Irreducible complexity

Irreducible complexity

: "This article covers irreducible complexity as used by those who argue for intelligent design. For information on irreducible complexity as used in Systems Theory, see Irreducible complexity (Emergence)."

Irreducible complexity (IC) is an argument made by proponents of intelligent design that certain biological systems are too complex to have evolved from simpler, or "less complete" predecessors, through natural selection acting upon a series of advantageous naturally occurring chance mutations. It is one of two main arguments intended to support intelligent design, the other being specified complexity.citation | url=| title = Understanding the Intelligent Design Creationist Movement: Its True Nature and Goals. A Position Paper from the Center for Inquiry, Office of Public Policy| first = Barbara| last = Forrest| author-link = Barbara Forrest | date = May,2007| month = May| year = 2007| publisher = Center for Inquiry, Inc.| place = Washington, D.C.|accessdate = 2007-08-22.] It is dismissed by the scientific community ["We therefore find that Professor Behe’s claim for irreducible complexity has been refuted in peer-reviewed research papers and has been rejected by the scientific community at large." ] and intelligent design has been referred to as pseudoscience. ["True in this latest creationist variant, advocates of so-called intelligent design ... use more slick, pseudoscientific language. They talk about things like 'irreducible complexity'" — cite book | last = Shulman | first = Seth | authorlink = | coauthors = | title = Undermining Science: Suppression and Distortion in the Bush Administration| publisher = University of California Press | date = January 8, 2007 | location = | pages = p 13 | url = | doi = | id = | isbn = 0520247027"for most members of the mainstream scientific community, ID is not a scientific theory, but a creationist pseudoscience." [ Trojan Horse or Legitimate Science: Deconstructing the Debate over Intelligent Design] David Mu. Harvard Science Review, Volume 19, Issue 1, Fall 2005. [ Why Intelligent Design Isn't Intelligent Review of: Unintelligent Design, by Mark Perakh] Mark D. Decker. College of Biological Sciences, General Biology Program, University of Minnesota [ Frequently Asked Questions About the Texas Science Textbook Adoption Controversy] "The Discovery Institute and ID proponents have a number of goals that they hope to achieve using disingenuous and mendacious methods of marketing, publicity, and political persuasion. They do not practice real science because that takes too long, but mainly because this method requires that one have actual evidence and logical reasons for one's conclusions, and the ID proponents just don't have those. If they had such resources, they would use them, and not the disreputable methods they actually use."]

Biochemistry professor Michael Behe, the originator of the argument of irreducible complexity, defines an irreducibly complex system as one "composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning". ["Darwin's Black Box: The Biochemical Challenge to Evolution", Michael Behe, 1996, quoted in [ Irreducible Complexity and Michael Behe] (retrieved 8 January 2006)] These examples are said to demonstrate that modern biological forms could not have evolved naturally. Critics consider that most, or all, of the examples were based on misunderstandings of the workings of the biological systems in question, and consider the low quality of these examples excellent evidence for the argument from ignorance. In the 2005 Kitzmiller v. Dover Area School District trial, Behe gave testimony on the subject of irreducible complexity. The court found that "Professor Behe's claim for irreducible complexity has been refuted in peer-reviewed research papers and has been rejected by the scientific community at large."] Nonetheless, irreducible complexity continues to be cited as an important argument by creationists, particularly intelligent design proponents.


The term "irreducible complexity" was originally defined by Behe as:

A single system which is composed of several interacting parts that contribute to the basic function, and where the removal of any one of the parts causes the system to effectively cease functioning. ("Darwin's Black Box" p39 in the 2006 edition)

Supporters of intelligent design use this term to refer to biological systems and organs that they believe could not have come about by any series of small changes. They argue that anything less than the complete form of such a system or organ would not work "at all", or would in fact be a "detriment" to the organism, and would therefore never survive the process of natural selection. Although they accept that some complex systems and organs "can" be explained by evolution, they claim that organs and biological features which are "irreducibly complex" cannot be explained by current models, and that an intelligent designer must have created life or guided its evolution. Accordingly, the debate on irreducible complexity concerns two questions: whether irreducible complexity can be found in nature, and what significance it would have if it did exist in nature.

A second definition given by Behe (his "evolutionary definition") is as follows:

An irreducibly complex evolutionary pathway is one that contains one or more unselected steps (that is, one or more necessary-but-unselected mutations). The degree of irreducible complexity is the number of unselected steps in the pathway.

