As the next installment of our Reviewing Darwin’s Doubt series, we present part one of Robert Bishop’s four-part review of the book.
Probably no one has done more to popularize the argument for Intelligent Design (ID) in recent years than Stephen Meyer. In his books, Signature in the Cell: DNA and the Evidence for Intelligent Design and Darwin’s Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design, Meyer has given what I think is the strongest argument for ID to be found anywhere. Both of these books are clearly written and nicely illustrated. I believe readers will come away with a thorough understanding of Meyer’s views.
As a Christian, I’m convinced that the universe is a creation of God and, hence, designed. Indeed, the universe appears finely tuned as a life affirming creation. So Meyer and I share a lot in common on these points. As a philosopher and historian of science, I’m also very interested in everything science, particularly intersections between evolutionary biology, philosophy, and theology. Therefore, I was very interested in reading Darwin’s Doubt.
Meyer’s latest book takes its point of departure from what’s often called the Cambrian explosion. This is the “rapid” diversification and proliferation of the major animal body plans taking place in the Ediacaran and Cambrian periods (following Meyer, I will refer to these periods together as “the Cambrian”). Meyer’s treatment of paleontology has already been discussed last week in Ralph Stearley’s review. In this series of posts I will critically examine some features of Darwin’s Doubt that are of interest from the perspective of history and philosophy of science and the case he builds for Intelligent Design. I’ll start with how Meyer frames the current status of neo-Darwinian evolution. In subsequent posts, I will examine two important rhetorical strategies in Meyer’s argumentation and assess his design inference.
Neo-Darwinian Evolution under Attack
The scene is set in the prologue, where Meyer paints a picture of neo-Darwinian evolution as being under attack in the biology literature because it cannot explain macroevolution.Neo-Darwinian evolution (microevolution for Meyer) is a term often used to refer to random genetic variations plus natural selection, whereas macroevolution is the origin of new organs or body plans. According to him, a “host of distinguished biologists have explained in recent technical papers” that microevolution cannot give rise to macroevolution, and “an increasing number of evolutionary biologists have noted [that] natural selection explains ‘only the survival of the fittest, not the arrival of the fittest’” (p. x).
There is a sense in which Meyer is right that the adequacy of strict neo-Darwinian evolution (as he defines it) to produce macroevolution has been discussed in the biology literature. The impression he communicates to the reader is that scientists increasingly recognize this inadequacy and are searching for alternatives to neo-Darwinian evolution to “solve the problem.” Meyer argues that ID is the best available alternative. But the picture of the literature he paints leaves the reader with a mis-impression of the kind of revolutionary synthesis that seems to be shaping up in evolutionary biology.
To see this, let’s start with the quotation Meyer uses to great rhetorical effect, that natural selection explains “only the survival of the fittest, not the arrival of the fittest.” This quote comes from a paper by Gilbert et al. (1996)and certainly sounds as if natural selection is ineffective for explaining macroevolution. In their 1996 paper, Gilbert et al. recount the history of the rise of population genetics as the dominant understanding of evolution. As part of this story, embryology and macroevolution were displaced by or reduced to changes in gene frequencies as early forms of gene-centrism took over in evolutionary biology. That is, focusing on only the genetic underpinnings for change within a species was a hallmark of much early evolutionary theory. The history is fascinating, but the actual story these authors tell is different (and also much more interesting) than the impression Meyer gives.
Consider the passage from which Meyer cites the quote:
The Modern Synthesis is a remarkable achievement. However, starting in the 1970s, many biologists began questioning its adequacy in explaining evolution. Genetics might be adequate for explaining microevolution, but microevolutionary changes in gene frequency were not seen as able to turn a reptile into a mammal or convert a fish into an amphibian. Microevolution looks at adaptations that concern only the survival of the fittest, not the arrival of the fittest. As Goodwin (1995) points out, “the origin of species–Darwin’s problem–remains unsolved.” This reexamination of the Modern Synthesis has led to three great re-discoveries in modern biology. These are the simultaneous rediscoveries of macroevolution, homology, and the morphogenic field. A new synthesis is emerging from these three areas, and this developmentally oriented synthesis may soon be able to explain macroevolutionary as well as microevolutionary processes. The first condition for their rediscovery came from scientists such as R. B. Goldschmidt and C. H. Waddington, who saw that all changes important in evolution are alterations to development. (1996, p. 361, emphasis added)
The story that these biologists and historians of biology tell narrates a fairly typical episode in the course of theory development in the sciences–evolutionary biology in this case. Often when developing a new scientific theory, other relevant disciplines can be ignored or even dismissed if it’s thought that the new theory can replace those disciplines. This is what happened in evolutionary biology, where the field of genetics pushed aside embryology, developmental biology, and related disciplines. Sometimes scientists discover that a theory, such as population genetics, cannot replace the fields of study it initially displaced. Gilbert et al. tell the story of how embryology, developmental biology, and other fields have had to be brought back into evolution.
