EUGENE M. MCCARTHY, PHD GENETICS
That with this bright believing band
I have no claim to be,
That faiths by which my comrades stand
Seem fantasies to me,
And mirage-mists their Shining Land,
Is a strange destiny.
I have now presented the facts and inferences that have convinced me that the typical form treated as a species (1) is produced rapidly by a stabilization process; (2) has a distinctive and characteristic set of traits from the time of its inception that does not change significantly thereafter. The data and their implications seem clear. Why, then, have other biologists not come to similar conclusions? It is not easy to say. After all, who has seen evidence that one fossil form typically changes gradually into another? Who would deny that a single description generally allows us to identify individual specimens of a fossil form even when vast ages intervene between the times at which they lived? How could a single description suffice if the typical fossil form gradually changes? What biologist would claim that the production of new types of organisms via stabilization processes is poorly known? Perhaps it is only the weight of tradition that has prevented others from advocating the same views.
Perhaps, too, in the absence of a more plausible alternative theory, my colleagues have not been forced by logic to acknowledge counterevidence. They have instead been able to respond to the pattern of sudden change followed by stability observed in the fossil record (see Section 6) either with the peripheral isolates scenario or with the notion of speedy gradualism. They could claim the preservation of fossils has been too imperfect for gradualism to be properly documented. They could also argue that the reason we do not observe gradual evolution is that it is unobservable within the time span of systematic human observation (though it should be observable in the fossil record, even if we cannot observe it directly). If they had no satisfactory explanation of the fact that the typical hybrid is of reduced fertility, it was enough merely to shrug their shoulders and walk away. Or they could accept inadequate explanations of the general phenomenon of hybrid infertility, such as the Dobzhansky-Muller model. Independent studies could yield conflicting phylogenetic trees and such results could be viewed merely as puzzling and any data that did not agree with the accepted view could be dismissed as statistical “noise.” In the absence of a more satisfactory explanation, the claim could be made that conventional theory simply must be correct. Any shortcomings of the theory could be dismissed as a matter of future fine-tuning. In previous arguments I have attempted to show that stabilization theory, on scientific grounds, is demonstrably superior to orthodox theory. This alternative theory does, in fact, explain numerous phenomena that seem inexplicable under neo-Darwinian theory. Furthermore, stabilization processes, the mechanisms on which stabilization theory is based, are firmly founded on observation — forms of known origin are typically derived from such processes.
But I cannot pretend certain aspects of stabilization theory have not been previously expressed. Long ago, Locke realized that the word species was badly defined. Many others have reached the same conclusion. Cuvier saw that the typical fossil form is morphologically stable over time. So did Lyell. Many others have said the same. In recent years, Gould and Eldredge did evolutionary biology a service by calling attention to this fact once again. De Vries observed and reported that certain forms treated as species arise repeatedly as individuals in the progeny of another type. Others, too, have since corroborated this fact. Goldschmidt realized that processes producing forms treated as distinct species often also change the karyotype. Again, others have since said the same (M. J. D. White, in particular). Ledyard Stebbins and Verne Grant enumerated many of the stabilization processes discussed in previous sections. They and others showed that many existing forms have actually been derived from such processes. But Stebbins and Grant never extended their claims beyond the plant kingdom and, even there, they never argued that the production of new forms by such processes is typical. Innumerable naturalists, from Linnaeus and Lamarck up to the present, have pointed out that hybridization occurs in a natural setting and that it can produce new types of organisms. Therefore many of the components used to construct the world view expressed here were the insights of others. But perhaps such is the case with any theory.
Many biologists would readily admit new forms do come into being via stabilization processes. But in the case of forms of unknown origin — that is, in the case of the vast majority of all organisms — many still imagine new types come into being gradually under the influence of natural selection. This conclusion violates all scientific tradition, in which we are taught to suppose unobserved cases are probably like observed ones. Somehow, with people who think this way, inductive inference breaks down. They accept that a multitude of forms, once thought to be of gradual origin, are now known to be the products of stabilization processes. But they view these cases as exceptional and continue to believe the typical process is gradual natural selection. They refuse to extend the same view even to other, very slightly different types of organisms. By induction, one would suppose that, among forms of unknown origin, the percentage of forms produced by stabilization processes would be about the same as among forms of known origin. And among forms of known origin, virtually all are indeed derived from stabilization processes. Nevertheless, most biologists would admit such processes are the typical source of new forms only for those cases where origins are known. They arbitrarily reject it when origins are unknown. They not only fail to estimate the fraction of the unknown cases based on the proportion observed in known cases, but even go so far as to assume the fraction must be small, or even insignificant, when the observed fraction is large. If they cannot appeal to observed cases, on what basis can they justify such a claim? Such thinkers seem happy to explain evolution in terms of processes they have never seen, when they could just as easily construct their explanations in terms of observed processes. But do they really believe a single type of organism, which occurs in a variety of different environments, has been shaped by each of those various environments, even though the same distinctive traits are found in all the individual constituents of that form in all environments where that form occurs? In such cases, is it not far more plausible to suppose a single type of organism arose via a single stabilization process and that it then spread into a variety of environments to which it was suited? Although biologists quite properly demand evidence from creationists, they themselves gloss over, or are even unaware of, the fact that there is little, if any, evidence demonstrating that the forms they treat as species come into being gradually.
