As startling as his specific claims may be, I am more interested in Velikovsky’s unorthodox method of inquiry and physical theory. He begins with the working hypothesis that all stories reported as direct observation in the ancient chronicles are strictly true—if the Bible reports that the sun stood still, then it did (as the tug of Venus briefly halted the earth’s rotation). He then attempts to find some physical explanation, however bizarre, that would render all these stories both mutually consistent and true. Most scientists would do exactly the opposite in using the limits of physical possibility to judge which of the ancient legends might be literally accurate. (I devoted essay 17 to the last important scientific work that used Velikovsky’s method—Thomas Burnet’s Sacred Theory of the Earth, first published in the 1680s.) Secondly, Velikovsky is well aware that the laws of Newton’s universe, where forces of gravitation rule the motion of large objects, will not allow planets to wander. Thus, he proposes a fundamentally new physics of electromagnetic forces for large bodies. In short, Velikovsky would rebuild the science of celestial mechanics to save the literal accuracy of ancient legends.
Having devised a cataclysmic theory of human history, Velikovsky then sought to generalize his physics by extending it throughout geologic time. In 1955 he published Earth in Upheaval, his geologic treatise. With Newton and modern physics already under siege, he now took on Charles Lyell and modern geology. He reasoned that if wandering planets had visited us twice within a mere 3,500 years, then the history of the earth should be marked by its catastrophes, not by the slow and gradual change that Lyell’s uniformitarianism requires.
Velikovsky scoured the geologic literature of the past hundred years for records of cataclysmic events—floods, earthquakes, volcanoes, mountain building, mass extinctions, and shifts of climate. Finding these aplenty, he sought a common cause:
Sudden the agent must have been and violent; recurrent it must have been, but at highly erratic intervals; and it must have been of titanic power.
Not surprisingly, he invoked the electromagnetic forces of celestial bodies external to the earth. In particular, he argues that these forces rapidly perturb the earth’s rotation—literally turning the earth over in extreme cases and exchanging poles for equators. Velikovsky offers a rather colorful account of the effects that might accompany such a sudden shift in the earth’s axis of rotation:
At that moment an earthquake would make the globe shudder. Air and water would continue to move through inertia; hurricanes would sweep the earth and the seas would rush over continents.… Heat would be developed, rocks would melt, volcanoes would erupt, lava would flow from fissures in the ruptured ground and cover vast areas. Mountains would spring up from the plains.
If the testimony of human narrators provided the evidence for Worlds in Collision, then the geologic record itself must suffice for Earth in Upheaval. Velikovsky’s entire argument hinges on his reading of geological literature. This, I feel, he does rather badly and carelessly. I will focus upon the general faults of his procedure, not the refutation of specific claims.
First, the assumption that similarity of form reflects simultaneity of occurrence: Velikovsky discusses the fossil fishes of the Old Red Sandstone, a Devonian formation in England (350–400 million years old). He cites evidence of violent death—contortion of the body, lack of predation, even signs of “surprise and terror” engraved forever on fossil faces. He infers that some sudden catastrophe must have extirpated all these fishes; yet, however unpleasant the death of any individual, these fishes are distributed through hundreds of feet of sediments that record several million years of deposition! Likewise, the craters of the moon are similar in appearance, and each one formed by the sudden impact of a meteorite. Yet this influx spans billions of years, and Velikovsky’s favored hypothesis of simultaneous origin by bubbling on the surface of a molten moon has been conclusively disproved by the Apollo landings.
Second, the assumption that events are sudden because their effects are large: Velikovsky writes graphically about the hundreds of feet of ocean water that were evaporated to form the great Pleistocene ice sheets. He can envisage the process only as a result of oceanic boiling followed by a general refrigeration:
An unusual sequence of events was necessary: the oceans must have steamed and the vaporized water must have fallen as snow in latitudes of temperate climates. This sequence of heat and cold must have taken place in quick succession.
Yet glaciers are not built overnight. They formed “rapidly” by geological standards, but the few thousand years of their growth allowed ample time for the gradual accumulation of snow by new precipitation supplied each year. One need not make the oceans steam; it still snows in northern Canada.
