Paradoxes in Darwinian Theory Resolved by a Theory of Macro-Development
Robert F. DeHaan*
7714 McCallum Street
Philadelphia, PA 19118-4308
From PSCF 48 (September 1996): 180.
Darwinian theory suffers from many paradoxes - unexplained and contradictory facts. This article identifies and explains twelve of them with regard to the history of organic life in the last 530 million years. It addresses the paradoxes with a more comprehensive theory of development, called macro-development, by adding a historical, ancestral dimension to individual development; and shows how this new and more complete developmental framework not only resolves the paradoxes but also offers a fresh perspective on the history of life of higher animals. Ancestral development becomes the original and major change agent in phyletic lineages; Darwinian mechanisms make later, adaptive changes.
It is well known that Darwinian evolutionary theory reveals many paradoxes, relevant facts that contradict or are unexplained by the theory.1 What has not been fully recognized, however, is that the paradoxes are not randomly distributed. They fall into a distinct pattern. The pattern suggests that the paradoxes may be interrelated, and that there may be a latent conceptual framework, macro-development, that not only explains them, but also offers an alternative - even a more compelling - view of organic life than that given by Darwinian evolution.
First to be delineated will be the version of evolutionary theory that will form the focus of this discussion. Paleontological and biological facts that contradict the theory will then be presented. The pattern of paradoxes and a unifying conceptual framework underlying the pattern will be explicated and enlarged to form an alternative explanation of the history of organic life since the Cambrian explosion, 530 million years ago.
The following statements constitute the version of evolution that will be used in this discussion.
Natural selection. The heart of Darwinian evolution is natural selection. It is a two-step process consisting first, of mutations and rearrangements of the germ-line that are random with respect to the future of the organism and species; and second, sorting and selecting by the environment of the most adaptive organisms produced by the mutations. The heart of the concept has remained essentially the same as formulated by Darwin.2
Slow, gradual process. Because mutations must be beneficial and small, natural selection is a slow and gradual process, requiring long periods of time to accomplish adaptive change. Punctuated equilibrium refers to rapid speciation that sometimes occurs in small, isolated populations following long periods of stasis. The overall pace of evolution is slow even with punctuated equilibrium.
Natural selection begins with species. Evolution begins at the bottom, with varieties and species, which become modified into other species and eventually into higher categories of organisms by means of natural selection.
Blind automatic process. Natural selection is a blind, automatic process; it has no long-range purpose or plan in mind. AEvolution is random and undirected,@ according to a popular high school biology textbook.3
Change. Change is a universal characteristic of the organic world. To many evolutionary authors the ubiquity of change provides sufficient evidence that evolution has occurred.
Continuity of life forms. According to evolutionary authors the reality of evolution is demonstrated by continuous descent with modification from the first single, living cell to the multitudinous forms of life that exist today and ever have existed.
More than a scientific theory. It is now recognized that the theory of evolution constitutes more than a scientific theory or paradigm. It has become the philosophical foundation of the naturalistic view of the universe that has replaced the Judeo-Christian worldview which once dominated western culture.
The interpretation of Darwinian evolution given above will form the focus of this article.
Paradoxes in Darwinian Evolution
The pattern of paradoxes begins with the ACambrian explosion@ that occurred about 530 million years ago. The explosion refers to the outburst of complex, higher animals. The event is unique in the history of life on this planet; nothing like it happened before or since. Paleontologists are unusually profuse in their expressions of wonder at the biological fireworks set off during the early Cambrian.4 Gould summarized the explosion as follows:
The Cambrian explosion is the key event in the history of multicellular animal life. The more we study the episode, the more we are impressed by its uniqueness and of its determining effect on the subsequent pattern of life's history. These basic anatomies that arose during the Cambrian explosion have dominated life ever since, with no major additions. Y The pattern of life's history has followed from the origins and successes of this great initiating episode.5
The sheer magnitude of the Cambrian explosion is difficult to appreciate. Consider the following summary of observations that suggests its scope and complexity. In what may be considered (1) a geological Ainstant@ (2) approximately 50 animals with (3) body plans that were (4) novel, (5) disparate, (6) complex, and (7) of stable modern design (8) appeared roughly synchronously in the Lower Cambrian. Each descriptive adjective or phrase suggests a paradox in Darwinian theory.