Stabilization theory clarifies recent evolutionary history. But it may make ancient events seem more nebulous, given that orthodox theory makes so many specific, though largely unsubstantiated, claims about ancient evolutionary history. Thinking of evolution in terms of stabilization processes does not usually allow us to identify the exact ancient forms remotely ancestral to a modern form. As we pass back through time, it becomes increasingly difficult to say anything conclusive. But stabilization theory does specify the nature of the processes producing new types of organisms and it does allow the positive identification of the immediate ancestors of many particular extant forms treated as species. It provides science with the proof needed to counter allegations that evolutionary study is mere irreligious speculation. In many cases we can now irrefutably show that entities traditionally regarded as "species" are not immutable. That is, it is now known that many such forms have produced other stable types unlike themselves and also treated as species. Given the apparent prevalence of stabilization processes among known forms, both extant and fossil, we can reasonably suppose such processes have always been at work, even among the earliest known forms of life. I therefore can only believe that all organisms are enmeshed in a web of life, united by ancient strands and new, that "the mingled, mingling threads of life are woven warp and woof." Our ancestral forms must be legion.
Many of the most respected scholars in biology seem completely satisfied with the view that the typical new form comes into being gradually under the influence of natural selection. To me, it accords far better with what we know of evolution to suppose stabilization processes are the usual source of organic innovation. If the reader has been persuaded by the arguments given up to this point, she will find inescapable the logical consequences of the theory, which are broadly destructive of neo-Darwinian theory. If we accept the claim that stabilization theory is better supported than neo-Darwinism, then we must, for example, reject the notion that taxonomic classifications should reflect a branching history of descent, a method of classification that neo-Darwinians term “natural.” We will instead be forced to suppose the history of evolution is analogous to a multidimensional web, not a tree. Taxonomists will no longer be able to pursue their work in the same manner as they now do because they will have no intellectual touchstone by which to judge the validity of their classifications. Indeed, the activity of classifying natural forms would lose much of its zest — for a taxonomist much of the satisfaction provided by the activity of constructing classifications comes from the feeling of getting history right. Under stabilization theory, systems of classification will have no more grandeur than an office filing system. There will be few or no historical implications. Indeed, classifications will no longer be taxonomic because the structure of the classification system will not reflect the presumed nature of the relationships of the forms classified. Existing, supposedly taxonomic, classifications will be seen as mere artificial constructs bereft of any basis other than the weight of usage and tradition.
The traditional account of descent will be replaced with a very different one. Instead of divergent trees, there will be similarity chains and similarity sets, sets of forms that give rise over time to new sets. Some of the forms in a given generation of a similarity set survive into the succeeding generation. Others go extinct. If we look at any one of the forms occurring in successive generations of a similarity set, we will expect it to show an insignificant amount of change over time. Preexisting forms add new forms to the set via the various stabilization processes. As a result, the composition of the set changes over time as old forms drop out and new ones enroll. Here, no modern set of forms is defined in terms of a single common ancestor (as is typically the case under neo-Darwinian theory). Presumably, some forms will survive longer and produce more offspring forms than others because they have traits favoring survival and the parenting of new forms. Over time, then, such advantageous traits will tend to occur in a larger number of different forms within a similarity set. This picture of descent suggests an interconnectivity of relationship among forms that is in no way implied by — or even logically consistent with — neo-Darwinian theory.