Intelligent design advocate William Dembski gives this definition:

A system performing a given basic function is irreducibly complex if it includes a set of well-matched, mutually interacting, nonarbitrarily individuated parts such that each part in the set is indispensable to maintaining the system's basic, and therefore original, function. The set of these indispensable parts is known as the irreducible core of the system. (No Free Lunch, 285)



The argument from irreducible complexity is a descendant of the teleological argument for God (the argument from design or from complexity). This states that because certain things in nature are very complicated, they must have been designed. William Paley famously argued, in his 1802 watchmaker analogy, that complexity in nature implies a God for the same reason that the existence of a watch implies the existence of a watchmaker. This argument has a long history, and can be traced back at least as far as Cicero's "De natura deorum" ii.34. [ [ "On the Nature of the Gods"] , translated by Francis Brooks, London: Methuen, 1896.] [See Henry Hallam's "Introduction to the Literature of Europe" part iii chapter iii paragraph 26 footnote "u"]

The idea that the interrelationship between parts of living things would have implications for their origins was raised by writers starting with Pierre Gassendi in the mid 17th century ["De Generatione Animalium", chapter III. Partial translation in: Howard B. Adelmann, "Marcello Malpighi and the Evolution of Embryology" Ithaca, New York, Cornell University Press, 1966, volume 2, pages 811-812.] In the late 17th century, Thomas Burnet referred to "a multitude of pieces aptly joyn’d" to argue against the eternity of life. [ [ "The Sacred Theory of the Earth"] , 2nd edition, London: Walter Kettilby, 1691. Book I Chapter IV page 43] In the early 18th century, Nicolas Malebranche ["De la recherche de la verité" 6.2.4, 6th edition, 1712. English translation "The Search after Truth", tr. and ed. Thomas M. Lennon and Paul J. Olscamp, Cambridge University Press, 1997, ISBN 0-521-58004-8. See page 465.] used this idea to argue in favor of preformation (see homunculus), rather than full development (see epigenesis), of the individual embryo; and a similar argument about the origins of the individual was made by other 18th century students of natural history. Chapter XV of Paley's "Natural Theology" discusses at length what he called "relations" of parts of living things as an indication of their design. [ William Paley: "Natural Theology; or, Evidences of the Existence and Attributes of the Deity. Collected from the Appearances of Nature" 12th edition, 1809] ] In a different application, in the early 19th century Georges Cuvier used the concept of "correlation of parts" in establishing the anatomy of animals from fragmentary remains. [Andrew Pyle, Malebranche on Animal Generation: Preexistence and the Microscope, in Justin E.H. Smith, ed. (2006) "The Problem of Animal Generation in Early Modern Philosophy" ISBN 0-521-84077-5, pg 202-203] [ [ The Chicken or the Egg] ]

While he did not originate the term, Charles Darwin identified the argument as a possible way to falsify a prediction of the theory of evolution at the outset. In "The Origin of Species", he wrote, "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case." [Darwin, Charles (1859). "On the Origin of Species". London: John Murray. [ page 189, Chapter VI] ] Darwin's theory of evolution challenges the teleological argument by postulating an alternative explanation to that of an intelligent designer—namely, evolution by natural selection.Clarifyme|date=March 2008 The argument from irreducible complexity attempts to demonstrate that certain biological features cannot be purely the product of Darwinian evolution.

Hermann Muller, in the early 20th century, discussed a concept similar to irreducible complexity. However, far from seeing this as a problem for evolution, he described the "interlocking" of biological features as a consequence to be expected of evolution, which would lead to irreversibility of some evolutionary changes. [ [ Hermann J. Muller: Genetic variability, twin hybrids and constant hybrids, in a case of balanced lethal factors, "Genetics" 1918 3: 422-499] , especially pages 463-464.] He wrote, "Being thus finally woven, as it were, into the most intimate fabric of the organism, the once novel character can no longer be withdrawn with impunity, and may have become vitally necessary." [Hermann J. Muller: Reversibility in evolution considered from the standpoint of genetics, "Biological Reviews of the Cambridge Philosophical Society", 4(3) 1939, 261-280, quotation from page 272.]

In 1974, Young Earth Creationist Henry M. Morris introduced a similar concept in his book "Scientific Creationism" in which he wrote; "This issue can actually be attacked quantitatively, using simple principles of mathematical probability. The problem is simply whether a complex system, in which many components function unitedly together, and in which each component is uniquely necessary to the efficient functioning of the whole, could ever arise by random processes." ["Scientific Creationism", edited by Henry M. Morris, Master Books; General ed., 2nd ed edition (October 1974), ISBN-10: 0890510032 , page 59.]

