NATURAL DISCONTINUITIES

AND THE FOSSIL RECORD



One often encounters several objections to the notion of intelligent design. One is that intelligent design is non-natural and hence outside the scope of the natural sciences. Another is that intelligent design may be invoked to explain virtually anything. Yet another is that intelligent design is empirically ambiguous: a continuous evolutionarily developed cosmos may be as intelligently designed as a discontinuous one in which God periodically infused new information. Henry Morris and Howard Van Till, for example, both claim to believe in intelligent design yet hold to radically different views on natural history and God's means of creation.

These apparent disadvantages can be turned into a tremendous advantage for an open-minded scientist (or honest lawyer, for that matter). Obviously, one of the greatest advantages of an intelligent design paradigm over a naturalistic one is that it is open to more empirical possibilities.

Philosophical naturalism requires that nature be fully continuous. The history of life must be represented by a tree. All life must have a common ancestor. All genetic change must ultimately be the result of purely unguided, materialistic processes. Theism or intelligent design, on the other hand, is much less restraining. Life may be either continuous or discontinuous. It follows that life on earth may be modeled as a either a tree or a forest.

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"If any event in life's history resembles man's creation myths, it is this sudden diversification of marine life when multicellular organisms took over as the dominant actors in ecology and evolution. Baffling (and embarrassing) to Darwin, this event still dazzles us and stands as a major biological revolution on a par with the invention of self-replication and the origin of the eukariotic cell. The animal phyla emerged out of the Precambrian mists with most of the attributes of their modern descendants."

... The number of intermediate varieties, which have formerly existed on the earth, (must) be truly enormous. Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory.

"It is still, as it was in Darwin's day, overwhelmingly true that the first representatives of all the major classes of organisms known to biology are already highly characteristic of their class when they make their initial appearance in the fossil record. This phenomenon is particularly obvious in the case of the invertebrate fossil record. At its first appearance in the ancient paleozoic seas, invertebrate life was already divided into practically all the major groups with which we are familiar today.

Biology in the early decades of the nineteeth century was dominated by the idea that the organic world was a fundamentally discontinuous system in which all the major groups of organisms were unique and isolated and unlinked by transitional forms. ... Where there was variation, it was only trivial variation within the clearly defined limits of the species or type. Thus to the naturalists of the nineteenth century the basic order of nature was static and discontinuous, very different from the dynamic continuous model which was later to become axiomatic for most biologists after 1859. (p. 18)

Before 1859 it was fashionable and intellectually respectable to view the organic world as a discontinuous system-- the result of successive creation interventions in the history of the world. After 1859 it became intellectually respectable to view life as the natural product of purely natural processes operating over long periods of time. Changing one's interpretation of the world is not, however, the same as establishing a new fact. The facts were the same in 1850 as they were in 1870, only the perception of them had changed. (p. 73)

The so-called typological model of nature adhered to by biologists early in the (19th) century was not without a considerable degree of empirical support. ... [T]he work of the great nineteenth century comparative anatomists such as Cuvier and, later, Owen had shown that the living world could be considered divided into distinct types or phyla and that organisms clearly intermediate between different classes were virtually unknown.

Comparative anatomy had also revealed that organisms were integrated wholes in which all the components were coadapted to function together; and this seemed to many to preclude any sort of major evolutionary transformation. As William Coleman, an authority on Georges Cuvier, points out:

The organism, being a functionally integrated whole each part of which stood in close relation to every other part, could not, under pain of almost immediate extinction, depart significantly from the norms established for the species by the first anatomical rule.

A major change, for example, a sharp increase in the heart beat or the diminution by half of the kidney and thus a reduction in renal secretion, would by itself have wrought havoc with the general constitution of the animal. In order that an animal might persist after a change of this magnitude it would be necessry that the other organs of the body be also proportionally modified. In other words, an organism must change en bloc or not at all. Only saltatory modification could occur, and this idea was to Cuvier, as it is to most modern zoologists, but for very different reasons, unverified and basically absurd. Transmutation by the accumulation of alterations, great or small, would thus be impossible.

