Animation of a Cilium

Cilia are hairlike organelles on the surfaces of many animal and lower plant cells that serve to move fluid over the cell's surface or to "row" single cells through a fluid. In humans, for example, epithelial cells lining the respiratory tract each have about 200 cilia that beat in synchrony to sweep mucus towards the throat for elimination. A cilium consists of a membrane-coated bundle of fibers called an axoneme. An axoneme contains a ring of 9 double microtubules surrounding two central single microtubules. Each outer doublet consists of a ring of 13 filaments (subfiber A) fused to an assembly of 10 filaments (subfiber B). The filaments of the microtubules are composed of two proteins called alpha and beta tubulin. The 11 microtubules forming an axoneme are held together by three types of connectors: subfibers A are joined to the central microtubules by radial spokes; adjacent outer doublets are joined by linkers that consist of a highly elastic protein called nexin; and the central microtubules are joined by a connecting bridge. Finally, every subfiber A bears two arms, an inner arm and an outer arm, both containing the protein dynein.

But how does a cilium work? Experiments have indicated that ciliary motion results from the chemically-powered "walking" of the dynein arms on one microtubule up the neighboring subfiber B of a second microtubule so that the two microtubules slide past each other. However, the protein cross-links between microtubules in an intact cilium prevent neighboring microtubules from sliding past each other by more than a short distance. These cross-links, therefore, convert the dynein-induced sliding motion to a bending motion of the entire axoneme.

Schematic drawing of part of a cilium. The power stroke of the motor protein, dynein, attached to one microtubule, against subfiber B of a neighboring microtubule causes the fibers to slide past each other. The flexible linker protein, nexin, converts the sliding motion to a bending motion.

Now, let us sit back, review the workings of the cilium, and consider what it implies. Cilia are composed of at least a half dozen proteins: alpha-tubulin, beta-tubulin, dynein, nexin, spoke protein, and a central bridge protein. These combine to perform one task, ciliary motion, and all of these proteins must be present for the cilium to function. If the tubulins are absent, then there are no filaments to slide; if the dynein is missing, then the cilium remains rigid and motionless; if nexin or the other connecting proteins are missing, then the axoneme falls apart when the filaments slide.

What we see in the cilium, then, is not just profound complexity, but also irreducible complexity on the molecular scale. Recall that by "irreducible complexity" we mean an apparatus that requires several distinct components for the whole to work. My mousetrap must have a base, hammer, spring, catch, and holding bar, all working together, in order to function. Similarly, the cilium, as it is constituted, must have the sliding filaments, connecting proteins, and motor proteins for function to occur. In the absence of any one of those components, the apparatus is useless.

The components of cilia are single molecules. This means that there are no more black boxes to invoke; the complexity of the cilium is final, fundamental. And just as scientists, when they began to learn the complexities of the cell, realized how silly it was to think that life arose spontaneously in a single step or a few steps from ocean mud, so too we now realize that the complex cilium can not be reached in a single step or a few steps. But since the complexity of the cilium is irreducible, then it can not have functional precursors. Since the irreducibly complex cilium can not have functional precursors it can not be produced by natural selection, which requires a continuum of function to work. Natural selection is powerless when there is no function to select. We can go further and say that, if the cilium can not be produced by natural selection, then the cilium was designed.

Irreducible Complexity of the Flagellum

The structure of a flagellum is quite different from that of a cilium. The flagellum is a long, hairlike filament embedded in the cell membrane. The external filament consists of a single type of protein, called "flagellin." The flagellin filament is the paddle surface that contacts the the liquid during swimming. At the end of the flagellin filament near the surface of the cell, there is a bulge in the thickness of the flagellum. It is here that the filament attaches to the rotor drive. The attachment material is comprised of something called "hook protein." The filament of a bacterial flagellum, unlike a cilium, contains no motor protein; if it is broken off, the filament just floats stiffly in the water. Therefore the motor that rotates the filament-propellor must be located somewhere else. Experiments have demonstrated that it is located at the base of the flagellum, where electron microscopy shows several ring structures occur. The rotary nature of the flagellum has clear, unavoidable consequences ... (Darwin's Black Box, p. 70-72)

