The Metaphor and the Rock

Ever since the appearance of Ontogeny and Phylogeny a decade ago, Stephen Jay Gould has continued to delight and inform a wide spectrum of readers and, in doing so, to defy C.P. Snow’s lament about the “two cultures” of the sciences and the humanities. Gould’s monthly column in Natural History magazine, published under the heading “This View of Life,” has led to a series of highly praised volumes of essays—Ever Since Darwin (1977), The Panda’s Thumb (1980), Hen’s Teeth and Horse’s Toes (1983), and most recently The Flamingo’s Smile (1985). In addition, Gould’s Mismeasure of Man (1981), which won the National Book Critics’ Circle Award, analyzed the questionable character of intelligence testing and emphasized the many personal and cultural biases that have led researchers astray in this field. Given the sheer amount of Gould’s publications, which include numerous scientific publications as well, Gould’s readers have been kept busy indeed absorbing his prodigious output.

Now, with Time’s Arrow, Time’s Cycle, Gould has turned to the history of geology, a field very close to his main concerns as a paleontologist. In this new work he offers a revisionist historical account of the discovery of geological time. If anyone suspects that Gould has at last written a book on a rather dry historical question, I should emphasize that he has hit upon a rich subject and has written a highly perceptive and fascinating book. Furthermore, his latest volume offers his readers a valuable insight into his wider intellectual vision, providing them with a literary blueprint for a number of the basic concerns that unite his many essays and books. To understand Gould one should read his new book. In this review I shall try to illustrate some of the connections between it and the rest of his work.

The Discovery of Deep Time

Geological time is so immense compared with the human experience of time that we can only hope to grasp it dimly through analogies. “Consider the earth’s history,” Gould suggests, “as the old measure of the English yard, the distance from the king’s nose to the tip of his outstretched hand. One stroke of a nail file on his middle finger erases human history.” This discovery of “deep time,” which involved abandoning biblical standards of time for nearly incomprehensible eons, Gould ranks with the monumental intellectual revolutions associated with Copernicus and Darwin. He has picked three major figures in the history of geology, one traditional villain (Thomas Burnet) and two traditional heroes (James Hutton and Charles Lyell), to illustrate the nature of this discovery.

Standard textbook accounts of the achievements of these three figures have long provided what Gould describes as a “self-serving mythology.” These flimsy “cardboard” accounts vaunt the superiority of empiricism and inductivism over the scientific nemesis of religious bigotry. According to the textbooks, geology remained in the service of the Mosaic story of creation as long as armchair geological theorists refused to place fieldwork ahead of scriptural authority. Thomas Burnet, author of the Sacred Theory of the Earth (1681–1689), was just such an archetypical spokesman for religious interests. A century later the Scottish geologist James Hutton finally broke with this biblical zealotry by arguing that geological evidence must rest upon a solid empirical foundation (literally, the rocks themselves) and that the earth’s strata, once carefully examined, betray “no vestige of a beginning—no prospect of an end.” But Hutton was far ahead of his time (and also not a very persuasive writer). It was therefore not until Charles Lyell published the Principles of Geology (1830–1833) that geologists finally came to accept Hutton’s basic message and banished miraculous intervention, catastrophes, and biblical deluges from their science.

Other historians of geology, Gould acknowledges, have refuted this textbook mythology, and he claims no originality in this respect. But he does believe that the real sources of inspiration in the discovery of deep time have not been properly understood. It is this aspect of the story that he sets out to rectify, and he does so with imagination and flair. In this respect Gould should be seen as part of the generation of historians who have been affected by T.S. Kuhn’s Structure of Scientific Revolutions (1962). Kuhn argued, in part, that science is a social activity and that theories are intellectual constructions imposed on data, not demanded by them. The views of Kuhn and other philosophers and sociologists of science have helped historians of science to recognize, as Gould emphatically does, that mental constructs (metaphors, analogies, personal philosophies, imaginative leaps)—not empirical discoveries—are what bring about scientific advance. “Facts” are so embedded in theory that they simply do not have the kind of independent probative power they were once supposed to possess.

