Irreducible complexity

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Irreducible complexity is the controversial idea that certain biological systems are too complex to have evolved naturally from simpler, or "less complete", predecessors, usually based on the idea that a structure's constituent parts would be useless prior to their current state. An "irreducibly complex" system is defined as one that could not function if it were any simpler, and therefore could not possibly have been formed by successive additions to a precursor system with the same functionality. The concept is generally used as an argument for the intelligent design of life, and as a counterargument used by creationists against the theory of evolution.

Irreducible complexity is a strongly disputed concept, and is viewed as pseudoscience by the overwhelming majority in the scientific community.[Harvard Science Review] "for most members of the mainstream scientific community, ID is not a scientific theory, but a creationist pseudoscience." [Review of scientists' anti Irreducible Complexity books] in which "pseudoscience" is one of the nicer epithets used. The contempt of the scientific community towards what it sees as anti-science is barely concealed. [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." Irreducible complexity has been rejected on a variety of grounds, such as its utilization of a God of the gaps-style argument from ignorance, its failure to provide a testable or falsifiable hypothesis, and the lack of evidence in support of the claim.

The concept was popularized by Lehigh University biochemist leading intelligent design proponent and Discovery Institute Fellow Michael Behe in his 1996 book Darwin's Black Box, wherein Behe argued that there are biochemical systems which are "irreducibly complex" because he saw no way in which these systems could be broken down into smaller functioning systems. In 2001, Michael Behe admitted that his work had a "defect" and does not actually address "the task facing natural selection".Behe, Michael (2001). [Reply to My Critics]. See also [Behe's testimonial in Kitzmiller v. Dover] Additionally, in the 2005 Kitzmiller v. Dover Area School District trial, Behe testified under oath that irreducible complexity did not rule out known evolutionary mechanisms, and that there existed no peer-reviewed articles supporting his argument that certain complex molecular structures are "irreducibly complex".Behe, Michael 2005 [[Wikisource:Kitzmiller_v._Dover_Area_School_District_4:_whether_ID_is_science#Page_88_of_139|Kitzmiller v. Dover Area School District 4: whether ID is science (p. 88)]] The result of the trial was the ruling that "intelligent design is not science and is essentially religious in nature".[[Wikisource:Kitzmiller_v._Dover_Area_School_District_6:_curriculum,_conclusion#H._Conclusion|Kitzmiller v. Dover Area School District 6: Conclusion, section H]] However, irreducible complexity has remained a popular argument among advocates of intelligent design and other creationists.

Definitions

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 p9)

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.

''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)

History

Forerunners

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's theory of evolution challenges the teleological argument by postulating an alternative explanation to that of an intelligent designer—namely, evolution by natural selection. The argument from irreducible complexity attempts to demonstrate that certain biological features cannot be purely the product of Darwinian evolution.

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 1131792424 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. Jacques Monod's Chance and Necessity provides a good discussion of the "triumph" of the mechanistic view in biochemistry. However, Systems theory remained popular in the social sciences long after its demise in the physical and biological sciences.

Origins

Michael Behe's controversial book Darwin's Black Box popularized the concept of irreducible complexity.

Michael Behe 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.

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 not able 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.

Michael Behe believes that many aspects of life show evidence of design, using the mousetrap in an analogy which others dispute.[A reducibly complex mousetrap] (graphics-intensive, requires JavaScript)

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 there is no scientific literature on the evolution of biochemical systems is demonstrably false.

In his "Reply to My Critics", Behe, Michael (2001). [Reply to My Critics]. Behe admitted 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". 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 that article, Behe wrote that he hoped to "repair this defect in future work". However, such work has not yet been published.

Stated examples

Blood clotting cascade

The blood clotting cascade in vertebrates is another complex biological pathway 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. 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.

Eye

The human eye, demonstrating the iris.

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 oft-quoted passage from The Origin of Species, Charles Darwin himself acknowledged the eye's development as a major unanswered question for his theory, noting that "to suppose that the eye... could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree". However, he also noted that, if evidence could be found for the gradual evolution of the eye, "the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real".Darwin, Charles (1859). On the Origin of Species. London: John Murray.

The eyes of vertebrates (left) and invertebrates such as the octopus (right) developed independently: vertebrates evolved an inverted retina with a blind spot over their optic disc, whereas octopi avoided this with a non-inverted retina.

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).

Current evidence indicates 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 in order to focus the light, 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.

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 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 secretion system (TTSS), a needle-like structure that pathogenic germs such as salmonella use to inject toxins into living eucaryote cells. The needle's base has many elements in common with the flagellum, but it is missing most of the proteins that make a flagellum work. Thus, this system seems to negate the claim that taking away any of the flagellum's parts would render it useless. This has caused Miller to note that, "The parts of this supposedly irreducibly complex system actually have functions of their own." Manier, Jeremy [Unlocking cell secrets bolsters evolutionists] (Chicago Tribune, 2006 Feb 13)

Criticisms and contrary evidence

Reducibility of \"irreducible\" systems

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 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, it has been claimed that computer simulations of evolution demonstrate that it is possible for irreducible complexity to evolve naturally.

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 be spayed. Evolution has endowed it with redundant eyes, so if one eye goes blind, the cat can still catch mice. 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.

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. 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 the Graduate School, 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

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 claims 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 second 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

# A

# AK

# AMK

# MK

Handicaps and sexual selection

Imagine that a spontaneous hole formed in a pre-bird lizard's lung and quickly became a demonstration to potential mates that it has "energy to burn" because it was successful despite its handicap. Perhaps it evolved as a mating display because it made a distinctive sound like a frog's mating display. That feature could have been maintained by sexual selection long enough to have evolved into the modern bird lung we see today.

However, this objection accounts for relatively few of the virtually unlimited potential intermediate stages of evolving features.

Falsifiability and experimental evidence

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 asserts is evidence that "Behe is wrong."

Argument from ignorance

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 implication 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.

Legal status

In the final ruling of Kitzmiller v. Dover Area School District, Judge Jones specifically mentions of Behe and irreducible complexity[Whether ID is science. Memorandum Opinion, Judge John E. Jones III, Kitzmiller v. Dover Area School District]:

• "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, 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 fiftyeight 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