In 1981, Ariel Roth, in defense of the creation science position in the trial McLean v. Arkansas, said of "complex integrated structures" that "This system would not be functional until all the parts were there ... How did these parts survive during evolution ...?" [Normal L. Geisler, A. F. Brooke II, Mark J. Keough, "The Creator in the Courtroom: "Scopes II", Milford, MI: Mott Media, 1982. ISBN 978-0-88062-020-8, p. 146 [] ]

In 1985 Cairns-Smith wrote of "interlocking", "How can a complex collaboration between components evolve in small steps?" and used the analogy of the scaffolding in building an arch: "Surely there was 'scaffolding'. Before the multitudinous components of present biochemistry could come to lean together "they had to lean on something else." [Pages 39, 58-64, A. G. Cairns-Smith, "Seven Clues to the Origin of Life: A Scientific Detective Story", Cambridge: Cambridge University Press, 1985. ISBN 0-521-27522-9]

An essay in support of creationism published in 1994 referred to bacterial flagella as showing "multiple, integrated components", where "nothing about them works unless every one of their complexly fashioned and integrated components are in place" and asked the reader to "imagine the effects of natural selection on those organisms that fortuitously evolved the flagella ... without the concommitant ["sic"] control mechanisms". [Richard D. Lumsden,"Not So Blind A Watchmaker", Creation Research Society Quarterly, vol. 31 no. 1 (June, 1994), pages 13-22. Quotations from pages 13 and 20.] [Eugenie C. Scott and Nicholas J. Matzke, Biological design in science classrooms, "Proceedings of the National Academy of Sciences", vol. 104 suppl. 1 (May 15, 2007), pp. 8669-8676. See page 8672.]

An early concept of irreducibly complex systems comes from Ludwig von Bertalanffy, a 20th-century Austrian biologist. [Ludwig von Bertalanffy (1952). "Problems of Life: An Evaluation of Modern Biological and Scientific Thought, pg 148" ISBN 1-131-79242-4] He believed that complex systems must be examined as complete, irreducible systems in order to fully understand how they work. He extended his work on biological complexity into a general theory of systems in a book titled "General Systems Theory". After James Watson and Francis Crick published the structure of DNA in the early 1950s, General Systems Theory lost many of its adherents in the physical and biological sciences. ["Chance and Necessity: An Essay on the Natural Philosophy of Modern Biology", Jacques Monod, 1971] However, Systems theory remained popular in the social sciences long after its demise in the physical and biological sciences.


Michael Behe developed his ideas on the concept around 1992, in the early days of the 'wedge movement', and first presented his ideas about "irreducible complexity" in June 1993 when the "Johnson-Behe cadre of scholars" met at Pajaro Dunes in California.Barbara Forrest, [ The Wedge at Work] . Talk Reason, Chapter 1 of the book "Intelligent Design Creationism and Its Critics" (MIT Press, 2001), Retrieved 2007-05-28.] He set out his ideas in the second edition of "Of Pandas and People" published in 1993, extensively revising Chapter 6 "Biochemical Similarities" with new sections on the complex mechanism of blood clotting and on the origin of proteins. [ [ The New Pandas: Has Creationist Scholarship Improved?] Comments on 1993 Revisions by Frank J. Sonleitner (1994)
[ Introduction: Of Pandas and People, the foundational work of the 'Intelligent Design' movement] by Nick Matzke 2004,
[ Design on Trial in Dover, Pennsylvania] by Nicholas J Matzke, NCSE Public Information Project Specialist

He first used the term "irreducible complexity" in his 1996 book "Darwin's Black Box", to refer to certain complex biochemical cellular systems. He posits that evolutionary mechanisms cannot explain the development of such "irreducibly complex" systems. Notably, Behe credits philosopher William Paley for the original concept, not von Bertalanffy, and suggests that his application of the concept to biological systems is entirely original.Intelligent design advocates argue that irreducibly complex systems must have been deliberately engineered by some form of intelligence.

In 2001, Michael Behe wrote: " [T] here is an asymmetry between my current definition of irreducible complexity and the task facing natural selection. I hope to repair this defect in future work." Behe specifically explained that the "current definition puts the focus on removing a part from an already functioning system", but the "difficult task facing Darwinian evolution, however, would not be to remove parts from sophisticated pre-existing systems; it would be to bring together components to make a new system in the first place". In the 2005 Kitzmiller v. Dover Area School District trial, Behe testified under oath that he "did not judge [the asymmetry] serious enough to [have revised the book] yet." [Behe, Michael (2001). [ Reply to My Critics] . See also [ Behe's testimonial in Kitzmiller v. Dover] ]

Behe additionally testified that the presence of irreducible complexity in organisms would not rule out the involvement of evolutionary mechanisms in the development of organic life. He further testified that he knew of no earlier "peer reviewed articles in scientific journals discussing the intelligent design of the blood clotting cascade," but that there were "probably a large number of peer reviewed articles in science journals that demonstrate that the blood clotting system is indeed a purposeful arrangement of parts of great complexity and sophistication." [Behe, Michael 2005 ] (The result of the trial was the ruling that "intelligent design is not science and is essentially religious in nature".) []

