Michael Behe, a creationist biochemist and a leading light in the intelligentdesign movement, has argued that there is a kind of complexity in nature called irreducible complexity that can exist only as the result of the activity of an intelligent designer (see chapter 4 in this book). An irreducibly complex system is one consisting of several components, all of which must be present if the system as a whole is to achieve its function. Dembski (1999, 149) has attempted to bolster these claims by arguing that irreducibly complex systems also manifest complex specified information, which, as we have seen, he takes as the hallmark of intelligent design.
Behe has illustrated his idea of irreducible complexity with the example of a mousetrap (1996; 2000; 2001a, 90-101; also see chapter 2 in this book). The mousetrap is a device that has several components, all of which are necessary to catch mice. Assume for the sake of argument that Behe is right about all this. He tells us that, although it is easy to see how such a complex, structured system could arise by intelligent design and construction (it is, after all, a human artifact), it is hard to see how it could have formed through the operation of unintelligent, natural mechanisms. The components of mousetraps will not self-assemble into a functioning mousetrap. Yet Behe intends the mousetrap to serve as a metaphor to illustrate the complexity of chemical reactions. It is far from obvious that chemical reactions with the property of irreducible complexity necessarily result from intelligent design.
In chemistry, self-assembly and self-organization are well-studied phenomena. One of the most famous and well-studied self-organizing chemical systems is the Belousov-Zhabotinski (BZ) reaction. The BZ reaction refers to a set of chemical reactions in which an organic substrate is oxidized in the presence of acid by bromate ions in the presence of a transition metal ion (Tyson
The version of the reaction that one of us (Niall Shanks) has used in classroom demonstrations has the following ingredients: potassium bromate, malonic acid, potassium bromide, cerium ammonium nitrate, and sulfuric acid. When the ingredients are placed in a beaker, the system self-organizes to perform a repeating cycle of reactions. It behaves as a chemical oscillator, and the oscillations can be monitored through cycles of color changes. You can use it to tell the time: it is a watch that forms in a beaker without the help of a watchmaker.
The oscillations result from the chemical system cycling through its component reaction pathways. What do we mean? Suppose the system starts out with a high concentration of bromide ions. In the first group of reactions, bromate and malonic acid are used in a slow reaction to produce bromomalonic acid and water. Bromous acid is one of the reaction intermediates in this pathway. Since the cerium is in the cerous state, the reaction medium remains colorless for this phase of the cycle. As time goes by, the concentration of bromide ions drops to a point at which bromous acid can initiate another mechanism to produce bromomalonic acid and water.
Here, in a fast reaction, bromate, malonic acid, bromous acid (a reaction intermediate from the first pathway), and cerous ions produce ceric ions, bromomalonic acid, and water. The reaction medium turns yellow as cerium enters the ceric state. The pathway also contains an autocatalytic step in which the very presence of bromous acid catalyzes the production of more of itself, so one molecule of bromous acid makes two molecules of bromous acid (this positive feedback effect is why this pathway is fast). As cerous ions are consumed and ceric ions accumulate, a critical threshold is achieved, and a third pathway opens. This pathway consumes bromomalonic acid, malonic acid, and ceric ions to produce carbon dioxide and bromide ions, and to regenerate cer-ous ions, thereby setting the system up for a new cycle (Babloyantz 1986).
Neither the law of conservation of energy nor the second law is violated. To get the oscillations, the system begins far from chemical equilibrium. The oscillations continue until equilibrium is reached: the period gradually gets longer and the color changes become less pronounced as equilibrium is approached. Like more familiar mechanical watches, it runs down unless it is rewound by the addition of more reagents. We have had the system oscillate for more than an hour in typical classroom demonstrations. That the reaction manifests self-organization means nothing more than that the invisible hand of the chemical interactions between molecules, in accord with the laws of chemistry, brings about highly ordered, organized behavior of the system as a whole in the form of regular temporal oscillations. This behavior does not require the intervention of a supernatural intelligence.
