Dawkins vs. Gould: Survival of the Fittest is a book about the differing views of biologists Richard Dawkins and Stephen Jay Gould by philosopher of biology Kim Sterelny. When published in 2001, it became an international best-seller. A new edition was published in 2007 to include Gould's The Structure of Evolutionary Theory finished shortly before his death in 2002, and recent works by Dawkins. The synopsis below is from the 2007 publication. Also
Synopsis
Part I—Battle Joined In the introductory chapter the author points out that there have been many conflicts in biology. Still, few have been as public or as polemical as the one between Dawkins and Gould. Dawkins sees evolution as a competition between gene lineages, where organisms are vehicles for those genes. Gould, a palaeontologist in the tradition of George Gaylord Simpson, has a different perspective. For example, he sees chance as very important, and views organisms as being more important than genes. Their world views also differ, for instance they have very different beliefs about the relationship between religion and science.
Part II—Dawkins' World This begins with a discussion on genes and gene lineages (chapter 2). Dawkins' view on evolution, as outlined in The Selfish Gene, has genes as the units of selection, both in the first replicators and in more complex organisms, where alliances of genes are formed (and sometimes broken). He then discusses in chapter 3, Dawkins' view of heritability, with genes as difference makers that satisfy replicator principles and have phenotypic power, increasing the likelihood of phenotypic expression, depending on environmental context. In chapter 4, he discusses aspects of genomes and genetic replication, using various examples. He notes that in a story about magpie aggression, "Dawkins' story will be about genes and vehicles", whereas Gould and others will describe it in terms of phenotypic fitness. (p. 39) He discusses ways in which genes "lever their way into the next generation", including genes that are loners, or 'Outlaws', and which promote their own replication at the expense of other genes in their organism's genome. He then discusses the role of extended phenotypes, in which genotypes that influence their environment further increase the likelihood of replication (chapter 4). Chapter 5 explores selfish genes and the selection within the animal kingdom of co-operation as opposed to altruism, levels of selection, and the evolution of evolvability itself. Sterelny notes that on the issue of high-level selection, "Dawkins and Gould are less sharp than they once were." (p. 65)
In chapter 6, Sterelny notes that "despite the heat of some recent rhetoric, the same is true of the role of selection in generating evolutionary change", (p. 67) and naive adaptationism. "Everyone accepts that many characteristics of organisms are not the direct result of selection", as in the example of redness of blood, which is a by-product of its oxygen-carrying properties. (p. 70) Numerous general truths are uncontroversial "though their application to particular cases may be. Nor is there disagreement between Gould and Dawkins on core cases", such as echolocation in bats, which "everyone agrees is an adaptation". (p. 71) They do however differ on the relative role of selection and variation. For example, they have different emphases on development. Developmental constraints are fundamental to Gould's approach. Dawkins gives this less weight, and has been more interested in enhanced possibilities open to lineages as a result of developmental revolutions. For example, the evolution of segmentation increases variation possibilities. He discusses this in Climbing Mount Improbable, and "returns to similar themes at the end of The Ancestor's Tale: major transitions in evolution are developmental transitions, transitions that make new variants possible, and hence new adaptive complexes possible". (pp. 77–78)
"Gould, on the other hand, is inclined to bet that the array of possibilities open to a lineage is tightly restricted, often to minor variants of its current state." (p. 78) Gould sees morphological stability as "probably explained by constraints on the supply of variation to selection". (p. 78) But whereas in his earlier work Gould considered variation supply as a brake on evolutionary change, in The Structure of Evolutionary Theory he carefully notes that it can also enhance possibilities for change. "So while both Dawkins and Gould recognise the central role of developmental biology in an explanation of evolutionary change, they make different bets as to what the role will be. Gould but not Dawkins thinks that one of these roles is as a brake", damping down change possibilities. (p. 78) Another difference is Dawkins conception of evolutionary biology's central problem as the explanation of adaptive complexity, whereas Gould has largely focused on the existence of large-scale patterns in the history of life that are not explained by natural selection. "A further disagreement concerns the existence and importance of these patterns", (p. 79) which leads on to Part III.
