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Walking It Back? Further Reflections on the Response to Darwin's Doubt from BioLogos

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In her conclusion to BioLogos's ten-part review series of my book, Darwin's Doubt, BioLogos President Deborah Haarsma suggested that I mischaracterized the perspective of the organization's reviewers in my response to them. She asserts that, contrary to my portrayal, the BioLogos scientists who reviewed Darwin's Doubt do not regard the Cambrian explosion as an unsolved problem from the standpoint of evolutionary theory.

After re-reading what the BioLogos reviewers actually wrote, I stand by my original assessment. As the record shows, the BioLogos scientists reviewing my book not only acknowledged the inadequacy of the neo-Darwinian mechanism as an explanation for the origin of the animal body plans that arose in the Cambrian period, but they also acknowledged that no other known evolutionary mechanism can explain this event.

Recall that my main argument in Darwin's Doubt is that the origin of the genetic (and epigenetic) information necessary to produce the novel forms of animal life that arose in the Cambrian period is best explained by intelligent design. To make this case, I showed first that neither the neo-Darwinian mechanism of natural selection acting on random mutations, nor more recently proposed mechanisms of evolutionary change (such as self-organization, neutral evolution, natural genetic engineering, etc. -- see Darwin's Doubt, Chapters 15-16) are sufficient to generate the biological information that arises in the Cambrian explosion. Instead, I show -- based upon our uniform and repeated experience -- that only intelligent agents have demonstrated the power to generate the functional information of the kind that is present in biological systems (and that arises with the Cambrian animals). Thus, I conclude that the action of a designing intelligence provides the best ("most causally adequate") explanation for the origin of that information.

In my response to the BioLogos critical review series, I noted that the main scientific reviewers (Falk and Stearley) had actually agreed with my scientific assessment of the inadequacy of the neo-Darwinian mechanism and that they had also acknowledged that no other known evolutionary mechanism can (yet, at least) account for the origin of novel animal body plans that arise in the Cambrian. Thus, I suggested that the series had unexpectedly clarified the true nature of the disagreement between proponents of intelligent design and the BioLogos scientists (though philosopher Robert Bishop is a partly different matter, see below). In particular, I suggested that our disagreement derives less from differing assessments of the current status of evolutionary theory (i.e., the science) than from differing views about the rules of science and, specifically, whether those rules preclude consideration of the design hypothesis and require scientists to search into the indefinite future for some materialistic cause or process as the best explanation for all phenomena and events whatever the evidence. In other words, I suggested that the series had clarified that our real disagreement mainly concerns the legitimacy of design inferences and the closely related issue of whether methodological naturalism should be regarded as a normative convention governing all scientific theorizing.

In her reply to my response, Haarsma maintained that I had mischaracterized the views of Falk and Stearley. Haarsma noted that Darrel Falk and Ralph Stearley did acknowledge the inadequacy of the standard neo-Darwinian mechanism of natural selection and random mutation as an explanation for the origin of novel forms of animal life. But she also explicitly stated that the BioLogos reviewers, including the two scientist reviewers, deny that the Cambrian explosion is an unsolved problem in evolutionary theory. As she wrote, "While the authors agree with Meyer and mainstream biologists that one mechanism of evolution (natural selection) is insufficient by itself to explain the development of animal body plans, they did not call the Cambrian explosion 'unsolved' or 'awaiting a solution.'" Instead, Haarsma suggested the opposite, namely, that both BioLogos scientists affirm the adequacy of other evolutionary mechanisms, perhaps in conjunction with the mutation/selection mechanism, as an explanation for the origin of the animal body plans that arise in the Cambrian period -- i.e., that the so-called "extended synthesis" has solved that problem.

Yet neither of the BioLogos scientists actually wrote this. Indeed, Darrel Falk -- the only biologist among the team of reviewers -- clearly said the opposite and Ralph Stearley characterized the current status of evolutionary theory in much the same way as did Falk.

Falk on the Mystery of the Cambrian Explosion

Much as I do in Darwin's Doubt, Darrel Falk calls the Cambrian explosion a "mystery" (actually a "big mystery") and acknowledges that none of the recently proposed evolutionary mechanisms or models has provided an adequate account of the origin of novel animal form. Referring specifically to these recently proposed (i.e., post neo-Darwinian) mechanisms, he wrote: "Stephen is right, that none of the other models fit the bill in a fully satisfactory manner yet."

