What Is Really Known About The Mechanism Of Organic Evolution?
by John A. Davison
December 28, 2009
I begin this essay by first eliminating that which I believe had nothing to do with the origin of species or of any other taxonomic category. Since sexual reproduction and the natural or artificial selection of Mendelian alleles has failed to result in speciation, these must be discarded as having played a primary role in creative evolution. In other words there is absolutely nothing in the Darwinian scheme that ever had anything to do with the ascending sequence that we know for certain characterizes the fossil record. I have presented evidence against the Darwinian model in my earlier essay "What's Wrong With Darwinism," so I will not devote any more time here to an hypothesis which I believe has no merit whatsoever. Having thus cleansed the theoretical slate, it is time to look at the living world as if the Darwinian paradigm never existed. I believe that is the only way one can begin to understand the great mystery of phylogenesis.
The most striking feature of the living world is the fact that it can be categorized in such a way that there is no question about the identity of any particular organism. We owe this taxonomy to the genius of Carolus Linnaeus, the latinized form of Carl von Linne, a Swedish botanist (1707-1778). It is my opinion that the Linnaean system is as valid today as it was in the past. Every biology student is familiar with the species, Genus, Family, Order, Class, Phylum sequence that serves to identify virtually every organism with certainty. Taxonomic keys proceed through a series of alternate choices to reach in very few steps an identification of virtually every organism being evaluated. That such a system succeeds is powerful evidence against the gradualism intrinsic in the Darwinian paradigm.
So the question becomes – what kind of mechanism can produce such a discrete pattern of living creatures in which morphological continuity is so obviously missing?
Morphological discontinuities can be interpreted to favor the Genesis account and the Fundamentalists have used these discontinuities to support their Biblical ideology of special creation. Until morphological discontinuity can be explained through demonstrable reproductive continuity, their thesis must be given serious consideration. This now raises a further question. To what extent can we demonstrate reproductive continuity throughout the living and fossil world? Evolution requires reproductive continuity and, until that is proven to exist, separate origin (polyphyleticism) must remain a viable alternative.
Before I go further I must emphasize that the Darwinians do not regard these as valid questions. They are convinced that life originated only once and everything we now see has resulted from the evolution of that single primordial organism; in other words, a monophyletic evolution. Stated another way, they believe that it is intrinsic in the nature of non-living matter to self-assemble spontaneously and then evolve, a belief, with Perre Grasse, I do not share. I am convinced that if that was possible, it would have been demonstrated experimentally long ago.
"To insist, even with Olympian assurance, that life appeared by chance and evolved in this fashion is an unfounded assumption which I believe to be wrong and not in accordance with the facts."
Pierre Grasse, Evolution of Living Organisms, page 107 (original French edition 1973).
At this point I will introduce a conclusion reached by Leo Berg, like Pierre Grasse, a biologist for whom I have great respect.
"Organisms have developed from tens of thousands of primary forms, i.e, polyphyletically."
Nomogenesis, page 406. (original Russian edition 1922).
You can imagine the effect that this remarkable statement had and still has on the Darwinians. Their reaction, then as now, was to pretend that Leo Berg never existed and one will find no reference to Berg's evolutionary views in the publications of the leading Darwinians of the past and present. These include Ernst Mayr, William Provine, Stephen Jay Gould and more recently Francis Ayala, Paul Zachary Myers and Richard Dawkins. Indeed, I know of no Darwinian who granted any credibility to Berg's heretical view of phylogeny. That does not mean that he was wrong!
The balance of this essay will be dedicated to the evidence relating to Berg's polyphyleticism. Stated another way, what is the hard evidence for evolution through reproductive continuity? I believe that the answer to this question will prove to be very interesting to those students of the great mystery of phylogeny who are able to examine the living and fossil world objectively.
Note that Berg suggested a limited number, "tens of thousands," of primordial forms and it is within these limits that he remains a strict evolutionist, deriving biological relationships on sound, scientific criteria.