Part III—The View from Harvard (Gould) In discussing Gould's perspective, Sterelny begins with two fundamental distinctions that Gould saw between his viewpoint and that of the Dawkins camp. Firstly, Gould thought that gene selectionists misrepresent the role of genes in microevolution, ascribing a causal role in evolution, rather than by-product record of evolutionary change. Moreover, evolutionary biologists have often neglected non-selective possibilities when formulating hypotheses about microevolutionary change. For example, contemporary sex differences in human males and females need not be adaptations, but could be evolutionary vestiges of a greater sexual dimorphism in ancestral species.
But Gould's main target is 'extrapolationism', concerning the relationship between evolutionary processes occurring within species and those of large-scale life histories. In this view, the evolution of species lineages is an aggregate of events at the local population scale, with major changes being the additive result of minor changes over successive generations. While not disputing the relevance of this, Gould argued that it is not the whole truth. "Indeed, it is not much of an exaggeration to say that Gould's professional life has been one long campaign against the idea that this history of life is nothing but the long, long accumulation of local events." (p. 86) Sterelny offers four highlights to illustrate this.
Firstly, punctuated equilibrium, in which new species arise by a split in a parental species, followed by geologically rapid speciation of one or both of the fragments. A period of stasis then occurs until the species either becomes extinct or splits again. Gould argued that punctuated equilibrium challenges the gradual change expected by extrapolationists. In the case of Hominid evolution, there is the evolutionary trend of marked increase in brain size. To Gould, this trend was the result of species sorting, in which species with relatively larger brains were more likely to appear, or to survive.
Secondly, in his Natural History writings, Gould often argued that the history of life was profoundly affected by mass extinctions caused by environmental catastrophes such as an asteroid impact causing the Cretaceous–Paleogene extinction event, which wiped out pterosaurs, large marine reptiles and non-avian dinosaurs 66 million years ago. Such a mass extinction would be sudden at not just the larger geological time-scale, but also the more ephemeral ecological one. "The properties that are visible to selection and evolution in local populations—the extent to which an organism is suited to life here and now" become irrelevant to survival prospects in mass extinction times. "Survival or extinction in mass extinction episodes determines the large-scale shape of the tree of life". Massive culling of synapsids at the end of the Permian "gave the dinosaurs their chance. The death of the dinosaurs opened the door for the radiation of mammals." (p. 89)
Thirdly, in Wonderful Life, Gould describes the Burgess Shale fauna, which is known in detail due to fortuitous preservation of both hard and soft tissue around 505 million years ago. Gould argues that the Burgess Shale fauna demonstrate both diversity of species and disparity of body plans. He accepts that diversity has probably increased over the last few million years, but argues that disparity of animal life peaked early in evolutionary history, with very little disparity generated since the Cambrian, and profound conservatism in surviving lineages. For example, despite diversity in beetle species their body plans follow the same general pattern. He argues that survival has been contingent, and that if the tape of life was replayed from the earliest Cambrian, with small alterations in the initial conditions, a different set of survivors may have evolved.
Fourth, in The Spread of Excellence, "Gould argues that evolutionary trends are not the scaled-up consequences of competitive interactions among organisms." (p. 90) For example, morphological changes in horses are not the cumulative result of the competitive success of horses better adapted to grazing. "Rather, Gould argues that this trend is really a change in the spread of variation within the horse lineage", which used to be species rich with a wide range of lifestyles and sizes. "But only a very few species survived, and those few happen to be largish horses. The average horse is larger now only because almost all horse species became extinct, and the few survivors happened to be somewhat atypical", and there is no evolutionary 'trend' towards increased size. (p. 91) Similarly with complexity. While complexity has increased over time, it is misleading to see this simply as a trend towards increased complexity, from simple organisms such as bacteria to complex organisms such as us. Rather, the distance from the least to the most complex living organism has increased. "The real phenomenon to be explained is this increase in variation rather than an upward trend in average complexity. There is, Gould argues, no such trend." (p. 92)
Sterelny notes two issues arising from consideration of Gould's case against extrapolationism. "Are the patterns in life's history that he claims to detect real? And do these patterns really show the existence of evolutionary mechanisms other than those operating at the scale of local populations?" (p. 92)
Sterelny then outlines in chapter 8 Gould and Eldredge's punctuated equilibrium hypothesis. They argued that the appearance of stability in species evolution is not a mere effect of the gappiness and imperfection of the fossil record. Rather, it is the result of discontinuous tempos of change in the process of speciation and the deployment of species in geological time.