In making this concession to the critical or negative part of my argument, Falk does add the important qualifying word "yet." But in saying that current evolutionary models have not yet solved the problem he is saying precisely what I said that he said and precisely what Haarsma denies that he said. Saying a problem has not yet been solved in a satisfactory way and saying that it "awaits its solution" are about as close to equivalent expressions as can be formulated in English.

Of course, Falk also expresses optimism about what he expects evolutionary theory to achieve in the future. As he states:

As Douglas Erwin elegantly argues in his 2011 paper, there must have been something different taking place as the system was being put in place 550 million or so years ago. I think figuring that out will turn out to be one of the most fascinating pieces of puzzle-solving that molecular biology has ever done. However, unlike Stephen, not only do I think this research is not at a dead-end, I think it will turn out to be among the most exciting frontiers in biological research over the next couple of decades. The work, as most developmental biologists see it, has only just begun, and it is the kind of thing that happens at this cutting edge stage, which makes science so much fun. I'm with Ralph Stearley [pdf] on this: to study the diversity of life and the mechanisms which characterize it is to be enraptured in joy.

I admire Darrel's enthusiasm for scientific investigation and duly noted his confidence in what evolutionary biology will one day discover. In my response, I acknowledged that Darrel expects biologists to find a materialistic evolutionary process that can account for the origin of animal body plans -- that was presupposed in my questions about the extent to which he is committed to methodological naturalism. Nevertheless, issuing promissory notes about the creative power of some as-yet undiscovered materialistic process is not the same thing as affirming that evolutionary biology has in fact discovered such a process with the capacity to generate novel animal body plans or that the mystery of the Cambrian explosion has been solved.

Stearley on Scientists "Looking to Build" an Adequate Model

Ralph Stearley similarly seems to believe that a "larger synthesis," which can explain the origin of animal life as "the outcome of biological processes," is in the works and forthcoming, but that biologists are still "looking to build" an adequate model, which is not yet sufficient or complete. Specifically, Stearley writes:

[W]hile it is true that Goodwin and others believe that their discoveries pose a major challenge to neo-Darwinian orthodoxy, this does not cause them to abandon their belief that the history of life can be explained as the outcome of biological processes! Indeed, many evolutionary biologists and paleontologists are looking to build the notions provided by morphogenetic fields and developmental constraints into a larger synthesis. [Emphasis added.]

Stearley characterizes evolutionary biologists as seeking to discover materialistic "biological processes" capable of accounting for the origin of morphological novelty, but he implies that the effort to produce this explanatory synthesis is a work in progress -- that evolutionary biologists are still "looking to build" an adequate model. To the extent that he is clear in his own views, therefore, he does not present current evolutionary theory as having provided an adequate explanation for the origin of animal body plans or macro-evolutionary innovation generally (problems of significant concern to structuralists such as the late Brian Goodwin as well as representatives of the many post-neo-Darwianian schools of thought).

That Stearley understands the Cambrian explosion to be an unsolved problem for evolutionary theory can be also clearly discerned in his parallel review of Douglas Erwin and James Valentine's 2013 book The Cambrian Explosion in the same essay in which his review of Darwin's Doubt appeared. Stearley quotes these two Cambrian experts approvingly as saying the Cambrian explosion represents "a tractable but unresolved problem" (The Cambrian Explosion, p. 330). He goes on to say:

Erwin and Valentine admit that there is much yet to be deciphered concerning the Precambrian-Cambrian biotic transition. They see two major unresolved questions:

First, what evolutionary processes produced the gaps between the morphologies of the major clades? Second, why have the morphologic boundaries of these body plans remained relatively stable over the past half a billion years? (p. 330)

In quoting Erwin and Valentine candidly acknowledging the lack of an adequate mechanism or known biological process (or processes) to account for "the Cambrian diversification event," Stearley does not dispute the judgment of these authorities, but instead reviews their book favorably. Thus, my representation of Stearley as viewing the Cambrian explosion as a problem "await[ing] a solution" seems to be entirely correct.

