The Story of Western Science

by Susan Wise Bauer

  Alfred Wegener, The Origin of Continents and Oceans, trans. John Biram, Dover Publications (paperback and e-book, 1966, ISBN 978-0486143897).

  EIGHTEEN

  Catastrophe, Redux

  Bringing extraordinary events back into the earth’s history

  After the impact at Chicxulub, 65 million years ago, life on

  Earth was changed forever.

  —Walter Alvarez, T. rex and the Crater of Doom, 1997

  Just seven years after the first publication of the drift theory, J. Harlen Bretz proposed an even more outrageous explanation for the shape of the earth.

  Bretz, a professor of geology at the University of Chicago, had just taken a field party of students to investigate the eastern Washington floodplain known as the Columbia Plateau. It was an eerie basalt landscape, pitted and carved into columns and channels; Bretz nicknamed it the “Channeled Scablands.” “Like great scars marring the otherwise fair face to the plateau,” he later wrote, “elongated tracts of bare, black rock carved into mazes of buttes and canyons . . . great wounds in the epidermis of soil with which Nature protects the underlying rock.” The tortured formations, Bretz thought, could only have been formed by some disastrous event, and the most reasonable explanation was a sudden inundation of water: a long-ago flood, probably caused by a melting glacier, that had suddenly torn down across the plateau, ripping streamways and gouging holes in the basalt plain. In 1923, he published two papers suggesting that the Channeled Scablands had been formed by “a great flood of glacial waters from the north,” a “debacle which swept the Columbia Plateau.”1

  Unlike Wegener’s theory, this proposal wasn’t intended to account for the form of the entire planet—just one small section of it. But the reaction to it was just as shrill. Immediately, prominent geologists took offense. A 1927 symposium assembled in Washington, DC, was almost entirely devoted to trampling Bretz’s theory: the “abnormal flood,” as one participant complained, was too “violent an assumption.” It was much more reasonable to assume that the Scablands had been shaped by “the same orderly and long-continued process of head-end erosion” that could be observed at any number of rivers and falls.2

  Bretz had just run, headfirst, into Charles Lyell.

  Lyell’s drastic uniformitarianism was still being shaped into a more flexible principle, one that would allow the earth to have a beginning, to change significantly over time. But geology remained passionately committed to long, slow change. Sudden catastrophes, even local ones, were considered to be no more “scientific” than those ancient comets and colliding planets.

  But Bretz dug in his heels. The features of the Scablands were extraordinary, and they required an extraordinary explanation. And he was willing to buck the academic consensus to provide one.

  “Ideas without precedent are generally looked on with disfavor,” Bretz wrote in 1928, “and men are shocked if their conceptions of an orderly world are challenged.” He spent the next thirty years challenging the uniform “orderliness” of the past: measuring, recording new data, assembling more proofs. In 1956 he published a massive study of the Scablands, demonstrating through the sheer accumulation of observable facts that slow and gradual erosion simply could not account for the landscape.3

  Up to this point, most of Bretz’s opponents had not visited the Scablands in person; they had attacked the “abnormal flood” on principle. Slowly, geologists began to file into the Columbia Plateau, study in hand, to see for themselves. Observation only confirmed what Bretz had been insisting all along: a catastrophe had descended on the Scablands. The venerable James Gilluly (much-honored author of the geology text used at most universities) stared up at the gashed columns of basalt, shook his head, and said, “Could anyone have been so wrong?” In 1965, a chartered busload of geologists completed a tour of the Scablands by sending Bretz (now eighty-three years old) a concession by telegram: “We are now,” the telegram ended, “all catastrophists.”4

  The slow accumulation of proof had demonstrated the possibility of sudden change. And new information was streaming to the earth from another source: the advancing space program. In 1968 the Apollo 8 expedition to the moon revealed dozens of impact craters; ancient comets (and asteroids) had struck not just once, but again and again. This, too, was sudden change—further proof that the sorts of calamities long off limits to geologic explanation did, in fact, sometimes happen.