Thus what underlies the discovery of deep time is by no means fieldwork, as the myths of geology textbooks would have us believe. Rather, Gould pinpoints a powerful pair of metaphors—time’s arrow and time’s cycle—by which humankind has always tried to grasp the concept of time. Time’s arrow captures the uniqueness and distinctive character of sequential events, whereas time’s cycle provides these events with another kind of meaning by evoking lawfulness and predictability. Gould notes that this metaphorical pair is common not only in the thinking of ancient and preliterate peoples but also in the Judeo-Christian tradition, in which time’s arrow nevertheless began to predominate. More importantly, this metaphorical pair of ideas was essential to the thinking of Gould’s three geological protagonists; and the paired concepts therefore offer the key, now obscured by textbook mythology, to unlocking their thinking about time.

Burnet and Newton

The frontispiece to Thomas Burnet’s Sacred Theory of the Earth embodies the essence of his argument. Christ, at the top, has his left foot on the earth as it was in the beginning of the creation (“without form and void”). Earth history moves clockwise, recording the perfect (featureless) earth of Eden, the Flood (with Noah’s ark floating just above the center), the present state of the earth, the coming conflagration that shall consume and purify the earth once more, and finally the earth transformed into a star after the righteous have ascended to heaven. Above Christ is the inscription from the Book of Revelation, “I am the alpha and omega,” that is, the beginning and the end. (See illustration on this page.)

Burnet’s theory illustrates the metaphors of time’s arrow and time’s cycle in unmistakable form. His is a one-cycle theory in which biblical narrative (time’s arrow) runs its course within a wider conception of “the great year” and “great circle of time and fate” that bring about the return of Paradise. It is precisely this literal belief in Scripture that has made Burnet a pariah in the history of geology. Yet Burnet, Gould demonstrates, was hardly the religious fanatic he is supposed to have been when he is placed within the context of contemporary scientific thought. Compared with the textbook legend, Burnet was, ironically, adamant about explaining the history of the earth as recorded in Scriptures entirely within the frame of natural science, devoid of all appeals to miracles or divine intervention. Whereas his contemporaries had to call upon God to create new and vast sources of water for the Flood, for example, Burnet tried to avoid such external interventions by positing an underground source of water released onto the earth’s surface through a fault in the crust. Similarly, Burnet believed that Vesuvius and Etna would provide the sources of fire that would ultimately consume and purify the world prior to the second coming of Christ.

In a revealing exchange, Burnet in 1681 argued with Isaac Newton over the length of the original “days” of creation. Newton saw a way out of the difficulty of assuming God had made the world in a week. He believed that the “days” of Genesis might have been much longer than present ones, and that God, when the job was finally done, intervened in order to speed up the earth’s rotation. Burnet regarded such a theory as totally unacceptable precisely because it required divine intervention. Thus the “bad guy” of geological textbook history was actually more devoted to rational, miraclefree science than the greatest scientist of his age.

Deep Time as Endless Cycles

Before James Hutton most geological theorists, working within a limited time scale for earth history, had dealt only with processes of decay. The earth was created, so their thinking went, and its geologic structures just wore down through catastrophic events like the biblical Flood and through more ordinary processes like weathering. Hutton’s genius was to introduce the concept of repair into geology and, with it, the notion of deep time. The textbooks, of course, see this as a triumph of science and empiricism over religion, but it was nothing of the kind. Ironically, Hutton’s entire theory of the earth was an a priori conception inspired jointly by religious considerations and “the most rigid and uncompromising version of time’s cycle ever developed by a geologist.”

Hutton’s theory grew out of a problem—what may be called “the paradox of the soil.” A gentleman farmer, Hutton was well aware that good soil, the product of the “denudation,” or eroding, of rock strata, eventually loses its richness to the plant life it sustains. Were there to be no geological source for continual new soil, Hutton believed, then the world would bear the intolerable stamp of an imperfectly designed abode for man’s existence. Hutton’s homocentric and teleological concept of the world therefore demanded that the soil, new soil, should never run out. This requirement in turn demanded the uplift of new strata to become the sources for soil replenishment. So Hutton, belatedly in his career, set out to find evidence for uplift (which he naturally did, since he was already looking for it). In fact, he found evidence for repeated uplifts of the earth’s crust. This realization led him inexorably to the discovery of deep time. In Hutton’s final theory the earth became an entirely self-regulating machine cycling its way, over and over again, through three geological stages: (1) denudation and decay; (2) the deposition of new marine strata; and (3) the melting, expansion, and uplift of the lowest strata as “igneous” rock ready to be broken down again for future plants. Hutton’s recognition that certain rocks had solidified from molten magma was a particularly powerful new insight.

