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The Plausibility of Life: Resolving Darwin's Dilemma

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The theory of evolution began as an alternative to what is now called creationism. But unlike the advocates of creationism, Charles Darwin did not attempt to build his theory of evolution by refuting the arguments of William Paley and the other creationists of the time. Instead, he based his theory on observations, on the many traits and characteristics that he observed on his long voyage on the Beagle. A successful theory of origins cannot be built merely on sophisticated rhetoric or logical argumentation. Darwin knew this and to his great credit he gave humanity a view of life that is more scientifically justified and based on common-sense observations. Any theory however has its weaknesses, due in part to the limited knowledge of the individuals that propose it. These individuals though usually recognize these weaknesses, and are cognizant that future generations may be able to resolve them, due to the more advanced experimental techniques that are then available.

Darwin knew the weakness in his theory: it could not explain variation. The authors of this book attempt to resolve this difficulty in his theory and account for the enormous novelty in the natural world. And like Darwin, the authors justify their theories with experimental results, particularly in the fields of genetics and embryology. The knowledge from these fields was of course not available in Darwin's time. The case that the authors make for the origins of novelty is both interesting and very plausible, and even though the book is targeted to a "popular" audience, readers will appreciate the book more if they have a fairly strong background in biology.

The authors emphasize early on that mutation only alters what already exists, and so it is imperative that an explanation be found that shows how one structure can be transformed into another. It must be shown how random genetic changes can result in innovations that have high utility for the evolved organism. The pillar of the authors' theory for how this is done centers on the notion of `facilitated variation', and they give detailed arguments throughout the book that support it. Most interestingly, this notion is not based on the genotype of the organism, but rather on its phenotype: random mutations lead to nonrandom phenotypic variation. The authors are careful though to point out to the skeptical reader that this notion is not Lamarkian, but instead refers to the capacity of the organism to generate phenotypic variation as a response to genotypic variation and the nature of this variation. They leave to other researchers the study of the capacity of a particular population to evolve.

Facilitated variation holds that since phenotypic variation is dependent on the modification of what already exists, it cannot be random (even though mutation is itself random). In addition, the variation of the phenotype of an organism, which involves the changes of components and processes, is subject to constraints. However, in this same variation, other components and processes of the phenotype can be deconstrained. There is therefore a trade-off involved, with the result that (less lethal) phenotypic variation can be accelerated when these deconstraints are present. The parts of the organism that are constrained that authors refer to as the `conserved core processes' of the organism. These processes can be viewed as those that remain fixed under the evolutionary transformations of the organism. Although the authors do not refer to it in the book, and in fact may not be aware of it, this view of conserved processes in evolution is discussed in the mathematical literature under the guise of what are called `evolution strategies.'

The authors give examples of some of these core processes, such as the DNA, RNA processes of replication and protein synthesis. These processes are identical in all living organisms. Other examples given by the authors include the functions of intracellular membranes in eukaryotes, the functions of the extracellular matrix in metazoa, the role of the Hox genes in bilateral metazoa, and the process of limb formation in land vertebrates.

The core processes are specially constructed so that they can be readily linked together to obtain new combinations and can be used at new times and locations. The net result of these changes is the generation of new phenotypes. The authors allude to `weak linkage' as being one of these special constructions. Weak linkage is primarily involved in signal transduction and transcription, resulting in weak and indirect protein interactions. They also point to `exploratory behavior' as being one that has the capacity to generate a large number of outcome states. Some of these outputs can then be selected and retained, then becoming stable. The unselected states remain nonfunctional but may be selected in the future. The authors believe that exploratory processes answer the "complexity" objections to evolution, in that they explain how new anatomical structures can arise and how these new structures or systems can repair damage. As an example of this, the authors name the adaptive immune system in vertebrates, but they do not give the detailed reasons for why they believe it is.

The authors' arguments are fascinating and the length of the book makes its study manageable. Many references are given for readers who need more details. The only part of the book that should probably be omitted entirely is the section entitled "Creationism and Intelligent Design." The proponents of these approaches to explaining novelty need to find constructive examples to substantiate the viability of their theories. Usually one only gets philosophical rhetoric from them, and this does not serve to further the understanding of biological systems. The authors do not need to answer their objections, as it only gives them free press. Emphasis should always be placed on obtaining a true understanding of adaptation and biological processes. Like Darwin, this entails meticulous observation and careful laboratory work. The authors are definitely in this tradition, and have provided the reader with a first look at their theory of facilitated evolution and its observational and experimental support.