By describing evolution in terms of similarity sets and by recognizing the existence of forms with traits linking major taxonomic categories, stabilization theory makes arbitrary the exact positioning of the lines of demarcation between higher categories. It suggests distinct higher categories correspond to similarity sets discrete today, but descended from ancient sets connected by extinct intermediate forms. Moreover, it implies that the main way in which natural selection produces new types of organisms is by choosing among forms within such a similarity set, not by selecting among the individuals. To investigate the production of new types of organisms via natural selection, evolutionary biologists have long used competition experiments in the laboratory or on computers. The competition is among genetically distinct individuals within a population. Under stabilization theory such experiments would lose their intellectual basis, though they are at present quite popular.
It is my hope there will at last be an end to the interminable disputes over whether this group or that one is truly a "species." I can foresee that our children will look back on our discussions of such issues and fail to understand our concerns. They will accept that geographically and morphologically intermediate hybrid populations connect many distinct types of organisms. They will think, too, that our nomenclatural delineations of such populations, if they understand them at all, were largely arbitrary. For they will see that such distinctions have been ruled not only by differences in form, but also to a great extent by the personal prejudices of those who devised the nomenclature and by traditions that ensconced such prejudices on the throne of accepted usage. In the future, naturalists will only have to consider what type of organism they wish to study. They won't need to decide whether it is a "species" or not. Determining the genus or class or phylum to which a given type of organism belongs will no longer be a crucial issue. The reprieve from the duty to make such decisions will in itself save untold hours of labor and tedium. It will in fact mark the demise of an entire branch of biological research. It will be no small additional blessing that we will be emancipated from the endless, unrewarding, and, in my opinion, medieval tasks of revising the taxonomic hierarchy and defining the word species.
Another basic biological concept, that of the common ancestor, also becomes obsolete under stabilization theory. Neo-Darwinian theory claims any two given forms share a single, most recent common ancestor. Likewise, the genes of the two forms are presumed descendants of genes present in the ancestor. No doubt many forms sharing a given trait are descended from some single form with that trait. But it seems just as certain, given the apparent prevalence of hybridization, that traits distinguishing such pairs will often be derived from ancestors not held in common. Each type of organism can have two or more parental forms and those parental forms, in turn, can each have two or more parents of their own. As the ramifications pass back through time, "the" common ancestor simply vanishes.
The terminology used to discuss the various aspects of "species," speciation, conspecific, interspecific, intraspecific, etc., will be recalled by historians of biology, but by few others. We will believe that the production of the typical form has not been a matter of tacking on one trait after another with the passage of time. Instead, we will think that typically an abrupt process creates at a single stroke a functionally integrated whole. We will then realize how much we have yet to learn about the genetic basis of development. No longer will an organic being be seen as if it were shaped for a purpose, as if it were a tool nature had honed and perfected for a particular task. The traits of an organism will be seen merely as adequate to permit its continued existence. We will think of the typical organism as having, from the time of its inception, a particular characteristic set of traits. We will think that many complex structures and traits have arisen at random from the billion trillion trillion varying gametes and zygotes generated by hybrids in past ages, and that some, but not all, of the structures so generated must have been useful to their possessors. When our outlook changes, we will see our own abilities and peculiarities in a more modest light. Along with our "speech and wind-swift thought," we will expect ever to retain certain flaws and shortcomings.
A wide field of research will be opened, in which we shall seek the limits and laws of hybridization. Very little research has been done on the ability of distantly related organisms to interbreed. The more different two parental forms are, the more novel their offspring forms can be. Thus, it is of interest under stabilization theory to know the true limits of hybridization. A research program designed to determine these limits might, for example, select organisms at random and cross them by artificial insemination or pollination. Other studies might seek to elucidate the poorly known phenomenon of a mother's immune response to hybrid offspring within her womb. Hybrids will be seen as wide avenues to new realms of form, not as futile cul-de-sacs abhorred by nature. No longer will they be regarded merely as entities that are selected against. Instead, they will be seen as an important source of variation, the grist of natural selection. For the student of evolution, the study of domestic breeding will become an essential topic. Historical studies of breeding records will allow us to document the origins of many forms. Currently emerging forms will be tracked and surveyed. The production of stabilized forms identical to existing natural forms will be a far more important source of information about origins than the stories of unobserved gradual change that now receive such avid attention. How much more interesting will the study of such matters become when we realize that it is possible, in many cases, to prove how a given type of organism has come into being, when fact constrains imagination. There is even the exciting prospect of being able to recreate certain extinct forms, in those cases where the relevant parental forms are still in existence. Orthodox theory excludes this "Lazarus" option from the realm of possibility. Obviously, an extinct agamosperm or polyploid would be a reasonable target for such a project. But even extinct forms that arose as recombinant derivatives have potential for resurrection.