In any case, if Stearley (and the other BioLogos reviewers) do think that these problems have been solved, as Haarsma now suggests, they would in so claiming certainly contradict leading Cambrian experts like Erwin and Valentine. Earlier in the same book where Erwin and Valentine note that major questions like "what evolutionary process produced the gaps between the morphologies of major clades?" are "unresolved,"1 they also question whether "uniformitarian explanations can be applied to understand the Cambrian explosion." (p. 9) Indeed, Erwin has pointedly taken a non-uniformitarian view of the evolution of body plans in which he maintains that no known biological process accounts for the Cambrian explosion of animal form -- i.e., that whatever caused the Cambrian explosion is unlike any biological process observed today.2

If Haarsma is correct that Stearley and other BioLogos reviewers actually do think the Cambrian explosion has been adequately explained by some known evolutionary mechanism (or combination of mechanisms), then it would be reasonable to expect that the reviewers would have provided descriptions of how these alleged processes account for the origin of novel animal form in the Cambrian period. It would also be reasonable to expect that they would explain how such a known mechanism solves the specific problems discussed in Darwin's Doubt.

In particular, they might have offered an explanation for how some proposed mechanism (or combination of mechanisms) explains: (1) the origin of genetic information and novel proteins (given the size of the combinatorial sequence space that must be searched in the available evolutionary time), (2) the origin of epigenetic information (given that genetic mutations only act on genes, not epigenetic sources of information), (3) the origin of body plans (given that developmental mutations invariably produce embryonic lethals), and (4) the origin of novel gene regulatory networks (given that all known experimentally induced perturbations in such networks disrupt animal development). Neither Stearley nor any of the other BioLogos reviewers attempted to explain how known evolutionary mechanisms resolve these difficulties -- a fact that reinforced my judgment that they were not claiming to have solved the problem of the origin of animal body plans in the Cambrian period, but instead that they appeared to view the problem as one "await[ing] a solution."3

Robert Bishop's Scientific Disagreement

In contrast to Falk and Stearley, philosopher Robert Bishop does seem to suggest that the problem of the origin of evolutionary novelty has been solved (or significantly minimized) by recognizing the role of new evolutionary mechanisms and by affirming that these additional mechanisms act in concert with the standard neo-Darwinian mechanism of natural selection and random mutation. Thus, he represents advocates of newer evolutionary theories and models as continuing to affirm the central importance of natural selection and random mutation in their newer theories, albeit in conjunction with other additional mechanisms.

For this reason, Haarsma is correct that Bishop (though not Falk and Stearley) has a significant scientific disagreement with me about the current status and adequacy of evolutionary theory as an explanation. First, he presents newer evolutionary models as mere supplements to a basically sound core of neo-Darwinian theory -- not, in many cases, radical departures from a failed theory as I do. Second, he seems to affirm that these other evolutionary mechanisms acting in concert with the standard neo-Darwinian mechanism of mutation and natural selection are adequate to explain macro-evolutionary innovation.

Nevertheless, Darrel Falk, BioLogos's own biological expert, pointedly contradicted Bishop's judgment about the extent to which these models represent only modest extensions or supplements of neo-Darwinian theory. Instead, Falk confirmed my description of many of these models as representing radical departures from neo-Darwinism. And Falk is clearly correct about this. Indeed, many of these models repudiate crucial aspects of the neo-Darwinian synthesis either by denying, for example, the central importance of natural selection (as do neutral theorists) or the central role of random mutations (as do self-organizational theorists) or the random nature of mutations (as do advocates of natural genetic engineering).

Thus, advocates of these and other new models of evolutionary theory do not continue to think that natural selection and random mutation play a central role in evolutionary innovation as Bishop seems to claim. Consequently, Bishop cannot be right that proponents of these new models see themselves as having solved the problem of the origin of evolutionary novelty by supplementing the selection and mutation mechanism with other mechanisms. Most proponents of these newer models see themselves as proposing new mechanisms to replace the mutation/selection mechanism as the key driver in evolutionary innovation. Since Falk criticized Bishop's depiction of the state of evolutionary theory (by pointing out that Bishop had incorrectly denied that these newer models represent radical departures from standard theory), I saw no need to belabor his criticism of Bishop's scientific judgment or to treat Bishop's view as characteristic of BioLogos's scientific position.

Why the Confidence in Materialistic Processes?

In any case, my interest in writing what I did was to probe exactly why Darrel and the other BioLogos reviewers appear so confident that materialistic processes will eventually prove sufficient to explain all phenomena in the history of life, including phenomena such as the origin of functional digital information that we know from experience to arise only from the activity of intelligent agents and including events such as the Cambrian explosion that have long -- since Darwin's time at least -- resisted materialistic explanation.