Coleman, W. (1964)
Georges Cuvier: Zoologist
Harvard University Press
Cambridge, Mass, pp 172-73

(Denton, 1986, p. 18)

When the appeal of the scientific paradigm and the natural desire of the scientific community to extend the range of scientific explanation are taken in conjunction with all the various intellectual trends and fashions of the later Victorian era, it is in retrospect perfectly easy to understand how Darwin's theory proved irresistible even though, as Darwin himself admitted, the actual empirical evidence was insufficient, and there was absolutely no evidence that any of the major divisions of nature had been crossed in a gradual manner. If nature was to be explained by natural processes, she had to be continuous. (p. 73)

As the years passed after the Darwinian revolution, and as evolution became more and more consolidated into dogma, the gestalt of continuity imposed itself on every facet of biology. The discontinuities of nature could no longer be perceived. (p. 74)

No wonder paleontologists shied away from evolution for so long. It never seemed to happen. Assiduous collecting up cliff faces yields zigzags, minor oscillations, and the very occasional slight accumulation of change--over millions of years, at a rate too slow to account for all the prodigious change that has occurred in evolutionary history. When we do see the introduction of evolutionary novelty, it usually shows up with a bang, and often with no firm evidence that the fossils did not evolve elsewhere! Evolution cannot forever be going on somewhere else. Yet that's how the fossil record has struck many a forlorn paleontologist looking to learn something about evolution.

Most families, orders, classes, and phyla appear rather suddenly in the fossil record, often without anatomically intermediate forms smoothly interlinking evolutionarily derived descendant taxa with their presumed ancestors.


[T]here are all sorts of gaps: absence of gradationally intermediate 'transitional' forms between species, but also between larger groups -- between, say, families of carnivores, or the orders of mammals. In fact, the higher up the Linnaean hierarchy you look, the fewer transitional forms there seem to be.


We are faced more with a great leap of faith -- that gradual, progressive adaptive change underlies the general pattern of evolutionary change we see in the rocks -- than any hard evidence.

The record jumps, and all the evidence shows that the record is real: the gaps we see reflect real events in life's history -- not the artifact of a poor fossil record.

The fossil record flatly fails to substantiate this expectation of finely graded change.

The fossil record suggests that the major pulse of diversification of phyla occurs before that of classes, classes before that of orders, and orders before families. This is not to say that each higher taxon originated before species (each phylum, class, or order contained at least one species, genus, family, etc. upon appearance), but the higher taxa do not seem to have diverged through an accumulation of lower taxa.

"The fossil record pertaining to man is still so sparsely known that those who insist on positive declarations can do nothing more than jump from one hazardous surmise to another and hope that the next dramatic discovery does not make them utter fools... Clearly, some people refuse to learn from this. As we have seen, there are numerous scientists and popularizers today who have the temerity to tell us that there is 'no doubt' how man originated. If only they had the evidence..."


“To take a line of fossils and claim that they represent a lineage is not a scientific hypothesis that can be tested, but an assertion that carries the same validity as a bedtime story — amusing, perhaps even instructive, but not scientific.”

To be sure there are still major groups whose origins remain enigmatic. Bats, for example, have the poorest fossil record of all major vertebrate groups despite their numerical abundance in the world today. ... There are some remarkably well preserved early Tertiary fossil bats, such as Icaronycteris index, but Icaronycteris tells us nothing about the evolution of flight in bats because it was a perfectly good flying bat.

"Moreover, within the slowly evolving series, like the famous horse series, the decisive steps are abrupt and without transition."

The history of most fossil species include two features particularly inconsistent with gradualism:

1) Stasis - most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear; morphological change is usually limited and directionless;

2) Sudden appearance - in any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and 'fully formed'.

The Meanings of Diversity and Disparity

"I must introduce at this point an important distinction that should allay a classic source of confusion. Biologists use the vernacular term diversity in several different technical senses. They may talk about "diversity" as number of distinct species in a group: among mammals, rodent diversity is high, more than 1,500 separate species; horse diversity is low, since zebras, donkeys, and true horses come in fewer than ten species. But biologists also speak of "diversity" as difference in body plans. Three blind mice of differing species do not make a diverse fauna, but an elephant, a tree, and an ant do -- even though each assemblage contains just three species.

