3 Can irreducible complexity be found in nature?

Behe and others, including some evolutionists, have suggested a number of biological features that they believe may be irreducibly complex.

3.1 The bombardier beetle

The bombardier beetleBombardier beetles : Eukaryota : Animalia : Arthropoda : Hexapoda : Insecta : Pterygota : Neoptera : Endopterygota : Coleoptera : Adephaga : Carabidae s: Brachinini, Paussini, Ozaenini, or Metriini Bombardier beetles are ground beetles ( Carabidae) in the (Genus Brachinus ) is an organism that has become somewhat of a standard bearer for irreducible complexity. These beetles have three chambers in their abdomen, two of which contain liquids that are chemically stable, but when mixed they create an incendiary combination. The third chamber is a reaction chamber into which the two chemicals are squeezed when danger is near, and then expelled explosively towards the perceived danger. Irreducible complexity asserts that, in order for any of the components of the system to function, all components of the system must have been present.

3.2 The bird lung

The bird lung is different from other lungs, such as the reptile lung (which evolutionists believe it evolved from). Proponents of irreducible complexity argue that the transition from a reptile lung ( bellows lung ) to a bird lung ( circulatory lung ) is unlikely since intermediate stages would be a detriment to the organism.

Recently, conventional wisdom has held that birds are direct descendants of theropod dinosaurs. However, the apparently steadfast maintenance of hepatic-piston diaphragmatic lung ventilation in theropods throughout the Mesozoic poses a fundamental problem for such a relationship. The earliest stages in the derivation of the avian abdominal airsac system from a diaphragmatic-ventilating ancestor would have necessitated selection for a diaphragmatic hernia [i.e. hole] in taxa transitional between theropods and birds. Such a debilitating condition would have immediately compromised the entire pulmonary ventilatory apparatus and seems unlikely to have been of any selective advantage. (Michael Denton)

3.3 Flagella

The flagella of certain bacteria constitute a molecular motor requiring the interaction of about 40 complex protein parts, and the absence of any one of these proteins cause the flagella to fail to function. Behe holds that the flagellum "engine" is irreducibly complex because if we try to reduce its complexity by positing an earlier and simpler stage of its evolutionary development, we get an organism which functions improperly.

This topic is discussed in the article on the Evolution of flagellaThe evolution of flagella is of great interest to biologists because the three known varieties of flagella ( eukaryotic, bacterial, and archaebacterial) each represent an extremely sophisticated cellular structure that requires the interaction of many dif.

3.4 Certain biological pathways

The biochemistry of light detection requires complex interactions among many different molecules, each performing a very specialized job. Eliminating even one component of the biological pathway can destroy the ability to detect light.

The blood clotting cascadeThe word cascade can have many meanings: In biochemistry, a cascade is a consecutive series of chemical reactions. There are several important biochemical cascade reactions in biochemistry, including the enzymatic cascades, like the coagulation cascade an in vertebrates is another complex biological pathway that is given as an example of irreducible complexity.

One evolutionary mechanism that may result in complex biological pathways such as these is " biochemical scaffolding ", where a set of biochemical reactions are used to build up a pathway and then are discarded, in much the same way that a building is built from the bottom up even though removing any of the columns would cause the building to collapse.

3.5 Other examples

• The cilium
• The ATP synthase molecule
• The woodpecker's hyoid
• The eyes of Strepsiptera
• Antibody example (see below)
• An artificially-evolved http://www.newscientist.com/hottopics/ai/primordial.jsp voice recognition circuit

3.6 Disputed examples

There is some research to indicate possible evolutionary mechanisms for the development of some purportedly irreducible systems. However, the research is not yet conclusive.

• The vertebrate eye
• Feathers

4 Opposition

It may be that irreducible complexity does not actually exist in nature: that the examples given by Behe and others are not in fact irreducibly complex, but can be explained in terms of simpler precursors. Thus they would either be merely very complex, or they would be misunderstood or misrepresented.

The precursors of complex systems, when they are not useful in themselves, may be useful to perform other, unrelated functions. Evolutionary biologists argue that evolution often works in this kind of blind, haphazard manner in which the function of an early form is not necessarily the same as the function of the later form. The mammalian ear (derived from a jawbone) and the panda's thumb (derived from a wrist bone spur) are considered classic examples.

Evolution can act to simplify as well as to complicate. This raises the possibility that apparently irreducibly complex biological features may have been achieved with a period of increasing complexity, followed by a period of simplification. By analogy, stone arches are irreducibly complex — if you remove any stone the arch will collapse — yet we build them easily enough, one stone at a time, by building over scaffolding that is removed afterward. Similarly, naturally occurring arches of stone are formed by weathering away bits of stone from a large concretion that has formed previously.