They go on to say that, “The homologies of process within morphogenic fields provide some of the best evidence for evolution–just as skeletal and organ homologies did earlier. Thus, the evidence for evolution is stronger than ever (p. 368, emphasis added). Moreover, they continue, natural selection “is merely a filter for unsuccessful morphologies generated by development” (p. 368). By “merely,” they mean that variations due to development are the main drivers of evolution, but natural selection ensures that developmental and other forms of genetic variations are filtered for what makes for sustainable ways of life for organisms. The overall picture of evolution is still one of variations filtered by natural selection. However, the sources of the most relevant variations, so they argue, are in developmental processes. The thrust of Gilbert et al., then, is a synthesis between neo-Darwinian and developmental biology. The synthesis these authors point to is much more developmentally-oriented, and that is revolutionary with respect to the old neo-Darwinian paradigm. But the emerging synthesis doesn’t leave genetic variations and natural selection out. Instead, developmental biology mediates between the functional biology of gene expression, cells, and anatomy, on the one hand, and the changes in gene frequencies of evolutionary biology, on the other (1996, p. 362). At the end of their article, Gilbert et al. write,
In declaring the morphogenetic field to be a major module of developmental and evolutionary change, we are, of course, setting it up as an alternative to the solely genetic model of evolution and development. This, however, is not to be seen as antagonistic to the principle that genes are important in evolution or development. This is not in any way denied. But just as the genes make the cells and the cells form the body, so the gene products first need to interact to create morphogenetic fields in order to have their effects. Changes in these fields then change the ways that animals develop. (p. 368, emphasis added)
Genes are what they are and do what they do largely due to their developmental context. That is, changes in the body or the environment throughout an organism’s lifetime can alter how genes are expressed, and these changes in gene expression sometimes affect fitness and thus evolution. The more accurate picture of the evolutionary and developmental biology literatures, according to Gilbert et al., is that evolutionary development and epigenetics along with other sources of genetic variation and natural selection are being forged into a new synthesis giving us insight into how both microevolution and macroevolution happen.
Another author Meyer cites in his critique of neo-Darwinian evolution, Wallace Arthur, a zoologist specializing in developmental biology, shares a similar vision as Gilbert, et al. Arthur actually argues against using any microevolution/macroevolution distinction for driving a wedge between genetic changes and the origin of higher taxa (Arthur 1997, chs. 2 and 8). Indeed, Arthur doesn’t see neo-Darwinian evolution and developmental biology as opposed to each other in contrast to the picture Meyer paints. Instead, he sees a kind of extended synthesis between the two branches of evolutionary study taking place:
True, neo-Darwinism has, to its detriment, been distinctly ‘non-developmental’. Yet there are parts of the theory which, when cast in a more developmental light, may have considerable explanatory power... essentially what I am proposing here is that Evolutionary Developmental Biology has the potential to form a bridge between population genetic processes and systematic patterns; and thus to help unify evolutionary biology in general. (p. 13-14)
Wallace thinks that developmental biology is contributing to neo-Darwinian evolution’s “missing developmental component” (p. 18).
Gilbert, et al., and Wallace are not alone. Many evolutionary and developmental biologists are pursuing an extended synthesis involving population genetics, developmental biology, epigenetics, and other recent developments. Yet Meyer presents their published research as offering an alternative to or replacement for neo-Darwinian evolution. It is true that some biologists, such as Jerry Coyne, dispute the importance of the contributions of evolutionary developmental biology and epigenetics, and continue to champion a fairly strict, gene-centric neo-Darwinian theory. But for every Coyne there is a Sean Carroll working out the kind of synthesis Gilbert et al. and Wallace are describing. It’s important to understand the difference between picturing the biology literature as working towards a new synthesis versus a literature that is developing mutually exclusive alternatives. Perhaps Meyers misreads the developing revolution as being one of several ideas competing to be the new paradigm, rather than as an emerging extended synthesis. The former picture is the basis for Meyer’s divide-and-conquer and question-shift strategies. I will discuss these in the next post.
- Scott F. Gilbert, John M. Opitz, and Rudolf A. Raff, “Resynthesizing Evolutionary and Developmental Biology,”Developmental Biology 173 (1996): 357-372. [return to body text]
- Wallace Arthur, The Origins of Animal Body Plans. Cambridge: Cambridge University Press (1997). [return to body text]
- For a good overview of the breadth and depth of this synthesis, see Massimo Pigliucci and Gerd B. Müller, eds., Evolution: The Extended Synthesis. Cambridge, MA: MIT Press (2010). I should note that it’s not clear what the final form of this synthesis will look like though an exciting outline has emerged. [return to body text]