The Flamingo’s Smile (12 page)

Throughout the 1820s, Buckland’s theory was a subject of lively debate within the Geological Society of London. The greatest geologists of Britain lined up on opposite sides. As his chief ally, Buckland could depend upon his Cambridge counterpart and fellow divine, the Reverend Adam Sedgwick. Leading the opposition were Charles Lyell, the great apostle of gradualism, and the aristocratic Roderick Impey Murchison. The debate surged with all the vigor of Buckland’s floodwaters, but within ten years both Buckland and Sedgwick had thrown in the towel.

Two primary discoveries forced Buckland’s retreat. First, he eventually had to admit that his deposits of loam and gravel were not distributed throughout the world (as “an universal deluge” would require) but only over lands in northern latitudes (reflecting—though Buckland did not yet know the reason—the limited extent of glaciers spreading from polar regions).

Second, and more importantly, the everyday dog work of geology proved that Buckland’s caves and gravels did not all correlate, or “match up,” as products of a single event in time and also that several deposits recorded more than one episode of flooding (or glaciation, as we would now say). “Correlation” is the basic activity of field geologists. We walk from outcrop to outcrop; we try to trace the beds of one location to the strata of another; we ascertain which beds at our first location match (or correlate in time with) sets of strata in other places.

As this basic work proceeded, geologists recognized that Buckland’s cave deposits and gravels represented many events, not a single universal flood. This discovery did not require that floods be abandoned as causal agents, but it did rob Noah of any special status. If numerous floods had occurred, then Buckland’s striking evidence could not be ascribed to any particular biblical event. Moreover, since Buckland found no human bones in any of his deposits (whereas Noah’s deluge occurred to extirpate rapacious humanity), he eventually concluded that
all
the many floods he now recognized had antedated the Noachian deluge.

In 1829, following a vigorous debate at the Geological Society over Conybeare’s paper on the Thames Valley (William Conybeare was a prominent member of Buckland’s team), Lyell wrote triumphantly to his supporter Gideon Mantell:

(For nonmusical readers, I point out that piano simply means “soft” in Italian. The instrument bears its name as a shortening of pianoforte for a device that can play both softly, or piano, and loudly, or forte.)

Buckland himself admitted defeat on the same grounds in his next major book of 1836, though he had not yet recognized the glacial alternative:

When their evidence fails, fine scientists like Buckland do not simply admit defeat, crawl into a hole, and don a hair shirt. They retain their interest and struggle to find new explanations. Buckland not only abandoned his flood theory when empirical work disproved it, but he eventually led the movement in Britain to substitute ice for water.

Although study in retrospect is unfair to historical figures, I must report that I experienced an almost eerie feeling while reading
Reliquiae diluvianae
in the light of later knowledge about glacial theory. So many of Buckland’s specific empirical statements almost cry out for interpretation by ice sheets rather than water. He continually reports, for example, that the inundation, both in Britain and in North America, must have come from the north, an obvious direction for advancing ice but not for universal floodwaters of a rising ocean. He also argues that blocks of granite moved to lower altitudes from the summit of Mont Blanc prove that the Flood rose high enough to cover all mountains—while we would simply say that descending glaciers brought the boulders down.

Louis Agassiz, the Swiss geologist who had grown up almost literally between mountain glaciers, developed the theory of ice ages during the 1830s. He and Buckland became fast friends and co-explorers. Buckland also became one of England’s first converts to glacial theory. He read three papers advocating this new interpretation of his old evidence before the Geological Society in 1840 and 1841, and he eventually even persuaded his old adversary Charles Lyell about the reality and power of continental ice sheets. Thus, Buckland not only promptly abandoned his flood theory when it failed the test; he also led the search for new explanations and rejoiced in their discovery.

Modern creationists, on the other hand, have dogmatically preached an even more outmoded and discredited version of flood theory since G.M. Price revived it fifty years ago. They do no fieldwork to test their claims (arguing instead by distorting the work of true geologists for rhetorical effect), and they will change not one jot or tittle of their preposterous theory.

