Over 500 million years ago, Pikaia, a two-inch-long worm-like creature, swam in the Cambrian seas. It was not particularly common, nor in anyway would it have appeared remarkable to a hypothetical naturalist surveying the fauna of the time. Pikaiais the first known chordate, the phylum to which Homo sapiens and all other vertebrates belong. As the late Stephen Jay Gould, paleontologist, evolutionary theorist, and dialectical biologist, posited in one of his most renowned books, Wonderful Life(1989), an exceptional level of human arrogance is necessary to argue that Pikaia was superior to its many contemporaries who either went extinct or, through the vagaries of history, dwindled to obscurity. Yet, despite the absurdity of it, bourgeois thought is so deeply committed to portraying history as a march of progress leading inexorably to the present that many natural historians have long argued that evolution on earth unfolded in a predictable, progressive manner, with the emergence of humanity, or at least a conscious intelligent being, as its inevitable outcome. This view fits well with the perspective of the dominant classes of various historical ages, who typically believe the particular hierarchical social order that supports them is both natural and inevitable, the point toward which history had been striving. As Marxist scholars have long recognized, ruling-class ideology gets smuggled into the damnedest places, including interpretations of the natural world. This elite construction of nature, which often involves demarcating so-called inherent hierarchies, is often used to justify inequalities in the social world. It would be wise to call into question such depictions of the social and natural world and to seek an understanding of natural history free of this ideology.
Running counter to much of prevailing thought, one of Gould’s central themes is that of historical contingency—events often occurring effectively by chance and that are not predictable before hand (although they may be rendered sensible in hindsight) may change the course of history, foreclosing some options and opening others. The trilobites so common before their disappearance in the granddaddy of all mass extinctions—that which ended the Permian period 250 million years ago—did not vanish due to inherent inferiority. After all, they had thrived for three hundred million years, longer than mammals have been around and over one thousand times longer than Homo sapiens has trod upon the earth. Rather, they likely blinked out due to bad luck in an unpredictable, and still unexplained, global shake up that took with it over 90 percent of all species then extant. It is hard to imagine that the descendants of Pikaia made it through this bottleneck due to anything but good fortune. Furthermore, had a comet not collided with the earth 65 million years ago, at the close of the Cretaceous period, the dinosaurs almost surely would have persisted in their dominance over the inconsequential rat-like ancestors of mammals, and their lineage would have taken a different path.
Due to the dominance of contingency in natural and social history, the world of the present is only one of the many worlds that are possible; it does not represent a foreordained order. Or to use Gould’s powerful metaphor, if we were to replay the tape of life, a different history would unfold, almost surely without the appearance of humans or any creature especially similar to us; a history that would appear just as sensible and even as inevitable as the history that actually occurred. At each moment in history we stand at a gate of worlds, and although it is not predictable where any path will ultimately lead, our actions nonetheless influence the path along which we travel, and the organization of the larger world will influence what constraints and possibilities we will confront as a new present emerges and eventually becomes history.
Our intent here is to compare the distinct views of historical processes presented by bourgeois scholars and by Marxist scholars and show how the dominant views of the former are embedded in particular scientific theories of natural history. In particular we will compare the uniformitarian/gradualist view with the catastrophist/punctuationalist view and discuss the different implications that these views have for the ideas of progress and predictability. Gould and other dialectical biologists, such as Niles Eldredge, Richard Levins, and Richard Lewontin, in advancing scientific understanding of natural history, struggle to root out fundamental aspects of the ideology of the controlling class that are embedded in the scientific enterprise. In the finest tradition of Marx, these scholars maintain a deep commitment to the virtues of a rational science that strives for objective understanding of the natural world, while recognizing that we are all inevitably influenced by our social position and intellectual milieu, and that the history of science, so far, has been influenced by the development of capitalism and its interests. These dialectical biologists recognize that the best way to approach objective understanding is not to deny social influences on scientific thought, since it is impossible to exist in an intellectual vacuum, but rather openly to acknowledge existing biases in ourselves and society and work to overcome these constraints with self-criticism, honesty, and integrity.