The revision of the Burgess Shale rests upon its diversity in this second sense of disparity in anatomical plans. Measured as number of species, Burgess diversity is not high. This fact embodies a central paradox of early life. How could so much disparity in body plans evolve in the apparent absence of substantial diversity in number of species? -- for the two are correlated, more or less in lockstep, by the iconography of the cone (see figure 1.16). ...

Several of my colleagues (Jaanusson, 1981; Runnegar, 1987) have siggested that we eliminate the confusion about diversity by restricting this vernacular term to the first sense -- number of species. The second sense--- difference in body plansshould then be called disparity. Using this terminology, we may acknowledge a central and surprising fact of life's history -- marked decrease in disparity followed by an outstanding increase in diversity within the few surviving designs."

Writing on Darwin's decision to portray evolution as a gradual and stately process, Gould states, "I do not know why Darwin chose to follow Lyell and the gradualists so strictly, but I am certain of one thing: preference for one view or the other had nothing to do with superior perception of empirical information. On this question, nature spoke (and continues to speak) ambiguously and multifariously. Cultural and methodological preferences had as much influence upon any decision as the actual data."

...

"... in defending gradualism as a nearly universal tempo, Darwin had to use Lyell's most characteristic method of argument -- he had to reject literal appearance and common sense for an underlying "reality." (Contrary to popular myths, Darwin and Lyell were not the heroes of true science, defending objectivity against the the theological fantasies of such "catastrophists" as Cuvier and Buckland. Catastrophists were as committed to science as any gradualist; in fact, they adopted the more "objective" view that one should believe what one sees and not interpolate missing bits of a gradual record into a literal tale of rapid change."

...

"The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology. The evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches; the rest is inference, however reasonable, not the evidence of fossils. Yet Darwin was so wedded to gradualism that he wagered his entire theory on a denial of this literal record:

The geological record is extremely imperfect and this fact will to a large extent explain why we do not find interminable varieties, connecting together all the extinct and existing forms of life by the finest graduated steps. He who rejects these views on the nature of the geological record, will rightly reject my whole theory.

Darwin's argument still persists as the favored escape of most paleontologists from the embarrassment of a record that seems to show so little of evolution. In exposing the its cultural and methodological roots, I wish in no way to impugn the potential validity of gradualism (for all general views have similar roots). I wish only to point out that it was never "seen" in the rocks.

Paleontologists have paid an exorbitant price for Darwin's argument. We fancy ourselves as the only true students of life's history, yet to preserve our favored account of evolution by natural selection we view our data as so bad that we never see the very process we profess to study."

...

Comment: Gould goes on to explain that Darwinian process do not require slow gradual change and that a model of punctuated equilibrium can explain the pattern of sudden appearance and stasis in the fossil record. "Eldredge and I believe that speciation is responsible for almost all evolutionary change." The problem is complicated, however, by the fact that species diversity is the one feature conspiculously absent upon the appearance of most phyla. See Valentine, J., and Erwin, D. (1985) "Interpreting Great Developmental Experiments: The Fossil Record", Development as an Evolutionary Process.

...

"The history of most fossil species include two features particularly inconsistent with gradualism:

1) Stasis - most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same as when they disappear; morphological change is usually limited and directionless;

2) Sudden appearance - in any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and 'fully formed'."

Gould honestly admits that the neo-Darwinian synthesis is not supported by the fossil evidence and "is effectively dead, despite its persistence as textbook orthodoxy."

[T]he absence of fossil evidence for intermediate stages between major transitions in organic design, indeed our inability, even in our imagination, to construct functional intermediates in many cases, has been a persistent and nagging problem for gradualistic accounts of evolution.

Indeed, it is the chief frustration of the fossil record that we do not have empirical evidence for sustained trends in the evolution of most complex morphological adaptations.

"As is now well known, most fossil species appear instantaneously in the fossil record."


