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154 of 162 people found the following review helpful:
5.0 out of 5 stars
An outstanding introduction, November 6, 2005
This review is from: The Plausibility of Life: Resolving Darwin's Dilemma (Hardcover)
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.
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94 of 97 people found the following review helpful:
5.0 out of 5 stars
Darwin's Dilemma Resolved - Faciliated Variation and Evolutionary Novelty, October 26, 2006
This review is from: The Plausibility of Life: Resolving Darwin's Dilemma (Hardcover)
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.
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65 of 69 people found the following review helpful:
4.0 out of 5 stars
How We Are Designed To Evolve, March 18, 2006
This review is from: The Plausibility of Life: Resolving Darwin's Dilemma (Hardcover)
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.]
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