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A Companion to GenethicsA Companion to GenethicsA Cooperative SpeciesA Mind So RareA Natural History of RapeAcquiring GenomesAdapting MindsAgeing, Health and CareAlas, Poor DarwinAn Introduction to Evolutionary EthicsAncient Bodies, Modern LivesAnimal ArchitectsAping MankindAre We Hardwired?Bang!BehavingBeyond EvolutionBeyond GeneticsBlood MattersBody BazaarBoneBrain Evolution and CognitionBrain StormBrave New BrainBrave New WorldsChoosing ChildrenCloneCloningConceptual Issues in Evolutionary BiologyConsciousness EvolvingContemporary Debates in Philosophy of BiologyControlling Our DestiniesCooperation and Its EvolutionCreatures of AccidentDarwin Loves YouDarwin's Brave New WorldDarwin's Gift to Science and ReligionDarwin's UniverseDarwin's WormsDarwinian ConservatismDarwinian PsychiatryDarwinism and its DiscontentsDarwinism as ReligionDebating DesignDecoding DarknessDefenders of the TruthDo We Still Need Doctors?Doubting Darwin?Early WarningEngineering the Human GermlineEnhancing EvolutionEnoughEntwined LivesEthical Issues in Human CloningEthical Issues in the New GeneticsEvil GenesEvolutionEvolutionEvolution and Human BehaviorEvolution and Human BehaviorEvolution and Human Sexual BehaviorEvolution and LearningEvolution and ReligionEvolution and the Human MindEvolution in MindEvolution, Gender, and RapeEvolution: The Modern SynthesisEvolutionary Ethics and Contemporary BiologyEvolutionary Origins of MoralityEvolutionary PsychiatryEvolutionary PsychologyEvolutionary Psychology and ViolenceEvolutionary Psychology as Maladapted PsychologyExploding the Gene MythFaces of Huntington'sFlesh of My FleshFrom Chance to ChoiceFrom Darwin to HitlerGenesGenes in ConflictGenes on the CouchGenes, Environment, and PsychopathologyGenes, Environment, and PsychopathologyGenes, Women, EqualityGenetic Nature/CultureGenetic PoliticsGenetic ProspectsGenetic ProspectsGenetic SecretsGenetics of Criminal and Antisocial BehaviourGenetics of Mental DisordersGenetics of Original SinGenetics of Original SinGenomeGenomeGenome: Updated EditionGenomes and What to Make of ThemGlowing GenesHow Women Got Their Curves and Other Just-So StoriesHuman CloningHuman Evolution, Reproduction, and MoralityImproving Nature?In Our Own ImageIn Pursuit of the GeneIn the Name of GodIngenious GenesInheritanceInside the Human GenomeInside the O'BriensIntegrating Evolution and DevelopmentIntelligence, Race, and GeneticsIs Human Nature Obsolete?Language OriginsLess Than HumanLiberal EugenicsLiving with Our GenesMaking Genes, Making WavesMaking Sense of EvolutionMan As The PrayerMean GenesMenMood GenesMoral OriginsMothers and OthersNature Via NurtureNever Let Me GoNot By Genes AloneOf Flies, Mice, and MenOn the Origin of StoriesOrigin of MindOrigins of Human NatureOrigins of PsychopathologyOur Posthuman FuturePhilosophy of BiologyPlaying God?Playing God?Portraits of Huntington'sPrimates and PhilosophersPromiscuityPsychiatric Genetics and GenomicsPsychologyQuality of Life and Human DifferenceRe-creating MedicineRedesigning HumansResearch Advances in Genetics and GenomicsResponsible GeneticsResponsible GeneticsScience, Seeds and CyborgsSex and WarSociological Perspectives on the New GeneticsStrange BedfellowsStrange BehaviorSubjects of the WorldSubordination and DefeatThe Age of EmpathyThe Agile GeneThe Ape and the Sushi MasterThe Biotech CenturyThe Blank SlateThe Book of LifeThe Boy Who Loved Too MuchThe Bridge to HumanityThe Case Against PerfectionThe Case for PerfectionThe Case of the Female OrgasmThe Century of the GeneThe Common ThreadThe Concept of the Gene in Development and EvolutionThe Debated MindThe Double-Edged HelixThe Epidemiology of SchizophreniaThe Ethics of Human CloningThe Evolution of CooperationThe Evolution of MindThe Evolution of MindThe Evolved ApprenticeThe Evolving WorldThe Fact of EvolutionThe Folly of FoolsThe Future of Human NatureThe God GeneThe Immortal Life of Henrietta LacksThe Impact of the GeneThe Innate MindThe Innate MindThe Innate Mind: Volume 3The Limits and Lies of Human Genetic ResearchThe Lives of the BrainThe Maladapted MindThe Meme MachineThe Misunderstood GeneThe Moral, Social, and Commercial Imperatives of Genetic Testing and ScreeningThe Most Dangerous AnimalThe New Genetic MedicineThe Nurture AssumptionThe Origin and Evolution of CulturesThe Origins of FairnessThe Paradoxical PrimateThe Perfect BabyThe Robot's RebellionThe Selfish GeneThe Shape of ThoughtThe Shattered SelfThe Stem Cell ControversyThe Story WithinThe Stuff of LifeThe Talking ApeThe Temperamental ThreadThe Terrible GiftThe Theory of OptionsThe Top 10 Myths About EvolutionThe Triple HelixThe Triumph of SociobiologyThe Woman Who Walked into the SeaTwinsUnderstanding CloningUnderstanding the GenomeUnnatural SelectionUnto OthersUp From DragonsWar Against the WeakWhat Genes Can't DoWhat It Means to Be 98 Percent ChimpanzeeWho Owns YouWhose View of Life?Why Evolution Is TrueWhy Think? WondergenesWrestling with Behavioral GeneticsYour Genetic Destiny
Wallace Arthur sets himself the goal to convince a wide audience that science can explain with ease the rise of complex creatures from simple beginnings. Explanations based on faith in an intelligent creator are not needed. Thus, we have another book in the fast growing intelligent design (ID) versus evolutionary theory (ET) literature. Arthur approaches his (non-scientific) audience with appropriate means: the conversational style makes it a pleasure to read the book, the chapters are short yet highly informative, technical jargon is kept to a minimum, and a well organized glossary identifies key terms. Further, the author was able to condense a tremendous amount of facts on less than 250 pages.