  •

  In 1968 the American geologist Walter Alvarez was twenty-eight years old and working for a petroleum company in the Netherlands. He had just finished his PhD at Princeton, but the truth was that he was slightly embarrassed by geology. His father was a Nobel Prize–winning physicist, and physics seemed like a much more enthralling field. Physicists were trying to “read the thoughts of God” (as Einstein put it), grappling with relativity, wrestling with quantum mechanics. Meanwhile, geologists were cataloguing rocks, drawing maps, and working for petroleum companies.

  But earth science was changing. It had been a discipline focused on a single planet; but now it was “overwhelmed” (as Alvarez himself later wrote) by “data from so many planets and moons that it was hard to remember them all. And most of those bodies were covered with impact craters.”5

  By 1977, Alvarez was teaching at the University of California at Berkeley, and using the new data from space missions to help interpret all those years of mapping and cataloguing rocks. He had discovered an odd phenomenon: a strange abundance of the element iridium in a layer of Italian rock where it had no business being. Radioactive dating put the rock’s age at about sixty-five million years—an intriguing date, since it represented the so-called K-T* boundary, a strata of rock where geologists had long noted a discontinuity in the fossil record. Before the K-T boundary, dinosaurs and ammonites abounded; after it, they “disappeared forever.”6

  Alvarez consulted his father about the odd iridium layer, and together the two men came up with an outlandish idea. Iridium is much more commonly found in comets and asteroids than in earth layers. Perhaps this iridium was left over from an asteroid collision with the earth. And if it was, could the collision have anything to do with the K-T boundary?

  Despite the increasing evidence that asteroids did collide with moons and planets, both of these ideas were far out of Alvarez’s comfort zone. “In the mid-1970s,” Alvarez later wrote, “the thought of a catastrophic event in Earth history was disturbing. As a geology student I had learned that catastrophism is unscientific. I had seen how useful the gradualistic view had been to geologists reading the record of Earth history. I had come to honor it as the doctrine of ‘uniformitarianism’ and to avoid any mention of catastrophic events in the Earth’s past. But Nature seemed to be showing us something quite different.” Observation, here as in the Scablands, was quietly disproving uniformitarianism.7

  Alvarez began to search for iridium layers in the K-T boundary elsewhere on the earth. When they turned up, he proposed, in a 1980 paper published in the journal Science (and coauthored by his father, Luis, along with fellow Berkeley scientists Frank Asaro and Helen Michel), that the “KT boundary iridium anomaly” might well be due to an asteroid strike. Furthermore, this impact might explain the fossil discontinuity:

  Impact of a large earth-crossing asteroid would inject about 60 times the object’s mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record.8

  The theory was greeted with skepticism—but nothing like the scorn and hostility generated by Wegener or Bretz. There was already too much evidence that such a strike was possible. What was unclear was whether it had actually happened.

  So the skepticism of the 1980s took the form of a vigorous hunt for proof. Since the iridium anomaly (as Alvarez later observed) was “clearly real and probably global, the impact hypo
thesis attracted hundreds of scientists, who dropped whatever they were doing and started to look for new evidence bearing on the extinction event.” Not only geologists, but paleontologists, chemists, physicists, meteorologists, and even statisticians, were drawn into different aspects of the problem. In the next ten years, more than two thousand scientific papers on the impact hypothesis were presented and published.9

  Alvarez’s own work centered on the search for an impact crater. Finally, in 1991, his decade-long hunt ended. The crater, concealed by millennia of accumulated sediment, lay on the Yucatán coast; and it was 125 miles across.

