Page 13 - The Restless Earth Fossils

12 Fossils

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reputation for himself as a master anatomist—a person skilled at
dissection and observation. By this time, he had already discovered
the duct that carries saliva from the parotid gland to the mouth
in humans—something that generations of physicians before him
had failed to notice.
A crowd gathered to watch Steno begin his dissection. The
sight of the dead shark with bulging eyes and jaws large enough
to consume a person must have presented an amazing spectacle.
Each jaw held 13 rows of teeth; the inner ones were soft and half
buried in the animal’s gums. Although the fishermen had cut
some of the shark’s teeth out for souvenirs, many of the teeth
remained; the largest ones were perhaps 3 inches (7.6 centi-
meters) long. Steno realized immediately that the shark’s teeth
closely resembled objects known as “tongue stones.” The mys-
terious tongue-shaped rocks were sold locally for their supposed
medical and magical powers; since their origins were unknown,
people thought that they grew inside the rocks in which they were
found. Steno realized that the shark’s teeth resembled tongue
stones because they were one and the same thing—“as alike as
one egg resembles another.” Yet somehow the tongue stones had
petrified, or turned to stone.
For many years naturalists and travelers explained away
things like seashells on mountaintops. The Earth has “plastic
forces” that just makes weird things, they said, or maybe the
rain causes fossils to sprout like plants. But Steno and other
careful observers saw that finding the assemblages of shells,
shark teeth, and other marine creatures all together only made
logical sense if these creatures had once been alive and living
in an ocean—even if that ancient ocean bed had since risen to
mountain heights.
Steno’s contemporary in England, Robert Hooke (1635–
1703), came to much the same conclusion a year later while
looking at fossil seashells and petrified wood through his newly
invented microscope. In his book Micrographia, which was writ-
ten for the scientists of the recently formed Royal Society and

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