Paradoxical fact #1:Rapid origin of Cambrian animals. Stem animals of the Cambrian came into existence with rapid speed in a geological instant. The rapidity of their formation has recently been confirmed. It is now judged that the Cambrian explosion lasted at most 10 million years, and as little as 5 million, beginning 530 million years ago.6 Valentine estimated that for brachiopods the time may have been well under 5 million years, probably under 1 million years, and perhaps significantly less in some cases.7 He even hinted at a time span of only "hundreds of thousands of years or less."8 Bowring said, "It has long been inferred that the Cambrian explosion was fast; now we have some idea of just what fast means."9
The paradox. Darwinian mechanisms work slowly and gradually, requiring extensive periods of geological time to bring about change.10 It is difficult to see how gradualistic natural selection, even punctuated equilibrium, could have been a significant causal factor in the extremely rapid formation of body plans in the Cambrian explosion.
Paradoxical fact #2 Body plan. The body plan of the stem animals is the central, most significant biological structure formed in the Cambrian explosion. The body plan - also called Bauplan, phylum, and class - refers to the most fundamental morphological and structural characteristics of the stem animals of the Cambrian. It refers to the basic architecture which defines the lineages founded by the stem animals; it is shared in common by all the subsequent descendants of the lineage. This is one of the most fundamental designs in the organic world. Lewin equated the term auplan with phylum, the highest taxonomic level of classification.11 Characteristics of the body plan are thus used to classify large groups of animals (phyla) founded by the stem animals of the Cambrian.
The paradox. Animal lineages started with body plans at the highest taxonomic level of phyla. This observation challenges a central tenet of Darwinian theory, namely, that evolution starts at the lowest level, with varieties and species12 and works upward into higher taxa. Some evolutionary authors have countered this paradox with the dubious argument that higher taxonomic categories are artificial and unrelated to real events in the organic world. Such authors and others, however, freely use these same taxonomic categories when it suits their purposes and where the use of them does not challenge evolutionary theory. The paradoxical evidence remains firm: Animals lineages originated as phyletic body plans of Cambrian animals, not as varieties and species.
Paradoxical fact #3 Fifty body plans. This is a staggering number of biological inventions. The variety of unique animal forms in the Cambrian is astounding, especially when compared with the relative uninventiveness and lack of diversity of the long previous Precambrian period.
The paradox. This flood of unique body plans further calls into question natural selection as the agent of change in the Cambrian. The probability of random mutations supplying the genetic variability for so many unique and novel animals seems remote, even though small initial genetic changes may result in large genetic morphological outcomes. There is no evidence, moreover, that environmental factors could select for so many unique forms.
Paradoxical fact #4 Novel body plans. Cambrian animals have few known or confirmed morphological antecedents from the earlier Precambrian period. This is an extraordinary discontinuity. It is estimated that only 5 percent or less of them show validated evidence of Precambrian parentage.13 Erwin, et al., said: AMost classes and orders of durably skeletonized marine animals also appear abruptly, without obvious linkage to their durably skeletonized antecedents.10 Miklos noted that Asome bona fide metazoans Y literally pop out of the blue above the Precambrian/Cambrian boundary at approximately 530 mya.15 AEvolutionary biology's deepest paradox concerns this strange discontinuity,@ observed Levinton.16
The paradox A morphological discontinuity between Cambrian animals and the Precambrian biota is strongly implied by the paucity of confirmed, architectural antecedents. This hiatus challenges the principle of continuity of all life forms, a major doctrine of evolutionary theory.
Whether Cambrian animals had Precambrian ancestors that were too small, too flimsy, and unmineralized to leave fossils has yet to be demonstrated, and is being actively debated.17 Two alternative positions have been put forth. The first is that the fossil evidence of a Cambrian explosion should be taken at face value, that the animals indeed developed almost instantaneously, sans Precambrian antecedents; and the second, that Cambrian animals have a long but invisible Precambrian history. Since it is unlikely that Cambrian animals sprang into existence without any antecedents whatsoever, it is probable that some precursors may eventually be found.18 This would not detract from the discontinuity between Precambrian and Cambrian biota.