In his review, Darrel himself explained the depth of the conceptual problems confronting evolutionary theory -- whatever his other expressions of confidence in the eventual adequacy of a purely naturalistic approach to the problem.

For example, he did a nice job of explaining how the functionally integrated networks of genes and gene products that control key aspects of animal development resist perturbation, and, thus, why it is hard to envision one animal body plan arising from another given what we know about the importance of these gene regulatory networks to animal development.

Given the depth of this and other related conceptual difficulties, such as the presence in developing animals of something akin to an integrated control system (or circuit), why not consider the possibility that systems at work in animal development bear witness to the Designing Agent that BioLogos scientists believe to be a reality? Despite his recognition of the depth of the conceptual problems confronting contemporary evolutionary theory, Darrel does not seem open to this possibility. My questions is simply: Why not?

For my part, I consider the recognition and detection of intelligent design to be a scientific possibility because of my study of the methodology of the historical sciences. The central methodological desideratum of the historical sciences -- as pioneered in large part by Darwin himself -- is the need to explain events in the remote past by reference to causes known from our present experience to have the power to produce the effects in question -- i.e., Darwin's vera causa criterion or what Lyell called "causes now in operation."

Modern molecular biology has revealed that building animal body plans requires vast infusions of new functional genetic information (stored in a digital form). Modern developmental biology has shown the need for networks of genes and gene products that function as integrated control systems or circuits. Developmental biology has also revealed the importance of other sources of "epigenetic" information for building animal form and, consequently, the existence of a hierarchically organized information processing system at work in animal development.

Yet, we know of one, and only one, type of cause capable of producing these necessary conditions of building animal form. In our experience, digital information, integrated control systems (and circuitry) and hierarchically organized information processing systems invariably arise from intelligent causes -- from conscious and rational activity. So why not consider the possibility that such a cause played a role in the origin of animal life?

The reason that Darrel and Ralph do not consider the possibility of design is not that they know of an evolutionary mechanism (or material process) that has demonstrated the power to produce these necessary features and conditions of building animal body plans.

Nor can they point with any specificity to what a possible solution to the problem of the origin of animal form and biological information will look like in materialistic terms. Instead, at best, they can affirm, as Darrel does in his almost creedal statement at the end of his first review, that all phenomena can (or must) be explained by reference to natural laws. As he explains:

I see no scientific, biblical, or theological reason to expect that [an intelligent agent might have acted discretely or discernably in the history of life]. Natural processes are a manifestation of God's ongoing presence in the universe. The Intelligence in which I as a Christian believe, has been built into the system from the beginning, and it is realized through God's ongoing activity which is manifest through the natural laws.[2] Those laws are a description of that which emerges, that which is a result of, God's ongoing presence and activity in the universe. I see no biblical, theological, or scientific reason to extend that to extra supernatural "boosts" along the way. . .

Darrel's description of his philosophy and theology of nature is admirably clear. It amounts to the a priori conviction that during natural history God acts mainly (or exclusively) through secondary causes such that we are justified in seeking -- into the indefinite future -- only law-like material processes to explain natural phenomenon -- including, the origin of fundamentally new forms of life and the origin of the information necessary to produce them. His philosophy of nature constitutes a tacit commitment to the idea that all phenomena and events in natural history can be (or should be) explained by reference to what theologians think of as "secondary causes." But that is just another way of expressing a commitment -- perhaps a distinctively Christian way of expressing a commitment -- to the principle of methodological naturalism. And that, of course, was exactly my point.

Robert Bishop actually makes such a commitment explicit in his response to me, stating (incorrectly, as it turns out) that "methodological naturalism is the way scientific investigation has been done since before the time of the Scientific Revolution and is well-grounded theologically." Given Falk's apparent commitment to some form of methodological naturalism (as shown above), Haarsma's argument that BioLogos as an organization "does not have a position on the use of the term" methodological naturalism would seem to be something of a red herring (and a bit disingenuous). It may be true that BioLogos has no official position on the use of the term, but the style of thinking (and limitation on scientific theorizing) that the term designates accurately describes the intellectual commitments of the BioLogos reviewers, and thus, may also help explain why those reviewers and ID proponents take different positions on the issue of design.