According to the theory of evolution, genetic variations occur without specific design or intent. The environment "selects" the variants that have the highest fitness, which are then passed on to the next generation of organisms. Change occurs by the gradual operation of natural forces over time, perhaps slowly, perhaps more quickly (see punctuated equilibrium). This process is able to adapt complex structures from simpler beginnings, or convert complex structures from one function to another (see spandrel). Most intelligent design advocates accept that evolution occurs through mutation and natural selection at the "micro level", such as changing the relative frequency of various beak lengths in finches, but assert that it cannot account for irreducible complexity, because none of the parts of an irreducible system would be functional or advantageous until the entire system is in place.

Behe uses the mousetrap as an illustrative example of this concept. A mousetrap consists of several interacting pieces—the base, the catch, the spring, the hammer. Behe contends that all of these must be in place for the mousetrap to work, and that the removal of any one piece destroys the function of the mousetrap. Likewise, biological systems require multiple parts working together in order to function. Intelligent design advocates claim that natural selection could not create from scratch those systems for which science is currently unable to find a viable evolutionary pathway of successive, slight modifications, because the selectable function is only present when all parts are assembled. Behe's original examples of irreducibly complex mechanisms included the bacterial flagellum of "E. coli", the blood clotting cascade, cilia, and the adaptive immune system.

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". In the last chapter of "Darwin's Black Box", Behe goes on to explain his view that irreducible complexity is evidence for intelligent design. Mainstream critics, however, argue that irreducible complexity, as defined by Behe, can be generated by known evolutionary mechanisms. Behe's claim that no scientific literature adequately modeled the origins of biochemical systems through evolutionary mechanisms has been challenged byTalkOrigins. [ [ Claim CA350: Professional literature is silent on the subject of the evolution of biochemical systems] TalkOrigins Archive.] [ cite book | last = Behe | first = Michael J. | authorlink = Michael Behe | title = Darwin's black box: the biochemical challenge to evolution | origdate = 1996 | isbn = 0684827549 | pages = 72 | chapter = | quote = "Yet here again the evolutionary literature is totally missing. No scientist has ever published a model to account for the gradual evolution of this extraordinary molecular machine" ] The judge in the Dover trial wrote "By defining irreducible complexity in the way that he has, Professor Behe attempts to exclude the phenomenon of exaptation by definitional fiat, ignoring as he does so abundant evidence which refutes his argument. Notably, the NAS has rejected Professor Behe’s claim for irreducible complexity..." [ Kitzmiller v. Dover Area School District, December 2005. Page 74.]

Stated examples

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

Blood clotting cascade

The blood clotting or coagulation cascade in vertebrates is a complex biological pathway which that is given as an example of apparent irreducible complexity. [Action, George [ "Behe and the Blood Clotting Cascade"] ]

The irreducible complexity argument assumes that the necessary parts of a system have always been necessary, and therefore could not have been added sequentially. However, in evolution, something which is at first merely advantageous can later become necessary. For example, one of the clotting factors that Behe listed as a part of the clotting cascade was later found to be absent in whales, demonstrating that it is not essential for a clotting system. [cite journal | author=Semba U, Shibuya Y, Okabe H, Yamamoto T | title=Whale Hageman factor (factor XII): prevented production due to pseudogene conversion | journal=Thromb Res | year=1998 | pages=31–7 | volume=90 | issue=1 | pmid=9678675 | doi = 10.1016/S0049-3848(97)00307-1 ] Many purportedly irreducible structures can be found in other organisms as much simpler systems that utilize fewer parts. These systems, in turn, may have had even simpler precursors that are now extinct. The "improbability argument" also misrepresents natural selection. It is correct to say that a set of simultaneous mutations that form a complex protein structure is so unlikely as to be unfeasible, but that is not what Darwin advocated. His explanation is based on small accumulated changes that take place without a final goal. Each step must be advantageous in its own right, although biologists may not yet understand the reason behind all of them—for example, jawless fish accomplish blood clotting with just six proteins instead of the full 10. [ [;jsessionid=MJJHNOPOKALE Creationism special: A sceptic's guide to intelligent design] , New Scientist, 9 July 2005]


The eye is a famous example of a supposedly irreducibly complex structure, due to its many elaborate and interlocking parts, seemingly all dependent upon one another. It is frequently cited by intelligent design and creationism advocates as an example of irreducible complexity. Behe used the "development of the eye problem" as evidence for intelligent design in "Darwin's Black Box". Although Behe acknowledged that the evolution of the larger anatomical features of the eye have been well-explained, he claimed that the complexity of the minute biochemical reactions required at a molecular level for light sensitivity still defies explanation. Creationist Jonathan Sarfati has described the eye as evolutionary biologists' "greatest challenge as an example of superb 'irreducible complexity' in God's creation", specifically pointing to the supposed "vast complexity" required for transparency.Sarfati, Jonathan (2000). [ Argument: 'Irreducible complexity'] , from "Refuting Evolution" (Answers in Genesis).]