Paradoxical fact #5 Disparate body plans. With few exceptions, the body plans of the Cambrian animals were architecturally different from each other and were novel and discontinuous from the Precambrian fauna. Gould used the new term, disparity, to designate the immense chasms separating most body plans from each other; whereas he used the conventional term, diversity to indicate the minuscule differences among species.19 Early in the Cambrian, phyletic disparity was high; species diversity was low.
Arguing from geometric principles, D'Arcy Thompson concluded that Athe breach between vertebrate and invertebrate, worm and coelenterate, coelenterate and protozoan, is in each case of another order, and is so wide that we cannot see across the intervening gap at all.20 Conway Morris wrote, AThe morphological gaps, that by definition, separate phyla remain invioloate.21 Writing about body plans of sea urchins Miklos noted that AThey were of course, not convertible into body plans of other marine phyla22
The paradox The disparity and inconvertibility among the body plans of the Cambrian stem animals further challenges the essential evolutionary principle of continuity of all life forms. This principle is difficult to maintain in the face of morphological discontinuities among many of the Cambrian stem animals themselves, to say nothing of the probable hiatus between the Cambrian and Precambrian biota.
As might be expected some evolutionary writers disagree with the concept of morphological disparity and discontinuity among groups of Cambrian animals. Conway Morris, for one, said, AI argue that Y the apparent absence of intermediate forms between major groups is an artifact.23 Valentine, on the other hand, argued that AThe missing intermediates [of some invertebrates] may be regarded as data,24 which may be taken to mean that lack of data provisionally constitutes data. That there were few, if any, intermediary architectural forms is the primary conclusion supported by the fossil record, and should be held unless it is contradicted by newly discovered, confirmed intermediate forms.
Paradoxical fact #6 Dearth of species. There were many body plans or phyla but few species in the early Cambrian. Specific diversity was low. The higher taxonomic forms were present, but the lower forms, the species, were largely absent. This observation is most astounding and of profound significance.
The paradox. Gould called the observed dearth of species a central paradox of early life.25 Many more species than phyla should have appeared, since a fundamental principle of Darwinian theory is that a large group of higher animals (phylum) has its origin in a long train of species. The paradox, however, lies not with early life; but with the incorrect evolutionary interpretation of it. Again, the logical conclusion is that ancestral lineages did not begin with varieties and species.
Paradoxical fact #7 Synchronous appearance of body plans. The fact that this large cohort of animals appeared approximately synchronously within roughly a 5-10 million year period deepens the mystery of the Cambrian explosion. Few Cambrian animals are the confirmed antecedent of another.
The paradox. The probability seems extremely low that natural selection could fully account for the synchronous appearance of 50 or so disparate body plans, in such a short time, in an environment presumably approximately common to all, as shown by the Burgess Shale. The synchronous appearance of Cambrian body plans is paradoxical to the Darwinian concept of natural selection.
Paradoxical fact #8 Stability of body plans. The body plans of the Cambrian stem animals that survived are extremely stable. They have remained essentially unchanged for more than 500 million years, to the present time, with no modernization or upgrading;26 (but with some Areconfiguring@ of sea urchin body plans.27) The Cambrian body plans exist today in our modern phyla and appear in an early embryonic stage in all members of a given phylum. Every descendant of the Cambrian stem animals shares in common the stable body plan of the original stem animal.
The paradox. Change is practically synonymous with evolution, according to some evolutionary authors.28 Yet the unchangeableness of body plans challenges this meaning. If body plans had been formed by natural selection, why would they not have continued to evolve over the past 530 million years? Yet they did not. This suggests that some other process has been at work to form and maintain the stability of phyletic body plans.
Paradoxical fact #9 Top-down direction of change in phyla<F255MI>. One of the most important phyletic patterns in the fossil record is the general-to-specific or top-down direction of change or modification in phyletic lineages. General, or higher taxonomic levels (phyla, classes, orders), of a given phyletic lineage appeared in the fossil record before specific, lower-level taxa (families, genera, species). Abundant fossil data from the Cambrian and later periods support the generalization that with few exceptions the order of appearance in the history of phyletic lineages works from general to specific taxa, from phyla clear down to species. Erwin et al., stated:
The fossil record suggests that the major pulse of diversification of phyla occurs before that of classes, classes before that of orders, orders before that of families Y most higher taxa were built from the top down, rather than from the bottom up.29 This top-down pattern is also found in trilobites;30 amphibians, reptiles, mammals;31 and in birds.32
The paradox The top-down direction of phyletic change clearly challenges the central concept of Darwinian evolution, namely, that evolution proceeds from the bottom up. Darwinian theory holds that varieties become species, which are modified until they can be considered genera, which become families, etc., through the process of natural selection. This doctrine was introduced by Darwin through his only diagram in Origin of Species, and has since been held without exception by evolutionary authors since his day.
