Leonardo’s Mountain of Clams and the Diet of Worms Read online

  Of the six parts in this humanist’s natural history of evolutionary essays, the first four—on art and science, mini-biographies, human prehistory with emphasis on paleolithic cave art, and human history from a naturalist’s standpoint—emphasize our side, though several focus on particular organisms, as in chapter 9 on giant deer (“Irish elks”) painted on cave walls, chapter 11 on Bahamian land snails for a fable about Columbus, and chapter 12 on the dodo’s fate, made even sadder by human insult added to the ultimate injury of extirpation. The essays of the last two sections—on evolutionary theory, and on perspectives of other organisms—focus on the nonhuman side (again with such exceptions, as chapter 14 on papal statements about evolution, chapter 15 on the contrast of Robert Boyle and Charles Darwin on natural design, and chapter 18 on Percival Lowell versus Alfred Russel Wallace on Martian canals and the true domination of earthly life by bacteria.)

  All these essays are grounded in a precious paradox that has defined the best of the genre ever since Montaigne: intimate and accurate detail—the foundation of most good essays—serves as a source of delight in itself, and also as a springboard to discourse about generalities of broadest scope. I would never dare to take on “the nature of truth” by frontal assault and abstract generalization—for fear of becoming an empty, tendentious buffoon, pontificating about the unanswerable and undefinable. But the subject must rivet us, and we can legitimately “sneak up on” (and even genuinely illuminate) this great issue by discussing how Darwin and his creationist American soulmate Dana constructed alternative taxonomies for toothed birds that should not have existed under previous concepts of reality, but had just been discovered as fossils (chapter 5). Similarly, if I tackled “the nature of tolerance” head-on, naked of intriguing and specific illustration, I would sound like a vain preacher crying in the wilderness (negative definition!). But if I confess some childhood humor in juxtaposing, for alliteration as well as content, the Diet of Worms with the Defenestration of Prague (chapter 13), then a seemingly superficial, even ridiculous, union wins legitimacy for joint illustration, and provides fair access to factual and moral dimensions of the general topic.

  These essays probe, arrange, join, and parry the details within a diverse forest of data, located both in nature and in the documents of human struggle—all to access an inherently confusing but infinitely compelling world. As I survey the contents of this eighth volume, I find that I have followed four primary strategies to promote these details into coherent frameworks with sufficient generality to incite an essay.

  1. In some cases, an intense study of original sources yields genuine discovery, despite the paradox that materials for a solution have always been patent. The story of nonuse for the giraffe’s neck by early evolutionists had not been documented before (chapter 16), and surprising absences often reveal as much as unrecognized presences. I located a new dimension, largely in favor of the “vanquished” Owen and not the “victor” Huxley, in the great hippocampus debate that animated evolutionary discussion in the 1860s (chapter 6). Dana’s important theory of cephalization, and its link with his natural theology (in interesting contrast with Darwin’s developing alternative), has never been elucidated, in part because Dana scattered his views through so many short and technical papers (chapter 5).

  But I am, I confess, most proud of the opening title essay on Leonardo’s paleontology. The excellence and prominence of his observations on fossils have been recognized—and dutifully honored in all accounts, popular, textbook, and technical—for more than a century, since the full publication of his private notebooks in the 1880s. But no one had identified the special reasons (based on his own, and largely medieval, views of the earth as analogous to a living body) for his intense focus on fossils, and for the placement of his statements in a codex largely devoted to the nature of water. So these wonderful observations had stood out, disembodied from context, and misinterpreted as the weird anachronisms of a transcendent and largely unfathomable genius. But the full document of the Leicester Codex sets the proper context, when read in its entirety and understood by the physics of Leonardo’s own time.