In an often mis-quoted [ [ CA113.1: Evolution of the eye ] ] passage from "The Origin of Species", Charles Darwin appears to acknowledge the eye's development as a difficulty for his theory. However, the quote in context shows that Darwin actually had a very good understanding of the evolution of the eye. He notes that "to suppose that the eye [...] could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree". Yet this observation was merely a rhetorical device for Darwin. He goes on to explain that if gradual evolution of the eye could be shown to be possible, "the difficulty of believing that a perfect and complex eye could be formed by natural selection [...] can hardly be considered real". He then proceeded to roughly map out a likely course for evolution using examples of gradually more complex eyes of various species. [Darwin, Charles (1859). "On the Origin of Species". London: John Murray. [ pages 186ff, Chapter VI] ]

Since Darwin's day, the eye's ancestry has become much better understood. Although learning about the construction of ancient eyes through fossil evidence is problematic due to the soft tissues leaving no imprint or remains, genetic and comparative anatomical evidence has increasingly supported the idea of a common ancestry for all eyes. [Halder, G., Callaerts, P. and Gehring, W.J. (1995). "New perspectives on eye evolution." "Curr. Opin. Genet. Dev." 5 (pp. 602 –609).] [Halder, G., Callaerts, P. and Gehring, W.J. (1995). "Induction of ectopic eyes by targeted expression of the "eyeless" gene in "Drosophila". "Science" 267 (pp. 1788–1792).] [Tomarev, S.I., Callaerts, P., Kos, L., Zinovieva, R., Halder, G., Gehring, W., and Piatigorsky, J. (1997). "Squid "Pax-6" and eye development." Proc. Natl. Acad. Sci. USA, 94 (pp. 2421–2426).]

As Behe admits, current evidence does suggest possible evolutionary lineages for the origins of the anatomical features of the eye, for example, that eyes originated as simple patches of photoreceptor cells that could detect the presence or absence of light, but not its direction. By developing a small depression for the photosensitive cells, the organisms obtained a better sense of the light's source, and by continuing to deepen the depression into a pit so that light would strike certain cells depending on its angle, increasingly precise visible information was possible. The aperture of the eye was then shrunk so that light is focused, turning the eye into a pinhole camera and allowing the organism to dimly make out shapes—the nautilus is a modern example of an animal with such an eye. Finally, the protective layer of transparent cells over the aperture was differentiated into a crude lens, and the interior of the eye was filled with humours to assist in focusing images. [Fernald, Russell D. (2001). [ The Evolution of Eyes: Why Do We See What We See?] "Karger Gazette" 64: "The Eye in Focus".] [Fernald, Russell D. (1998). "Aquatic Adaptations in Fish Eyes". New York, Springer.] [Fernald, Russell D. (1997). [" The evolution of eyes."] "Brain Behav Evol." 50 (pp. 253–259).] In this way, eyes are recognized by modern biologists as actually a relatively unambiguous and simple structure to evolve, and many of the major developments of the eye's evolution are believed to have taken place over only a few million years, during the Cambrian explosion. [Conway-Morris, S. (1998). "The Crucible of Creation". Oxford: Oxford University Press.] However, according to Behe, the complexity of light sensitivity at the molecular level and the minute biochemical reactions required for those first "simple patches of photoreceptor [s] " still defies explanation.


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 causes 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.

Mainstream scientists regard this argument as having been largely disproved in the light of fairly recent research. [Miller, Kenneth R. [ The Flagellum Unspun: The Collapse of "Irreducible Complexity"] with reply [ here] ] They point out that the basal body of the flagella has been found to be similar to the Type III secretory system (TTSS), a needle-like structure that pathogenic germs such as "Salmonella" and "Yersinia pestis" use to inject toxins into living eucaryote cells. The needle's base has ten elements in common with the flagellum, but it is missing forty of the proteins that make a flagellum work. [ [ Kenneth Miller's The Collapse of Intelligent Design: Section 5 Bacterial Flagellum] (Case Western Reserve University, 2006 January 3)] Thus, this system seems to negate the claim that taking away any of the flagellum's parts would render it useless. This has caused Kenneth Miller to note that, "The parts of this supposedly irreducibly complex system actually have functions of their own." [ [ Unlocking cell secrets bolsters evolutionists] (Chicago Tribune, 2006 February 13)] [ [ Evolution in (Brownian) space: a model for the origin of the bacterial flagellum] (Talk Design, 2006 September)]