Evolutionary writers such as Simpson and Mayr acknowledged that higher taxonomic forms appeared before lower forms in the fossil record, but went on to deny the biological reality of higher taxonomic categories. Their position is beginning to crumble, however, under the undeniable biological reality of the body plans of the Cambrian animals which are considered the equivalent of phyla. The paradox remains. Phyletic lineages develop from the top down, not from the bottom up.
Paradoxical fact #10: The rise and fall of ancestral lineages. Evidence from the fossil record, demonstrates that ancestral lineages start with a few small organisms, which subsequently rise to a maximum on many dimensions, such as size, complexity, population density, and which eventually decline on these and other variables. This pattern of increase to a maximum followed by decline is found in fishes, amphibians, reptiles33 and in many other lineages. For example, brachiopods declined systematically;34 as did corals.35 The decrease is especially significant. Young, for instance, said, AMammals are at present at their peak of development, perhaps they are already declining.36 The decline of lineages is supported by paleontological, biological evidence, and by the logic that if a lineage increases, it must eventually decline. The fact remains: Decline is as ubiquitous as increase in phyletic lineages.
The paradox The paradox is this: If increase in size, complexity, etc., in a lineage is adaptive, as evolutionists hold,37 how can later decrease in these dimensions also be adaptive? Decline itself is rarely adaptive. It is not regularly correlated with changes in the environment. The paradoxical decline in lineages is explained away by major evolutionary authors who hold that declining lineages are actually adapting to their environment.38 Of course! Declining lineages continue to adapt as best they can, even to the very end. But let that not hide the fact that they do decline, and that decline in lineages is paradoxical to Darwinian theory.
Paradoxical fact #11 Finality of body plans. The body plans of the Cambrian constitute the first and last manifestation of such an unprecedented scale of biological inventiveness on earth. After the Cambrian explosion not a single new, major group or phylum of animals has come into existence. This is especially significant in view of the relative openness of the environment after the great Permian extinction, 250 million years ago, which exterminated up to 80 percent of marine species leaving the environment about as empty as it had been at the Vendian-Cambrian boundary. Dry land, moreover, was a whole new habitat, a completely novel, vast and varied ecological niche. Yet no new phyla-level body plans developed when vertebrates and invertebrates invaded it 400-360 million years ago.39 In spite of this open invitation for innovation, no new classes or phyla appeared. Indeed, the history of life since the Cambrian shows a dramatic loss of major groups of animals that originated in the Cambrian explosion.
The paradox The finality of Cambrian body plans is inexplicable in evolutionary terms. If evolution is the creative force in the organic world, why have no new body plans evolved? The next section extends the paradox.
Paradoxical fact #12: Multiplicity of species since the Permian. A further astounding fact is that species have multiplied almost beyond count, starting 250 million years or so ago, and accelerating in the last 65 million years to the present.40 Natural selection seems to have Akicked in@ to produce abundant speciation after phyletic lineages passed their peak and began to run out of steam.
The paradox. If species are the evolutionary precursors of higher level taxa, and such a deluge of them has been occurring throughout the recent past, why have no new higher taxa been formed? With so many species emerging, this should be the age of new higher taxa. The reason it is not is that species evolve into other species, rarely if ever into higher level taxa. The present age is thus the age of new species. Rather than being the start-up mechanism for new major groups of animals, natural selection and speciation may more realistically be seen as the closeout process of phyletic lineages. They put the finishing touches on ancestral lineages. This obviously goes against the thrust of Darwinian evolution.
There may be a deeper significance to this recent exuberant speciation than is at first apparent. Since species result from natural selection, and are so numerous, it can be concluded that natural selection has been increasingly vigorous for the last 65 million years or so. Mutations, moreover, have presumably also been occurring in record numbers during this recent time span, since they are the first step in natural selection. What are the implications of this presumed increase in mutations?