Of course, if scientists and scholars have effectively ruled out the possibility of the design hypothesis as part of science, then no amount of evidence will suffice to justify such a hypothesis (or inference) for those thus committed. Given that the BioLogos reviewers did not provide, or even point to, anything like a detailed alternative scientific explanation for the origin of novel animal body plans (and/or the information necessary to produce them), it seems clear that their reasons for affirming the eventual adequacy of some materialistic evolutionary processes have little to do with the current state of scientific evidence or theorizing. This suggests that their opposition to considering the design hypothesis may be based upon extra-evidential commitments about the desirability of explaining all phenomena by reference to purely materialistic or naturalistic processes -- as the principle of methodological naturalism requires.

In any case, it is not at all clear that BioLogos has declined to take an official position on methodological naturalism. In their description of the theory of intelligent design on their website, BioLogos affirms its commitment to explaining all natural phenomena (including presumably the origin of life and novel forms of life) by reference to strictly natural causes. As the website explains:

[Intelligent Design] claims that the existence of an intelligent cause of the universe and of the development of life is a testable scientific hypothesis. ID arguments often point to parts of scientific theories where there is no consensus and claim that the best solution is to appeal to the direct action of an intelligent designer. At BioLogos, we believe that our intelligent God designed the universe, but we do not see scientific or biblical reasons to give up on pursuing natural explanations for how God governs natural phenomena. [Emphasis added.]

Indeed, BioLogos writers have repeatedly affirmed the principle of methodological naturalism -- as the preceding statement surely does -- in numerous contexts.4 Bishop critiqued my book precisely because it repudiates "methodological naturalism." All this would seem to make it entirely fair to question the extent to which a priori commitments to this principle disincline the BioLogos reviewers from considering the evidence for, and the logical basis of, intelligent design as an explanation for various classes of evidence. By denying that these commitments, or at least intellectual proclivities, played a significant role in the judgment of her team of reviewers, Haarsma denies the obvious and, in so doing, reverses some of the progress that her reviewers had made in clarifying the real issues that separate our two groups.


(1) Douglas Erwin and James Valentine, The Cambrian Explosion: The Construction of Animal Biodiversity (Roberts and Company, 2013), 330 (emphasis added). See also: Douglas H. Erwin & Eric H. Davidson, "The evolution of hierarchical gene regulatory networks," Nature Reviews Genetics, 10, 141-148 (February 2009).

(2) As Erwin also notes, "The crucial difference between the developmental events of the Cambrian and subsequent events is that the former involved the establishment of these developmental patterns, not their modification." (Douglas H. Erwin, "Early Introduction of Major Morphological Innovations," Acta Palaeontologica Polonica, 38 (1994): 281-94, 288, emphasis added). Or as Erwin puts it elsewhere: "There is every indication that the range of morphological innovation possible in the early Cambrian is simply not possible today." (Douglas H. Erwin, "The Origin of Bodyplans," American Zoologist, 39:617-629 (1999), emphasis added).

(3) I do acknowledge, in deference to one point made by Haarsma, that Ralph Stearley did take significant scientific issue with me about the duration of the Cambrian explosion, but my colleagues and I have replied to similar critiques here, here, and here. In any case, Stearley's attempt to extend the time available to the evolutionary process -- by defining the Cambrian explosion to include discrete events in the earlier Cambrian (such as the appearance of the small shelly fossils) or discrete events in the late Precambrian (such as the Ediacaran radiation) -- does not significantly diminish the difficulty of accounting for the amount of morphological novelty that arises so abruptly in the middle Cambrian, in particular in the crucial Tommotian and Atdabanian stages of the middle Cambrian (part of what are also called Cambrian stages 2 and 3). I follow Erwin, Valentine and other Cambrian experts in dating the duration of the Cambrian explosion as a whole to about 10 million years. But in Darwin's Doubt I also show, based upon separate analyses by Erwin and MIT geochronologist Samuel Bowring, that between 13-16 new animal phyla arose abruptly within just a 5-6 million year window of the middle Cambrian. Including earlier discrete paleontological events (as Stearley does) within the designation "Cambrian explosion" does nothing to explain how the novel forms of animal life (and the biological information necessary to produce them) arose in such a narrow window of geological time.

(4) For some other examples of BioLogos authors endorsing the principle of methodological naturalism, even sometimes using "the term" methodological naturalism itself, see here, here, here, here, here, here, here, or here.

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