  A crater that size implied a striking object about 10 kilometers in diameter—as big across as San Francisco, taller than Mount Everest. Its impact would have vaporized crust, set forests on fire, sent tsunamis ripping through the oceans, and thrown enough debris into the atmosphere to block the sun’s rays and create storms of poisonous acid rain. The impact, Alvarez concluded, changed the face of the planet—and wiped out the dinosaurs.10

  He did not convert the entire scientific world. A healthy subsection of respected paleontologists, led by Alvarez’s Berkeley colleague William Clements, argued (and are still arguing) for the slow, complex decline of the dinosaur population, not wholesale extinction stemming from a single event. But, like continental drift, the impact hypothesis provided a simple, elegant explanation for a whole range of strange phenomena, stretching across several different scientific fields.

  And science isn’t immune to a good story. Lyell’s long, steady history was not a particularly gripping one, and reintroducing catastrophism brought a bit of flair (not to mention melodrama) back to the field. In 1997, Alvarez published his account of the hypothesis’s formation in T. rex and the Crater of Doom. For the most part a carefully written, precise account of the clues that led Alvarez and his team to their conclusions, the book begins with a first chapter called “Armageddon,” a quote from The Lord of the Rings, and a dramatic account of what the impact must have looked like (“Entire forests were ignited, and continent-sized wildfires swept across the lands. . . . Even as the forests were set ablaze, another horror was approaching the coasts.”) As science writer Carl Zimmer puts it, “Suddenly the history of life was more cinematic than any science fiction movie.”11

  This cinematic history didn’t just belong to geology; catastrophism opened a whole range of scientific fields back up to the possibilities of extraordinary events. Comets, asteroids, supernovas, abnormal flares from the sun, supervolcanoes—each first entered the scientific world, and then popular culture (and then ended up as the Syfy movie of the week).

  “A series of catastrophes has brought each of us to our present state,” the Harvard astrophysicist Robert Kirshner was able to write in 2002. “The calcium and iron atoms that form our bones and blood were forged in the crucibles of stellar catastrophes.” It was now possible to introduce the onetime catastrophe into the history not just of the earth, but of the cosmos itself.12

  WALTER ALVAREZ

  T. rex and the Crater of Doom

  (1997)

  Alvarez’s readable and enlightening account is available in both print and digital formats.

  Walter Alvarez, T. rex and the Crater of Doom, Princeton University Press (paperback and e-book, 2008, ISBN 978-0691131030).

  * * *

  * The K-T (Cretaceous-Tertiary) extinction is now more commonly known as the K-Pg (Cretaceous-Paleogene) extinction.

  PART

  IV

  READING LIFE

  (With Special Reference to Us)

  Jean-Baptiste Lamarck, Zoological Philosophy (1809)

  Charles Darwin, On the Origin of Species (1859)

  Gregor Mendel, Experiments in Plant Hybridisation (1865)

  Julian Huxley, Evolution: The Modern Synthesis (1942)

  James D. Watson, The Double Helix (1968)

  Richard Dawkins, The Selfish Gene (1976)

  E. O. Wilson, On Human Nature (1978)

  Stephen Jay Gould, The Mismeasure of Man (1981)

  NINETEEN

  Biology

  The first systematic attempt to describe the history of life

  Life and organisation are . . . purely natural phenomena,

  and their destruction in any individual is also a natural

  phenomenon, necessarily following from the first.

  —Jean-Baptiste Lamarck, Zoological Philosophy, 1809

  Summer 1761. The Comte de Buffon was hard at work on the later volumes of his massive encyclopedia; James Hutton was tramping through the Scottish highlands, examining salt mines and coal pits; Bishop Ussher’s six-thousand-year-old history of the earth still, for the most part, ruled.

  And France and England were, yet again, at war.

  The ancient hostility between the two countries had been galvanized by competition for North American colonies. Across the Atlantic, British colonists, including a young George Washington, were carrying on a messy forest fight against the French and their Native American allies; in Europe, Great Britain and its last remaining major ally, the German kingdom of Prussia, were battling against the united front of France, Spain, Austria, and Russia.*

  Seventeen-year-old Jean-Baptiste de Monet was small for his age, but filled with French pride and a very young man’s sense of indestructibility. His father had died the year before, leaving him under the indifferent supervision of his ten older siblings; the French army, currently fighting against the Prussians in the German duchy of Westphalia, needed help; and so Jean-Baptiste found an ancient horse and rode off, ready to fight. He arrived at the front just in time for a major attack against the nearby Prussian-English camp.