Response of the scientific community

Like intelligent design, the concept it seeks to support, irreducible complexity has failed to gain any notable acceptance within the scientific community. One science writer called it a "full-blown intellectual surrender strategy." [Mirsky, Steve [ Sticker Shock: In the beginning was the cautionary advisory] "Scientific American", February 2005]

Reducibility of "irreducible" systems

Potentially viable evolutionary pathways have been proposed for allegedly irreducibly complex systems such as blood clotting, the immune system [Matt Inlay, 2002. " [ Evolving Immunity] ." In "".] and the flagellum, [Nicholas J. Matzke, 2003. " [ Evolution in (Brownian) space: a model for the origin of the bacterial flagellum] ."] [Mark Pallen and Nicholas J. Matzke, 2006, " [ From "The Origin of Species" to the origin of bacterial flagella] ." "Nature Reviews Microbiology", 4(10), 784-790.] which were the three examples Behe used. Even his example of a mousetrap was shown to be reducible by John H. McDonald. If irreducible complexity is an insurmountable obstacle to evolution, it should not be possible to conceive of such pathways—Behe has remarked that such plausible pathways would defeat his argument.

Niall Shanks and Karl H. Joplin, both of East Tennessee State University, have shown that systems satisfying Behe's characterization of irreducible biochemical complexity can arise naturally and spontaneously as the result of self-organizing chemical processes. [Shanks, Niall [ Redundant Complexity:A Critical Analysis of Intelligent Design in Biochemistry] ] [Niall Shanks and Karl H. Joplin. [ Redundant Complexity:A Critical Analysis of Intelligent Design in Biochemistry.] East Tennessee State University.] They also assert that what evolved biochemical and molecular systems actually exhibit is "redundant complexity"—a kind of complexity that is the product of an evolved biochemical process. They claim that Behe overestimated the significance of irreducible complexity because of his simple, linear view of biochemical reactions, resulting in his taking snapshots of selective features of biological systems, structures and processes, while ignoring the redundant complexity of the context in which those features are naturally embedded. They also criticized his over-reliance of overly simplistic metaphors, such as his mousetrap. In addition, research published in the peer-reviewed journal Nature has shown that computer simulations of evolution demonstrate that it is possible for irreducible complexity to evolve naturally. [cite journal | author=Lenski RE, Ofria C, Pennock RT, Adami C | title=The evolutionary origin of complex features | journal=Nature | year=2003 | pages=139–44 | volume=423 | issue=6936 | pmid=12736677 | doi=10.1038/nature01568]

It is illustrative to compare a mousetrap with a cat, in this context. Both normally function so as to control the mouse population. The cat has many parts that can be removed leaving it still functional; for example, its tail can be bobbed, or it can lose an ear in a fight. Comparing the cat and the mousetrap, then, one sees that the mousetrap (which is not alive) offers better evidence, in terms of irreducible complexity, for intelligent design than the cat. Even looking at the mousetrap analogy, several critics have described ways in which the parts of the mousetrap could have independent uses or could develop in stages, demonstrating that it is not irreducibly complex.

Moreover, even cases where removing a certain component in an organic system will cause the system to fail do not demonstrate that the system couldn't have been formed in a step-by-step, evolutionary process. 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.

Evolution can act to simplify as well as to complicate. This raises the possibility that seemingly irreducibly complex biological features may have been achieved with a period of increasing complexity, followed by a period of simplification.

In April 2006 a team led by Joe Thornton, assistant professor of biology at the University of Oregon's Center for Ecology and Evolutionary Biology, using techniques for resurrecting ancient genes, scientists for the first time reconstructed the evolution of an apparently irreducibly complex molecular system. The research was published in the April 7 issue of "Science". [ [ Press release] University of Oregon, April 4, 2006.]

It may be that irreducible complexity does not actually exist in nature, and that the examples given by Behe and others are not in fact irreducibly complex, but can be explained in terms of simpler precursors. There has also been a theory that challenges irreducible complexity called facilitated variation. The theory has been presented in 2005 by Marc W. Kirschner, a professor and chair of Department of Systems Biology at Harvard Medical School, and John C. Gerhart, a professor in Molecular and Cell Biology, University of California, Berkeley. In their theory, they describe how certain mutation and changes can cause apparent irreducible complexity. Thus, seemingly irreducibly complex structures are merely "very complex", or they are simply misunderstood or misrepresented.

