History, it is said, is always written by the winners. Ron Amundson rewrites the history of evolutionary biology from the perspective of what he takes to be the winning view in the old debate about the relation of embryonic development and evolution. According to this view, it is impossible to understand evolution without understanding development. Amundson calls this view “structuralism.” It was widely held in the nineteenth century, went hiding during the Evolutionary Synthesis in the 1930s and 1940s and the Darwin Centennial, was defended in the 1970s and 1980s by some anti-mainstream biologists such as Stephen Jay Gould, and is now enjoying a forceful comeback in the wake of recent research in evolutionary developmental biology, colloquially known as “evo-devo.” Before the advent of evo-devo in the 1990s, the history of evolutionary theory used to be written from the perspective of the Neo-Darwinian Synthesis. In a rather Whiggish manner, the history of biological thought was assessed according to how much any given idea advanced science on the road toward the Synthesis. Amundson refers to this as “Synthesis Historiography” (SH for short) and identifies the late Ernst Mayr—himself an architect of the Synthesis—but also a number of professional historians as the main suspects.
Without any aspiration toward eliminating the Whiggism, Amundson shows that the history of biology looks rather different if viewed from the perspective of structuralism. According to SH, biology could only advance by overcoming species fixism, essentialism, typology, and idealism. SH traced all these evils back to ancient metaphysical doctrines, especially Platonism. Amundson refers to this as the “Essentialism Story.”
Part I of the book opposes the Essentialism Story. Contrary to SH, Amundson argues that species fixism was not a result of ancient metaphysical beliefs. Rather, it was a result of an increase in knowledge about living organisms. Prior to this increase, transmutationism consisted of ill-founded, obscure stories about barnacles growing on trees and giving rise to geese and similar improbable processes. In other words, folklore and hearsay about animals and plants were replaced by scientific studies, and it was these scientific studies that led to species fixism. Furthermore, species fixism was a necessary prerequisite for the natural system of biological classification developed by Linnaeus and others. Hence, species fixism was everything but an impediment to progress in biology.
Amundson also reassesses the contributions to evolutionary biology made by Darwin's contemporary adversary Richard Owen. Synthesis Historiography has portrayed Owen as a scientific reactionary who opposed Darwinism on the grounds of outmoded metaphysical dogma, in particular Platonic idealism. What has not been properly appreciated is that Darwin and Owen had common adversaries, namely, the physico-theologists of the Bridgewater Treatise with their extremely teleological worldview. In fact, Darwin not only cited Owen approvingly on many issues, he even relied on Owen's work when arguing against certain teleological explanations of animal form. (How come that Darwin is always the good guy, no matter whose side you're on?) Thus, Owen's idealistic biology was much more than simply an obstacle to progress. Amundson convincingly demonstrates that nineteenth-century morphology and embryology in general have been much undervalued by SH and by the history of biology. It was not just backwards science driven by reactionary metaphysics.
In Part II, Amundson turns to the Evolutionary Synthesis and the reasons for which it almost completely ignored embryology and development. He traces this neglect of development back to classical geneticists working in the Mendelian tradition, such as Thomas Hunt Morgan (after 1910). Their work formed the basis of population genetics, which in turn was an important element of the Evolutionary Synthesis. Amundson attributes to Morgan and his coworkers a positivistic account of causation that allowed them to portray genes as heritable causes of form. He then argues that they did close to nothing toward explaining heredity in the classical sense of this term, according to which heredity is an aspect of development. The Evolutionary Synthesis inherited this neglect of development.
Amundson's picture of classical genetics is a bit too simple. First, the recent evo-devo work that he admires so much is deeply rooted in classical genetics. The first Hox genes were identified in Morgan's lab. E. B. Lewis's work on the determination of segment identity in Drosophila was an important step toward evo-devo (actually, Richard Owen would have loved it), yet it was essentially an exercise in classical genetics, complete with the positivistic gene concept. Amundson's claim that classical genetics was in principle incapable of identifying developmental genes is thus false. He tries to justify this view with an obscure argument that I simply fail to understand. Second, Amundson also ignores the entire tradition of somatic cell genetics in Drosophila, which has also been important for the recent advances in developmental biology and hence evo-devo. Thus, the relationship between classical genetics and developmental biology is more complex than Amundson makes it look. This weakens his claim that classical genetics is to blame for the neglect of development by evolutionary biologists. There is nothing intrinsically antidevelopment about it. It rather seems that the architects of the Synthesis selectively took from experimental genetics what fitted their own purposes.
Amundson nicely shows how the explanatory strategies of Synthesis evolutionary biology differ from what he calls “structuralism.” In a nutshell: “Adaptationists see structure as a mere consequence of previous adaptations; structuralists see adaptations as merely making adjustments on preexisting structure” (232). In retrospect, it seems remarkable just how blind Synthesis evolutionary biology was to the influence of developmental processes over evolution. However, I am less convinced that evo-devo requires a different ontology. Synthesis ontology was characterized by anti-essentialism or “population thinking.” Structuralism, according to Amundson, requires typological thinking. An example is the concept of developmental type (for example, “the vertebrate limb”). This concept is clearly important, but I do not see the need for reifying these types, as Amundson seems to do (he writes that developmental types “have causal influence”).
This is a timely book and a passionate plea for rethinking both the history of evolutionary theory and the conceptual foundations of evolutionary and developmental biology.