Mutations have a bright and a dark side. They are essential to natural selection because they provide genetic variability which results in new phenotypes for the environment to sort out, the bountiful speciation presently observed, and the minor variations that embellish the basic design of lineages. The function of natural selection, as van Inwagen states, Ais to insure that species possess sufficient diachronic flexibility that they aren't just automatically wiped out by the first environmental change that comes along.41 Vertebrate species last only several million years or so.
Most mutations, however, are deleterious rather than beneficial to the future of a lineage. One would expect, therefore, to observe many detrimental effects of deleterious mutations, as indeed, one does in the decline and aging of lineages, accompanied by bizarre forms and inadaptive trends in some lineages. The bright and dark sides of mutations thus combine to simultaneously extend and diminish lineages that are in the process of dying out.
In what is considered geological instant, approximately 50 animals with body plans that were novel, disparate, complex, and of stable modern design appeared roughly synchronously in the Lower Cambrian.
In summary, evidence from the fossil record shows the following patterns. Phyletic lineages originated rapidly, starting with stable body plans of Cambrian animals, differentiating downward taxonomically from general features of the lineage found in the body plan to the specific characteristics found in lower taxonomic levels, clear down to species. Phyletic lineages rise and fall, in some case with clear regularity. No new phyla have appeared since the Cambrian. Many phyla that originated in the Cambrian have disappeared. Although there was a dearth of species in the Cambrian, there has been an increasing abundance of them starting in the Permian. Mutations, the first essential step in natural selection, have presumably also been increasing, accounting both for the expanded speciation and for the deterioration and decline of lineages. Natural selection became increasingly operative late in the history of higher animal life to put the finishing touches on phyletic lineages and to prolong the life of the lineage.
Is There a Process that Explains the Pattern in the Paradoxes?
There is one process in the biological world that can explain the pattern of paradoxes presented above. Surprisingly, it is the process of development/growth. The process of development/growth is one of the most important processes in the biological world. It occurs universally among modern, higher, multicellular, complex animals. It has a similar profile across the whole range of higher animals and plants. It produces biological design. It arguably outperforms evolution on a day-to-day basis in producing change in the biological world.
Development is often equated with evolution. That is a mistake. The two processes are radically different from each other, as acknowledged by informed Darwinian authors. Development is genomic, hierarchically regulated, end-directed, and holistically organized; in stark contrast to the basically unpredictable, mindless, environmentally-directed process of Darwinian evolution.
The mystery is why development has been ignored for so long in discussions of the history of organic life. One need not look far for the reason. Natural selection has so dominated the thinking of Darwinists and others that they see no need to look for an alternate explanation for changes in organic life. According to some Darwinian authors, development contributes little to evolution.
A comprehensive theory of development, unfortunately, is totally lacking. Developmental theory is confined to the embryonic period of individual organisms, as dictated by current scientific fashion. This restriction is entirely unwarranted. Individual development needs a historical dimension to make it a more complete, comprehensive theory. The broad, historical theory of development proposed herein is predicated on the assumption that principles of development apply to large animal groups, existing over geologic time, as well as to individual animals. Such large-scale development will be called macro-development.
The focus in this discussion will be on principles of development applied to large groups of animals over geologic time. Below are five features of macro-development that qualify it to serve as an alternate explanatory framework for Darwinian mechanisms.
1. The sequence of morphological change in individual development is similar to changes in large-scale development. That is, they are isomorphic to each other. Their Aprofiles@ match up beautifully. Principles of development can be used as readily to describe the origin and historical trends in large animal groups as they can the embryological and subsequent life-spans of individual organisms.
2.Development of large groups of animals over geologic time is governed by genetic mechanisms in the phyletic germ line, just as individual development is controlled largely by the individual somatic genome.
3. Macro-development provides a smooth, seamless, inherited continuity between phyletic development on the one hand and individual development on the other. This continuity thus resolves a major, unresolvable problem C the theoretical gap between evolution and individual development C that most Darwinists seem unaware of or fail to acknowledge.
4.Macro-development defines a new role for Darwinian mechanisms in the history of organic life since the Cambrian. These mechanisms produce adaptive variations on major innovative themes created by macro-development. Development may be seen as the Aauthor@; Darwinian mechanisms, the Aeditor@ of the history of organic life.