  On the evening of July 15, his division stormed through the great Teutoburg Forest, fell on the nearest wing of the enemy, and was slaughtered. By the following day, over five thousand French soldiers were dead or had been taken prisoner; Jean-Baptiste and thirteen of his companions were the only survivors of his entire regiment.1

  The shaken teenager was rewarded with a commission as a lieutenant, but the following year a playful wrestling match with a companion apparently dislocated his neck, leaving him once again on the edge of death. A complicated operation, followed by months of convalescence, saved his life but left him both frail and poverty-stricken. He went to work for a banker and in his spare time pursued new interests: medicine first, then the study of living things, and finally, the nature of life itself.

  His first research project, a patriotic effort to identify all of the plants of France, drew the attention of the elderly Comte de Buffon, who nominated him for a post at the royal gardens. Over the next few years, as he continued his work in botany, Jean-Baptiste de Monet drew closer and closer to the core of his real interests: the definition of life, the inevitability of death, and the intertwined relationship of the two.

  He also began to sign himself as the Chevalier de Lamarck, a title that would normally have belonged to his oldest brother. There is no clear timeline of how this happened, or why. (Perhaps, one nineteenth-century commentator theorized, all ten older siblings had died?) But Lamarck, like his theory, was developing and changing over time. His reinvention was successful; he is now known, universally, as Lamarck.

  Hints of Lamarck’s developing thought appeared in his first nonbotanical publication, 1801’s Système des animaux sans vertèbres. This work dealt with the animals that Aristotle had described as “nonsanguinous,” or bloodless. Lamarck observed, accurately, that bloodless animals had no vertebrae, and so invented the modern term invertebrate. But the most groundbreaking observation in the Système came in the closing appendix, called “On Fossils.” Fossilized remains, Lamarck wrote, were signposts to “the state of the revolutions that different points on the surface of the globe have undergone . . . [and] of the changes that living beings have themselves successively experienced.”2

  Post-Buffon, it was hardly revolutionary to suggest that the earth had undergone changes. But changes in living creatures—that was a differen
t story. Up until this point, most natural historians had treated animals and plants as coming late to the surface of the globe, arriving more or less already in their present forms. Even the most cutting-edge work on living creatures, Carolus Linnaeus’s 1735 Systema naturae, dealt only with the existing characteristics of creatures—not their changes over time. But now Lamarck was marrying the history of life to the history of the globe. As the planet altered, so did the creatures on its surface.

  In his work Hydrogéologie, published the following year, Lamarck elaborated on this idea. Changes in the earth and in the life upon it were intimately related, but they were, nevertheless, separate fields of study. The natural historian, he proposed in his preface, should think of his studies as falling into three areas: the globe itself (the new field of geology); the skies; and living entities. This last field he gave a new name—biologie.3

  Beginning with Aristotle, various attempts had been made to categorize living things; animals, by their physical qualities, their habits, their food; plants, by their structure, their appearance. Lamarck had a much more fundamental division in mind: living (the subject of biology) and not living. Everything on earth was either organic or inorganic, alive or dead.

  This distinction required a definition of “living,” and Lamarck had long been contemplating one. A living body, he mused in his private papers, is naturally occurring, “organized in its parts,” and, by its nature, “limited in its duration.” Anything that possesses life is “necessarily doomed to lose it, that is, to suffer death.” Inorganic materials were immortal; living creatures were, without exception, sentenced to death.4

  Another half decade of study and writing led to the publication, in 1809, of Lamarck’s masterwork: Philosophie zoologique, or Zoological Philosophy, a natural history of life. “We may include what essentially constitutes life in the following definition,” Lamarck writes,