In considering the question of an evolution through reproductive continuity, we should remain aware that no one has ever witnessed the natural formation of a new true species from a known ancestor. All experimental attempts have failed. Speaking of experimental evolution, I offer the conclusions of Otto Schindewolf, with Leo Berg and Pierre Grasse, another critic of the Darwinian model.
"Many recent authors have spoken of EXPERIMENTAL EVOLUTION. There is NO SUCH THING. Evolution, a unique, historical course of events that took place in the past, is not repeatable experimentally and cannot be investigated in that way."
Otto Schindewolf, Basic Questions in Paleontology, page 311, Words in bold in italics in the original.
Note that Schindewolf emphasizes that evolution "took place in the past." This raises an interesting question. Is evolution still occurring? Are new species still being produced? Both Julian Huxley, a Darwinian and Robert Broom, an anti-Darwinian, claimed that a new Genus has not appeared in the last 2 million years. I long ago offered a challenge for someone to name an extant species along with its known immediate ancestor. I have yet to receive a satisactory response and don't anticipate that I will. All present evidence pleads that the production of new species is no longer in progress and what we now observe are the terminal products of a finished evolutionary process.
Pierre Grasse hinted at the same possibility in the form of three questions.
"Aren't we witnessing the remains of an immense phenomenon close to extinction? Aren't the small variations which are being recorded everywhere the tail end, the last oscillations of the evolutionary movement? Aren't our plants, our animals lacking some mechanisms which were present in the early flora and fauna?"
Evolution of Living Organisms, page 71.
I do not hesitate to answer yes to these three questions. Note the conflict between his questions and the title of his book.
Armed with this background, I am now prepared to answer the question – To what extent can we explain the "mechanism" of phylogeny, the means by which evolution took place?
If one examine our own taxonomic category, the mammalian Order Primates, one discovers an interesting situation. Within that category we discover a remarkable constancy in the amount of DNA/cell. Even more important, we also find that the karyotypes of the various members of that Order can be explained to a very large extent as several rearrangements of an original ancestral karyotype common to all the members of the Order Primates.
In other words, the evolution within that taxon is largely in accord with Richard B. Goldschmidt's insistence that it is changes in the chromosomes, not the genes, that produced those several species. It is my opinion that the several rearrangements of a single ancestral karyotype can largely explain the radiation that we know took place in the Order Primates. Such a position demands that the information for phylogeny was already present and was in no way dependent on allelic mutations of the genes. In other words, phylogeny was "prescribed" as I have proposed with the Prescribed Evolutionary Hypothesis (PEH), (Davison, 2005).
The karyotype of our closest living relative, the chimpanzee, differs from ours by about twelve chromosomal rearrangements which has led me to postulate that a similar number of species, now all extinct, existed since the chimp and ourselves shared a common ancestor. I believe this is a reasonable number of intermediates based on what we can deduce from the fossil record. Furthermore, such a reconstruction remains in accord with Robert Broom's conviction that evolution was the result of a Plan, a word he capitalized.
The moment we go beyond the limits of the Order, we encounter gaps yet to be explained through proven reproductive continuity. Until those hereditary gaps are closed through known cytological mechanisms, we must give serious consideration to Leo Berg's conviction that there may have been "tens of thousands of primary forms."
I will now present a hypothetical reconstruction of how Primate radiation might have taken place. I am convinced that the initial step, the step that led to a new species, could not have involved sexual reproduction but must have involved a known feature of present day gametogenesis. Viewed in this way, the present day formation of gametes reflects a history of the mechanism which operated in the past when creative evolution was still occurring. It is useful at the outset to compare meiosis with mitosis.
There are similarities as well as differences between mitosis and meiosis, the latter being the mechanism by which diploid (2N) cells give rise to haploid (1N) eggs and sperm. Each begin by a duplication of the chromosomes resulting in a 4N state. In mitosis a single nuclear and cytoplasmic division restores the diploid (2N) condition, each chromosome behaving independently of the others. The result is that the products, barring mutation, will be identical with the original chromosomes of the diploid complement, a highly conservative form of reproduction. Note that mitosis involves only a single step.
