Recently in Blood clotting Category

.. I might add a few brief notes. After Carl Zimmer’s Unicycle-bicycle transitional form, the detailed rebuttal by Keith Ken Miller (Part 1, Part 2 and Part 3), and Nick Matzke revealing that Behe wrote the Pandas’s clotting chapter that Luskin dismisses, there is not much left for me to add*.

I want to highlight two things though. One is a quote that keeps turning up in discussions of Behe’s concept of Irreducible Complexity.

Just as none of the parts of the Foghorn system is used for anything except controlling the fall of the telephone pole, so none of the cascade proteins are used for anything except controlling [he formation of a blood clot. Yet in the absence of any one of the components, blood does not clot, and the system fails. (Behe 1996, pp. 85-86)

Actually, the clotting cascade proteins do have functions other than clotting, indeed Casey’s so-called “Irreducible Core” proteins have other important functions. I go into greater detail in this post about how these functions may have pre-adapted the clotting proteins for their role in clotting. This exposes a major flaw in the concept of irreducible complexity (read the post for the full argument).

Casey also chides Miller for not doing any knock-out experiments on blood clotting systems. This is heavily ironic as no ID proponent, not even Behe, has done any experiments on the blood clotting system. As I point out in my post Behe vs Lampreys+, it’s the evolutionary biologists that have been doing all the heavy lifting in regard to understanding the clotting system. In fact I issued a challenge to the ID proponents, the Amphioxus genome had just been published at http://genome.jgi-psf.org/Brafl1/Brafl1.home.html. Amphioxus is a primitive chordate, more primitive than lampreys, that clot their haemolymph. I challenged the ID proponents to predict which coagulation factors are present in Amphioxus, search the Amphioxus genome database and report on whether the genes found match their predictions.

Since then, silence. I can tell you one thing for sure. The Amphioxus has no gene for fibrinogen, the final step in the modern clotting cascade, yet it still clots its haemolymph. So the very basis of the “Irreducible Core” that Casey goes on about is absent in these animals, and one of Behe’s iconic pathways is exposed as reducible.

Notes:
UPDATE: Yeah, yeah: I can’t spell when writing at 1 am in the morning. But the most embarrassing bit was I got Ken Miller’s name wrong (sorry Ken). Still, the science is right.
* I could have contributed sooner, but I could be playing frisbee on the beach with my kids or surfing the internet. Guess which one I chose.
+This post also has a very nice diagram of the reducibly complex clotting system that Ken Miller discusses (section 4, “An Irreducible Core”). This diagram looks eerily similar to the diagram that Casey uses, as he copied the diagram that I provided for Barbara Forrest and Paul Gross for “Biochemistry by design,” Trends in Biochemical Sciences, Vol. 32(7):301-310 (2007). He’s made a few minor modifications (hint Casey, the correct citation method is “diagram redrawn from” not “information obtained from”), but if he asked nicely, I could have given him the original diagram.

The PNAS Early Edition webpage has just posted a series of papers from the December 2006 National Academy of Sciences Sackler Colloquium, “In the Light of Evolution: Adaptation and Complex Design,” organized by Francisco Ayala and John Avise. The series of papers, on topics ranging from color vision to beetle horns, is now available (I will post the list below the fold). Eugenie C. Scott (aka Genie) was invited to speak at this meeting about evolution education and the history of opposition to it, and the speakers wrote papers to be published in PNAS and a forthcoming NAS volume.

Genie brought me on as a coauthor on the paper she was asked to write. This became:

Behe vs Sea Squirts

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Recent research has thrown an interesting spanner into one of the key, but slightly obscure claims Behe makes about “irreducible complex” (IC) systems. In Behe’s discussion of the mammalian clotting system (Darwin’s Black Box [DBB], 1996, page 86, 1st edition) he claims:

”…none of the cascade proteins are used for anything other than the formation of a blood clot”.

This is a fundamental claim with important implications. If components of an allegedly IC system have other functions, this would violate his “well matched parts” condition for an IC system. Also, if these enzymes have other functions, they could be coopted from those functions to form a clotting system. If the clotting enzyme thrombin’s only function was to cut fibrinogen to make fibrin, then, if a mutation produced a thrombin-like enzyme in the absence of fibrin, natural selection would be unlikely to preserve this enzyme (but see below). On the other hand, if a general protease (an enzyme that cuts up lots of different proteins) were to gain the ability to break down fibrinogen, then its other functions would keep it preserved until a fibrinogen-like substrate appeared.

Contrary to Behe’s statement, many of the clotting proteins have other roles. Several of these non-clotting functions were known when Behe wrote DBB [1,2 and Note 1]. These roles, in wound healing and in tissue remodelling and embryogenesis, give us useful clues to their evolution. They also demolish Behe’s claims about IC.

Jonathan Wells (2006) The Politically Incorrect Guide to Darwinism and Intelligent Design. Regnery Publishing, Inc. Washington, DC.Amazon

Read the entire series.

No book on “intelligent design” would be complete without a mention of the concept of irreducible complexity. Jonathan Wells’s The Politically Incorrect Guide to Darwinism and Intelligent Design does not disappoint in this regard; it is the actual discussion of irreducible complexity that is very disappointing and down right misleading.

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