The consequences Behe refers to are inferred by the nature of its irreducibly complex components, the discovery of which undermines a Darwinian explanation of origins. Behe concludes:

In summary, as biochemists have begun to examine apparently simple structures like cilia and flagella, they have discovered staggering complexity, with dozens or even hundreds of precisely tailored parts. It is very likely that many of the parts we have not considered here are required for any cilium to function in a cell. As the number of equired parts increases, the difficulty of gradually putting the system together skyrockets, and the likelihood of indirect scenarios plummets. Darwin looks more and more forlorn. New research on the roles of the auxiliary proteins cannot simplify the irreducibly complex syetem The intransigence of the problem cannot be alleviated; it will only get worse. Darwinian theory has given no explanation for the cilium or flagellum. The overwhelming complexity of the swimming systems push us to think it may never give an explanation. (p. 73)

This process involves over a dozen different proteins like thrombine, fibrinogen, accelerin and many more. Some of these proteins are involved in forming the clot. Others are responsible for regulating clot-formation. Regulating proteins are needed because there should only be clots forming at the site of a wound, not in the middle of flowing arteries. Other proteins take care of removing the clot once it is no longer needed.                                                                                                            

Behe explains that the formation, limitation, strenghtening and removal of a blood clot form an integrated biological system. If one factor fails, the whole system of clot-formation fails.

So again this leaves us with the question: How could this system have been evolved from a 'simple' to a 'complex' form if it only functions as a whole, all systems included...?                                        

Blood Clotting: complex?

What exactly happens when we cut ourselves?

1. A cut occurs and Hageman Factor sticks to the surface of cells near the wound. Bound Hageman Factor reacts with another enzyme called HMK to produce Activated Hageman.

2. Pre Kallikrein reacts with Activated Hageman to produce Kallikrein.

3. Hageman Factor also reacts with HMK and Kallikrein to form Activated Hageman.

4. PTA reacts with Activated Hageman and HMK to produce Activated PTA.

5. Christmas Factor reacts with Activated PTA and Convertin to produce Activated Christmas Factor.

6. Antihemophilic Factor is activated by Thrombin to produce Activated Antihemophilic Factor.

7. Stuart Factor reacts with Activated Christmas Factor and Activated Antihemophilic Factor to produce Activated Stuart Factor.

8. Proconvertin is activated by Activated Hageman Factor to produce Convertin.

9. When a cut occurs, Tissue Factor (which is only found outside of cells) is brought in near the wound where it reacts with Convertin and Stuart Factor to produce Activated Stuart Factor. 

10. Proaccelerin is activated by Thrombin to produce Accelerin.

11a. GLU-Prothrombin reacts with Prothrombin Enzyme and Vitamin K to produce GLA-Prothrombin. (Note that Prothrombin cannot be activated in the GLU form so it must be formed into the GLA form. In this process ten amino acids must be changed from glutamate to gama carboxy glutamate.)

11b. GLS-Prothrombin is then able to bind to Calcium. This allows GLA-Prothrombin to stick to surfaces of cells. Only intact modified Calcium-Prothrombin Complex can bind to the cell membrane and be cleaved by Activated Stuart and Accerlerin to produce Thrombin.

12. Prothrombin-Ca (bound to cell surface) is activated by Activated Stuart to produce Thrombin.

13.Prothrombin also reacts with Activated Stuart and Accelerin to produce Thrombin. (Step 13 is much faster than step 12.)

14. Fibrinogin is activated by Thrombin to produce Fibrin. Threads of Fibrin are the final clot. However, it would be more effective if the Fibrin threads could form more cross links with each other.

15. FSF (Fibrin Stabilizing Factor) is activated by Thrombin to form Activated FSF.

16. When Fibrin reacts with Activated FSF many more cross ties are made with other Fibrin filaments to form a more effective clot.