In meiosis the chromosomes also duplicate resulting in a 4N configuration as in mitosis. This is where the similarities end. In meiosis the two daughter chromosomes, also know as sister strands, remain together during the first meiotic division which returns the chromosome complement to the diploid (2N) state. Prior to the first meiotic division the chromosomes can be observed to exist as two closely associated chromosome pairs (tetrads) sometimes described as chromatids. That is an unfortunate terminology because a chromatid is a chromosome and calling it something else can be misleading. This 4N tetrad state is a universal feature of meiosis and it is at this time that an important source of genetic variation takes place. Breaks take place in corresponding parts of the non-sister strands which when healed lead to chromosomes containing information from each of the chromosome pairs depending on how large the broken portions were. Don't let this event mislead you as it need not have anything to do with speciation.
Note that meiosis consists of two steps. It is reasonable that the first step is the more primitive and must have preceeded the second historically. It is my conviction that the first of these steps, the one that takes the chromosomes from the 4N to the 2N state, provides the mechanism for speciation within the confines of those animals and plants that belong to the same taxonomic order or other taxonomic category including closely related creatures. To understand how this can, in a single cytogenetic event, produce a new karyotype I refer you to either my 1984 paper or to my unpublished "An Evolutionary Manifesto: A New Hypothesis for Organic Change," both of which contain an explanatory diagram and detailed description.*
In short, a female organism that is carrying a chromosome rearrangement in heterozygous form can produce normal diploid (2N) female offspring, half of which will be like the original female, the other half, in principle, a new female species. Note that this event needs to take place only once and only a single female new species need be produced.
In order to complete the establishment of this new species, such a female must be able to hybridize with a male of the original species. The products of such a cross will be hybrids which when bred with each other will establish the new species as homozygotes in one fourth of their progeny in traditional Mendelian (sexually mediated) fashion. The question of whether Homo sapiens and Neanderthal hybridized is at present unresolved, but I feel it must have occurred since there are no other known hominid species who could have served as our ancestors, at least in Europe. However, there is nothing in the Prescribed Evolutionary Hypothesis that precludes an independent origin of Homo sapiens from other hominid ancestors. I am inclined to believe that the races of man may have had independent origins with the original racial differences having since been diluted due to interbreeding. I cannot easily imagine how it can be otherwise. I trust this will not serve to label me a racist.
I believe that this hypothetical reconstruction, which I have named the Semi-Meiotic Hypothesis (SMH), can serve to explain the radiation that we know has taken place during the evolution of our ancestors within the Order Primates, an evolution which ended with the production of Homo sapiens, the terminal product of what I am convinced was a planned sequence.
Sooner or later this hypothesis will be tested experimentally and, until it has proven to be without merit, will remain a viable explanation for the evolution of creatures which share similar chromosome karyotypes. The SMH does NOT provide an adequate explanation for the evolution leading to creatures having chromosomal complements markedly disimilar to those of their presumed ancestors. The origin of those categories requires another mechanism, a mechanism presently unkown, one which may involve separate origin (polyphyleticism) as proposed by Leo Berg. That may or may not require supernatural intervention as only the furure can determine.
In any event, the Darwinian model is hopelessly inadequate as an explanatory thesis and should have been abandoned long ago..
* diagrams for this step can be found in the two papers available under Evolutionary Works on the opening page of my weblog -
Berg, L.S., Nomogenesis or Evolution Determined By Law. M.I.T. Press, (1969). (original Russian edition 1922).
Davison, J.A., Semi-meiosis as an Evolutionary Mechanism, J. Theor. Biol. 111:725-735, (1984).
Davison, J.A., A Prescribed Evolutionary Hypothesis, Rivista di Biologia/Biology Forum 98: 155-166, (2005).
Goldschmidt, Richard B., The Material Basis of Evolution. Yale University Press, New Haven, (1940).
Grasse, Pierre, Evolution of Living Organisms. Academic Press, New York, (1977). (original French edition 1973).
Schindewolf, Otto, Basic Questions in Paleontology. University of Chicago Press. (1993). (original German Edition 1950).