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Acquiring Genomes: The Theory of the Origins of the Species

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Lynn Margulis has been a maverick all her life. Early in her career she shocked her biological colleagues by arguing that the mitochondria that power our cells and the chloroplasts that let plants transform solar into chemical energy once were free-living bacteria. As soon as scientists could isolate and decode the scraps of DNA in those vital organelles, they found that she was right. Margulis went on to develop her Serial Endosymbiosis Theory, which attempted to trace the development of all creatures with nucleated cells, from yeasts to humans, to a series of genetic mergers between different kinds of organisms. According to Margulis, all the familiar family trees of life, which show only diverging branches, are wrong. Ancient roots and current branches cross and merge to produce new species. To Margulis, nature is far more promiscuous and much more creative than most biologists dream.

Her new book, Acquiring Genomes: A Theory of the Origins of Species, extends and deepens that argument. Margulis sets out to prove that new species rarely if ever appear as the result of mutation, isolation, genetic drift, or population bottlenecks--the meat and potatoes of neo-Darwinism. Instead she maintains that the major engine of evolutionary change, the source of most of the new forms that natural selection edits, is symbiogenesis--the acquisition of whole genomes as the result of symbiotic associations between different kinds of organisms. (Knowing that some people will seize on her thesis as an attack on the theory of evolution as a whole, Margulis makes it clear that she fully supports Darwin's great discovery of the mechanism of natural selection. She simply thinks that neo-Darwinists have failed to recognize the enormous creative power of genomic mergers.)

Readers who are familiar with Margulis' earlier works will recognize her vivid, personal and sometimes impressionistic writing style. I found this book, co-authored by her son, Dorion Sagan, to be clear and accessible. Starting with Chapter 9, where Margulis presents her latest ideas on the symbiotic origin of the nucleus itself, things get a bit more technical. Margulis makes every effort to help readers through the thicket of important, but at times tongue-twisting terms, and supplements explanations in the text with an excellent glossary. Margulis also presents the findings of several other researchers whose work supports or relates closely to her own.

Readers may or may not close the book convinced that Margulis is right and the neo-Darwinists are wrong. But they will come away with a vastly deeper understanding of the pervasive nature and power of the microbial world, and of symbiosis. Margulis reveals a hidden side of nature, in which microbes have generated most if not all of life's metabolic machinery, in which vastly different life-forms consort in a myriad of ways, and in which the acquisition of entire genomes provides the raw material for great evolutionary leaps. Anyone with a deep interest in biology will gain important insights from "Acquiring Genomes."

Robert Adler, author of Science Firsts: From the Creation of Science to the Science of Creation (Wiley & Sons, 2002).

First of all let me apologize for criticizing this work, not only because I wrote part of it and don't want to hurt my own feelings (any more than is absolutely necessary), but to you for any appearance of arrogance or impropriety. However, some more evidence in its favor has come to light since this book was written; in addition, there are a few mistakes (some corrected in proof which somehow Basic Books neglected to fix) and, more importantly, a basic potential misunderstanding about what the book does and does not say, which I see no reason not to address.

The main point of this book, which I cowrote, is that, although mutation leads to evolutionary change, all the best examples of speciation, including all that have actually been observed, have been through symbiosis. The greatest amount of biodiversity, including all basic metabolic modes from photosynthesis to oxygen respiration, evolved in the bacteria via mutation and gene transfer. But although given Linnean species names for the sake of convenience and via convention, speciation does not really apply to bacteria, which trade genes (via techniques borrowed by human beings practicing biotechnology) with little regard for species barriers. True speciation only evolved in the eukaryotes--protists, fungi, plants, and animals. These largely sexed beings pose the Darwinian problem of speciation proper. And here all the best examples of speciation involve symbiosis, the coming together of different kinds of organisms. Since Acquiring Genomes was written, more evidence has come to the fore to show that its central thesis--that the presence or absence of genomes, particularly those of microbes, can lead to speciation--is correct. In a recent Montreal conference on molecular biology and phylogeny, for example, John Werren from the University of Rochester in New York showed a picture of a chromosome of a sperm cell from a parasitic wasp: rod-shaped bacteria, Wolbachia, were nestled in the chromosome. Wasps can have their sex change due to the presence of bacteria, and antibiotics can make separate species of jewel wasps interbreed again. At this same meeting Professor Harold Morowitz (who is developing a Universal Metabolic Chart, on the model of the Periodic Table of the Elements) was impressed by the plasticity of ever-changing gene formations--emphasizing the need to look for metabolic pathways shared by most or all organisms to understand life's origins. Because life is an open thermodynamic system, as well as an open informational one, genomic transfer is rampant.