Third, the inference of worldwide events from local catastrophes: no geologist has ever denied that local catastrophes occur by flooding, earthquake, or volcanic eruption. But these events have nothing to do, one way or the other, with Velikovsky’s notion of global catastrophe caused by sudden shifts in the earth’s axis. Nevertheless, most of Velikovsky’s “examples” are just such local events combined with an unwarranted extrapolation to global impact. He writes, for example, of the Agate Springs Quarry of Nebraska—a local mammalian “graveyard” containing the bones (according to one estimate) of nearly 20,000 large animals. But, this large aggregation may not record a catastrophic event at all—rivers and oceans can gradually accumulate vast quantities of bone and shell (I have walked on beaches composed entirely of large shells and coral rubble). Also, even if a local flood drowned these animals, we have no evidence that their contemporary brethren on other continents were the least bit bothered.
Fourth, the exclusive use of outdated sources: before 1850, most geologists invoked general catastrophes as the major agent of geologic change. These men were not stupid, and they argued their position with some cogency. If we read only their works, their conclusions seem to follow. Velikovsky’s entire discussion of the catastrophic death of European fossil fishes cites only the works of Hugh Miller in 1841 and of William Buckland in 1820 and 1837. Surely the past hundred years, with its voluminous literature, contains something worth noting. Likewise, Velikovsky relies on John Tyndall’s work of 1883 for his meteorological notions about the origin of ice ages. Yet scarcely any subject has been more actively discussed in geological circles during this century.
Fifth, carelessness, inaccuracy, and sleight of hand: Earth in Upheaval is studded with minor errors and half-truths, unimportant in themselves, but reflecting either a cavalier attitude toward the geologic literature or, more simply, a failure to understand it. Thus, Velikovsky attacks the uniformitarian postulate that present causes can explain the past by arguing that no fossils are forming today. Anyone who has dug old bones from lake beds or shells from beaches knows that this claim is simply absurd. Likewise, Velikovsky refutes Darwinian gradualism with an argument “that some organisms, like foraminifera, survived all geological ages without participating in evolution.” This claim was occasionally made in older literature written before anyone had seriously studied these single-celled creatures. But no one has maintained it since J. A. Cushman’s voluminous descriptive work of the 1920s. Finally, we learn that igneous rocks—granite and basalt—“have embedded in them numberless living organisms.” This is news to me and to the entire profession of paleontology.
But all these criticisms pale to insignificance before the most conclusive refutation of Velikovsky’s examples—their explanation as consequences of continental drift and plate tectonics. And here Velikovsky is not to blame at all. He has merely fallen victim—as have so many others with the most orthodox among previously cherished opinions—to this great revolution in geological thought. In Earth in Upheaval, Velikovsky quite reasonably rejected continental drift as an alternate explanation for the most important phenomena supporting his catastrophic theory. And he rejected it for the reason then most commonly cited among geologists—the lack of a mechanism to move the continents. That mechanism has now b
een provided with the verification of sea-floor spreading (see essays 16 and 20). The African rift is not a crack formed when the earth turned over rapidly; it is a part of the earth’s rift system, a junction between two crustal plates. The Himalayas did not rise when the earth shifted but when the Indian plate slowly pushed into Asia. The Pacific volcanoes, a “ring of fire,” are not the product of melting during the last axial displacement; they mark the boundary between two plates. There are fossil corals in polar regions, coal in Antarctica, and evidence of Permian glaciation in tropical South America. But the earth need not turn over to explain all this; the continents have only to drift from different climatic realms into their present positions.
Ironically, Velikovsky has lost more to plate tectonics than his mechanism of axial shifting; he has probably lost the entire rationale for his catastrophist position. As Walter Sullivan argues in his recent book on continental drift, the theory of plate tectonics has provided a stunning confirmation of uniformitarian preferences for ascribing past events to present causes acting without great deviation from their current intensity. For the plates are actively moving today, carrying their continents with them. And the sweeping panorama of attendant events—the worldwide belt of earthquakes and volcanoes, the collision of continents, the mass extinctions of faunas (see essay 16)—can be explained by the continuous movement of these giant plates at rates of only a few centimeters a year.