  2. In most cases, I do not report observations never made before, but try to place unfamiliar (or even well-known) items into a novel context by juxtaposition with other subjects not previously viewed as related—invariably in the service of illuminating a general point about the practice of science, the structure of nature, or the construction of knowledge. In reviewing the essays for this volume (not planned as an ensemble when first written, but collected from my monthly series for Natural History magazine), I noticed that I had most often made such a juxtaposition by the minimal method of pairing, or contrast between two—perhaps a general mode of operation for the human mind, at least according to several prominent schools of research (discussed here in the context of paleolithic cave art in chapter 8). For example, all the essays in part 2 on mini-biographies, although focusing on one previously unappreciated or misunderstood character, interpret their subject by his contrast with a standard figure—Linnaeus and the eighteenth-century English Jewish naturalist Mendes da Costa (chapter 4), James D. Dana and his British soulmate Darwin (chapter 5), Richard Owen versus T. H. Huxley (chapter 6), and the tragic Russian genius Vladimir Kovalevsky (and his equally tragic and more brilliant wife, Sophia, one of the greatest mathematicians of the nineteenth century) with Darwin on the potential of error to illuminate scientific truth (chapter 7).

  Many other essays also pursue this strategy of illumination by paired contrast, with novelty in the joining: Boyle and Darwin on natural theology and evolution (chapter 15); Percival Lowell versus Alfred Russel Wallace on the canals of Mars and the uniqueness of life (chapter 18); sloths and vultures as prototypes for traits that we, in our parochial and irrelevant way, judge as negative but yearn to understand (chapter 20); the Diet of Worms and the Defenestration of Prague as events of European history, related by more than their shared initial D and funny names (chapter 13); the Abbé Breuil and André Leroi-Gourhan for two sequential and maximally contrasting (but strangely similar) theories about the genesis of cave art (chapter 8); the great artist Turner and the prime engineer Brunel on the similarity of art and science (chapter 2); a forgotten theory about the origin of vertebrates with stunning new data to validate an even older view, all as an entrée to the subject of major evolutionary transitions and the prejudices that impede our understanding of this topic (chapter 17); the dodo of Mauritius and the first New World victims of Western genocide (chapter 12); and the striking difference between two popes in their common willingness to support the factual truth of evolution (chapter 14).

  3. If my second category works by joining disparate details, a third strategy operates by careful excavation—elucidation by digging rather than elucidation by joining. As the mineshaft widens and deepens, one may reach a richness of detail justifying promotion to an essay because the requisite generality has been attained by one of two routes: (1) By casting a truly novel, or at least sufficiently different, light on an old subject, so that readers become willing to devote renewed interest, and may even obtain some provocative insight (Darwin always wrote to his creationist friends that he dared not expect to change their minds, but did hope to “stagger” them a bit)—as when intricate details of the life cycle of the maximally “degenerate” parasite Sacculina suggest new attention to the fallacies of evolutionary progress (chapter 19), and when the subtle (and almost entirely unreported) distinctions in the affirmation of evolution by two very different popes (Pius XII and John Paul II) illuminate the old and overly discussed issue of proper relationships between science and religion (chapter 14). (2) By gaining the “right” to address a large and general issue through the new perspective of previously unapplied detail (as in the examples of chapters 5 and 13, previously discussed, and chapter 10 on the relevance of new data about the multiplicity of human species until 30,000–40,000 years ago and the consequent oddity of our current status as a single species spread throughout t
he globe) for a discussion of predictability versus historical contingency in the evolution of self-conscious life on Earth.

  4. “Promotion” to an essay may depend upon the coalescence of details into a general theme worthy of report, but sometimes those details, all by themselves, become arresting enough to merit treatment entirely for their own value (and then I will confess to using the emerging generality as an excuse for almost baroque attention to the details). I do value the theme eventually addressed, but don’t you adore, entirely for their own sake as stories, the four tales of conventional prey that devour their predators (chapter 21), or the excruciatingly intricate and beautiful details of the bizarrely complex life cycle of the barnacle parasite, the “root-head” Sacculina (chapter 19)? And, as my personal favorite (and here I do rest my case), how could anyone but a dolt not be moved by the fact that we know about the giant deer’s hump only because paleolithic cave painters left us a record—and that no other even potential source of evidence exists (chapter 9). I tell this story within a perfectly valid and sufficiently interesting context of discourse on biological adaptation as a general evolutionary principle, but don’t you thrill to the notion of this kind of gift provided by such distant forebears; and aren’t you riveted by the details of these rare images, and the story of their discovery and recognition?