So rigid was Hutton’s vision of an endlessly cycling earth having “no vestige of a beginning” and “no prospect of an end” that he lost all interest in the historical nature of geological change. The divine benevolence entailed in these cycles was everything to Hutton, who, in a Newtonian rather than a historical image, compared them to the planets revolving ceaselessly about the sun. “Through the thousand pages of Hutton’s treatise [1795],” Gould poignantly remarks, “we find not a single sentence that treats the different ages and properties of strata as interesting in themselves—as markers of distinction for particular times.”

Hutton, an unlikely hero for empiricist geology, nevertheless became one. Gould reconstructs this process of mythification and sees it as involving several stages. First, Hutton’s long and turgid Theory of the Earth (1795) was popularized by his friend John Playfair (1802). Not only did Playfair make up for Hutton’s difficult prose, but he also modernized Hutton’s theory by soft-pedaling both his “denial of history” and his repeated appeals to final causes. Subsequently Charles Lyell, who needed an empiricist hero for his own account of the warfare between science and religious bigotry, bolstered Hutton’s image as a fieldworker who had no conceptual bias. Finally the legend was consolidated in the writings of later geologists, who rarely bothered to read Hutton in the original.

The Return of the Ichthyosaurs

It is important to bear in mind that Charles Lyell was trained as a lawyer. His rhetorical skills were considerable indeed, and, as Gould makes clear, they are crucial to understanding his impact upon the history of geology. When pleading for his favorite client, which became known as the “uniformitarian” theory of geology, he portrayed the previous history of his discipline as a gradual overcoming of primitive superstitions, wild speculations, and biblical allegiances. In doing so he created his own legend, much as Sigmund Freud did, as an archempiricist free of all bias and preconception. But Lyell was not selling just evidence and fieldwork over previous dogma and speculative theory. Rather he foisted upon his contemporaries a “fascinating and particular theory rooted in…time’s cycle.”

This theory, which set itself up against the prevailing geological “catastrophism,” confused a number of distinct meanings under the banner of “uniformitarianism.” First, Lyell argued for the uniformity of nature’s laws (that is, the notion that laws do not change with time or place). Second, he argued for the uniformity of process, which simply means always explaining past changes by currently known causes as long as these will suffice. Contrary to the legend, Lyell’s geological opponents accepted both of these methodological aspects of “uniformity.” What Lyell’s critics did not accept were two further substantive claims about the world that he also made under the heading of good (uniformitarian) science. These claims were that rates of geological change are always uniform (that is, gradual) and that the general state of the world also remains uniform (that is, there is no progression or directionality in the long run).

The last of these claims was the most peculiar of all within Lyell’s vision of earth history. It led him to deny all evidence of progression in the fossil record and hence to reject not only Lamarck’s theory of evolution but also contemporary creationist notions, in which “higher” organisms were thought to replace “lower” ones after mass extinctions. So wedded was Lyell to his conception of nondirectional change occurring within great geological cycles that he even believed the more temperate climate of the Carboniferous period might one day return and, with it, the great dinosaurs of that age. “The huge iguanodon,” Lyell argued, “might reappear in the woods, and the ichthyosaur in the sea, while the pterodactyle might flit again through umbrageous groves of tree-ferns” (1830–1833, 1: 123). It was this curious passage in Lyell’s Principles that inspired Henry De la Beche’s celebrated lithograph (see opposite) in which a professorial ichthyosaur of some future earth discusses the geological significance of a fossilized human skull.

Lyell was even less of an empiricist, Gould points out, than most of his catastrophist opponents. For Lyell was constantly forced to deny the literal evidence of the geological record, which shows whole groups of organisms being abruptly replaced by different sets of organisms in adjacent strata. His gradualist reading of the geological record therefore required his constant “interpretation” of the recalcitrant evidence in order to reconcile it with his notions of time’s stately cycle and a world without abrupt changes. Nor was Lyell’s eventual conversion to evolution a strictly empirical affair. When he finally took this step publicly, in 1868, it was not because he had been persuaded by Darwin’s theory of natural selection. In fact, Lyell rejected that theory, accepting only a general evolutionary process without its celebrated Darwinian mechanism. Admitting nonmiraculous progression (that is, evolution) in turn allowed him to preserve three of his other four uniformities (uniformity of law, process, and rate) while giving up only uniformity of state. This was as Gould notes, “the most conservative intellectual option available to him.”