Gradual adaptation to new functions

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 term used for this process is "exaptation". The mammalian middle ear (derived from a jawbone) and the panda's thumb (derived from a wrist bone spur) are considered classic examples. A 2006 article in "Nature" demonstrates intermediate states leading toward the development of the ear in a Devonian fish (about 360 million years ago). [cite journal|journal=Nature|volume=439|pages=318–321|date=January 19, 2006|author=M. Brazeau and P. Ahlberg|doi=10.1038/nature04196|issue=7074|title=Tetrapod-like middle ear architecture in a Devonian fish] Furthermore, recent research shows that viruses play a heretofore unexpectedly great role in evolution by mixing and matching genes from various hosts.

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.

Falsifiability and experimental evidence

Some critics, such as Jerry Coyne (professor of evolutionary biology at the University of Chicago) and Eugenie Scott (a physical anthropologist and executive director of 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 flagellum 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 G. Hall] on E. coli, which he asserts is evidence that "Behe is wrong." [Finding Darwin's God Kenneth Miller. Harper Collins, 1999]

Other evidence that irreducible complexity is not a problem for evolution comes from the field of computer science, where computer analogues of the processes of evolution are routinely used to automatically design complex solutions to problems. The results of such Genetic Algorithms are frequently irreducibly complex since the process, like evolution, both removes non-essential components over time as well as adding new components. The removal of unused components with no essential function, like the natural process where rock underneath a natural arch is removed, can produce irreducibly complex structures without requiring the intervention of a designer. Researchers applying these algorithms are automatically producing human competitive designs--but no human designer is required. [ [ 36 Human-Competitive Results Produced by Genetic Programming] ]

Argument from ignorance

Intelligent design proponents attribute to an intelligent designer those biological structures they believe are irreducibly complex and where a natural explanation is absent or insufficient to account for them. [Michael Behe. Evidence for Intelligent Design from Biochemistry. 1996. [] ] However, critics view irreducible complexity as a special case of the "complexity indicates design" claim, and thus see it as an argument from ignorance and God of the gaps argument. [Index to Creationist Claims. Mark Isaak. The Talk.Origins Archive. "Irreducible complexity and complex specified information are special cases of the "complexity indicates design" claim; they are also arguments from incredulity." [] "The argument from incredulity creates a god of the gaps." [] ]

Eugenie Scott, along with Glenn Branch and other critics, has argued that many points raised by intelligent design proponents are arguments from ignorance. [Eugenie C. Scott and Glenn Branch, [ "Intelligent Design" Not Accepted by Most Scientists] , National Center for Science Education website, September 10, 2002.] Behe has been accused of using an "argument by lack of imagination", and 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.

Irreducible complexity is at its core an argument against evolution. If truly irreducible systems were found, the argument is that intelligent design is the correct explanation for their existence. However, this conclusion is based on the assumption that current evolutionary theory and intelligent design are the only two valid models to explain life, a false dilemma. [ [ IC and Evolution] makes the point that: if "irreducible complexity" is tautologically redefined to allow a valid argument that intelligent design is the correct explanation for life then there is no such thing as "irreducible complexity" in the mechanisms of life; while, if we use the unmodified original definition then "irreducible complexity" has nothing whatever to do with evolution.]

Irreducible complexity in the Dover trial

While testifying at the Kitzmiller v. Dover Area School District trial Behe conceded that there are no peer-reviewed papers supporting his claims that complex molecular systems, like the bacterial flagellum, the blood-clotting cascade, and the immune system, were intelligently designed nor are there any peer-reviewed articles supporting his argument that certain complex molecular structures are "irreducibly complex."