In this vein, Gould and Eldredge published a famous article in the scientific journal Paleobiology in 1977, where they noted that many of the premises of nineteenth-century European ruling-class ideology about the nature of history are embedded in the natural sciences, with Lyellian uniformitarianism in geology and Darwinian gradualism in biology providing the prime examples. They went on to explain the alternative view of historical change represented by Marx, a punctuational view that does not assume historical change occurs in a slow, smooth, and seamless manner. Gould and Eldredge were not arguing that gradualist or punctuationalist views are either right or wrong per se, but rather, different views may have various degrees of utility in helping us to understand the patterns of nature. Their case is that the Marxist tradition’s conceptualization of the nature of historical change can open our eyes to possibilities that are not readily visible from other perspectives.
In one of the most renowned scientific textbooks ever written, Principles of Geology (183033), Charles Lyell developed his case for a reform of the science of geology based on his methodological and substantive doctrine of uniformitarianism. Although Lyell in his development of uniformitarianism surely did a great deal to further the science of geology, he also misrepresented other contemporary theories and mixed together under the banner of uniformity a variety of disparate claims, some of which remain widely accepted by scientists as fundamentally important and others of which have been politely ignored so as to avoid embarrassing a key founder of modern geology. Gould notes in Ever Since Darwin (1977) that Lyell’s concept of uniformity has four distinct major components, but Lyell typically neglected to make explicit the differences among them (14752). First, Lyell argued for the spatiotemporal invariance of natural laws. This is one of the basic assumptions of modern science and was to a large extent as uncontroversial among Lyell’s scientific contemporaries as it is among scientists today. In this, Lyell was merely affirming the materialist approach, which by necessity looks for natural causes of phenomena, rather than invoking sporadic intervention in the physical world by a capricious deity, in order to establish the independence of science from theology.
The second claim involves the uniformity of process, the assertion that only processes that can be observed to operate in the present should be used to explain events in the past. This is now, as it was then, a somewhat more controversial claim. Scientists generally agree on a preference for invoking presently observable processes to explain the past, but some scholars, particularly those in the catastrophist tradition during Lyell’s time (more on this below), suggested that some past events required the inference of causes no longer acting or acting now at markedly slower rates (151). Third, Lyell asserted the rate of geologic change was uniformly slow, gradual, and steady, not cataclysmic or paroxysmal (151). This third claim is closely related to the second, and these two claims together provided the basis for Darwin’s gradualism.
The fourth and final component is based on the assertion that the general configuration of the earth has remained basically the same since its formation, with only minor non-directional change—e.g., while some mountains erode, others are built up so that the average state of the world remains largely unchanged with time’s passage. In other words, the earth is effectively in a dynamic steady-state. In this claim, Lyell was apparently hoping that terrestrial geologic processes mimicked the ahistorical characteristics of Newton’s universe, where the planets revolve around the sun in the same fashion they have done for eternity. Ironically, although this forth component was part of a larger view that argued for the antiquity of the earth, in its insistence on enduring stasis, it effectively denied history. This is the component of Lyell’s uniformitarianism that is most typically ignored by modern geologists because a large body of evidence indicates that the character of the earth has changed dramatically over its history.
Counter to Lyell, catastrophists argued that a few cataclysmic events over the course of earth’s history were responsible for the major aspects of the geologic world of the present. Lyell, a master rhetorician, presented his uniformitarianism as the scientific alternative to catastrophism, which he characterized as a theologically motivated defense of the Biblical timescale of earth’s history and of claims for God’s direct intervention in worldly affairs. This characterization was highly misleading, since at the time of Lyell’s writing nearly all informed scholars, uniformitarians and catastrophists alike, accepted that the earth was ancient and sought to explain geologic history based on material causes (e.g., volcanism, earthquakes). In fact, catastrophists were arguably more scientific than uniformitarians in that they advocated a literal interpretation of the empirical geologic record, which provided abundant evidence for catastrophic change (e.g., mass extinctions). For them, the hand of God was not needed to explain dramatic events in natural history. Materialist explanation, then, was central to catastrophism and uniformitarianism alike. Nonetheless, Lyell tried to explain away the evidence for catastrophic events by arguing for the imperfection of the geologic record, noting that geologic forces erased many pages of earth’s history as they wrote new ones. In effect, he argued that we should distrust empirical evidence. Properly understood, then, the uniformitarian-catastrophist debate primarily occurred within the scientific enterprise and was centered on two contrasting materialist explanations of the tempo and mode of historical change; it was not as often contended principally a clash between scientists (uniformitarians) and theologians (catastrophists). Nonetheless, Lyell won the day, and his interpretation was the one generally accepted by subsequent generations of geologists.