Charles Lyell may have lost the battle over progressionism to Darwinism, but he won the geological war against catastrophism, which enabled his belief in the uniformity of rate to become a textbook shibboleth. The catastrophists of Lyell’s day, Gould nevertheless maintains, were right all along. The literal fossil evidence of major rapid changes in previous faunas does not need to be interpreted away, as Lyell tried to do by appealing to the imperfection of the geological record. The theory of “punctuated equilibria,” by which Gould and Niles Eldredge (1972) have sought to accept and explain this nongradual record, is as much a reply to Lyell’s baneful legacy as it is a challenge to current Darwinian theory. Gould even sees supreme irony in the recent hypothesis of the Berkeley scientists Luis and Walter Alvarez that mass extinctions were caused by asteroidal or cometary impacts (a hypothesis now made plausible by the discovery of a worldwide iridium layer deposited at the Cretaceous-Tertiary boundary); for this is precisely the sort of wild “cosmological” speculation that Lyell derided in seventeenth-century writers like William Whiston.

Gould concludes Time’s Arrow, Time’s Cycle by insisting that arrows and cycles are “eternal metaphors” in the understanding of time. In a thoughtful complement to his discussion of the history of geology, he shows how these two metaphors have figured in the art and sculpture associated with major biblical themes. Both metaphors, he concludes, are needed “for any comprehensive view of history.”

All in all Gould has written a fine book that tells a fascinating story. Like most of his other books, it is original in parts but also synthesizes the scholarship of many other writers. It is not without some methodological shortcomings. As Gould himself acknowledges, his historical approach relies largely on the old-fashioned method of explication de texte and does so, moreover, within the limited sphere of British geology. Furthermore, some nonscientific readers may find certain of Gould’s geological discussions too dry or technical. One also feels that Gould pushes his temporal metaphors too far. For example, he occasionally tends, for the sake of his central argument, to play down the religious nature of the controversies surrounding the discovery of deep time. But his viewpoint is nevertheless a healthy corrective to the mythologies we find in textbooks, and his general argument is convincing.

Gouldian Themata

If time’s arrow and time’s cycle are “great” and “eternal” metaphors for others, they have also given direction to Gould’s work and theoretical interests. It hardly seems coincidental that his first published essay (1965) was an article on the confusion of meanings in Lyell’s concept of uniformitarianism (a confusion about uniformity as immanent laws—or time’s cycle—and uniformity as states—or time’s arrow). Nor is it coincidental that Gould’s first book, Ontogeny and Phylogeny (1977), drew its title and subject matter directly from another version of time’s arrow and time’s cycle. The more one reviews his writing over the years, the more one sees just how central this and another thematic pair of ideas—continuity and discontinuity—are in his thinking.¹ To elucidate the pervasiveness of these metaphors in Gould’s writings we must first identify, following Gould’s lead, some of the other intellectual guises in which they appear.

If time’s cycle stands for the immanence of law and time’s arrow for the uniqueness of history, then Gould’s dual career as a scientist and as a historian of science represents perhaps his greatest commitment to these two ways of understanding time. Gould is one of those rare scientists who fully appreciates that the past is not always “just history” and that many problems in science cannot be conceptualized correctly unless one escapes the intellectual straitjacket of prevailing scientific mythologies. In this sense scientists are actually influenced by history all the time, even though they often disdain the subject as a waste of time. The textbook legends they fashion around their scientific heroes are value-laden visions of the world that often limit “the possibility of weighing reasonable alternatives,” as Gould has emphasized about the history of geology. Thus doing the history of science is, for Gould at least, an essential part of doing good science.

Many of his Natural History essays, as well as The Mismeasure of Man and Ontogeny and Phylogeny, have been inspired by this fruitful union of history and science. It is the historian’s perspective, for example, that allows Gould to see that early practitioners of both geology and psychology envied the predictability and mathematical exactitude of hard sciences like physics. This circumstance led Hutton, for example, to ignore the historical nature of geological change in favor of a Newtonian view of the world. The same motive, Gould believes, has led psychologists to portray intelligence as a monolithic, quantifiable entity, an approach that he has attacked in The Mismeasure of Man. Thus in emulating the immanent laws and procedures of the physical sciences, both geology and psychology (which are partly historical sciences) have sometimes lost sight of the uniqueness that characterizes their subject matter.