The Velikovsky affair raises what is perhaps the most disturbing question about the public impact of science. How is a layman to judge rival claims of supposed experts? Any person with a gift for words can spin a persuasive argument about any subject not in the domain of a reader’s personal expertise. Even von Daniken sounds good if you just read Chariots of the Gods. I am in no position to judge the historical argument of Worlds in Collision. I know little of celestial mechanics and even less about the history of the Egyptian Middle Kingdom (although I have heard experts howl about Velikovsky’s unorthodox chronology). I do not wish to assume that the nonprofessional must be wrong. Yet when I see how poorly Velikovsky uses the data I am familiar with, then I must entertain doubts about his handling of material unfamiliar to me. But what is a person who knows neither astronomy, Egyptology, nor geology to do—especially when faced with a hypothesis so intrinsically exciting and a tendency, shared, I suspect, by all of us, to root for the underdog?
We know that many fundamental beliefs of modern science arose as heretical speculations advanced by nonprofessionals. Yet history provides a biased filter for our judgment. We sing praises to the unorthodox hero, but for each successful heretic, there are a hundred forgotten men who challenged prevailing notions and lost. Who among you has ever heard of Eimer, Cuénot, Trueman, or Lang—the primary supporters of orthogenesis (directed evolution) against the Darwinian tide? Still, I will continue to root for heresy preached by the nonprofessional. Unfortunately, I don’t think that Velikovsky will be among the victors in this hardest of all games to win.
20 | The Validation of Continental Drift
AS THE NEW Darwinian orthodoxy swept through Europe, its most brilliant opponent, the aging embryologist Karl Ernst von Baer, remarked with bitter irony that every triumphant theory passes through three stages: first it is dismissed as untrue; then it is rejected as contrary to religion; finally, it is accepted as dogma and each scientist claims that he had long appreciated its truth.
I first met the theory of continental drift when it labored under the inquisition of stage two. Kenneth Caster, the only major American paleontologist who dared to support it openly, came to lecture at my alma mater, Antioch College. We were scarcely known as a bastion of entrenched conservatism, but most of us dismissed his thoughts as just this side of sane. (Since I am now in von Baer’s third stage, I have the distinct memory that Caster sowed substantial seeds of doubt in my own mind.) A few years later, as a graduate student at Columbia University, I remember the a priori derision of my distinguished stratigraphy professor toward a visiting Australian drifter. He nearly orchestrated the chorus of Bronx cheers from a sycophantic crowd of loyal students. (Again, from my vantage point in the third stage, I recall this episode as amusing, but distasteful.) As a tribute to my professor, I must record that he experienced a rapid conversion just two years later and spent his remaining years joyously redoing his life’s work.
Today, just ten years later, my own students would dismiss with even more derision anyone who denied the evident truth of continental drift—a prophetic madman is at least amusing; a superannuated fuddy-duddy is merely pitiful. Why has such a profound change occurred in the short space of a decade?
Most scientists maintain—or at least argue for public consumption—that their profession marches toward truth by accumulating more and more data, under the guidance of an infallible procedure called “the scientific method.” If this were true, my question would have an easy answer. The facts, as known ten years ago, spoke against continental drift; since then, we have learned more and revised our opinions accordingly. I will argue, however, that this scenario is both inapplicable in general and utterly inaccurate in this case.
During the period of nearly universal rejection, direct evidence for continental drift—that is, the data gathered from rocks exposed on our continents—was every bit as good as it is today. It was dismissed because no one had devised a physical mechanism that would permit continents to plow through an apparently solid oceanic floor. In the absence of a plausible mechanism, the idea of continental drift was rejected as absurd. The data that seemed to support it could always be explained away. If these explanations sounded contrived or forced, they were not half so improbable as the alternative—accepting continental drift. During the past ten years, we have collected a new set of data, this time from the ocean basins. With these data, a heavy dose of creative imagination, and a better understanding of the earth’s interior, we have fashioned a new theory of planetary dynamics. Under this theory of plate tectonics, continental drift is an inescapable consequence. The old data from continental rocks, once soundly rejected, have been exhumed and exalted as conclusive proof of drift. In short, we now accept continental drift because it is the expectation of a new orthodoxy.