Described recently as "the most important evolutionary event during the entire history of the Metazoa," the Cambrian explosion established virtually all the major animal body forms -- Bauplane or phyla -- that would exist thereafter, including many that were 'weeded out' and became extinct. Compared with the 30 or so extant phyla, some people estimate that the Cambrian explosion may have generated as many as 100. The evolutionary innovation of the Precambrian/Cambrian boundary had clearly been extremely broad: "unprecedented and unsurpassed," as James Valentine of the University of California, Santa Barbara, recently put it (Lewin, 1988).

Lewin then asked the all important question:

"Why, in subsequent periods of great evolutionary activity when countless species, genera, and families arose, have there been no new animal body plans produced, no new phyla?"

Paleontologists had long been aware of a seeming contradiction between Darwin's postulate of gradualism ... and the actual findings of paleontology. Following phyletic lines through time seemed to reveal only minimal gradual changes but no clear evidence for any change of a species into a different genus or for the gradual origin of an evolutionary novelty. Anything truly novel always seemed to appear quite abruptly in the fossil record.

What one actually found was nothing but discontinuities. All species are separated from each other by bridgeless gaps; intermediates between species are not observed. ... The problem was even more serious at the level of the higher categories.


[W]e have so many gaps in the evolutionary history of life, gaps in such key areas as the origin of the multicellular organisms, the origin of the vertebrates, not to mention the origins of most invertebrate groups.


With the benefit of hindsight, it is amazing that palaeontologists could have accepted gradual evolution as a universal pattern on the basis of a handful of supposedly well-documented lineages (e.g. Gryphaea, Micraster, Zaphrentis) none of which actually withstands close scrutiny.


[T]ransitions between major groups of organisms ... are difficult to establish in the fossil record.

[G]aps between higher taxonomic levels are general and large.

Well, we are now about 120 years after Darwin, and knowledge of the fossil record has been greatly expanded ... ironically, we have even fewer examples of evolutionary transition than we had in Darwin's time. By this I mean that some of the classic cases of darwinian change in the fossil record, such as the evolution of the horse in North America, have had to be discarded or modified as a result of more detailed information ....

"A large number of well-trained scientists outside of evolutionary biology and paleontology have unfortunately gotten the idea that the fossil record is far more Darwinian than it is. This probably comes from the oversimplification inevitable in secondary sources: low-level textbooks, semipopular articles, and so on. Also, there is probably some wishful thinking involved. In the years after Darwin, his advocates hoped to find predictable progressions. In general these have not been found yet the optimism has died hard, and some pure fantasy has crept into textbooks."

  • Science
    July 17, 1981, p. 289


    • The known fossil record is not, and has never has been, in accord with gradualism. What is remarkable is that, through a variety of historical circumstances, even the history of opposition has been obscured. ... 'The majority of paleontologists felt their evidence simply contradicted Darwin's stress on minute, slow, and cumulative changes leading to species transformation.' ... their story has been suppressed.

    Evidence of gradualism between phyla, classes and even orders is either non-existent or is much disputed. Certainly, no pervasive pattern of gradualism exists. George Gaylord Simpson acknowledged this decades ago as he described the situation in these terms:

    "This is true of all thirty-two orders of mammals...The earliest and most primitive known members of every order already have the basic ordinal characters, and in no case is an approximately continuous sequence from one order to another known. In most cases the break is so sharp and the gap so large that the origin of the order is speculative and much disputed...

    This regular absence of transitional forms is not confined to mammals, but is an almost universal phenomenon, as has long been noted by paleontologists. It is true of almost all classes of animals, both vertebrate and invertebrate...it is true of the classes, and of the major animal phyla, and it is apparently also true of analogous categories of plants."

    "It remains true, as every paleontologist knows, that most new species, genera, and families, and that nearly all categories above the level of families, appear in the [fossil] record suddenly, and are not led up to by gradual, completely continuous transitional sequences"


    [F]or more than a century biologists have portrayed the evolution of life as a gradual unfolding ... Today the fossil record ... is forcing us to revise this conventional view.

    [T]he fossil record itself provided no documentation of continuity -- of gradual transitions from one kind of animal or plant to another of quite different form.

