Recently in Blood clotting Category

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:

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, 1^st 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.