Darwin was strongly influenced by Lyell, and, arguably, his intellectual commitment to gradualism was second only to his commitment to natural selection. Darwin was an advocate of the claim generally attributed to Linnaeus: Natura non facit saltum (nature does not make leaps). Like Lyell, Darwin invoked the imperfection of the fossil record to explain away apparent periods of dramatic change in geologic history and sought to deny the reality of a handful of global mass extinctions that were followed by the instantaneous (in the geological sense) appearance of a suite of new species, which a literal reading of the fossil record suggested. Darwin consistently argued that extinctions and the emergence of new species were spread out in time, as organic history was the result of the accumulation of the imperceptibly small changes occurring all around us each day, where organisms struggle for their existence against one another and the physical environment.
Thus both geology (from Lyell) and biology (from Darwin) inherited a deep commitment to the view that historical change comes slowly and an explicit denial of the likelihood of occasional episodes of rapid and dramatic upheaval. Despite the deep commitment in the historical natural sciences to gradualism, the view that change is necessarily slow is more a social creation than a reflection of the factual operations of nature. As Gould and others have argued, there is substantial evidence that counters the two central claims for gradualism in Lyell’s uniformitarian doctrine.
First, it has become clear that there have been catastrophic events that differ qualitatively from presently observable forces shaping the earth. In the most striking example, over the past two and a half decades it has become widely accepted that the impact of a comet on earth was the cause of the Cretaceous extinction, which wiped out the dinosaurs. The key evidence for this conclusion (among several other important pieces of evidence) is a layer of iridium found all around the world at the Cretaceous-Tertiary boundary of the geologic record. The fact that iridium is very rare on earth, but abundant in comets, strongly suggests that the source of the iridium was extraterrestrial. This is a key example of a catastrophic mechanism of change operating in the past that is distinct from forces in operation today. Counter to Lyell’s assertion that only forces in operation today explain geologic history, and counter to Darwin’s assertion that no mass extinctions occurred in earth’s history, it now appears nearly certain that at least one mass extinction was indeed abrupt, caused by forces not currently acting upon the earth, and not an illusion generated by an imperfect fossil record.
Second, there is also a substantially diverse body of evidence supporting the contention that forces in operation today have, at various times in the past, operated at different rates, occasionally leading to rapid change. Thus, as Marx asserted, it is necessary to understand the historical specificity of causes and events. One of the best examples of this, which Gould presents in The Panda’s Thumb (1980), comes from the scablands of Eastern Washington State. As Gould writes, In the area between Spokane and the Snake and Columbia rivers to the south and west, many spectacular, elongate, subparallel channel-ways [what locals refer to as coulees] are gouged through the loess and deeply into the hard basalt itself (196). It was readily recognized by geologists that glacial meltwaters had run through the coulees, and it was generally assumed that the coulees had formed from the gradual process of erosion. Challenging this gradualist assumption, in 1923 J Harlen Bretz argued, based on several unusual features of the channels, that the channeled scablands had been formed all at once by a single, gigantic flood of glacial meltwater (197). Due to the prevalent gradualist bias in geology, this catastrophic hypothesis was at first widely rejected, without being given serious consideration by most geologists. Eventually, Bretz proved to be in large part correct. Evidence was subsequently discovered indicating that an extensive, ice-dammed glacial lake, Lake Missoula, in Montana emptied abruptly when the dam to burst. Furthermore, aerial photographs of the scablands showing huge ripples on the floors of some coulees, up to 22 feet high and 425 feet long, largely cinched Bretz’s case. Bretz was wrong in his initial insistence on a single catastrophic event—Lake Missoula reformed and emptied several times—but he was correct that the scablands did not assume their current form as the result of slow and constant erosion. Countering Lyell’s third uniformitarian claim, Bretz helped establish that forces observed in operation today (e.g., erosion) have operated at dramatically different rates during certain times in the past.