Creationist luddites repeatedly claim that life's diversity and complexity could never arise from the progressive accumulation of random genetic change - they conveniently forget non-random selection. Also dismissed are the unimaginably vast stretches of geologic time available for the constant interplay of variation and selection to shape phylogeny. They also question how genetic changes coordinate to realize new types of organisms.

In "The Plausibility of Life: Resolving Darwin's Dilemma" Kirschner and Gerhart propose 'facilitated variation' as an evolutionary mechanism to resolve these and other issues. Recent advances in cellular and developmental biology have shed new light on how evolutionary biology generates novelty (new features). Although natural selection is well understood, variation as a component of evolutionary theory has been less well developed.

Darwinian orthodoxy aggregates a large number of successive mutations, each usefully selected for the survival of the organism, to produce novel structures such as wings or eyes. Facilitated variation posits that physiologically adaptable 'core processes' (conserved by evolution across vast periods of time and groups of organisms) - along with properties such as weak linkage and exploratory processes - enable proteins, cells, and body structures to interact in numerous ways to create novelty from a limited number of genes and mutations. Life has evolved an evolutionary architecture (or toolbox) that promotes novelty and complexity - and minimizes deleterious outcomes.

Several hundred core processes generate the morphology, physiology, and behavior of an organism during development. Some have remained unchanged for hundreds of millions or even billions of years. Even though they are strongly conserved their behavior can be altered by signals that are often quite simple. A process may only have two states - on or off - and signals switch it from one state to the other. The presence or absence of these signals, and their timing, can produce large changes in the organism's phenotype.

The concept of 'weak regulatory linkage' plays a vital role by allowing reconfigurability and providing a degree of instability - essential ingredients that promote the key biological advantage of flexibility. Weak regulatory linkage is also important to evolution because it plays a large part in the repertoire of core processes. Genes don't need to provide detailed instructions on how an organism should develop - they only have to modify the way in which conserved core processes function during development. Several detailed examples are provided to show how this works - ranging from the placement of microtubules in eukaryotic cells to the distribution of whiskers and their central connections on mice. The role of Hox and other selector genes in embryology are also discussed.

This important book convincingly answers critics who claim that Darwinian evolution is unable to explain novelty and complexity. Facilitated variation is supported by the latest science. Unfortunately this book will not be widely read by non-specialists. The difficulty level is significantly above the popular science mainstream and careful attention from the reader is required - but the journey is well worth the effort. By closing the major gap in Darwin's theory Kirschner and Gerhart provide a timely scientific rebuttal to the schizophrenic post-modern medievalists who shill illusory 'irreducible complexity' or peddle vacuous 'explanatory filters' in a sterile attempt to hype the natural theology makeover known as 'intelligent design.'

Other books you might enjoy include Genesis: The Scientific Quest for Life's Origins by Robert M. Hazen; The Emergence of Life On Earth by Iris Fry; Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom and The Making of the Fittest: DNA and the Ultimate Forensic Record of Evolution by Sean Carroll; or Creatures of Accident: The Rise of the Animal Kingdom by Wallace Authur.

As the title The Plausibility of Life suggests, this book is intended to counter a central claim of creationism, the claim that it is implausible -- indeed virtually impossible -- for complex life to have evolved through variation and selection. Instead of taking a defensive position and trying to prove that evolution really did happen, he is demonstrating that the creationist argument is lame. He does this by showing that organisms have built-in processes which promote evolution.

Central to the argument is the notion of "conserved core processes". An example given here is a protein called Ras, which acts as an on-off switch for a variety of processes. Having evolved in one context, it was later combined with other components to control other processes. It is rather like using off-the-shelf parts to build automobiles instead of designing each new model from scratch.

There are too many other examples to summarize them here. The author's point is that nature has ways of promoting evolution beyond simple point mutations. It is worth noting that, regardless of how life came to be, evolution is now part of the design.

The book is rather elementary in that there is little technical jargon and no molecular biology. On the other hand, it will probably not be accessible to those who have not already read a couple of books on evolution. I decided to rate it 4 stars instead of five because it drags in spots (but only in spots) and it is sometimes unclear (but only sometimes). In high-school terms, I would give it A-.