5. Macro-development is the major instrument of morphological design in the organic world.
The striking similarities between the features of development of individual animals and the pattern of paradoxes found in the fossil record presented above invite comparisons. Below is a summary of the resemblances.
Both individuals and phyletic lineages begin with a general body plan. The body plan is among the first structures to appear in individual embryological development. The earliest and defining feature of the Cambrian animals was their basic body plan.
Both individuals and phyletic lineages develop very rapidly at the start. Early development in the embryo is extremely rapid. In human beings all systems and morphological features are in place in slightly more than three months after conception.42 The formation of body plans in the Cambrian occurred with extreme rapidity, geologically speaking C paralleling the very rapid formation of the body plan early in individual embryonic development and growth.
Body plans are extremely stable. Individual body plans are extremely stable in embryonic development. Early stages of development are remarkably resistant to adaptive, evolutionary change. Only later-appearing, superficial features of the animal, such as coloration, are subject to adaptive change. Young summarized the situation well.
The basic construction of an organism (Bauplan) limits the possibilities of adaptive change. Y An organism must adapt to its surroundings as best it can with its given Bauplan. Y This is particularly obvious during the early stages of development, which are remarkably resistant to evolutionary change. Y Mutants affecting early embryological stages survive only in the laboratory. Adaptational changes mostly come relatively late in ontogeny.43
Thomson and Waddington made the same point.44 All three authors acknowledge that early morphological and anatomical patterns are untouched by evolution. Adaptational changes occur later in development. Evolution thus does not change the body plan and other early-appearing features of the embryo. It affects the more peripheral, external morphological features that appear later in the developmental process.
It is not surprising then that phyletic body plans have not changed in more than 500 million years.
Development proceeds in characteristic time sequences.45 One of the most fundamental principles of development is that the general features, which the embryo shares in common with all members of its phylum, appear before more specific features; and that specific features emerge out of general ones, according to basic laws of development formulated by von Baer almost two centuries ago.46 This is the top-down direction of development.
After the Cambrian explosion, phyletic lineages differentiated from the top down - from the few, most general taxonomic features (such as the body plan) held in common by all members of the lineage, to the most specific and diverse features distributed among its multitudinous species. The top-down direction of both individual and phyletic development represents a realistic link between individual and large-scale development.<P7MJ247>47<P255DJ0>
The shape of the life span is curvilinear. The entire life span of individual animals is a manifestation of development. All organisms start small and simple at conception, rise rapidly through the prenatal and juvenile stages, grow large and complex, reach a rounded maximum on many variables in maturity, decline in old age, and eventually die. The rise and subsequent decline is an invariant characteristic of lifelong individual development.
The broad, historical theory of development proposed herein is predicated on the assumption that principles of development apply to large animal groups, existing over geologic time, as well as to individual animals. Such large-scale development will be called macro-development.
There is also an unvarying succession of changes in ancestral lineages, starting with a few, small, insignificant animals, that increase in size, complexity, population density, and on many other dimensions; reach a rounded maximum, and then decline to fewer, smaller, less robust groups. This orderly sequence is isomorphic to development in the individual life span.
Eventual decline. All individual organisms show signs of senescence if they live long enough. Phyletic lineages of higher, complex animals begin to show signs of decline and aging after they reach and pass their maximum growth and development, and will eventually die if they do not first become extinct.
In short, the overall Ashape@ of individual development and the general Ashape@ of ancestral lineages are remarkably similar. The only major difference between them is the time scale C enormous for the historical lineages, insignificantly short for individual organisms. The resemblance between large-scale sequence of changes covering millions of years and the sequence of changes in early embryonic and lifelong development of individual organisms is quite astounding. It cannot be a meaningless coincidence that so many phyletic patterns of change in the fossil record are found to resemble patterns of development found in individual organisms. These similarities are surely not trivial or merely coincidental. On the contrary, they point to a deep unity between the overarching historical processes, called macro-development, and small-scale individual development. Patterns in the fossil record are sufficiently similar to patterns in development of individual organisms that those in the fossil record can provisionally be considered the results of development on a large historical scale.