When we accept an evolutionary explanation for the diverse life forms on our planet, we have to accept that all life on Earth, no matter how complex, shares a common, very simple, ancestor. From this starting point organisms could either diversify sideways (generating the numerous groups and subgroups of modern prokaryotes) or upward a 'ladder' of increasing complexity. Arthur illustrates the different perspectives of diversification with an analogy to molehills (creatures of varying complexity) on a vast bacterial lawn (p.5). This analogy attempts to correct a common misconception: creatures do not purposefully climb up a straight ladder towards maximal complexity. Instead, most changes happen slowly over time within existing levels of complexity and increases in complexity occur rather accidentally. Nevertheless, the aim of Arthur is to focus on the ascents in complexity and to provide an explanation for "how complex life-forms like ourselves arose from very simple beginnings" (p. 26).
Living creatures reproduce and the reproduction of creatures is based on the reproduction of cells (p.37). Reproduction depends on the precise replication of genetic material (DNA) and, in the case of complex creatures, on an intricate developmental process that leads from fertilized egg via embryo to adult. Several chapters (Building a Castle of cells, Dances with Genes, The Embryo Wars) describe the interactions between genes and environment en route towards a new organism and provide some historical background about the progression of our knowledge about these processes. But the reader has to wait until chapter 12 (Duplicate and Diversify) to get to "the book's heart" (p.136). Here Arthur introduces the key feature of the evolutionary process (the unbreakability of the flow of life across the generations) and it's implications for the 'design' of organisms. Accidental mutations, that affect individuals (as opposed to species), sometimes result in an 'improved' organism and the mechanism of natural selection can spread such an advantageous mutation through an entire species (p.138). Complex creatures have numerous different cell types and body parts on which mutation can 'work'. Using the example of arthropod segments Arthur shows that individual body components can be duplicated. Superfluous copies can change over time and fulfill new functions (p.139ff). Thus, redundant parts can diverge in structure and function, allowing for increased complexity.
Duplication and diversification 'works' at the gene level as well. In the 1990s it was discovered that all bilaterally symmetrical animals (from worms to humans) share the same underlying Hox gene mechanism to pattern their bodies. And again, we encounter the possibility that mutations cause the accidental duplications of single genes, Hox genes or the entire genetic material. Redundant copies of genes can evolve over time to fulfill new functions and over evolutionary time the genetic material of some creatures becomes more complex. "So the diversification of replicated parts is a key process-perhaps the key process- in the ascent of life's ladder in both genetic and structural domains" (p.160). In the following four chapters (From Simple to Complex, From Complex to even more Complex, Acquiring your Head, Crossing the Threshold) Arthur applies the general principle of diversification of replicated parts to particular evolutionary events. The first steps upward in organismic complexity lead from simple single celled organisms (prokaryotes) to more complex single celled organisms (eukaryotes) to multi cellular creatures. The step from single- to multi-cellular organism required the evolution of sticky cell-membrane structures that 'glued' two or more cells together. Multicellular organisms in turn could evolve different types of cells for different purposes (e.g., different organs composed of different cell types). Further, from simple body plans (lacking any symmetry) evolved more complex body plans (radial and bilateral symmetry). The evolutionary shift from radial to bilateral symmetry allowed for subsequent steps up the ladder of complexity. Why? Most importantly bilateral symmetry allows for the evolution of a head at the 'front-end' of the creature. Head evolution is another instance of increasing complexity that leads externally from headless via protohead to proper head and internally from nerve-cell concentration via simple brain to complex brain.
The evolutionary story that has brought us from our single celled Urancestor to modern human being is complemented by two chapters (Dinosaur blues and Beyond Pluto) that address the importance of mass extinctions (opening ecological niches for radiation of already existing creatures) in the evolution of complexity and the question of the nature of possible extraterrestrial life. From this context somewhat surprisingly, the final chapter (Big Questions) is an attack on fundamentalism of every stripe: atheism and theism are equally irrational in Arthur's view. "I see no more reason for a rational scientist to be a committed atheist than to be a committed theist" (p.231). This conclusion seems to require some further argument; an agnostic world-view doesn't flow necessarily from the story told in the preceding chapters. But this is a rather small flaw in a book that can add greatly to the education of lay readers interested in evolution.
© 2007 Christina Behme
Christina Behme, MSc (1986, Biology, University Rostock, Germany), MA (2005, Philosophy, Dalhousie University) is currently a PhD student in the philosophy department at Dalhousie University, Halifax, Nova Scotia, Canada. Her research interests are philosophy of mind and psychology, cognitive science, and philosophy of language.