Let us next consider that this irreducibly complex system of blood clotting must have a way to remove the clot once the wound has healed. How is this done?

17a. A blood protein, Plasminogin is activated by + - Pa to produce Plasmin. This acts like tiny chemical scissors which cuts up the Fibrin filaments of the clot.

17b. The rate at which the clot is broken up is controlled by yet another blood protein named Alpha 2 Antiplasm, which in turn inactivates Plasmin. One of the most important parts of this whole blood clotting machine is the ability it has to keep the clotting localized to the area of the wound and to stop the clotting cascade. Most heart attacks and strokes are caused by blood clots lodging. You could say the blood-clot is the biggest killer of human beings. 

18. Antithrombin inactivates Activated Christmas, Activated Stuart and Thrombin.

19. Protein C is activated by Thrombin to produce Activated Protein C.

20. Activated Protein C inactivates Accelerin and Activated Antihemophilic.

21. Finally, Thrombomodulin which lines the inside of your blood vessels prevents Thrombin from activating Fibrinogin. A logical question is : How do we know that we have to be able to produce the whole set of enzymes or factors in the clotting cascade in order to successfully accomplish the procedure?

Probably the best answer is illustrated by the disease hemophilia. Hemophilia A is the form of the disease that 85% of hemophiliacs have and it is caused by a deficiency of Stuart Factor. The 14% that have hemophilia B are deficient in Accelerin. People who have severe hemophilia A are able to produce 2-5% of normal levels while another 15% are mild and are only able to make 5-30% of normal levels of Stuart Factor output.

Like all enzymes, Stuart Factor is produced by protein synthesis. Amino acids are joined together one at a time by this orderly process. The gene for Stuart Factor contains 186,000 base pairs and occupies 0.1% of the X chromosome. Note that this does not translate into Stuart Factor having 62,000 amino acids because only the "exon" portions of the DNA molecule are expressed. The largest portion of the DNA in this gene is found in the "intron" base pair sequences. The gene for Accelerin contains 31,000 base pairs.

Why can a hemophiliac not stop bleeding? They cannot stop because they either do not produce enough Stuart Factor or they produce defective Stuart Factor. And why do they not produce the right amount to type of Stuart Factor? The answer is, because their body does not know how. Their parent passed on defective information on their X chromosome, and incidentally, they will pass on the same defective information on to their offspring.

No one knows how this defective genetic condition got started but it probably got started by a mutation or a change in the DNA. Possibly a deletion, addition, or substitution at the exact site where Stuart Factor protein must be cleaved to become activated. In this case sufferers produce the normal amount of Stuart Factor in their blood but it cannot be activated.

What is the reasonable conclusion? It seems like it is very important to have the proper amount and type of Stuart Factor and I see no reason why we could logically conclude that proper blood clotting would be performed without each step in the clotting cascade.

Conclusion

What is the state of the art explanation offered by evolutionists for the development of blood clotting? Russell Doolittle is a professor of biochemistry at the Center for Molecular Genetics at the University of California at San Diego. He is one of the most prominent people who is interested in discovering how blood clotting evolved. Professor Doolittle wrote an article in Thrombosis and Homeostasis in which he attempted to answer the question, "How in the world did this complex and delicately balanced process evolve?"

In his article, meant for other professionals, Dr. Doolittle used the following phrases in his explanation: "Tissue Factor appeared...", "Prothrombin appears...", "Fibrinogin is born...", "Antithrombin appears...", "Plasminogin is generated...", "Antiplasmin arises...", "TPA springs forth...". "Proconvertin is duplicated from Stuart Factor." If you duplicate this sentence do you get anything different?

"Protein C is genetically derived from Prothrombin." Unless Dr. Doolittle has Lamarkian evolution in mind, proteins like Prothrombin cannot influence the animal's DNA to produce a different enzyme known as Protein C. "Prothrombin engages in an exchange (of gene pieces)." Prothrombin is a protein and as such it cannot influence any specific "gene exchange."