The lesson to be learned here is that catastrophist claims about change in the material world are no less scientific than those of gradualism and are widely supported by empirical evidence. The preference for gradualism common in the natural sciences, therefore, cannot be justified on scientific grounds. Rather, to some degree at least, it reflects a social bias, likely stemming in part from ideology of the social elite, for slow, predictable change and against the notion that dramatic historical change occasionally occurs in brief, revolutionary moments.
Eldredge and Gould allied themselves with the catastrophist/punctuationalist perspective in developing their theory of punctuated equalibria, the claim that the history of most species is best characterized as long periods of relative stasis, where there is only minor, non-directional change in organismal structure, punctuated by brief periods of rapid change where new species emerge from old in a geological moment (which may be thousands or tens of thousands of years). In proposing this theory, Eldredge and Gould were, like catastrophists before them, arguing for a more literal interpretation of the fossil record. They were not proposing a new mechanism of change, relying on natural selection as the primary force behind evolution, but were challenging widespread gradualist assumptions about the speed with which evolution can occur. However, they did suggest that most evolutionary change occurs at the point of speciation corresponding to the moment of punctuational change. Speciation often occurs when a small population becomes isolated from a larger population for an extended period of time. The isolated and initially small population is free to diverge from the parent population as it accumulates fortuitous mutations via natural selection. In large populations, genetic innovations are generally watered down and mutations are slow to spread throughout the population; thus large populations tend to remain stable or change slowly. However, in a small population, a favored mutation can spread rapidly, becoming ubiquitous in subsequent generations. The initial isolation of a population may occur due to a variety of forces: rivers changing course, island formation, continental drift, mountain building, and so forth. The emergence of new species, then, is, in part, a consequence of chance events and changing environmental conditions and can happen rapidly (in the geologic sense).
In his magnum opus, The Structure of Evolutionary Theory, Gould provides an extended discussion of what punctuated equilibria and punctuational views in general suggest about the nature of history. If evolution unfolds in the manner suggested by the theory of punctuated equilibria—and Gould presents an array of evidence that suggests punctuated equilibria better characterizes evolutionary history than does gradualism—change over the geologic long haul cannot be properly understood as simply the steady accumulation of small changes happening during the typical period. This insight suggests that we cannot readily predict future conditions via the smooth extrapolation of current trends. In particular, if the world is shaped by occasional contingent events that have dramatic consequences—e.g., comet impacts, massive floods from glacial lakes—then history cannot be understood as a march of progress along a mandated path. Many paths exist, and the one that is actually trod upon is not foreordained, but rather determined by the often unpredictable events that actually occur and the historical-structural constraints that exist in tension. Every historical moment contains possibilities, and the future is not predetermined.
Our purpose here has been to show that the widespread teleological assumption in the natural sciences that natural history unfolds in a predictable, progressive, and gradual manner is not necessarily a reflection of the factual processes of the natural world. Rather, it is the product of social history and ideology, and in large part reflects the ruling elite’s preference for the view that the present state of the world is the inevitable outcome of natural forces and that change is unlikely to come abruptly. We should reject this view and not foreclose the possibility of a different future. Factual questions cannot be answered by ideology. In order to be properly addressed, they require a rational, empirical science. But social biases often distort our view of the world, and scientists are not free from their sway. The Marxist tradition helps us to shed the ideological blinders of the bourgeois worldview and its assumptions about the progressive and predictable nature of history. Marxist scholars in the natural sciences have helped to open our eyes to the possibility that the world as it is did not have to be so and that the future remains open.
In addition to sources directly referenced in the text, our discussion of uniformitarianism drew upon Gould’s essay Lyell’s Pillars of Wisdom in his book The Lying Stones of Marrakech. For contemporary adherents to gradualism and the view that history unfolds in a slow and orderly manner, see Daniel Dennett’s Darwin’s Dangerous Idea, Richard Dawkins’s The Ancestor’s Tale, and Simon Conway Morris’s The Crucible of Creation and Life’s Solution. For an analysis of the causes of mass extinctions, including a presentation of the evidence indicating that the Cretaceous extinction was caused by the collision of a comet with the earth, see David Raup’s Extinction.