Leonardo’s Mountain of Clams and the Diet of Worms by Stephen Jay Gould Read Free Book Online Page B

height, for so one sees the layers of the rocks [with their fossils], formed by the changes which the water has undergone, at the summits of the high mountains.
    The exterior method of lightening by erosion can enhancethis process once the mountains rise. Rivers will now erode the sides of the mountains and carry the resulting sediment away to the oceans. Some of this sediment will flow to the opposite hemisphere, thus further increasing the imbalance of weight, and causing the mountains to rise still higher as a consequence.
    And now these beds are of so great a height that they have become hills or loftymountains, and the rivers which wear away the sides of these mountains lay bare the strata of the shells, and so the light surface of the earth is continually raised, and the antipodes [the opposite side of the earth] draw nearer to the center of the earth, and the ancient beds of the sea become chains of mountains.
    Thus, and finally, we grasp the central importance of Leonardo’s paleontologicalobservations in the Leicester Codex. He featured fossils in order to validate the cherished centerpiece of his premodern worldview—the venerable argument, urged throughout classical and medieval times, for interpreting the earth as a living, self-sustaining “organism,” a macrocosm working by the same principles and mechanisms as the microcosm of the human body. Leonardo required, above all,a general device to make the heavy elements, earth and water, move upward against their natural inclination—so that the earth could sustain itself, like a living body, by constantly cycling all its elements, rather than reaching inert stability with heavy elements in permanent layers below lighter elements.
    Leonardo could not find such a mechanism for the chief subject of the Leicester Codex:water—and this failure caused him great frustration. But he succeeded for the even heavier element of earth. He extended a mechanism proposed by Scholastic philosophers for causing the lighter hemisphere of an inhomogeneous planet to rise. He proposed both internal and external erosion by water as processes that could lighten a hemisphere—but he needed observational evidence that land did, in fact,rise. His crowning jewel of confirmation lay in a well-known phenomenon that had provoked intense debate ever since the days of classical Greek science—fossils of marine organisms in strata on high mountains.
    Leonardo also needed to assert that the elevation of strata with fossils must represent a general and repeatable feature of the earth’s behavior, not an odd or anomalous event. Thus he hadto refute the two explanations for fossils most common in his time—for Noah’s flood could only be viewed as a strange and singular phenomenon, and if all fossils derive from this event, then paleontology illustrates no general mechanism for the rising of land. And if fossils grow as objects of the mineral kingdom within rocks, then the mountains may always have stood high, and we can derive noevidence for any uplift at all. Thus Leonardo made his superb observations on fossils in order to validate his lovely, but ever so antiquated, view of a causally meaningful and precise unity between the human body as a microcosm and the earth as a macrocosm. Leonardo, the truly brilliant observer, was no spaceman, but a citizen of his own instructive and fascinating time.
    I like to contemplateLeonardo, this complex man of peace, of gentleness, of art, of scholarship; this military engineer who designed (but generally did not build) ingenious instruments of war, but who would not reveal his ideas for a submarine, as he stated in the Leicester Codex:
    This I do not publish or divulge on account of the evil nature of men who would practice assassinations at the bottom of the seas, bybreaking the ships in their lowest parts and sinking them together with the crews who are in them.
    And I like to compare his views on the mechanism for raising mountains from the sea (and