It is important to realize two things that Acquiring Genomes does not say. The book does not say that all bacterial diversity is the result of genome acquisition. As suggested above, and by Canadian biologist Sorin Sonea and others, despite the bacteriological convenience of their species names, bacteria arguably do not have species due both to rampant genetic transfer as well as the premier, zoological definition of species as an interbreeding population; since all bacteria can theoretically trade genes with each other either directly or through through vectors (and do not need to reproduce to do so), the animal definition of species does not really apply to them. The original genetic and metabolic diversity in bacteria must owe significantly to neodarwinian-style mutations but, since bacteria arguably do not possess species, such mutations do not occur for speciation.

As Ernst Mayr suggests in his Foreword, the evidence for speciation by genome acquisition in birds and mammals is not compelling. The argument for genome acquisition here depends on the possible symbiotic status of the ends of chromosomes, called kinetochores. (Bacteria don't have true chromosomes, they have chromonemes.) Because chromosome arrangements differ slightly in closely related mammal species (e.g., dogs and wolves) that no longer breed with each other, and because the spontaneous splitting of these chromosomes may owe to their separate bacterial origin, we make the argument that even vertebrate speciation may owe to the symbiotic aftershocks of microbial genome acquisition. The main point to remember is for every example of speciation for which there is actual evidence, genome acquisition is the causative factor; and that, despite mountains of theory, this is not the case for mutations.

Finally, the thermodynamics section is only an at best tantalizing foretaste of a much more comprehensive argument and regrettably contains a couple of mistakes, such as the characterization of Benard cells as octagonal (they're hexagonal) and appearing from a chemical gradient (they don't; they appear in a temperature gradient). And one final comment: both Lynn and I read Stephen King's On Writing after A.G.'s composition and realized belatedly how much it could have been improved, despite the complexity of some of the arguments, by eliminating further needless words.

Acquiring Genomes: A Theory of the Origins of Species written by Lynn Margulis and Dorion Sagan will definitly open your eyes and is on the cutting edge of how species are formed.

This is one of those groundbreaking books that trys to answer one of Charles Darwin's long standing mysteries... how do species originate. Darwin could never quit put his finger on the answer, he was close and I'm sure with time and the right equipment, like what is available today, he might have even solved this nagging question.

Margulis has been working on this same question for the last thirty years and she makes a very convincing argument, symbiotic merger is the main thrust of her thesis in this book. This book has some real mind-spinning ideas and you'll have to know some biochemistry, biology, chemistry, cell-biology to prepare yourself for a provocative wild ride through this book as some of the material directly challenges the assumptions that we hold about diversity in the living world.

Margulis has for many years been the leader in the interpretation of evolutionary entities as the products of symbiogenesis. Symbiogenesis is the major theme of this book. The authors show convinvingly that an unexpectedly large proportion of the evolutionary lineages had their origins in symbiogenesis. Ok, I know some of you are saying what is symbiogenesis, well it's the combination of two totally different genomes form a symbiotic consortium which becomes the target of selection as a single entity. This is achieved by the mutual stability of the relationship, symbiosis differs from other cases of interaction such as carnivory, herbivory, and parasitism.

Now, that I've said all of that, you realize that this book can get pretty deep at times, but the author has a pleasent styled narrative, always keeping the reader involved. Prehaps the greatest merit of this book is that it introduces the reader to the fascinating world of microbes, delving into providing an enthralling description of protists and bacteria.

I found this book to be most enlightening about the enigma of evolutionary biology and how species are formed, comprehensive in scope and supported by scientific theory. This book will make you think. If you want to know about the cutting edge of evolutionary thinking then this is the book for you. To realize that everything on earth is inter-related and that life will carry on when faced with tragedy.

Acquiring Genomes will not appeal to all readers. First of all, the authors clearly have little use for current dogma, that is: local mutations in chromosomes fuel evolution and, particularly, speciation. I received my degree in Zoology back in a time when paleontologists called `em like they saw them, and lock-step conformity was a sign of a weak mind. I learned, in 1975, that there is precious little in the fossil record to support the concept of gradual evolution. Apparently, that has not changed.

