Leonardo’s Mountain of Clams and the Diet of Worms Read Online Free PDF

can,Leonardo writes, “count on the shells of cockles and snails the numbers of months and years of their lives just as one can on the horns of bulls.”
    I have often quoted a favorite line from Darwin in these essays: “How can anyone not see that all observation must be for or against some view if it is to be of any service?” Leonardo’s keen observations do seem to emit a wondrous whiff of modernity,but when we learn why he made his inquiries, and note how he ordered his facts, we can begin to place him into the proper context of his own world. Leonardo did not observe fossils for pure unbridled curiosity, with no aim in mind and no questions to test. He recorded all his information for a stated and definite purpose—to confute the two major interpretations of fossils current in his day. Boththeories had been proposed to resolve a problem that had troubled Western natural history ever since antiquity: If fossil shells are the remains of marine organisms (and some are virtually indistinguishable from modern species), how did they get entombed in strata that now lie within mountains, several thousand feet above current sea level?
    First, Leonardo disproves and ridicules the common ideathat all fossils reached the mountains by transport on the high waters and violent currents of Noah’s flood. Observations 3 through 6 of my list refute this theory by noting that many fossils are preserved in their position of life, undisturbed by any movement after death. One flood cannot produce a fossil record in several sequential layers (observation 3). Strata formed by violent currents couldnot preserve the feeding tracks of worms (observation 4). Noah’s floodwaters would have disarticulated all fossil clams into separate valves (observation 5). As for the cockle, laboriously moving but six to eight feet a day in its furrow, forty days and nights of rain would scarcely provide enough time for a journey 250 miles inland (where fossil cockles now reside) from the nearest modern sea:

    With such a rate of motion it would not have traveled from the Adriatic Sea as far as Monferrato in Lombardy, a distance of 250 miles, in forty clays—as he has said who kept a record of this time.
    Moreover, Leonardo adds, cockle shells are too heavy to be carried at the tops of waves, while they cannot be swept up the mountains along the bottom of the waters because Leonardo believed thatbottom currents always move down from higher to lower elevations, even while waves and surface currents sweep inland.
    The explicit refutation of Noah’s flood as a cause of fossils forms a major theme of the Leicester Codex, and occupies several full pages of text—one, for example, titled “of the Flood and of marine shells,” and another, “Refutation of such as say that the shells were carrieda distance of many days’ journey from the sea by reason of the Deluge.”
    Second, Leonardo dismisses, even more contemptuously, various Neoplatonic versions of the theory that fossils are not remains of ancient organisms at all, but manifestations of some plastic force within rocks, or some emanation from the stars, capable of precisely mimicking a living creature in order to illustrate the symbolicharmony among realms of nature: animal, vegetable, and mineral. For if fossils really belong to the mineral kingdom, then their position on the tops of mountains ceases to be anomalous, as we need no longer believe that these objects ever inhabited the seas.
    Leonardo made observations 7 through 9 to refute this Neoplatonic theory that fossils “grew” within their entombing rocks and do not representthe remains of organisms. If marine fossils are inorganic, why don’t they “grow” in all strata, rather than only in rocks carrying abundant evidence of an oceanic origin (observation 7)? If fossils belong to the mineral kingdom, why should they so often grow in fragments and jumbles looking exactly like piles of shells on our beaches, or layers deposited by rivers