For evolution to create new body plans for animals, it must modify discrete Gene Regulatory Networks (dGRNs). 1 However, dGRNs are such interconnected and complex circuits 2 that modifications always have catastrophic negative effects. 3 Like highly complex and integrated systems in manmade applications, dGRNs cannot be altered without terrible results. 4
Thus, small, step-by-step changes cannot change one dGRN into another. 5 Building a dGRN from the ground up is the only choice.
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Meyer, S. C. (2013). Darwin's Doubt: The Explosive Origin of Animal Life And the Case for Intelligent Design. New York: HarperOne.
- Meyer, 2013, p. 269: Darwinian mechanism. Buidling a new animal body plan requires not just new genes and proteins, but new dGRNs. But to build a new dGRN from a preexisting dGRN by mutation and selection necessarily requires altering the preexisting developmental gene regulatory network (the very kidn of change that, as we saw in Chapter 12, cannot arise without multiple coordinated mutations). In any case, Davidson’s work has also shown that such alterations inevitably have catastrophic consequences.” ↩
- Meyer, 2013, p. 268: “Davidson notes that, once established, the complexity of the dGRNs as integrated circuits makes them stubbornly resistant to mutational change—a point he has stressed in nearly every publication on the topic over the past fifteen years. “In the sea urchin embryo,” he points out, “disarming any one of these subcircuits produces some abnormality in expression.””
p. 268: “Developmental gene regulatory networks resist mutational change because they are organized hierarchically. This means that some developmental gene regulatory networks control other gene regulatory networks, while some influence only the individual genes and proteins under their control. At the center of this regulatory hierarchy are the regulatory networks that specify the axis and global form of the animal body plan during development. These dGRNs cannot vary without causing catastrophic effects to the organism.” ↩
- Meyer, 2013, p. 268: Quoting Davidson: “There is always an observable consequence if a dGRN subcircuit is interrupted. Since these consequences are always catastrophically bad, flexibility is minimal, and since the subcircuits are all interconnected, the whole network partakes of the quality that there is only one way for things to work. And indeed the embryos of each species develop in only one way.” ↩
- Meyer, 2013, p. 269: “Davidson’s work highlights a profound contradiction between the neo-Darwinian account of how new animal body plans are built and one of the most basic principles of engineering—the principle of constraint. Engineers have long understood that the more functionally integrated a system is, the more difficult it is to change any part of it without damaging or destroying the system as a whole. Davidson’s work confirms that this principle applies to developing organisms in spades. The system of gene regulation that controls animal-body plan development is exquisitely integrated, so that significant alterations in these gene regulatory networks inevitably damage or destroy the developing animal. But given this, how could a new animal body plan, and the new dGRNs necessary to produce it, ever evolve gradually via mutation and selection from a preexisting body plan and set of dGRNs?” ↩
- Meyer, 2013, p. 269: “Davidson makes clear that no one really knows: “contrary to classical evolution theory, the processes that drive the small changes observed as species diverge cannot be taken as models for the evolution of the body plans of animals.”” ↩