    Since the time of Darwin, paleontologists have found themselves confronted with evidence that conflicts with gradualism, yet the message of the fossil record has been ignored. This strange circumstance constitutes a remarkable chapter in the history of science, and one that gives students of the fossil record cause for concern.


    The success of Darwinism was accompanied by a decline in scientific integrity. This is already evident in the reckless statements of Haeckel and in the shifty, devious and histrionic argumentation of T. H. Huxley...

    To establish the continuity required by the theory, historical arguments are invoked even though historical evidence is lacking. Thus are engendered those fragile towers of hypotheses based on hypotheses, where fact and fiction intermingle in an inextricable confusion.


    The gaps in the fossil record are real, however. The absence of a record of any important branching is quite phenomenal. Species are usually static, or nearly so, for long periods, species seldom and genera never show evolution into new species or genera but replacement of one by another, and change is more or less abrupt.

    [T]he origin of no innovation of large evolutionary significance is known.

    [L]arge evolutionary innovations are not well understood. None has ever been observed, and we have no idea whether any may be in progress. There is no good fossil record of any.

    Taxa recognized as orders during the (Precambrian-Cambrian) transition chiefly appear without connection to an ancestral clade via a fossil intermediate. This situation is in fact true of most invertebrate orders during the remaining Phanerozoic as well. There are no chains of taxa leading gradually from an ancestral condition to the new ordinal body type. Orders thus appear as rather distinctive subdivisions of classes rather than as being segments in some sort of morphological continuum.

    Valentine and Erwin review hypotheses as to the mode of origin of animal body plans for consistency with the fossil evidence. They conclude that both Darwinian gradualism and punctuated equilibrium are inadequate to account for the appearance of invertebrate body plans and their major modifications:

    "The models we consider are of three sorts: those that extrapolate processes of speciation to account for higher taxa via divergence, those that invoke selection among species, and those that emphasize that many higher taxa originated as novel lineages in their own right, not only as a consequence of species-level processes. It is in this latter class of model that we believe the record favors." (Valentine and Erwin, 1985, p. 71)

    If large populations have gradually evolved there should be unmistakable evidence in the fossil record, yet it is simply not found.

    "... many of the large populations should have been preserved, yet we simply do not find them. Small populations are called for, then, but there are difficulties here also. The populations must remain small (and undetected) and evolve steadily and consistently toward the body plan that comprises the basis of a new phylum (or class). This is asking a lot. Deleterious mutations would tend to accumulate in small populations to form genetic loads that selection might not be able to handle. Stable intermediate adaptive modes cannot be invoked as a regular feature, since we are then again faced with the problem of just where their remains are. We might imagine vast arrays of such small populations fanning continually and incessantly into adaptive space. Vast arrays should have produced at least some fossil remains also. Perhaps an even greater difficulty is the requirement that these arrays of lineages change along a rather straight and true course --- morphological side trips or detours of any frequency should lengthen the time of origin of higher taxa beyond what appears to be available. Why should an opportunistic, tinkering process set on such a course and hold it for so long successfully among so many lineages?

    We conclude that the extrapolation of microevolutionary rates to explain the origin of new body plans is possible, but does not accord with the primary evidence." (Valentine and Erwin, 1985, pp. 95, 96)

    The model of punctuated equilibrium or species selection attempts to account for the lack of evidence by relying primarily on the evolution of small isolated populations which would have a diminished chance of leaving a fossil record. This scenario has its difficulties, however, as Valentine and Erwin point out:

    "The required rapidity of the change implies either a few large steps or many and exceedingly rapid smaller ones. Large steps are tantamount to saltations and raise the problems of fitness barriers; small steps must be numerous and entail the problems discussed under microevolution. The periods of stasis raise the possibility that the lineage would enter the fossil record, and we reiterate that we can identify none of the postulated intermediate forms. Finally, the large numbers of species that must be generated so as to form a pool from which the successful lineage is selected are nowhere to be found. We conclude that the probability that species selection is a general solution to the origin of higher taxa is not great, and that neither of the contending theories of evolutionary change at the species level, phyletic gradualism or punctuated equilibrium, seem applicable to the origin of new body plans." (p. 96)