Our classifications will cease to be perceived as genealogies. Rules of classification will no doubt be more straightforward when we no longer feel compelled to decide whether the entities in question are truly related in the way that we choose to classify them, and we are no longer concerned with whether they are "species." We need not — indeed, in most cases we cannot — discover and trace the many lines of descent in a complex web of ancestry long lost in the depths of time. Nor would traditional systems of classification be able to replicate their topology. It will be far more interesting to reproduce as many types of organisms as possible, and so to verify their origins. Functionless organs will no longer suggest the former existence of long-lost structures serving some purpose now unknown. They will not be vestigial. They will simply be by-products of a stabilization process. Living fossils will become something more than simple illustrations of ancient forms of life. They will become emblematic of the remarkable genetic stability inherent in living forms. Embryology will no longer be seen as the study of a process that somehow recapitulates past events or reveals the general plan of broad classes of organisms. Instead it will be seen in a straightforward way as providing information on the developmental processes that change a zygote into a mature organism. When we can feel assured that natural processes of descent are not reflected in the basic topology of our bifurcating systems of classification, we will feel free to choose other systems with other topologies that suit our convenience and intellectual needs. For example, we might find it easier to list types of organisms linearly by name, as in a dictionary, with cross-references to relevant topics. When we become convinced that those patterns of descent have been largely weblike because most types of organisms have more than one parental form, the quest for the "true" Tree of Life will be at an end. For, so long as they differ, all things of any kind, even inanimate ones, can be assigned positions in a treelike classification on the basis of their traits. The mere possibility of arranging a set of organisms into such a classificatory scheme does not in any way imply that a process of gradual divergence has produced them. If it did, we could infer that such a process produced the various items in my attic.
Because they describe the behavior of paired chromosomes during meiosis, Mendel’s Laws, axiomatic to neo-Darwinian theory, will be far less important in describing processes producing new types of organisms. In general, such rules have nothing to say about stabilization processes. Thus, the traditional ways of thinking about the origins of new forms — the sorts of evolutionary models offered by neo-Darwinian theory — will become largely irrelevant. For the most part, such mechanisms describe how genes subject to Mendel's Laws change in frequency over time under various hypothetical circumstances. Under stabilization theory such processes have only a minor role in the production of new types of organisms. There will be a new emphasis on the role of chromosomes as structural units determining the characteristics of chromotypes and limiting their range of variation. The study of meiotic mechanisms that rearrange and reassort chromosomes will then be directly relevant to our understanding of the production of new types of organisms. Mutations in genes and changes in their regulation will become issues more relevant to the medical student than to the evolutionist.
Interest in "isolation mechanisms" would also be at an end. Most of the models discussed in neo-Darwinian theory describe forms as evolving in reproductive isolation. Stabilization theory, in contrast, assumes a lack of reproductive isolation (hybridization) greatly increases the potential to create new types of organisms and, thus, further invalidates neo-Darwinian explanations of evolution. Therefore, assumptions concerning the nature of the environmental context in which new types of organisms are likely to occur will also change. Stabilization theory tells us isolated lakes and islands are not the crucibles of change many neo-Darwinians would say they are. Instead, stabilization theory claims new forms arise most frequently in environments where stabilization processes are likely to occur. Therefore we should expect new forms to arise more frequently where the opportunities for highly varied hybridization events are maximized, as in large landmasses or in the oceans and their connected waters.
Geology will gain in evolutionary stature. Fossils are the only reliable source of information on rates of morphological change in prehistoric times. Such rates, it will be realized, provide a vital clue to the genetic nature of evolutionary processes. Given the present state of geological knowledge, the conclusion seems unavoidable that the typical fossil form comes into being abruptly at a particular stratigraphic level and remains largely unchanged thereafter until the time of its extinction. This finding is wholly consistent with the hypothesis that new forms of life typically come into being via stabilization processes. Neo-Darwinians have claimed the fossil record is imperfect. The processes they accept must have occurred, they say, in strata that have not been preserved. Anyone who accepts stabilization theory doesn't have to make such claims. There will be no need to posit undiscovered "small, generalized" common ancestors "radiating" into arrays of diverse, "specialized" descendants. The existence of sets of fossil forms with particular traits will simply imply the existence of ancestral sets of forms with similar traits. Study of the fossil record will focus on identification of such successive similarity sets and on the documentation of discontinuity of origin and stability of form. The science of plate tectonics will allow us to determine where similarity sets with particular characteristics first came into being. The facts of ancient geography will place limits on potential patterns of past migration.
