petrified shark teeth, but in 1666 such a presumption was a tremendous leap. Few could imagine how living matter could be turned to stone, and beyond that, encased in solid rock—especially if the rock were well above sea level and contained remnants of a marine organism. Fossils were instead thought to have fallen from the sky, or to be “sports of nature”—peculiar geometrical shapes impressed on the rocks themselves.


From Living Tissue to Stone
Steno made the leap and declared that the tongue stones indeed came from the mouths of once-living sharks. He showed how precisely similar the stones and the teeth were. But he still had to account for how they could have turned to stone and become lodged in rock. Naturalists of Steno’s day were becoming convinced that matter was composed of different combinations of tiny “corpuscles”—what today we would call molecules. Steno argued that the corpuscles in the teeth were replaced bit by bit, by corpuscles of minerals. In this gradual process, the teeth didn’t lose their overall shape as they turned from tissue to stone.

Steno's shark teeth
Steno’s drawing of a shark head helped him see that “tongue stones” were actually fossil shark teeth (right).

next page

Search · Site Index · Navigation · Copyright · Credits · Contact
Understanding Evolution For Teachers Home · Understanding Evolution Home

Read how others have recognized the Understanding Evolution website

Spanish translation of Understanding Evolution For Teachers from the Spanish Society of Evolutionary Biology.