Other books look at this aspect of evolution from different points of view and using other examples. I recommend some of the books I have reviewed. (Click above on "See all my reviews." You will have to go beyond the first page.) The books by Sean Carroll, one elementary and one advanced, look at a number of core processes and show how evolution has combined them to make ever more complex organisms. Another elementary book, by Debra Niehoff, shows how a lot of intercellular communication comes from a few basic components. Nick Lane's book about mitochondria, a little more advanced, shows how this single advance led to most of the complexity we can see today. Watson et al., describe, at the molecular level, genetic mechanisms that allow enhanced evolution, but it is recommended only for readers who are very comfortable with molecular biology. The collection Macroevolution is also rather technical, but I was able to read most of it and I learned quite a bit. Darwin in the Genome is quite elementary and describes molecular mechanisms which operate on the genome to promote evolution.

When reading a review, I often find it useful to know something about the reviewer's background. If you feel the same way, click on my name, above, for information.

[All except perhaps 3 of the unhelpful votes for this review appeared suddenly in July 2007. They are almost certainly due to an error in Amazon's software.]

[Original review 12 Jan 2006. Updated 12 April 2006 to include the book Macroevolution and the book Darwqin in the Genome.]

Darwin struggled with questions about the mechanisms of his ideas and how they were played out in the real world of nature. His genius is even more pronounced when we realize that he worked before genetic and molecular concepts were understood. As biologists began to delve into genetics and the molecular basis of heredity Darwin's ideas were bolstered and looked at in new light. This ability to modify ideas in light of new work is one of the most powerful elements of science and differentiates it from other realms of knowledge where rules are set by fiat

The sciences of genetics and molecular biology have fully matured now and can give new insights into the workings of selection. In this book the authors look at selection and mutation from a molecular view point and argue that the rearrangement of already useful molecular packages can aid and speed evolution. They argue that natural selection isn't entirely random but that these packages can be altered and put together in novel ways when called upon by adaptive needs. Kind of like Tinker Toys for nature.

The book is thorough and the prose can be a bit heavy. The authors go in to some depth concerning molecular biology and this can be hard going for those not familiar with its concepts. Oddly, I think, they include a chapter in creationism and the notion of intelligent design. Neither have merit as a scientific concept and would be better left out.

Darwin developed his treatise on evolution using his skills of obsessive observation stacked on top of his thorough knowledge of the botany, biology, and geology of the 1800's. "Origin of the Species" suggested that all existing life evolved from its ancestors through variation, natural selection, and survival of the fittest. Then he anticipated possible objections, presented them in his book, and pre-emptively answered them all - except one. He didn't know what it was that varied.

Although Gregory Mendel had published his pea experiments in the late 1800's and Darwin had a copy of the article, he must not have read it - nor did anyone else put this puzzle together till the early 1900's. After genetics matured as a science, Neo-Darwinism (The Modern Synthesis) became the new standard. Variation was caused by mutations in DNA, the resulting phenotypes that were fitter created more progeny, and life evolved gradually - no change in the basic theory, just enhancement by this key factor and other fine-tunings from routine use of the scientific method.

There have been major advancements in our understanding of evolution over the past twenty years. For example: Scientists expected a lot more human genes than 22,500 - that's not too many more than are in a worm. Embryologists began to study evo-devo - how the embryo changed into an adult. Geneticists discovered Hox genes that direct body segmentation by the mechanism of switching other genes on and off. It came as a surprise that virtually the same (modular?) genes have been found amongst diverse species - from fungi to humans.

Most successful (nonlethal) mutations were found amongst the gene switches. Complexity and variety may be created by shuffling the patterns of control on the core control genes rather than by mutative changes in the core genes themselves. Constraints imposed by these core genes and deconstraint on the switches could enhance the novelty that begged for more explanation.

Many have wanted to find "something more" than evolution by genetic variation and natural selection. Gould and his group wanted "Punctuated Equilibrium." Creationists and IDer's just want evolution disrupted and they don't care how. Well, folks, here it is. "Facilitated Variation" incorporates these new findings of evo-devo with The Modern Synthesis. Other authors, notably Sean B. Carroll in "Endless Forms Most Beautiful" and Nobel Prize winner Christiane Nusslein-Volhard in "Coming to Life" describe the same recently discovered processes for lay readers, but don't give it a name. Our authors obviously hope their new term catches on. Here's a how it works:

1. The constrained (hard to change) parts of the genome are the "conserved core processes." These include metabolic processes of: the first bacteria, first eukaryocytes, first multicellular organisms, bilateral body plans of metazoans, Hox genes for embryonic segmentation, neural crest cells in vertebrates, limb formation in the first land vertebrates, and the neocortex. They include basic information processing of DNA, RNA, protein synthesis and all aspects of cellular metabolism.