I regard this tale as typical of scientific progress. New facts, collected in old ways under the guidance of old theories, rarely lead to any substantial revision of thought. Facts do not “speak for themselves”; they are read in the light of theory. Creative thought, in science as much as in the arts, is the motor of changing opinion. Science is a quintessentially human activity, not a mechanized, robotlike accumulation of objective information, leading by laws of logic to inescapable interpretation. I will try to illustrate this thesis with two examples drawn from the “classical” data for continental drift. Both are old tales that had to be undermined while drift remained unpopular.
I. The late Paleozoic glaciation. About 240 million years ago, glaciers covered parts of what is now South America, Antarctica, India, Africa, and Australia. If continents are stable, this distribution presents some apparently insuperable difficulties:
A. The orientation of striae in eastern South America indicates that glaciers moved onto the continent from what is now the Atlantic Ocean (striae are scratches on bedrock made by rocks frozen into glacier bottoms as they pass over a surface). The world’s oceans form a single system, and transport of heat from tropical areas guarantees that no major part of the open ocean can freeze.
B. African glaciers covered what are now tropical areas.
C. Indian glaciers must have grown in semitropical regions of the Northern hemisphere; moreover, their striae indicate a source in tropical waters of the Indian Ocean.
D. There were no glaciers on any of the northern continents. If the earth got cold enough to freeze tropical Africa, why were there no glaciers in northern Canada or Siberia?
All these difficulties evaporate if the southern continents (including India) were joined together during this glacial period, and located farther sout
h, covering the South Pole; the South American glaciers moved from Africa, not an open ocean; “tropical” Africa and “semitropical” India were near the South Pole; the North Pole lay in the middle of a major ocean, and glaciers could not develop in the Northern Hemisphere. Sounds good for drift; indeed, no one doubts it today.
II. The distribution of Cambrian trilobites (fossil arthropods living 500 to 600 million years ago). The Cambrian trilobites of Europe and North America divided themselves into two rather different faunas with the following peculiar distribution on modern maps. “Atlantic” province trilobites lived all over Europe and in a few very local areas on the far eastern border of North America—eastern (but not western) Newfoundland and southeastern Massachusetts, for example. “Pacific” province trilobites lived all over America and in a few local areas on the extreme western coast of Europe—northern Scotland and northwestern Norway, for example. It is devilishly difficult to make any sense of this distribution if the two continents always stood 3,000 miles apart.
But continental drift suggests a striking resolution. In Cambrian times, Europe and North America were separated: Atlantic trilobites lived in waters around Europe; Pacific trilobites in waters around America. The continents (now including sediments with entombed trilobites) then drifted toward each other and finally joined together. Later, they split again, but not precisely along the line of their previous junction. Scattered bits of ancient Europe, carrying Atlantic trilobites, remained at the easternmost border of North America, while a few pieces of old North America stuck to the westernmost edge of Europe.
Both examples are widely cited as “proofs” of drift today, but they were soundly rejected in previous years, not because their data were any less complete but only because no one had devised an adequate mechanism to move continents. All the original drifters imagined that continents plow their way through a static ocean floor. Alfred Wegener, the father of continental drift, argued early in our century that gravity alone could put continents in motion. Continents drift slowly westward, for example, because attractive forces of the sun and moon hold them up as the earth rotates underneath them. Physicists responded with derision and showed mathematically that gravitational forces are far too weak to power such a monumental peregrination. So Alexis du Toit, Wegener’s South African champion, tried a different tack. He argued for a local, radioactive melting of oceanic floor at continental borders, permitting the continents to glide through. This ad hoc hypothesis added no increment of plausibility to Wegener’s speculation.
Ever Since Darwin: Reflections in Natural History Page 14