Michael Behe has the following observations about Dr. Doolittle's explanation of clotting evolution:

 "At no step--not even one--does Dr. Doolittle give a model that includes numbers or quantities; without numbers there is no science. When a merely verbal picture is painted of the development of such a complex system there is absolutely no way to know if it would actually work. When such crucial questions are ignored we leave science and enter the world of Calvin and Hobbes" (Darwin's Black Box, p. 95).

Behe's major objection to the "state of the art" evolutionary models is his concern for irreducible complexity. Darwinian evolution is theorized to be directed by "natural selection." Natural selection only selects from the structures and biochemistry that are present and cannot work on some kind of future structure.

The engine of Darwinian evolution only works if there is something to select--something that is useful right now, not in the future. Even if we accept his scenario for purposes of discussion, however, by Doolittle's own account no blood clotting appears until at least the third step.

 "The formation of tissue factor at the first step is unexplained, since it would then be sitting with nothing to do. In the next step (prothrombin popping up already endowed with the ability to bind tissue factor, which somehow activates it) the poor proto-prothrombin would also be twiddling its thumbs with nothing to do until, at last, a hypothetical thrombin receptor appears at the third step and fibrinogin falls from heaven at step four. Plasminogin appears in one step, but its activator (TPA) does not appear until two steps later. Stuart factor is introduced in one step and somehow tissue factor decided that this is the complex it wants to bind. Virtually every step of the suggested pathway faces similar problems" (Darwin's Black Box, p. 95). 

In order to have a controlled clotting mechanism you have to have two proteins for each step. Both the pro enzyme (non-activated) and its activator are required. Behe calculated that the odds of getting factor TPA and its activator to be 1/10 to the thirty-sixth power! To compound the problem, if "...a protein appeared in one step with nothing to do, then mutation and natural selection would tend to eliminate it." To prevent this from happening, evolutionists are forced to imagine large clusters of proteins evolving all at once. This reminds one of Goldschmitt's hope monster in which a reptile laid an egg and a bird hatched out.

Is it not much more satisfying to simply believe that God created the whole mechanism fully functional and ready to go? It does not go against reason to believe that intricate design, especially when irreducible complexity is involved, demands an intelligent Designer. On the other hand, it does go against reason to "believe" that natural, pure chance changes in DNA (mutations) are capable of producing a process that is so irreducibly complex such as "simple" blood clotting.

Clearly, the irreducible complexity inherent in many biochemical systems not only precludes the possibility that they evolved by Darwinian natural selection, but actually suggests the strong conclusion that intelligent design is necessary.

Yet the amazing complexity of these systems has gone largely unnoticed and greatly unreported to the general public. There is a great silence. Behe gives us a possible reason why, he says:

"Why does the scientific community not greedily embrace its startling discovery? Why is the observation of design handled with intellectual gloves? The dilemma is that while one side of the elephant is labeled intelligent design, the other side might be labeled God." (Darwin's Black Box, p.233).

"There is no doubt that the pathways described by Behe are dauntingly complex, and their evolution will be hard to unravel. Unlike anatomical structures, the evolution of which can be traced by fossils, biochemical evolution must be reconstructed from highly evolved living organisms, and we may forever be unable to envisage the first proto-pathways. It is not valid, however, to assume that, because one man cannot imagine such pathways, they could not have existed."

Doesn't that rise the question if it is valid to assume that there is no Designer, because certain scientists cannot 'imagine such pathways' purely on hypothetical grounds? It would be fair and honest to review the macro-evolution theory in the light of modern-day discoveries. Irreducible complexity certainly stands out as a large obstacle for evolution. The simplicity of the idea of design has always disturbed scientists, claiming that this kind of 'simple thinking' is not scientific. But how 'simple' would believing in design be? The process of designing is intricate, fascinating and complex. Many pro-design scientists are studying the same thing as their pro-evolution colleagues. While the one group attributes this to a Designer, the other group attributes it to a process called 'natural selection'. Let the facts prove which explanation would be most justifiable.

With gratitude to Access Research Network. Visit their website here...