Prof. Margulis' book also assumes a reader with a broad scientific background , largely in areas considered "old fashioned" in the 21st century. She demands an upper college level familiarity with invertebrate biology, physiology, microbiology, ultrastructure, biophysical chemistry, metabolic pathways and *GASP* thermodynamics. Then she integrates molecular biology and genomics, as needed, into the picture, to make a very convincing case for symbiogenesis. She also evokes wrath for bringing up the name of Jean Baptiste Lamarck, which is sure to raise a red flag in neodarwinist circles. Last, she does not refute the contribution of neodarwinists, she simply tries to put them in perspective.

The founding premise is that mutations constantly occur during the natural history of a species. Many experiments suggest 99% of these mutations are either silent or deleterious. Therefore, they probably cannot be counted on to drive evolution to improve on a species, let alone create new ones. Instead, a more likely pathway is for two species, with one bacterial, one eucaryotic, to coexist if it causes them to have a survival advantage when they do so. If it is in both organisms' best interest, this coexistance becomes more intimate, and can lead to the eucaryotic organism taking the smaller genome into its chromosome and making one very new and improved species. This, and many intermediate stages, are seen among invertebrates, such as Geosiphon pyriforme, a hybrid organism with a fungal (Endogone) and a cyanobacter (Nostoc) ancestor. The Geosiphon has retained the ability to fix carbon dioxide and nitrogen, receiving one multigene trait from one ancestor and the other from the partner species. Examples like this are why a reader needs a strong invertebrate biology background in order to appreciate these chimera.

She ends the discussion with another tantalizing mechanism, called the kinetichore reproduction theory. In this process, environmental stress can lead to an additional round of kinetichore - centromere reproduction in an organism's chromosomes which leads to twice as many half-sized acrocentric chromosomes. Fertilization where one donor has undergone this alteration still leads to diploid progeny, but the diversity generated is the engine for adaptive radiation of species.

Obviously, I am not ashamed to say I have bought into her arguments. If I were an academic scientist, I could have a field day testing some of her hypotheses. Instead, I am an industrial biochemist without the necessary time or manpower. That is the power of this book, however. It moves the receptive reader to want to take the bull by the horns and challenge or expand Margulis' hypotheses. She even suggests research strategies for potentially fruitful lines of inquiry.

Drs Margulis and Sagan have written a lightning-rod kind of book that will attract wrath from some, and heartfelt praise from others. If you feel indifferent toward this book, I suggest you reread it with a copy of an invertebrate biology reference book at your side.

Lynn Margulis and Dorion Sagan continue their series of books on highlighting Margulis's evolving and elaborative theory on evolution. Margulis, with her symbiosis concept, is science's only significant spearhead on the creation of Darwinian evolutionary theory not strictly within the vague limits of Darwinian framework. This book gives us hints on her progress to moving closer to understanding the origin and evolution of eucaryotic mitosis and meiosis mechanisms.

In the book, Sagan and Margulis outline their major objections with neo-darwinian orthodoxy: the notion of mutation and its inherent implications, and argue that its current role in theory is misguided and overemphasized. They argue, rightfully so, the concepts of symbiogenesis and Gaia give much better traction to explaining change from a procaryotic world to the current world of the living than the doctrines of neo-darwinian selection via mutation.

Margulis and Sagan give a interesting account, and more importantly, several detailed examples of symbiosis, where the genome has clearly changed. Whether or not one is familar with Margulis's work, the accounts are enlightening, although I wouldn't recommend this book as an introduction to Margulis's symbiosis and Gaia metaphors, it gives enough to wet the appetite for more. I would recommend Microcosmos as better introductory book to get a better glimpse of the scope and revolutionary nature of Margulis's ideas. If one is interested in other details, her other books, such as the Symbiotic Planet are worth reading.

Clearly the most important part of the book, besides a few more of her and Dorion's insights into Gaia, is the report on her latest publishable material on evidence of the steps from procaryotic to eucaryotic organisms. She concentrates more on her evidence for the first major symbiotic pairing (amitochondriates) which eventually leads to the mitosis and meiosis mechanisms. Her detailing of karyomastigont and akaryomastigont mechanisms and their relations, gives one a better understanding of some of the major steps that most likely occurred from the transition from gross bacterial genetic mechanisms (e.g., plasmids, bacteriophages, and conjugation) to the full blown eucaryotic mitosis and meiosis mechanisms. Obviously, despite their compelling evidence, there looks to be a great deal of work to done to fill in gaps between the connected dots. But Margulis and Sagan provide an entertaining and informative overview on some of the issues entailed in determining the details.