Behe has been accused of using an argument by lack of imagination, or constructing a " God of the gaps". Behe himself acknowledges that simply because scientists cannot currently see how an "irreducibly complex" organism could evolve, it does not prove that there is no possible way for it to have occurred.

4.1 Gradual Replacement

Arguments for irreducibility often assume that things started out the same way they ended up (as we see them now). However, that may not necessarily be the case.

Regarding Behe's antibody example, we have the "marker" substance and the "killer" substance, that together hunt and kill marked invaders. Behe is saying that by themselves, the marker and the killer are useless, and thus must have been made at the same time. The killer cannot kill what it cannot find and the marker has no ability to kill even if it can find a target.

However, under gradual replacement, a different marker may have started out as an independent hunter AND killer. After a while, a helper killer joined this army because it had some nice specialties. However, this second killer still depended on the first one to find the target. Thus the first killer served as both a marker and a killer, and the second killer is just a killer, relying on the first to hunt.

Perhaps over time it is more efficient to have the 2nd killer specialize in killing and the first specialize in marking, and so the first killer is replaced by a similar substance that is merely a marker (perhaps a better marker than the first dual-purpose one).

Thus, each step is an advantage, yet the final result is a dependent pair that does not resemble the proto-killer. This example can be laid out as:

A = original killer and marker

K = second killer

M = replacement marker

1. A
2. AK
3. AMK
4. MK

All we see today is "MK". Opponents of irreducible complexity state that Behe erroneously assumes that if the structure ended up MK, then it must have started out as M or K by themselves.

5 Falsifiability and experimental evidence

Some critics, such as Jerry Coyne (professor of evolutionary biology at the University of Chicago) and Eugenie Scott (pro-evolution activist, Executive Director at the National Center for Science Education) have argued that the concept of irreducible complexity, and more generally, the theory of Intelligent Design is not falsifiable, and therefore, not scientific.

Behe argues that the theory that irreducibly complex systems could not have been evolved can be falsified by an experiment where such systems are evolved. For example, he posits taking bacteria with no flagella and imposing a selective pressure for mobility. If, after a few thousand generations, the bacteria evolved the bacterial flagellum, then Behe believes that this would refute his theory.

Other critics take a different approach - pointing to experimental evidence that they believe falsifies the argument for Intelligent Design from irreducible complexity. For example, Kenneth Miller cites the lab work of Barry Hall on E. coli, which he presents as conclusive evidence that "Behe is wrong".

6 Significance of irreducible complexity, if found

Behe argues that organs and biological features which are irreducibly complex cannot be wholly explained by current models of evolution. He argues that:

"An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional".

Irreducible complexity is not an argument that evolution does not occur, but rather an argument that it is incomplete. If irreducible complexity is found and it cannot be wholly explained by current models of evolution, then, it is argued, alternative models may be considered such as:

• Intelligent Design - the argument that irreducible complexity occurs through the input of some "intelligent designer". One example of an Intelligent Design theory is Creationism.
• Francis Crick's suggestion that life on Earth may have been seeded by aliens.
• Stuart Kauffman's complexity theory, which promotes self-organisation as an additional factor in producing the complexity of biological systems and organisms.
• The hypothesis of quantum evolution.

7 External links

• Kenneth Einar Himma, "Design Arguments for the Existence of God", Internet Encyclopedia of Philosophy

7.1 Pro-irreducible complexity

• Michael J. Behe home page

7.2 Anti-irreducible complexity

• Talk.origins archive (see talk.origins)
  • Irreducible Complexity and Michael Behe: Do Biochemical Machines Show Intelligent Design?
  • Darwin's Black Box: Irreducible Complexity or Irreproducible Irreducibility? by Keith Robinson
  • Is the Complement System Irreducibly Complex? by Mike Coon
  • Genetic Algorithms (Genetic algorithms have produced irreducibly complex solutions to real problems)
  • Index to Creationism Claims: Claim CB200
    • Claim CI102
• TalkDesign.org (sister site to talk.origins archive on intelligent design
  • Irreducible complexity demystified by Pete Dunkelberg.
• Kenneth Miller's textbook website
  • A Darwinian explanation of the blood clotting cascade
• A reducibly complex mousetrap (graphics-intensive, requires Javascript)
• Researchers provide concrete evidence about how the human eye evolved

8 References

• Luther D. Sunderland. "Miraculous Design in Woodpeckers", Creation Research Society Quarterly, March 1976.
• Michael Behe, " Darwin's Black Box " (New York: The Free Press, 1996, BooksEnthsiast.com).
• Ruben, J.A., Jones, T.D., Geist, N.R., and Hillenius, W.J., Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds, Science 278(5341):1267–1270, 14 November 1997.
• Dr Michael Denton, M.D., Ph.D. "Evolution: A Theory in Crisis", Adler & Adler (1996).

intelligent design

<Hide>