The Metaphor and the Rock
Review of Gould's Time's Arrow, Time's Cycle (1987)
by Frank J. Sulloway
ver
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 The 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.
Notes
- Gerald Holton has argued that all science is
inspired by such bipolar "themata," which transcend the strictly empirical
character of science by giving a primary role to human imagination. It is
curious that Holton's views, so relevant to Gould's own thesis, go unmentioned
in this book. See Holton, The Thematic Origins of Scientific Thought:
Kepler to Einstein (Harvard University Press, 1973).
- Gould is aware of the Hegelian-Marxist character
of this style of dialectical thinking (The Panda's Thumb, p. 184).
Similarly, Gould notes in Time's Arrow, Time's Cycle that the concept
of repetitive cycles moving onward is dialectical (p. 48n).
- Ernst Mayr, "Change of Genetic Environment and
Evolution," in J. Huxley, A.C. Hardy, and E.B. Ford, eds, Evolution as a
Process (Allen & Unwin, 1954), pp. 157–180; and Animal Species
and Evolution (Harvard University Press [Belknap], 1963).
[ Frank Sulloway, "The Metaphor and the Rock: A Review of
Time's Arrow, Time's Cycle by Stephen Jay Gould,"
The New York Review of
Books, 34 (May 28, 1987): 37-40. ]
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