I can present no greater contrast between this modern pseudoscience and the truly scientific spirit than Adam Sedgwick’s recantation in his presidential address before the Geological Society of London in 1831. As Buckland’s chief supporter, he had led the fight for flood theory; but he knew by then that he had been wrong. He also recognized that he had argued poorly at a critical point: he had correlated the caves and gravels not by empirical evidence, but by a prior scriptural belief in the Flood’s reality. As empirical evidence disproved his theory, he realized this logical weakness and submitted himself to rigorous self-criticism. I know no finer statement in all the annals of science than Sedgwick’s forthright recantation, and I wish to end this essay with his words. As a witness at the Arkansas creationism trial in December 1981, I also read this passage into the courtroom record because I felt that it illustrated so well the difference between dogmatism, which cannot change, and true science, done in this case by people who happened to be creationists. The final irony and deep message is simply this: flood theory, the centerpiece of modern creationism, was disproved 150 years ago, largely by professional clergymen who were also geologists, exemplary scientists, and creationists. The enemy of knowledge and science is irrationalism, not religion:

MY VOTE
for the most arrogant of all scientific titles goes without hesitation to a famous paper written in 1866 by Lord Kelvin, “The ‘Doctrine of Uniformity’ in Geology Briefly Refuted.” In it, Britain’s greatest physicist claimed that he had destroyed the foundation of an entire profession not his own. Kelvin wrote:

I apologize for inflicting so long a quote so early in the essay, but this is not an extract from Kelvin’s paper. It is the whole thing (minus the appended calculation). In a mere paragraph, Kelvin felt he had thoroughly undermined the very basis of his sister discipline.

Kelvin’s arrogance was so extreme, and his later comeuppance so spectacular, that the tale of his 1866 paper, and of his entire, relentless forty-year campaign for a young earth, has become the classical moral homily of our geological textbooks. But beware of conventional moral homilies. Their probability of accuracy is about equal to the chance that George Washington really scaled that silver dollar clear across the Rappahannock.

The story, as usually told, goes something like this. Geology, for several centuries, had languished under the thrall of Archbishop Ussher and his biblical chronology of but a few thousand years for the earth’s age. This restriction of time led to the unscientific doctrine of catastrophism—the notion that miraculous upheavals and paroxysms must characterize our earth’s history if its entire geological story must be compressed into the Mosaic chronology. After long struggle, Hutton and Lyell won the day for science with their alternative idea of uniformitarianism—the claim that current rates of change, extrapolated over limitless time, can explain all our history from a scientific standpoint by direct observation of present processes and their results. Uniformity, so the story goes, rests on two propositions: essentially unlimited time (so that slow processes can achieve their accumulated effect), and an earth that does not alter its basic form and style of change throughout this vast time. Uniformity in geology led to evolution in biology and the scientific revolution spread. If we deny uniformity, the homily continues, we undermine science itself and plunge geology back into its own dark ages.

Yet Kelvin, perhaps unaware, attempted to undo this triumph of scientific geology. Arguing that the earth began as a molten body, and basing his calculation upon loss of heat from the earth’s interior (as measured, for example, in mines), Kelvin recognized that the earth’s solid surface could not be very old—probably 100 million years, and 400 million at most (although he later revised the estimate downward, possibly to only 20 million years). With so little time to harbor all of evolution—not to mention the physical history of solid rocks—what recourse did geology have except to its discredited idea of catastrophes? Kelvin had plunged geology into an inextricable dilemma while clothing it with all the prestige of quantitative physics, queen of the sciences. One popular geological textbook writes (C.W. Barnes, in bibliography), for example:

Fortunately for a scientific geology, Kelvin’s argument rested on a false premise—the assumption that the earth’s current heat is a residue of its original molten state and not a quantity constantly renewed. For if the earth continues to generate heat, then the current rate of loss cannot be used to infer an ancient condition. In fact, unbeknown to Kelvin, most of the earth’s internal heat is newly generated by the process of radioactive decay. However elegant his calculations, they were based on a false premise, and Kelvin’s argument collapsed with the discovery of radioactivity early in our century. Geologists should have trusted their own intuitions from the start and not bowed before the false lure of physics. In any case, uniformity finally won and scientific geology was restored. This transient episode teaches us that we must trust the careful empirical data of a profession and not rely too heavily on theoretical interventions from outside, whatever their apparent credentials.

So much for the heroic mythology. The actual story is by no means so simple or as easily given an evident moral interpretation. First of all, Kelvin’s arguments, although fatally flawed as outlined above, were neither so coarse nor as unacceptable to geologists as the usual story goes. Most geologists were inclined to treat them as a genuine reform of their profession until Kelvin got carried away with further restrictions upon his original estimate of 100 million years. Darwin’s strong opposition was a personal campaign based on his own extreme gradualism, not a consensus. Both Wallace and Huxley accepted Kelvin’s age and pronounced it consonant with evolution. Secondly, Kelvin’s reform did not plunge geology into an unscientific past, but presented instead a different
scientific
account based on another concept of history that may be more valid than the strict uniformitarianism preached by Lyell. Uniformitarianism, as advocated by Lyell, was a specific and restrictive theory of history, not (as often misunderstood) a general account of how science must operate. Kelvin had attacked a legitimate target.

KELVIN’S ARGUMENTS AND THE REACTION OF GEOLOGISTS

As codiscoverer of the second law of thermodynamics, Lord Kelvin based his arguments for the earth’s minimum age on the dissipation of the solar system’s original energy as heat. He advanced three distinct claims and tried to form a single quantitative estimate for the earth’s age by seeking agreement among them (see Joe D. Burchfield’s
Lord Kelvin and the Age of the Earth
, the source for most of the technical information reported here).

Kelvin based his first argument on the age of the sun. He imagined that the sun had formed through the falling together of smaller meteoric masses. As these meteors were drawn together by their mutual gravitational attraction, their potential energy was transformed into kinetic energy, which, upon collision, was finally converted into heat, causing the sun to shine. Kelvin felt that he could calculate the total potential energy in a mass of meteors equal to the sun’s bulk and, from this, obtain an estimate of the sun’s original heat. From this estimate, he could calculate a minimum age for the sun, assuming that it has been shining at its present intensity since the beginning. But this calculation was crucially dependent on a set of factors that Kelvin could not really estimate—including the original number of meteors and their original distance from each other—and he never ventured a precise figure for the sun’s age. He settled on a number between 100 and 500 million years as a best estimate, probably closer to the younger age.

Kelvin based his second argument on the probable age of the earth’s solid crust. He assumed that the earth had cooled from an originally molten state and that the heat now issuing from its mines recorded the same process of cooling that had caused the crust to solidify. If he could measure the rate of heat loss from the earth’s interior, he could reason back to a time when the earth must have contained enough heat to keep its globe entirely molten—assuming that this rate of dissipation had not changed through time. (This is the argument for his “brief” refutation of uniformity, cited at the beginning of this essay.) This argument sounds more “solid” than the first claim based on a hypothesis about how the sun formed. At least one can hope to measure directly its primary ingredient—the earth’s current loss of heat. But Kelvin’s second argument still depends upon several crucial and unprovable assumptions about the earth’s composition. To make his calculation work, Kelvin had to treat the earth as a body of virtually uniform composition that had solidified from the center outward and had been, at the time its crust formed, a solid sphere of similar temperature throughout. These restrictions also prevented Kelvin from assigning a definite age for the solidification of the earth’s crust. He ventured between 100 and 400 million years, again with a stated preference for the smaller figure.