Within Gould’s biological writings the themes of time’s arrow and time’s cycle are also ubiquitous. Gould touches upon this in the conclusion of his book, and the point is worth elaborating upon here. For example, biologists distinguish between homologies and analogies. Homologies are organs or structures that are similar owing to communality of descent. The wing of a bat, the front flipper of a seal, and the upper limb of a human being are all homologous, fashioned from a similar phylogenetic prototype by time’s arrow of evolution. Analogies, on the other hand, owe their similarity to immanent principles of function. Thus the wings of birds, bats, and pterodactyls are functionally analogous rather than the product of common descent. Similarly, we see the contrast between time’s arrow and time’s cycle in the tension between evolutionary explanations stressing optimality, on the one hand, and imperfection on the other. Optimal designs are equal evidence both for Darwinian natural selection and divine creation. Proofs of evolution are therefore, as Darwin understood, just those instances where imperfection betrays the historical process by which some structure was acquired.

Two of Gould’s books, The Panda’s Thumb and The Flamingo’s Smile, draw their titles from essays that elaborate this basic principle. Gould’s role as a critic of the “adaptationist program” within current evolutionary biology—see his “The Spandrels of San Marcos” (1979)—is also rooted in his conviction that history, which is full of evidence of structural constraints and other peculiarities defying optimal development, must not be forgotten in evolutionary explanations. Biology is thus filled with issues and tensions that touch upon Gould’s two temporal metaphors. As he remarks in this connection, “Two world views, eternal metaphors, jockey for recognition within every organism—receiving special attention according to the aims and interests of students: homology and analogy; history and optimality; transformation and immanence.” Much of Gould’s work as a scientist consists, to put it simply, of redressing the metaphorical balance whenever he believes his colleagues have opted for an explanation that ignores the inextricable duality of these concepts.²

No better example of this last statement can be given than the theory of punctuated equilibria, which involves not only the metaphors of time’s arrow and cycle but also those of continuity and discontinuity. In setting forth this theory, Eldredge and Gould (1972) were reacting against a paleontological tradition in which gradual evolution (time’s arrow) was seen as the primary mode of species change. The theory of punctuated equilibria draws upon two aspects of time’s cycle in challenging this view of evolution: the speciation cycle and the ontogenetic cycle. Following Ernst Mayr’s fundamental insight into the splitting of species and rapid evolution of new genetic patterns under conditions of geographic isolation,³ Eldredge and Gould inferred that most evolutionary change occurs during these brief moments of emergence, which usually leave no traces in the fossil record. They also concluded that the subsequent history of the species, when fossils do accumulate, is primarily one of stasis.

Gould subsequently added to this theory, which is “catastrophic” only in comparison with the paleontological gradualism that preceded it, a conceptual twist involving time’s ontogenetic cycle. This aspect of the theory, which has been more controversial, argues that rapid changes during the cycle in which new species develop become possible by changes in genes that control rates of development (ontogeny). Gould (The Panda’s Thumb, pp. 186–193) even went so far as to argue in this connection that Richard Goldschmidt’s discredited theory of “hopeful monsters” might finally be ready for a comeback. Goldschmidt believed that new species could arise by sudden macromutations (or large genetic changes). Most of these mutations would result in maladapted monsters, but an occasional “hopeful monster,” Goldschmidt argued, would prove viable and then give rise to a new evolutionary line. To his colleagues in evolutionary theory, Gould’s endorsement of this non-Darwinian view was comparable to arguing that parapsychology should be taken seriously.

The concept of ontogeny has also been of special importance to Gould in his role as a critic of adaptationism. Like the romantics and idealists of early nineteenth-century biology, Gould sees the organism as an indivisible whole. Development, in his view, is constrained by a host of interacting genetic systems and functional requirements. A proper understanding of ontogeny is therefore a prerequisite for appreciating the ways and means of phylogeny. In any event, it is enough to point out here that Gould appears to have made good use of metaphorical thinking (especially time’s arrow and time’s cycle) both in his historical work and in his contributions to biological theory.

I have been able only to sketch briefly the unity that Gould’s favorite metaphors and themes give to his work. At the same time, I certainly do not wish to over-simplify the diversity of Gould’s literary and scientific efforts, which are hardly reducible to these metaphors. Gould, moreover, will probably develop new metaphors to guide his future research and writing, thus exercising the privilege that comes with time’s arrow—unpredictable change and uniqueness. In the meantime, inspired by such “eternal” metaphors about time and change, Gould’s thinking will doubtless continue to move forward in creative and fruitful cycles.