The reaction is important because advocates of intelligent-design theory claim that irreducible complexity can appear only as the result of the actions of an intelligent designer who takes the components of the system and assembles them into a functioning whole. In saying this, they evidently mean that they cannot see how unguided mechanisms operating in accord with the laws of nature could give rise to this type of complexity. But the BZ system manifests irreducible complexity, and it does so without any help from intelligent designers (Shanks and Joplin 1999, 2001; Shanks 2001). How can this be so?
Behe (1996, 2000) tells us that three conditions must be satisfied if a system is to be irreducibly complex: (1) the system must have a function, (2) the system must consist of several components, and (3) all the components must be required for the achievement of function. The function of the BZ reaction is to oscillate. The BZ system consists of several key reactions. The key components of the BZ reaction are all needed for the oscillatory cycle to exist. The disruption of any of these key reactions results in the catastrophic failure of the system. The BZ system manifests the same irreducible complexity found in a mousetrap, yet it requires no intelligent designer to arrange the parts into a functioning whole. Apparently, the unguided laws of chemistry will generate irreducibly complex systems.
Yet Behe (2000) has objected to this example. He observes, "Although it does have interacting parts that are required for the reaction, the system lacks the crucial feature—the components are not well-matched" (157). This charge has been reiterated by Dembski (2002b), who tells us that being well-matched means being like the fan belt of a car: "specifically adapted to the cooling fan" (283). Behe (2000) thus objects that the reagents used in the BZ reaction have a wide variety of uses. In his terminology, they have low specificity (158). For example, one ingredient, sodium bromate, is a generalpurpose oxidizing agent; and ingredients other than those we mentioned can be substituted. As we have noted, the term BZ reaction refers to a family of chemical reactions.
If Behe is right, then mousetraps are not irreducibly complex either. Their components also have low specificity. The steel used in their construction has a wide range of uses, as does the wood used for the base. You can substitute plastic for wood and any number of metals for the spring and hammer. Mousetraps are easy to make (which is why they are cheap) and will work with metals manifesting a wide range of tensile strengths. Either the BZ system is an irre-ducibly complex system, or the mousetrap is not a model for irreducible complexity. Take your pick, because you cannot have it both ways.
Moreover, crucial components of Behe's own biochemical examples of irreducible complexity have multiple uses and lack substrate specificity (interact with a wide variety of substrates). For example, plasminogen (a component of the irreducibly complex blood-clotting cascade) has been documented to play a role in a wide variety of physiological processes, ranging from tissue remodeling, cell migration, embryonic development, and angiogenesis as well as wound healing (Bugge et al. 1996). And although Behe (1996) tells us that plasmin (the activated form of plasminogen) "acts as scissors specifically to cut up fibrin clots" (88), we learn in one of the very papers he cites that "plasmin has a relatively low substrate specificity and is known to degrade several common extracellular-matrix glycoproteins in vitro" (Bugge et al. 1996, 709). This component of an irreducibly complex system is evidently nothing like the fan belt of a car "specifically adapted to the cooling fan."
Nor, for that matter, are all the components of the clotting pathway necessary for function. Plasminogen-deficient (Plg—/—) mice (hence, mice lack ing plasmin) have been studied. As noted, plasmin is needed for clot degradation, yet as Bugge at al. (1996) comment,
Plasmin is probably one member of a team of carefully regulated and specialized matrix-degrading enzymes, including serine-, metallo-, and other classes of proteases, which together serve in matrix remodeling and cellular reorganization of wound fields. . . . However, despite slow progress in wound repair, wounds in Plg—/— mice eventually resolve with an outcome that is generally comparable to that of control mice. Thus an interesting and unresolved question is what protease(s) contributes to fibrin clearance in the absence of Plg? (717)
The reasonable conclusion is that, if Behe's examples are indeed examples of irreducibly complex systems, then so is the BZ system. Hence, self-organization is evidently a pathway to irreducible complexity and one that involves no intelligent design, supernatural or otherwise.
Was this article helpful?