Tuesday, August 08, 2006

Blood clots hold nature's most stretchable fibres

Darwinism's problem of explaining by its `blind watchmaker' mechanism of the natural selection of random micromutations, Professor Michael Behe's claimed irreducibly complex blood-clotting cascade just got harder!

[Graphic: Blood clotting cascade, Drexsel University]

It turns out that the fibres (a protein called fibrin) generated to form a clot to plug a bleeding wound, is not just any old fibre, but "nature's most stretchable fibre," having "Extraordinary Extensibility and Elasticity," being even "More Elastic Than Spider's Web" (see below):

Blood clots hold nature's most stretchable fibres, CBC, 03 Aug 2006 ... The tiny fibres in blood clots can stretch to more than six times their length before breaking - a discovery that could help doctors better understand wound healing and heart disease. The results mean the fibres are the most stretchable known in nature, beating the record of spider silk, the team reported in Friday's issue of the journal Science. [Isn't it lucky that the `blind watchmaker' just stumbled onto "nature's most stretchable fibre" (or even - for the sake of argument - the gradual pathway leading to it)?! However, as Richard Dawkins himself conceded, "We can accept a certain amount of luck in our explanations, but not too much (my emphasis)":

"We can accept a certain amount of luck in our explanations, but not too much. The question is, how much? The immensity of geological time entitles us to postulate more improbable coincidences than a court of law would allow but, even so, there are limits. Cumulative selection is the key to all our modern explanations of life. It strings a series of acceptably lucky events [random mutations] together in a nonrandom sequence so that, at the end of the sequence, the finished product carries the illusion of being very very lucky indeed, far too improbable to have come about by chance alone, even given a timespan millions of times longer than the age of the universe so far. Cumulative selection is the key but it had to get started, and we cannot escape the need to postulate a single-step chance event in the origin of cumulative selection itself." (Dawkins R., "The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design," W.W Norton & Co: New York NY, 1986, pp.139-140)]

The fibres, called fibrin, form a three-dimensional mesh in blood clots that seal wounds. To do its job, a blood clot needs to be strong and flexible enough to withstand the pressure of blood flow. "For all naturally occurring fibres, fibrin fibres are the ones you can stretch the furthest before they break," said one of the study's lead authors, Martin Guthold, a physics professor at Wake Forest University in Winston-Salem, N.C. "This was a stunning revelation because people hypothesized that these fibres stretched but broke much easier." [Note that it was "a stunning revelation," not "we expected it on Darwinian `blind watchmaker' principles. However no doubt after the event, Darwinists will start claiming that!

Abnormal blood clots can cause strokes or heart attacks. [So how could the `blind watchmaker' start with "1 per cent" of clotting and then work its way "on up the gradual, continuous series":

"In a primitive world where some creatures had no eyes at all and others had lensless eyes, the ones with lensless eyes would have all sorts of advantages. And there is a continuous series of Xs, such that each tiny improvement in sharpness of image, from swimming blur to perfect human vision, plausibly increases the organism's chances of surviving. The book [Hitching, F., "The Neck of the Giraffe," Pan: London, 1982, p.103)] goes on to quote Stephen Jay Gould, the noted Harvard palaeontologist, as saying: `We avoid the excellent question, What good is 5 percent of an eye? by arguing that the possessor of such an incipient structure did not use it for sight.' [Gould, S.J., "Ever Since Darwin," Penguin: London, 1978, p.107) An ancient animal with 5 per cent of an eye might indeed have used it for something other than sight, but it seems to me at least as likely that it used it for 5 per cent vision. And actually I don't think it is an excellent question. Vision that is 5 per cent as good as yours or mine is very much worth having in comparison with no vision at all. So is 1 per cent vision better than total blindness. And 6 per cent is better than 5, 7 per cent better than 6, and so on up the gradual, continuous series." (Dawkins, Ibid., p.81)]

It's hoped the findings could lead to better clot-busting treatments, as well as therapies for the opposite problem: fluid that doesn't clot as it should in hemophilia or other blood disorders. [This is why blood-clotting is irreducible complex, i.e. it is inaccessible to a `blind watchmaker', natural selection of random micromutations, process. Blood-clotting has to be (with apologies to "The Story of Goldilocks and the Three Bears"), `not too thick' (otherwise the animal would die of a heart attack or stroke), `not too thin' (otherwise it would bleed to death), but `just right'!] ...