The book is a tantalizing look at the edge of science, for if one is informed, one can see some interesting signposts ahead. The only problem I have with the book is once you start looking beyond the edge, you realize indeed Margulis has only a few explorers with her, and they haven't gotten very far. But that's the nature of science, isn't it.

My review will take the form of a critique of an earlier review and then I will provide a couple comments thereafter.

An earlier reviewer erroneously states, "Lynn Margulis has joined the pack, attempting a direct refutation of Darwin's idea of evolution by natural selection. In her view, natural selection plays only a minimal role in the story of life."

She neither dismisses Darwinism nor Natural Selection. She actually questions Neo-Darwinism and her view strongly supports natural selection.
The authors question the Neo-Darwinist's over-reliance and exaggeration of gradual accumulation by random mutations (which they don't altogether dismiss). She raises the fact that most mutations are deleterious and neutral and do not provide evidential support for MOST/ALL speciation. She does provide abundant evidence that supports her idea of symbiogenesis as the driver of evolutionary novelty.

An earlier reviewer also points out,"Instead, like Gould, she demolishes not only "Origin," but all those scientists adhering to its tenets, as well."

Again she intends to complement Darwin and demonstrate the shortcomings of the Neo-Darwinian synthesis. Your critique clearly conflates the two.

I do agree with another reviewer that the book at times feel strangely disjointed at times (and why I gave it a 4). Even so the work provides some revolutionary concepts that are worth further investigation.

I also agree that the book at times feel polemical, but I think given the over dominant, current point of view that a few extremities might be useful in calling attention to the current view's shortcomings and the sublimity of their theory of symbiogenesis. I really don't care how polemical a work is as long as it supports itself with evidence and I think the authors do a fantastic job of doing so. Even if they turn out to be wrong about the tertiary role of mutations in speciation, their theory adds another layer of provable facts, namely speciation through symbiosis, to the overall Theory of Evolution.

Lastly, no Creationist can successfully hijack this book for their own agenda. To do so is an intellectual act of dishonesty and ignorance.

Numerous titles have explored how species evolved; but there's not a single example among them of species arising by a gradual accumulation of random gene mutations. Acquiring Genomes poses a new theory of development, maintaining that individual gene mutations are minor events and that big evolutionary changes occur when different types of organisms merge with their genomes - all the genes they possess. An intriguing discussion and convincing argument emerges.

I heard Margulis on the radio. She said that truth is stranger than fiction: the cells of our bodies have multiple bacterial ancestors--we are like mermaids, griphons, phoenixes and other combined beasts once thought real. But there is more: new species evolve by the coming together of separate genomes. I read the bad reviews and had to put my two cents' worth in: this is a great book by a great scientist, and the first to show how species really evolve. There have been several books on symbiosis but none on speciation by symbiosis. Did you know that there are beetles that cannot fly without their inherited bacteria? That butterflies probably are a combination of more than one species? That there is mounting evidence that new species in birds and mammals come from the chromosome-splitting activity of trapped but still frisky former bacteria? I noticed in Stephen Jay Gould's new book how he describes cancer as a natural state to which stressed cells revert, becoming more like their microbial ancestors. This is a Margulis idea. I did not find the book bitter or disorganized but full of examples. The book doesn't pull punches--but if you're a scientist after the truth, rather than looking to kiss... for grant applications and acceptance, you'll be more interested in the evidence than the latest theory. And the evidence is that species evolve not (as the neodarwinists have long held) by random variation, but by symbiosis, "a genome at a swallow." That may be hard to swallow if you've studied biology in the last twenty years, but apparently it is correct. Truth is stranger than fiction.

I have been a somewhat critical fan of Lynn Margulis since the 1970s when I became aware of her as the leading revivalist of the theory of the endosymbiotic orgin of mitochondria and chloroplasts, to which she added her own appealing but unsupported idea of the endosymbiotic origin of flagella (or "undulipodia") from spirochaetes. I share her interest in symbiotic relationships and in the diversity of microbes. I therefore looked forward with both excitement and trepidation to reading Acquiring Genomes, and was not disappointed in either expectation.