In summary, a proposed theory of macro-development and growth as large-scale historical processes holds that -the principles of development and growth apply to all biological systems, regardless of their size, temporal duration, or the number of generations they span. Development and growth are primarily determined, internally and hierarchically regulated processes which result in determinate temporal sequences and patterns of morphological changes which are found (1) in all individual higher, complex, multicellular organisms throughout their entire life spans, and (2) in all ancestral lineages of higher organisms, throughout their entire phyletic histories. The terms phyletic, historical, ancestral, large-scale, and macro-development can be used interchangeably in this definition.
Genetic mechanisms of macro-development and the intergenerational overlap of individual developmental mechanisms need to be explicated. Space limitations, unfortunately, prevent a full discussion of them here. Suffice it to say that the phyletic germ line is the primary source of developmental changes inherited by the individual somatic genome and expressed in the individual organism. The mechanisms of individual development, moreover, span two generations, originating in the parent and continuing through the death of their offspring.48 The intergenerational feature of development supports the historical dimension of development.
An Additional Theoretical Bonus
There is a theoretical gap between evolution and individual development that needs to be resolved but cannot be closed as long as Darwinian mechanisms are considered the major force for change in the biological world. The problem is how development as a hierarchical, highly ordered, intrinsically directed process can be produced by the basically linear, unpredictable, externally directed process of Darwinian evolution. The bonus is that an expanded concept of development as a historical as well as an individual process offers a new solution to this intractable problem.
Darwinian authors have failed to provide a logical and empirical bridge between these two fundamental but irreconcilable biological processes C one of the most profound unresolved problems in biology. The difference between the two processes was emphatically expressed by Mayr, a major architect of the New Synthesis. He stated,
There is a fundamental difference between end-directed behavioral activities or developmental processes of an individual or a system, which are controlled by a program, and the steady improvement of the genetically coded program. This genetic improvement is evolutionary adaptation controlled by natural selection.49
Thomson said: ASome kind of connection between evolution and development seems obvious, but at the same time remains as elusive as a butterfly.50 Gould concurred. AThat some connection exists cannot be denied.51
From [the Cambrian explosion] on, lineages began their long journey of phyletic development, with each individual progeny inheriting its developmental processes from the major morphological features of the ancestral lineage.
A fundamental recognition is emerging, moreover, that the theoretical disjunction between development and evolution cannot be allowed to continue. It must be addressed. Both must be articulated in one complete, coherent theory in order for both to be complete. Thomson said:
J. Maynard Smith (1983) has written that Aalthough we have a clear and highly articulated theory of evolution, we have no comparable theory of development.@ I would turn this statement around somewhat and say that until we have a general theory of development we are unlikely to derive a complete theory of evolution.52
To start with evolution as the major force and then try to insert individual development into it - as evolutionary authors do - is to encounter the insurmountable problem of explaining logically and biologically how the essentially unordered, unpredictable process of mutational variation, directed by opportunistic extrinsic environmental conditions, can produce the fundamentally autonomous embryo, exquisitely regulated and intrinsically ordered.
The developmental perspective solves the problem by making individual development continuous with and inherited from large-scale, historic development. This view provides a seamless continuity between large scale lineal changes and individual development. Both individual and macro-development originated in the Cambrian explosion. From that point on lineages began their long journey of phyletic development, with each individual progeny inheriting its developmental processes from the major morphological features of the ancestral lineage. Large-scale historical development, not Darwinian mechanisms, is the source of individual development, and individual development reflects significant aspects of the large scale process.
The developmental perspective is compatible with creative activity of an intelligent designer. The concept of body plan itself connotes planning and design. Body plans could also be called body designs. The determined, intrinsically regulated processes of phyletic development on the large scale, matched by individual development on the small scale, also hint at intelligent design.
Conclusions and Implications
Macro-development is proposed in this article as the major force for the origination of major groups of animals and for large-scale change in the history of these groups in the past 530 million. The events surrounding and following the Cambrian explosion show unmistakable characteristics of development that, in addition, challenge Darwinian theory.
Darwinian mechanisms become a major force in the organic world primarily after the fires of macro-development begin to burn low, specifically in the past 250 million years, and provide adaptive embellishments that enhance the survivability of species. They put the finishing adaptive touches on phyletic lineages and produce a plethora of species as a hedge against phyletic decline and impending termination.
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