Kelvin based his third argument on the earth’s shape as a spheroid flattened at the poles. He felt that he could relate this degree of polar shortening to the speed of the earth’s rotation when it formed in a molten state amenable to flattening. Now we know—and Kelvin knew also—that the earth’s rotation has been slowing down continually as a result of tidal friction. The earth rotated more rapidly when it first formed. Its current shape should therefore indicate its age. If the earth formed a long time ago, when rotation was quite rapid, it should now be very flat. If the earth is not so ancient, then it formed at a rate of rotation not so different from its current pace, and flattening should be less. Kelvin felt that the small degree of actual flattening indicated a relatively young age for the earth. Again, and for the third time, Kelvin based his argument upon so many improvable assumptions (about the earth’s uniform composition, for example) that he could not calculate a precise figure for the earth’s age.

Thus, although all three arguments had a quantitative patina, none was precise. All depended upon simplifying assumptions that Kelvin could not justify. All therefore yielded only vague estimates with large margins of error. During most of Kelvin’s forty-year campaign, he usually cited a figure of 100 million years for the earth’s age—plenty of time, as it turned out, to satisfy nearly all geologists and biologists.

Darwin’s strenuous opposition to Kelvin is well recorded, and later commentators have assumed that he spoke for a troubled consensus. In fact, Darwin’s antipathy to Kelvin was idiosyncratic and based on the strong personal commitment to gradualism so characteristic of his world view. So wedded was Darwin to the virtual necessity of unlimited time as a prerequisite for evolution by natural selection that he invited readers to abandon
The Origin of Species
if they could not accept this premise: “He who can read Sir Charles Lyell’s grand work on the
Principles of Geology
, and yet does not admit how incomprehensively vast have been the past periods of time, may at once close this volume.” Here Darwin commits a fallacy of reasoning—the confusion of gradualism with natural selection—that characterized all his work and that inspired Huxley’s major criticism of the
Origin:
“You load yourself with an unnecessary difficulty in adopting
Natura non facit saltum
[Nature does not proceed by leaps] so unreservedly.” Still, Darwin cannot be entirely blamed, for Kelvin made the same error in arguing explicitly that his young age for the earth cast grave doubt upon natural selection as an evolutionary mechanism (while not arguing against evolution itself). Kelvin wrote:

Thus, Darwin continued to regard Kelvin’s calculation of the earth’s age as perhaps the gravest objection to his theory. He wrote to Wallace in 1869 that “Thomson’s [Lord Kelvin’s] views on the recent age of the world have been for some time one of my sorest troubles.” And, in 1871, in striking metaphor, “But then comes Sir W. Thomson like an odious spectre.” Although Darwin generally stuck to his guns and felt in his heart of hearts that something must be wrong with Kelvin’s calculations, he did finally compromise in the last edition of the
Origin
(1872), writing that more rapid changes on the early earth would have accelerated the pace of evolution, perhaps permitting all the changes we observe in Kelvin’s limited time:

Darwin’s distress was not shared by his two leading supporters in England, Wallace and Huxley. Wallace did not tie the action of natural selection to Darwin’s glacially slow time scale; he simply argued that if Kelvin limited the earth to 100 million years, then natural selection must operate at generally higher rates than we had previously imagined. “It is within that time [Kelvin’s 100 million years], therefore, that the whole series of geological changes, the origin and development of all forms of life, must be compressed.” In 1870, Wallace even proclaimed his happiness with a time scale of but 24 million years since the inception of our fossil record in the Cambrian explosion.

Huxley was even less troubled, especially since he had long argued that evolution might occur by saltation, as well as by slow natural selection. Huxley maintained that our conviction about the slothfulness of evolutionary change had been based on false and circular logic in the first place. We have no independent evidence for regarding evolution as slow; this impression was only an inference based on the assumed vast duration of fossil strata. If Kelvin now tells us that these strata were deposited in far less time, then our estimate of evolutionary rate must be revised correspondingly.