2. The core processes have special properties that allow them to be linked together in new combinations, generating new phenotypes. These properties are "weak linkage" - the way proteins interreact; "exploratory behavior" - a property of the processes forming the cytoskeleton and of processes operating in developing cell groups; and "compartmentation" - a property of embryonic spatial organization and cell type control.

3. Originally described as the "Baldwin Effect," a stressful environment causes the above-mentioned special properties to stretch phenotypic expression, creating outlying (physiologically exceptional) individuals who are fitter models for a stabilizing mutation.

4. Despite the randomness of mutations, phenotypic variation cannot be random because it involves modification of what already exists in the core processes - yet, the possible varieties of combinations amongst the core processes are limitless.

5. Core processes arose hundreds of millions of years ago in a few intermittent waves of innovation. Most evolutionary change since the Cambrian has not changed core process genes significantly. Instead, mutations have been on regulatory DNA altering core gene expression - placing core processes into new combinations and amounts at new times and places. Lethal mutations are minimized and evolutionary change is facilitated.

The authors state, "The facts used to support our arguments, though mostly recent, are widely accepted. It is their application to the problem of phenotypic variation that is new, and we believe it to be of great explanatory power in completing Darwin's theory."

Comment: Science, by its very methods, is always incomplete. Although this book suggests resistance to the idea of "facilitated variation," I doubt that believers in the Modern Synthesis will find much wrong with these principles, although they might think the authors presumptive to appropriate the concepts and give them a name.

Another concept recently advocated by many followers as a mechanism for producing novelty is called "epigenetic variation." I know next to nothing about it and it's not on Wikipedia yet (If something is not on Wikipedia, I'm not sure it really exists), but the short story is that selective methylation on a cytosine site on DNA does something to influence phenotype. This proposed theory, supposedly inheritable, independent of genes, and a little shy of adequate evidence, is much more likely to raise the eyebrows and ire of mainstream evolutionists.

I am impressed with the vast amount of new knowledge about evolution that is presented here for that group that is well-read on this subject. Any reader who made it through to the end of this review will have no trouble with this book. For anyone who wants some of the newest information in genetics, embryology, and developmental evolutionary theory, I highly recommend this thoughtful book.

Most readers, I assume, would declare that Life is Plausible enough, as long as they haven't overspent their Visa cards. Obviously authors Kirschner and Gerhart must mean something else, but their literary gifts are not always equal to their scientific insights. This is difficult matter, made more difficult by somewhat obtuse writing. It took me weeks to read this book and fathom its particular content, and yet I'm giving the book all five stars because of the importance of its insghts.

A more informative title would be "The Plausibility of Evolution as an Explanation of the Diversity of Life." The most inveterate critics of the neo-Darwinian theory of evolution point to the diversity of life forms and the implausibility that such diverse forms, each functionally adapted, could have evolved by random mutation, through minute increments of change, evn in the course of billions of years. Kirschner and Gerhart attempt to answer that objection with a new theory of evolution at the sub-cellular level, which they call "facilitated variation." Honestly, I think they're on to something, though I don't find their new synthesis so very different from the ideas implicit in Sean Carroll's notions of evo-devo -- evolutionary development. Rather than try to express the core ideas of facilitated evolution by myself, I'll give you the authors' own words:

The selection for a small number of conserved core processes versatile enough to be used in many different contextsto support the complexity of large multicellular organisms is a product of selection for physiological adaptability. As a side effect, core processes with high adaptability have a high capacity for weak linkage. Such processes are responsive to genetic changes of regulation. They have been used inmany different combinations at many different times and places in the organism's development and physiology, so that it is likely the processes capable of weak linkage pose little barrier to future use in different combinations, times, places, and amounts...
Much of the skepticism over the years about the capacity of random mutation or genetic reassortment to generate phenotypic change has arisen from the assumption that genetic changes must create very specific, multiple, complex phenotypic changes. Our view is that specificity and complexity are already built into the conserved processes, as is the propensity for regulatory coupling.