Until now, scientists were unable to study the mechanical properties of individual fibrin fibres because of their size - 1,000 times smaller than the diameter of human hair. Guthold and his colleagues found a way to see and stretch the fibres using a combination of two microscopes. They suspended each dyed fibre across one microscope while using the special tip on an atomic force microscope to stretch it. All the fibres stretched to four times the original length on average, but were able to resist up to six times before breaking, the team found. ... [Note that: "1,000 times smaller than the diameter of human hair" (as they presumably would have to be for the tiniest capilliaries) yet they "were able to resist [being stretched] up to six times before breaking!]

Fibrin Fibers Have Extraordinary Extensibility and Elasticity, Liu, W., et al., Science, Vol. 313, 4 August 2006, p.634, ... Blood clots perform an essential mechanical task, yet the mechanical behavior of fibrin fibers, which form the structural framework of a clot, is largely unknown. By using combined atomic force-fluorescence microscopy, we determined the elastic limit and extensibility of individual fibers. Fibrin fibers can be strained 180% (2.8-fold extension) without sustaining permanent lengthening, and they can be strained up to 525% (average 330%) before rupturing. This is the largest extensibility observed for protein fibers. The data imply that fibrin monomers must be able to undergo sizeable, reversible structural changes and that deformations in clots can be accommodated by individual fiber stretching. ... [Again, "This is the largest extensibility observed for protein fibers"!]

Blood Clot Fibers More Elastic Than Spider's Web, ScienceDaily, August 4, 2006 ... The tiny fibers that comprise blood clots show extraordinary elasticity, on average stretching to almost three times their length while still retaining their ability to go back to their normal shape and expanding to more than four times their length before breaking ... In some cases, fibrin fibers had the ability to be stretched more than six times their length before they broke." Blood clots are a three-dimensional network or mesh of fibrin fibers, stabilized by another protein called factor XIIIa. Because of its important function of stemming the flow of blood in the body, clots have to be both strong and pliable. [So since "clots have to be both strong and pliable" to work at all in the first place, clotting could not have arisen via a Darwinian, step-by-tiny-step, gradual pathway up the smooth slopes of Dawkins' imaginary "Mt Improbable" A blood clot that starts off "1 percent" of "strong and pliable" would not work at all!] ...

"The fibrin fibers need to stop the flow of blood, so there is a lot of mechanical stress on those fibers," Guthold said. [So the very first "1 percent" of blood clot in the putative Darwinian "up the gradual, continuous series" would have to be able to withstand "a lot of mechanical stress" from the outset.]

"Our discovery of these mechanical properties of individual fibrin fibers shows that these fibers likely endow blood clots with important physiological properties. They make blood clots very elastic and very stretchable." .... Roy Hantgan ... said the study findings have significant implications for human health. "Knowing that the fibrin strands that make up a human blood clot are more stretchable than a spider's web helps us to understand how clots can seal wounds tightly and withstand the pressure in our blood vessels," [This is an important point. If fibrin wasn't very stretchable, then blood clots would not only not be able to "withstand the pressure in our blood vessels" but also they would not be able to "seal wounds tightly." A blood clot that did not "seal wounds tightly" would be a contradiction in terms! ...

See also The truth about blood clots? It's a stretch, The Boston Globe/AP, Lauran Neergaard, August 7, 2006 ...

For quotes of Professor Behe's argument for the irreducible complexity of the blood-clotting cascade, which I don't have space to post here, see my post "Pierre Grasse and the `irreducible complexity' of the blood-clotting cascade."]

Stephen E. Jones, BSc (Biol).
`Evolution Quotes Book'

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