  The foregoing discussion accounts for all individual bits in this eighth piece of my series. But just as the “two bits” of legend represented a cut from a totality called a “piece of eight,”1 my bits have no coherence or valid generality without an overarching rationale or coordinating theme to make them whole. I pay my homage to evolution in the preface to every volume of this series, and will now do so again. Of all general themes in science, no other could be so rich, so deep, so fascinating in extension, or so troubling (to our deepest hopes and prejudices) in implication. Therefore, for an essayist in need of a ligature for disparate thoughts and subjects, no binder could possibly be more appropriate—in fascination and legitimacy—than evolution, the concept that inspired the great biologist Theodosius Dobzhansky to remark, in one of the most widely quoted statements of twentieth-century science, that “nothing in biology makes sense except in the light of evolution.”

  Moreover, and finally, with this series’ emphasis on a humanistic natural history—an account of evolution that focuses as much on how we come to know and understand this great principle as on how such a process shapes the history of life—we encounter an endless recursion that provides even greater scope and interest to the subject. The wondrously peculiar human brain arose as a product of evolution, replete with odd (and often misleading) modes of reasoning originally developed for other purposes, or for no explicit purpose at all. This brain then discovers the central truth of evolution, but also constructs human cultures and societies, replete with hopes and prejudices that predispose us toward rejecting many modes and implications of the very process that created us. And thus, in a kind of almost cosmically wicked recursion, evolution builds the brain, and the brain invents both the culture that must face evolution and the modes of reasoning that might elucidate the process of its own creation. Round and round we go—into a whorl that may be endless and eternal, yet seems to feature some form of increasing understanding in all the gyrations that, at the very least, give us topics for essays and, at best, provide some insight into the nature of our being.

  I

  ART AND SCIENCE

  1

  THE UPWARDLY MOBILE FOSSILS OF LEONARDO’S LIVING EARTH

  MORGAN DESCRIBES HIS DESPAIR AS THEIR CAPTORS STRING UP KING Arthur for a hanging: “They were blindfolding him! I was paralysed; I couldn’t move, I was choking, my tongue was petrified . . . They led him under the rope.” But, in the best cliff-hanging traditions, and at the last conceivable instant, Sir Lancelot comes to the rescue with five hundred knights—all riding bicycles. “Lord, how the plumes streamed, how the sun flamed and flashed from the endless procession of webby wheels! I waved my right arm as Lancelot swept in. I tore away noose and bandage, and shouted: ‘On your knees, every rascal of you, and salute the king! Who fails shall sup in hell to-night!’”

  I am not citing either Monty Python or Saturday Night Live, and I didn’t mix up my genders in the first sentence. The speaker is not Morgan le Fay (who, no doubt, would have devised a magical, rather than a technological, solution to the same predicament), but Hank Morgan, the Connecticut Yankee in King Arthur’s court, and the hero in Mark Twain’s satirical novel of the same name. Morgan, transported from nineteenth-century Hartford, wreaks mayhem in sixth-century Camelot by introducing all manner of “modern” conveniences, including tobacco, telephones, baseball—and bicycles.

  As a literary or artistic device, anachronism exerts a powerful hold upon us, and has been a staple of all genres from the highest philosophy to the lowest comedy—as Jesus is crucified in a corporate board room by Dali, condemned at his Second Coming by Dostoyevsky’s Grand Inquisitor, but only offered a half-price discount (as he changes to modern dress) by the Italian barber or the Jewish tailor of various ethnic, jokes, now deemed tasteless and untellable.