Well, there you have it, from roughly the middle of the book. If it makes crystalline sense to you, perhaps you don't need to read further. If it makes no sense at all, perhaps you'd better read something else. If it makes some sort of sense but you want a good deal more evidence and explication, then you might consider taking on the whole book.

The most fundamental idea here is that evolution MUST occur first at the level of molecules. Darwin was looking through the wrong end of the telescope by theorizing evolution of species, though in his time and place no other viewing point was available. Darwin observed evolution of whole organisms as "descent with modification," just as any orchid fancier, guppy breeder, or paleontologist can and must observe it. Then came the geneticists, who salvaged Darwinian evolution from the critics who demanded evidence of a mechanism. But even the mapping of the genome hasn't quelled all objections of implausibility, for reasons that Kirschner and Gerhart restate in their opening chapters. At the cellular component level, however, the mathematically possible mutations are so incredibly numerous that success by random variation, again and again in the course of phenotypic evolution, seems utterly unbelievable. That's where our authors enter the discussion.

Advocates of "Intelligent Design"! If you detect a note of challenge in my erratic summary of The Plausibility of Life, you're on the money. I challenge you to read this book carefully and critically. If you can't make heads or tails of it, you'd better modestly trim your ID sails. If you understand it well enough to venture a refutation, I'll be happy to hear from you.

To a large degree the question posed by Marc W. Kirschner and John C. Gerhart in "The Plausibility of Life: Solving Darwin's Dilemma" has been the elephant in the room of evolutionary theory. Exactly how does the variation arise that is the target of natural selection? Random mutation does not seem (at least on the surface) to be a powerful source, as mutations are more often likely to be deleterious. The depth of time could perhaps allow random mutation to be effective, but I also doubt that we are totally able to understand how this occurs. Still something drives the huge variety of life we see on earth- what is it? Creationists would find the hand of God in this, but I have serious doubts that they can do anything but point to scripture as authority. They simply have no scientific basis for their ideas. There is almost certainly a natural explanation for this variety, but I think that it is more complex than is often thought.

Something appears to have occurred at the level of the gene that may be more powerful as an engine for change than is random mutation alone. The authors point out that humans have fewer genes than we originally thought- only six times the number for bacteria! We are also very close to chimpanzees in our genetic make up, yet we are quite different (despite the obvious anatomical similarities). Much of this shared genetic make up has to do with coding the physiological and developmental aspects of any organism, but the amazing thing is that the same genes which code for one activity in one organism may do something quite different in another, or they may do similar things with different results. HOX genes, which apparently serve as the organizer of embryonic development in all organisms, are a case in point. While they function the same generally (organize embryological development), the results are quite different, depending on the nature of the other genes (a grasshopper is not a zebra!) Thus genes are even more flexible than was once thought.

The authors put together all of the most modern research on the subject and come to the conclusion that the organism is to a large degree the source of the variation (facilitated variation). This is not in a Lamarckian way (inheritance of acquired characteristics), but is based on the genetic materials available and the ability of the organism to avoid lethal phenotypes under environmental change. At the same time core activities of DNA and RNA information processing and protein coding, as well as HOX gene developmental roles, are maintained.

I found one irritating typo- it is Trofim D. Lysenko, not Fyodor Lysenko (p. 77). As near as I can tell Fyodor was a lieutenant in the Russian army!

That said, this is reasonably good introduction to some modern thinking on variation. It should be read by anyone interested in the subject.

The great question presented to Darwinists has always been not how selection works, but how such diversity arises from random mutation.

Extraordinary advances in molecular biology in the past decade help answer this question, and the authors have targeted their book at biologists from every field, scientists in general, and the educated and motivated lay public.

A fascinating read that takes you through a story almost too amazing to believe, yet too plausible to ignore. In the end, I turn to the button on my refrigerator: "Fine, I evolved, you didn't."

Three problems that studies of evolution must address: (1) why do species change; (2) How are these changes inherited; (3) What is source of individual variety, the raw material upon which 1 and 2 must work?

It is question 3 that this book addresses. Darwin himself was understandibly vague on the sources of variety, since he had no idea what the mechanisms of heredity were, nor how, in detail, bodies were built. It turns out that question 3 is only just starting to be answered. It was the dirty little secret of biology that we really had no idea how useful mutations arose, when it seemed that pure chance operating on genes was EXTREMELY unlikely to produce anything useful, and that, if one thought about it, the probabilites became even more daunting inasmuch as many things had to go right at once. (It was not enough to experimentally grow a new proto-limb. That had to be supplied with nerves and blood vessels at the same time.)

