Suroof writes:
Yes, if you have any idea as to how the irreducible core of the blood clotting system (as described in message 65) evolved in a Darwinian step-by-step model please show us.
From TalkOrigins:
Here then is an example of how such "irreducible" mutual dependencies can arise by evolution, illustrating the same process described by Muller in 1918. Miller's article goes into more detail and covers stages that I omit in this shorter account. I am simply focused here on showing the evolution of mutual dependencies, or interlocking complexity.
(A) Start with a system consisting simply of two proteins; the clot-maker and the protease. The protease is "activated" by contact with tissue proteins - as would happen when there is a break in a blood vessel. The activated protease is then able to activate the clot-maker, and the clot is formed.
(B) Now have a gene duplication for the protease. This is a reasonably common process in evolution; an entire section of the genome gets doubled; so that now there are two genes, both producing the same protease protein. There is no difference to the working of blood clotting; as all the proteins involved are the same.
(C) Now have a small modification to one of the duplicated genes. There are now two slightly different forms of the protease. Call them protease-A and protease-B. Either one would manage fine for blood clotting. In that sense, the system of three proteins is no longer irreducible; it has redundancy.
(D) Now suppose that there are mutations to protease-A which give it a capacity to activate protease-B. That is, both proteins get activated at the break in a vessel by contact with tissue proteins; but protease-B gets additional activation from the activated protease-A. This kind of additional activation can have some selective benefits, in speeding up the response of the whole system.
(E) Finally, now that protease-B is activated by protease-A, it no longer depends on activation from the tissue proteins, and further modifications can reduce this activation pathway. This makes the whole system "irreducible" again, because all three proteins are now required for clotting.
The fundamental point here is that an irreducibly complex core of three proteins can arise from a simpler system by evolutionary changes. Behe's argument depends on a strawman of evolution. Behe ignores the role of modifications to proteins, and bases his argument simply on the problem with getting a system by adding parts one by one.
Link here.
Much more interesting than "Godidit"....
™ Version 4.2