Under neo-Darwinian theory, new forms are imagined as coming into being by a gradual process of natural selection as small differences accumulate over time. Once a type has been shaped by this process, it is maintained in the same way — the type is supposedly ideally suited ("adapted") to its "environmental niche," and is therefore maintained by natural selection that eliminates any individuals with new traits differing from that ideal because they are not as well suited to the "niche." The environment is the great shaper and maintainer under this view. All living beings are the passive products of this process. This milquetoast determinism plays itself out on a cosmic scale.
To me, the various forms of life have a far greater value when they are seen as ancient and unchanging, existing today much a they did when they came into being long ago, in the remoteness of time. They become something more than mere pawns, forever changing at the behest of a tyrannical environment. When a new type of organism comes into being via a stabilization process, the primary selective factor is reproductive stability — a stable reproductive cycle must be established or the new form will fail to maintain itself in existence. If it survives, the new type spreads into all geographic regions to which it is suited and has access. If it ceases to have access to a suitable environment, it simply goes extinct. It does not gradually change into a new type that can tolerate a new environment. Under this view, a form's genetic make-up plays at least as great a role in determining its characteristics as does the environment. In fact, it generally plays a far greater one. Once a new type of organism has stabilized, the environment may place limits on growth, health, and activities, but it does not significantly change the nature or potential of that type of organism, even with the passage of time on a geological scale. Living forms, under this view, are beyond and above the environment.
In fact, we know actual organisms have an active, creative nature. An animal typically selects an environment suited to its unchanging nature. A bird that cannot tolerate the cold of winter flies to tropical climes. A landed fish will flip and flop until it drops back into the water. Even a plant passively selects its environment since a seed will mature only in a setting that suits its nature. A banana tree does not grow on an arctic island. Indeed, a plant or animal will often alter its environment and, in the process, make that environment either more or less habitable. The environment does not create a nest. Each type of nest is a characteristic environment created by a particular type of animal that builds a certain type of nest. Through their ability to produce oxygen, photosynthetic organisms have completely changed the atmosphere of the earth, and, in consequence, have vastly altered the array of organisms that exist there. Even the lowly worm, crawling blind through the soil, shapes its world. Under stabilization theory, the living organism is the initiative force and creative power — a positive agent, selecting and reconstructing its environment. It is not mere wax upon which an indifferent environment writes at will. Each living thing has its own potent nature. In fact, its choice of environment and its actions upon that environment are aspects of its nature. Yeats saw better than Darwin:
O body swayed to music, O brightening glance,
How can we know the dancer from the dance?
On the basis of stabilization theory, we may conclude that evolutionarily successful forms will spawn many offspring forms, heirs to their genes, when they themselves cease to exist. Such forms have a birth and death, just as an individual does. But they are more stable than an individual because they do not undergo gradual change in the time between inception and demise. Under this view, elimination of certain types of individuals does not result in progress toward perfection. It merely reduces the scope of diversity. Indeed, severe selection against all types deviating from a single ideal would eventually reduce a form to a clone-like uniformity in which no change, progressive or otherwise, would be possible.
It is encouraging to imagine a world in which individual competition and selfishness cease to be biological givens, where each type of organism has a fixed nature that holds its own against an impotent environment. There is hope in this view of life, in which nature is no longer "red in tooth and claw," where the necessity of struggle ceases to be an axiom. In such a world we will be able to abandon the factory metaphor, turn our backs on the efficient assembly line, and instead embrace alternative ideals more consistent with our own nature. Relieved of the grim duty of destroying our imagined competitors for the sake of mere survival, we can escape Darwin's ruthless ratios of increase and rise to a higher moral plane where we, as individuals and as societies, can build ourselves environments filled with "sounds and sweet airs, that give delight and hurt not." And in this new world we will be able to study, and perhaps come fully to know, the origins of new forms of life.
|Stabilization theory provides an intellectual basis for Charlie Chaplin's dream:|
1. Cuvier (1827: 10).
2. Cuvier (1827: 242).
3. Milner (1993: 6).
4. Quoted in Darwin (1872: xvii-xviii).
5. Mayr (1982: 536).
6. Milne-Edwards (1867: 429), translated in Russell (1982: 245).