The book is full of interesting examples of symbiosis and is worthwhile reading on this basis alone. I was particularly intrigued by the arguments for symbionts in Olenid trilobites and the leaf margin bacteria of Ardisia. I fully agree that symbiogenesis is an important source of evoutionary innovation and that the role of symbiosis in biology is much greater than is generally acknowledged. However, the central thesis that symbiogenesis is the major or exclusive mode of speciation is completely unsupported. I could not find a single example in the book of evidence that a speciation event had occurred as a result of genome acquisition.

This may not be surprising since there was little discussion of what speciation is and how one could know whether a genome acquistion had resulted in speciation. What would prevent the organism acquiring a genome from continuing to interbreed with its conspecifics that lack the genome? Do the authors mean to argue, based on their stated preference for the morphological species concept, that acquiring a genome would result in a new morphological 'species' that interbreeds freely with its ancestral species? But then why do they reject morphological change in Darwin's finches as evidence for speciation? And with regard to the biological species concept, they appear to reject reproductive isolation as evidence of speciation in Dobzhansky's frutiflies, but argue that lack of reproductive isolation among bacteria make them all one species. It's difficult to see whether genome acquisition has any relationship to speciation if there are not reasonably clear criteria for what speciation entails, but the authors provide none.

Speciation is generally a hard event to observe, accounting for the authors' (incorrect) assertion that "speciation ... has never been traced". In fact, a handful of genes involved in speciation have been identified in the last decade in a few Drosophila (fruitfly) species, and most appear to be DNA-binding proteins that are rapidly evolving (by random base substitution), such as the Odysseus gene. No evidence of genome acquisition has been found to differentiate these closely related Drosophila species.

Oddly, the authors fail to mention that one kind of speciation is not hard to observe and that actually involves genome acquisition. That is tetraploidization, which is rather frequent in plants. A tetraploid offspring with 4 copies of each chromosome can arise from a normal diploid parent with 2 copies either by doubling the copy number of the parent chromosomes or by acquiring two sets of chromosomes from two different (but closely related) species. This results in instant speciation, because crossing back to (either) parent will lead to unbalanced chromosome numbers in the offspring, resulting in severe reduction in fertility and reproductive isolation. Tetraploid plants are also usually larger than their diploid relatives, and so qualify as new species by both the morphological and biological species concepts. Although tetraploidization has occurred many times in plant evolution, it by no means accounts for all plant speciation events, and it is quite rare in animal evolution.

There are other disappointments in the book besides the failure to establish (or even discuss in depth) the central thesis. I have to admire the sheer spunk of Margulis and Sagan for their diatribe against the neo-Darwinian synthesis, but again their arguments are inconsistent and not very substantive. Aside from sharing with intelligent designers a lack of belief that random mutations can be the main engine of evolution, their arguments are mostly philosophical, linguistic or mere name-calling rather than data-based. They strongly criticize the language of neo-Darwinism for being based on "pseudoscientific" metaphors for which "no adequate quantitative measure" exists, but proceed to devote an entire chapter to the vague metaphor of Gaia without blinking an eye.

While the prose is reasonably clear, the book skips from topic to topic in a manner that seems to lack order and purpose, as noted by other reviewers, and the figures seem to have been offered as an afterthought. I can't recall a single one that was adequately explained with a clear legend that pointed out salient features.

The chapter on the origin of the eukaryotic cell was among the best. Margulis' and Sagan's theories here (which have evolved a bit over time) are as plausible as anyone's, and could have been highlighted a bit more by a fuller dicussion of what the alternative models are. But perhaps they thought so much detail was inappropriate for a popular book.

On the other hand, the chapter proposing genome acquisition as the basis of larval forms of invertebrates seems not only intrinsically implausible, but failed entirely to mention that virtually all available evidence from the best-studied invertebrate Drosophila indicates that larval and adult body patterns are largely the result of the exact same patterning genes (differently expressed), directly contradicting the notion of a separate set of genes responsible for larval development. Although their larvae are less distictly different from adults, work in nematodes leads to the same conclusion.