In the final ruling of Kitzmiller v. Dover Area School District, Judge Jones specifically singled out Behe and irreducible complexity:]
* "Professor Behe admitted in "Reply to My Critics" that there was a defect in his view of irreducible complexity because, while it purports to be a challenge to natural selection, it does not actually address "the task facing natural selection." and that "Professor Behe wrote that he hoped to "repair this defect in future work..." (Page 73)
* "As expert testimony revealed, the qualification on what is meant by "irreducible complexity" renders it meaningless as a criticism of evolution. (3:40 (Miller)). In fact, the theory of evolution proffers exaptation as a well-recognized, well-documented explanation for how systems with multiple parts could have evolved through natural means." (Page 74)
* "By defining irreducible complexity in the way that he has, Professor Behe attempts to exclude the phenomenon of exaptation by definitional fiat, ignoring as he does so abundant evidence which refutes his argument. Notably, the NAS has rejected Professor Behe’s claim for irreducible complexity..." (Page 75)
* "As irreducible complexity is only a negative argument against evolution, it is refutable and accordingly testable, unlike ID [Intelligent Design] , by showing that there are intermediate structures with selectable functions that could have evolved into the allegedly irreducibly complex systems. (2:15-16 (Miller)). Importantly, however, the fact that the negative argument of irreducible complexity is testable does not make testable the argument for ID. (2:15 (Miller); 5:39 (Pennock)). Professor Behe has applied the concept of irreducible complexity to only a few select systems: (1) the bacterial flagellum; (2) the blood-clotting cascade; and (3) the immune system. Contrary to Professor Behe’s assertions with respect to these few biochemical systems among the myriad existing in nature, however, Dr. Miller presented evidence, based upon peer-reviewed studies, that they are not in fact irreducibly complex." (Page 76)
* "...on cross-examination, Professor Behe was questioned concerning his 1996 claim that science would never find an evolutionary explanation for the immune system. He was presented with fifty-eight peer-reviewed publications, nine books, and several immunology textbook chapters about the evolution of the immune system; however, he simply insisted that this was still not sufficient evidence of evolution, and that it was not "good enough." (23:19 (Behe))." (Page 78)
* "We therefore find that Professor Behe’s claim for irreducible complexity has been refuted in peer-reviewed research papers and has been rejected by the scientific community at large. (17:45-46 (Padian); 3:99 (Miller)). Additionally, even if irreducible complexity had not been rejected, it still does not support ID as it is merely a test for evolution, not design. (2:15, 2:35-40 (Miller); 28:63-66 (Fuller)). We will now consider the purportedly “positive argument” for design encompassed in the phrase used numerous times by Professors Behe and Minnich throughout their expert testimony, which is the “purposeful arrangement of parts.” Professor Behe summarized the argument as follows: We infer design when we see parts that appear to be arranged for a purpose. The strength of the inference is quantitative; the more parts that are arranged, the more intricately they interact, the stronger is our confidence in design. The appearance of design in aspects of biology is overwhelming. Since nothing other than an intelligent cause has been demonstrated to be able to yield such a strong appearance of design, Darwinian claims notwithstanding, the conclusion that the design seen in life is real design is rationally justified. (18:90-91, 18:109-10 (Behe); 37:50 (Minnich)). As previously indicated, this argument is merely a restatement of the Reverend William Paley’s argument applied at the cell level. Minnich, Behe, and Paley reach the same conclusion, that complex organisms must have been designed using the same reasoning, except that Professors Behe and Minnich refuse to identify the designer, whereas Paley inferred from the presence of design that it was God. (1:6- 7 (Miller); 38:44, 57 (Minnich)). Expert testimony revealed that this inductive argument is not scientific and as admitted by Professor Behe, can never be ruled out. (2:40 (Miller); 22:101 (Behe); 3:99 (Miller))." (Pages 79-80)

Notes and references

Additional references

* Behe, Michael (1996). "Darwin's Black Box". New York: The Free Press. ISBN 0-684-83493-6
* Denton, Michael (1986). "". Adler & Adler.
* Sunderland, Luther D. (March 1976). Miraculous Design in Woodpeckers. "Creation Research Society Quarterly".
* [ Testing Darwin] Discover Magazine [ Vol. 26 No. 02] | February 2005

External links

* Himma, Kenneth Einar. [ Design Arguments for the Existence of God] . "Internet Encyclopedia of Philosophy".

;In support
* [ Michael J. Behe home page]
* [ About Irreducible Complexity] Discovery Institute
* [ How to Explain Irreducible Complexity -- A Lab Manual] Discovery Institute
* [ Institute for Creation Research] (pdf)
* [ Irreducible Complexity Revisited] (pdf)
* [ Behe's Reply to his Critics] (pdf)
* [ Response to Avida computer simulations]

;In opposition
* [ Behe, Biochemistry, and the Invisible Hand]
* [ Facilitated Variation]
* [ Darwin vs. Intelligent Design (again), by H. Allen Orr (review of Darwin's Black Box)]
* [ archive] (see
** [ 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.)
** [ Discussion of the Bombardier Beetle] at
* [] (sister site to archive on intelligent design)
** [ Irreducible complexity demystified] by Pete Dunkelberg.
* [ Professor Kenneth R. Miller's textbook website]
** [ A Darwinian explanation of the blood clotting cascade]
* [ "The Flagellum Unspun: The Collapse of "Irreducible Complexity"] by Professor Miller
* [ A rigorous mathematical analysis of the concept of irreducible complexity] by Mishkin Berteig.
* [ PDF. 139 page in-depth analysis of Intelligent Design, Irreducible Complexity, and the book "Of Pandas and People" by a judge and based on expert testimony]
* [ Devolution: Why intelligent design isn't] (The New Yorker)
* [,1,1538105.story?page=1&ctrack=1&cset=true Unlocking cell secrets bolsters evolutionists] (Chicago Tribune)
* [ Does irreducible complexity imply Intelligent Design?] by Mark Perakh
* [ Evolution of the Eye (Video)] Zoologist Dan-Erik Nilsson demonstrates eye evolution through intermediate stages with working model. (PBS)

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