Darwin Devolves: Miller's Coagulation Pathway Proposal

[swamidass (S. Joshua Swamidass)]

We were asked about this line in our review of Darwin Devolves:

He includes a lengthy appendix that argues that the blood-clotting cascade is irreducibly complex, for example, but fails to mention Kenneth Miller’s simple, elegant scheme for its stepwise evolution (3).

[3] K. R. Miller, in Philosophy of Biology: An Anthology, A. Rosenberg, R. Arp, Eds. (Wiley-Blackwell, 2004), pp. 439–449.

The citation does not explain in detail Miller’s mechanism for evolving the blood-clotting cascade.

First of all, this is not the best reference to use. This is a more complete explanation of Miller’s proposal we would have preferred to reference (The Evolution of Vertebrate Blood clotting). The reason we used a differeeent reference is because in a Science article we are restricted in the type of references we can use, and can’t refer to web pages. We wanted to give credit to Miller for his case, but had to use an allowable reference. I actually think that science publishing needs to reform in this way, to legitimize references to web pages (especially when dealing with ID), but this the context in which we used the less than ideal reference.

Third, the basic mechanism Miler is appealing is well studied. Another article to which we cite (reference 11) directly demonstrates how new functions can quickly evolve (seriously challenging Axe’s work) is here.

http://science.sciencemag.org/content/338/6105/384

Third, remember this quote:

@swamidass

I remind those from the DI responding to this review (e.g. @pnelson and @Agauger) that we had merely <1000 words, and were not able to explain any thing in detail. All the points we are making can be fleshed out at your request. We left out important points too, in the interest of space. Each point we reference is a strong critique or counter example on its own.

We acknowledge upfront that every sentence in that article requires more support. We are ready and willing to engage with Behe to clarify our point. We can do this privately, or publicly. For this reason, I’m glad that this question was brought to us so we could answer it.

Finally, this issue of holding back from ideal references (due to venue) arises at other points. Specifically in regards to IC, I would direct Behe to this post (Which Irreducible Complexity?). In Muller’s Two Step, there is a simple and observable mechanism for seeing how IC systems arise. There is more to just about every line in that article. We had to leave out several points due to space restriction.

It is my sincere hope that our article opens an opportunity for dialogue with ID, rather than a volley of articles back and forth. Come reason with us.

[swamidass (S. Joshua Swamidass)]

@swamidass

One of the great advantages of having the e-book version is that we can search its text. I just checked again to be 100% sure. The only time Miller is referenced is in reference to the Flagellum. No mention of his proposal is made in the update on Irreducible Complexity of the Coagulation pathway. This is all a grand distraction, because have clear pathways and mechanisms (Muller’s Two Step and exaptation) for the evolution of IC systems. Behe does not engage with these critiques, nor does he alert the readers to them. His entire Devolution argument depends on IC, so this is crumble point for his argument.

Just to quote some of the key parts of Miller’s proposal:

There is no doubt that these three steps, each one supported by classic Darwinian mechanisms, would have been sufficient to fashion a rudimentary clotting system. This would leave us with system in which circulating plasma contains both an inactive serine protease and its fibrinogen target. The protease would activated by contact with tissue factor, and the active protease, in turn, would cleave sensitive sites in fibrinogen to form a clot. This system wouldn’t be nearly as quick, as responsive, or as sensitive as the current system of vertebrate clotting, but it would work a little better than the system that preceeded it, and that’s all that evolution requires.

And right here:

In short, the key to understanding the evolution of blood clotting is to appreciate that the current system did not evolve all at once. Like all biochemical systems, it evolved from genes and proteins that originally served different purposes. The powerful opportunistic pressures of natural selection progressively recruited one gene duplication after another, gradually fashioning a system in which high efficiences of controlled blood clotting made the modern vertebrate circulatory system possible.

And

Now, it would not be fair, just because we have presented a realistic evolutionary scheme, supported by gene sequences from modern organisms, to suggest that we now know exactly how the clotting system has evolved. That would be making far too much of our limited ability to reconstruct the details of the past. But nonetheless, there is little doubt that we do know enough to develop a plausible and scientifically valid scenario for how it might have evolved. And that scenario makes specific predictions that can be tested and verified against the evidence.

It is plausible mechanism that Miller proposes, and it decomposes an IC system into a serious of reducible and independent steps. Behe does not address this in any way in his book. He just ignores it.

[swamidass (S. Joshua Swamidass)]

Behe, to be clear, does not deal with this in his appendix on Irreducible Complexity. We were reviewing his book.