Equally disappointing was the chapter on chromosome evolution. In part this is a matter of bad timing. Acquiring Genomes was probably already in press when Carmen Sapienza published a much more plausible explanation of the chromosome fission and fusion noted by Todd as an evolutionary consequence of preferential chromosome segregation in female meiosis, and when Malik and Henkoff proposed their centromere drive model of centromere evolution and noted that it might help explain speciation. Nevertheless, the discussion of the unlikley theory of Kolnicki to the exclusion of essentially all other literature on centromeres and how they work seems to represent a superficial investigation of their topic.

Despite these serious disappointments and annoyances, the book is still an interesting read and presents many interesting discussion topics. There is little available that covers these ideas, and I hope that this book will serve not only as a starting point for thinking about these problems, but as an impetus for someone to write a better book.

Lynn MARGULIS has been one of the great microbiologists and evolutionary biologists of the XXth century. Her research on symbiogenesis will one day be remembered as a breathtaking and path breaking discovery. She had the imagination to see, and the stamina to prove, that Neo-Darwinian selection could not be the only game in town, when speaking of evolution.

She was not properly honoured for this insight, which is an enduring shame, for which the profession should apologize. Reading Thomas Kuhn should have provided her some solace, and the realisation that a profession battling creationist dogmas could not let go of its own dogma without "loss of face".

Alas, in this book she grossly overstates her case - and destroys her credibility. Not only is the argument inadequate, but the acid, rambling, digressive and aggressive style does her good case great disservice. It is tragic to see a good case self-destruct.

The issue is not - and I emphasise NOT - whether symbiogenesis occurs. That this is so to me is obvious. The issue is whether symbiogenesis is the ONLY source of evolutionary innovation. The author states this repeatedly, particularly in the first part of the book. And here she is wrong.

If a "species" is composed of all beings that are composed of precisely the same set of symbionts (pg. 142), then symbiogenesis should occur every time a new species arises. The cells of each new species should show evidence of this process, either in form of a new chimera, or by incorporation of a new genome somewhere in the old set. This Dr. Margulis fails to show. If we take as a point of departure than homo sapiens sapiens is 97% the same genome as apes, which are "new genomes" that were acquired on the way - and not just once, but 5-7 times at least over the last million years? Furthermore, if she postulates a mechanism for acquisition, she better have one for shedding genomes that are no longer useful. Alas, "de-acquiring" does not appear in her text. Yet, if the only way to change is to acquire, either we have a portentous "chain of being" or genomes have been shed along the way. It would make sense: if two is bliss and three is a crowd, recurrent symbiogenesis would soon tear the chimera apart. Which may be the reason why symbiogenesis might less frequent nowadays - and overlooked when generalising from mammals.

Another way to look at it is to think in terms of frequency of occurrence. Given that there are several million species alive, and many more dead, symbiogenesis should have occurred on a time scale of what, one hundred thousand years (there were 5-7 species on the way to homo sapiens sapiens). The examples Dr. Margulis presents (the eukariotes, multicellular structures) are changes that may have occurred on a timescale of hundred of millions of years. Dr. Margulis quotes Dr. Williamson (pg. 166) to indicate that "successful matings between distantly related animals occurred (...) roughly once in 10 million years" - and this strictly among the lower orders. So the timescale seems wrong.

Yes, symbiogenesis is probably the most important evolutionary process, at work when big evolutionaryjumps, like the emergence of new phyla or taxa arise, but not the most common source, or the one most active today, or among the more complex orders. It is quite possible that it was predominant in the past and among the less complex orders, petering out as we move on. Dr. Williamson is probably closer to the mark in arguing that genome transfers are superimposed on "descent with modification" (pg. 166). There is nothing to preclude parallelism and/or succession of selective processes over time.

This could have been a great book, had Dr. Margulis had the courage of her own convictions and attempted to portray an evolution of evolutionary processes, with symbiogenesis maybe at dawn of life, yielding or being enriched by other forms during the evolutionary day, when coming to more complex organisms. By going to the other extreme of claiming exclusivity for symbiogenesis Dr. Margulis performs a useful function nevertheless: to bracket the diversity of evolutionary processes, so we can better see and explore the range of options and their succession over time.

As for the evolutionary dogmatists, they should see plurality of evolutionary mechanisms as strength, rather than a weakness in their argument against creationists. For by arguing from monocausality they implicitly espouse and confirm the principle of some kind of "design" uniqueness - albeit with an opposite sign. Nature will not be constrained to just one method, and will glory only and fully in "anything goes". Life is messiness - that is what makes it so much fun.