Our authors are saying that problem 3 is, in principle, solved. Innumerable details remain, of course, but certain things are now clear. Because of the way the eucaryotic DNA is set up, plus the way bodies are built, it is a lot easier than we thought to get USEFUL variations. There are other features of creatures that also facilitate change, and the authors go through the main categories, explaining how they work. This is exciting stuff, especially since it answers questions that you didn't even know you had, but that turn out to be fundamental questions. I only wish their writing was equal to their ideas. It is journal article prose; although they do not assume expertise, they do require a willingness to wade through repetitive latinate sentences. Their references, too, are generally to the original paper on a topic, rather than some more modern (and accessible) textbook or popularization. For these two sins I removed a star in my rating, but the material is so important that anyone who wants to know how evolution actually works should read this book.

There seems to be a cottage industry among life scientists in the US. Their self-assigned role of this scattering of scholars is chipping away of the Darwin icon. As serious scholars, they have little desire to "overturn". Instead, they produce a constant barrage of "Darwin got this wrong" or "Darwin didn't answer that question". In this case, Kirschner and Gerhart are "resolving Darwin's dilemma". The dilemma is the lack of understanding of genetics when Darwin published "The Origin of Species". Without knowledge of how traits are passed down the generations, neither Darwin, nor anybody else, could envision how traits might be modified. Mendel's work opened the door to this mystery, and Crick and Watson provided the mechanism. Although that trio's insights gave rise to what is now known as "neo-Darwinism", the authors aren't satisfied with a "gene-centred" mechanism for heredity. They propose a new concept they dub "facilitated variation".

The past two decades have seen a massive increase of what occurs in the "development" phase of an organism. The authors draw on this work, expanding it by demonstrating how an organism does more than react to its environment. Cells can direct changes that bypass the "classical" picture of new traits occurring only over successive generations. Variations can happen during life, making the organism more "fit" to meet challenges. This ability produces the "novelties" that appear in the evolutionary record ultimately leading to new species. Change, then, in the best Gouldian sense, can indeed be abrupt. It can also produce radical new complexities, such as eyes, enlarged brains and novel limb forms such as wings or fins. These changes, the authors insist, are all natural and perfectly in order due to mechanisms used in building the body. The organism can drive transformation through an almost infinite set of options. These options provide the foundation for "facilitated variation".

As so many authors in this field seem impelled to do, they start with William Paley's "watch on the heath". The watch implied life is too complex to be anything but the product of a "designer". They go on to recount how Darwin's "three pillars" - variation, heredity and selection - working over time produces complexity. Although Darwin explained what they were, he couldn't describe how these three processes interact. The authors recount the history of studies attempting to piece together the mechanisms. As detailed knowledge was accumulated, it became clear that an element of "plasticity" was in place. Organisms were not fixed within a species designation, but varied over time and place. To the authors, this condition implies that it's not the genes driving change, but the variable options available in body development that lead to new structures and traits. They refer to this process as "exploratory behaviour" on the part of various cell types. Genetic change becomes smothered in the many choices available to an organism as it develops. "Random" change, a term the authors overwork, has little role to play. That's not surprising, since "random" in evolutionary biology remains a poorly defined term. What "random change" are we to consider, the organism? the environment? the gene?

In conclusion, the authors, as so many writers from the US feel compelled to do, address the fallacies of "intelligent design", a concept rendered meaningless at Dover, Pennsylvania. Kirschner and Gerhart note how Darwin's opponents in their country have made much of "holes" in the theory of evolution. Those "gaps" have been used to weaken or destroy the entire Darwinian edifice. The authors of this book credit "facilitated variation" with plugging the gaps and reinforcing the entire structure on a firm foundation. Given that there exist shelves of books refuting all forms of Christian "creationism", it's inexplicable why this pair deems it necessary to devote any time to the issue. Except for claiming their concept of how variety drives selection is the final nail in creationism's false notions, there is nothing here that hasn't been written. Since their book is obviously intended for a lay, and not a scientific audience, perhaps they feel their explanation will gain a wider audience. [stephen a. haines - Ottawa, Canada]