  Anachronism works this eerie and potent effect, I suppose, because we use the known temporal sequence of our history as a primary device for imposing order upon a confusing world. And when “the time is out of joint. O cursèd spite,” we really do get discombobulated. We also know that correction of a perceived time warp cannot be achieved so easily in real life as in magical fiction (where Merlin can put Hank Morgan to sleep for 1,300 years, or Dracula can be dispatched with a wooden stake driven into the right spot). We regard Hamlet’s blithe confidence as a mark of his madness when he completes his rhyming couplet with the Shakespearean equivalent of “no sweat” or “hakuna matata”: “. . . That ever I was born to set it right!”

  Science, for reasons partly mythical, but also partly accurate and honorable, presents itself as the most linear and chronologically well ordered of all disciplines. If science, working by fruitful and largely unchanging methods of reason, observation, and experimentation, develops progressively more accurate accounts of the natural world, then history provides a time line defined by ever-expanding success. In such a simple linear ordering, mediated by a single principle of advancing knowledge, any pronounced anachronism must strike us as especially peculiar—and subject to diametrically opposite judgment depending upon the direction of warp. An ancient view maintained in the present strikes us as risible and absurd—the creationist who wants to compress the history of life into the few thousand years of a literal biblical chronology, or the few serious members of the Flat Earth Society. But a “modern” truth, espoused out of time by a scholar in the distant past, fills us with awe, and may even seem close to miraculous.

  A person consistently ahead of his time—a real-life Hank Morgan who could present a six-shooter to Julius Caesar, or explain the theory of natural selection to Saint Thomas Aquinas—can only evoke a metaphorical comparison with a spaceman from a more advanced universe, or a genuine angel from the realms of glory. In the entire history of science, no man seems so well qualified for such a designation as Leonardo da Vinci, who died in 1519, but filled his private notebooks with the principles of aeronautics, the mental invention of flying machines and submarines, and a correct explanation for the nature of fossils that professional science would not develop until the end of the eighteenth century. Did he have a private line across the centuries to Einstein, or even to God Himself?

  I must confess that I share, with so many others, a lifelong fascination for this man. I was not a particularly intellectual child; I played stickball every afternoon and read little beyond comic books and school assignments. But Leonardo captured my imagination. I asked, at age ten or so, for a book about his life and work, probably the only intellectual gift that I ever overtly requested from my parents. As an undergraduate geology major, I bought the two-volume Dover paperback edition of Leonardo’s notebooks (a reprint of the 1883 compilation by Jean
Paul Richter) because I had read some of his observations on fossils in the Leicester Codex,1 and had been stunned not only by their accuracy, but also by their clear statement of paleoecological principles not clearly codified before our century, and still serving as a basis for modern studies.

  Leonardo remains, in many ways, a frustrating and shadowy figure. He painted only about a dozen authenticated works, but these include two of the most famous images in our culture, the Mona Lisa (in the Louvre) and the Last Supper (a crumbling fresco in Milan). He published nothing in his lifetime, despite numerous and exuberant plans, though several thousand fascinating pages of manuscript have survived, probably representing only about a quarter of his total output. He did not hide his light under a bushel and was, in life, probably the most celebrated intellectual in Europe. Dukes and kings reveled in his conversation and his plans for war machines and irrigation projects. He served under the generous patronage of Europe’s most powerful rulers, including Ludovico il Moro of Milan, the infamous Cesare Borgia, and King Francis I of France.

  Leonardo’s notebooks did not become generally known until the late eighteenth century, and were not published (and then only in fragmentary and occasional form) until the nineteenth century. Thus, he occupies the unique and peculiar role of a “private spaceman”—a thinker of preeminent originality, but whose unknown works exerted no influence at all upon the developing history of science (for nearly all his great insights had been rediscovered independently before his notebooks came to light).2

  The overwhelmingly prevailing weight of public commentary about Leonardo continues to view him as Western culture’s primary example of a “spaceman,” that is, as a genius so transcendent that he could reach, in his own fifteenth century, conclusions that the rest of science, plodding forward in its linear march to truth, would not ascertain for several hundred years. Leonardo stood alone and above, we are told over and over again, because he combined his unparalleled genius with a thoroughly modern methodology based on close observation and clever experiment. He could therefore overcome the ignorance and lingering sterile scholasticism of his own times.