Irreducible complexity

Irreducible complexity is a controversial concept invoked in support of intelligent design which claims that the generally accepted scientific theory that life evolved through biological evolution by natural selection is incomplete and flawed and that some additional mechanism is required to explain the origins of life. 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 was popularized by Lehigh University biochemist and Fellow of the Discovery Institute 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. With this argument, the book in effect supports what is known as intelligent design, a form of the argument from design, which is one of the arguments for the existence of a supernatural deity.

In 2001, Michael Behe admitted that his work had a "defect" and does not actually address "the task facing natural selection." Furthermore, the concept of irreducible complexity is ignored or rejected by the majority of the scientific community. This rejection stems from the following: the concept utilises an argument from ignorance, Behe fails to provide a testable hypothesis, and there is a lack of evidence in support of the concept. As such, irreducible complexity is seen by the supporters of evolutionary theory as an example of creationist pseudoscience, amounting to a God of the gaps argument.

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 are no peer-reviewed articles supporting his argument that certain complex molecular structures are "irreducibly complex." The result of the trial was the ruling that "intelligent design is not science and is essentially religious in nature."

Irreducible complexity (IC)

An early concept of irreducibly complex systems comes from Ludwig von Bertalanffy, a 20th Century Austrian biologist. 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. Systems theory remained popular among social sciences long after its demise in the physical and biological sciences. Michael Behe uses 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 "create" 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—all of which must be in place for the mousetrap to work. 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.

Criticism

The irreducible complexity argument also assumes that the necessary parts of a system have always been necessary, and therefore could not have been added sequentially. But 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 simpler systems that utilize fewer parts. These systems may have had even simpler precursors that are now extinct.

Perhaps most importantly, potentially viable evolutionary pathways have been proposed for allegedly irreducibly complex systems such as blood clotting, the immune system and the flagellum, 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 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. 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 results 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 and an 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.

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)

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)

Stated examples

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

Flagella

Main article: Evolution of 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. The basal body of the flagella has been found to be similar to the Type III secretion system (TTSS), which many bacteria use to secrete toxins. This example of cooption is regarded as strong evidence against Behe's most developed example of irreducible complexity. However, a genetic study of Yersinia pestis bacteria has shown their TTSS is a degenerated flagellum. The bacteria have lost the ability to completely build the flagellum, though they own the complete set of genes for it.

Additionally, the argument regarding the complexity of the flagellum is being disproven by additional scientific experiments. Kenneth Miller, a professor of cell biology at Brown University and other evolutionary researchers have noticed that the flagellum resembled a needle-like structure that bacteria such as salmonella use to inject toxins into living 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. It also suggests how the marvelously complex flagellum could have evolved from simpler forms. This has caused Miller to note that, "The parts of this supposedly irreducibly complex system actually have functions of their own.”

Blood clotting cascade

The blood clotting cascade in vertebrates is another complex biological pathway that is given as an example of irreducible complexity.

Forerunners

The argument from irreducible complexity is a descendant of the teleological argument for God (the argument from design or argument from complexity). This states that because certain things in nature are very complicated, they must have been designed, just as the existence of a watch implies the existence of a watchmaker (in William Paley's famous argument of 1802). This argument has a long history and can be traced back at least as far as Cicero's De natura deorum, ii. 34 (see Hallam, Literature of Europe, ii. 385, note).

While he did not originate the term, Charles Darwin identified the argument as a testable 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 and sexual selection. The argument from irreducible complexity attempts to demonstrate that certain biological features cannot be purely the product of Darwinian evolution.

Criticisms of irreducible complexity

There has been much scientific opposition to the irreducible complexity, with one science writer calling it a "full-blown intellectual surrender strategy." 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. A current article in Nature, Vol. 439, pp. 318-321 (Jan 19, 2006) by M. Brazeau and P. Ahlberg demonstrates intermediate states leading toward the development of the ear in a Devonian fish (about 360 million years ago). Furthermore, recent research shows that viruses play a heretofore unexpectedly great role in evolution by mixing and matching genes from various hosts.

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.

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. They also assert that what evolved biochemical and molecular systems actually exhibit is redundant complexity \u2014 a kind of complexity that is the product of an evolved biochemical process. They argue that Behe overestimates the significance of irreducible complexity because his simple, linear view of biochemical reactions results 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 and an over-reliance of overly-simplistic metaphors such as his mousetrap.

There has also been a theory that challenges irreducible complexity called facilitated variation. The theory has been presented 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. Their book was published in 2005.

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.

Handicaps and sexual selection

According to critics, another overlooked source of "irreducibly complex" features in a sexually reproducing organism is the Handicap principle. Sexual selection often favors those who can demonstrate to their mates a surplus of energy by maintaining a feature or behavior that is unnecessary for basic survival — sometimes even a hindrance. Examples include certain horns and antlers, display feathers, skin or hair colors and patterns, bony structure, scents, songs, symmetry, and elaborate ritualistic behavior. It is not unreasonable to imagine a handicapping feature eventually developing a useful purpose in a changing environment or for two or more handicapping features to become useful when combined. Conversely, a useful feature may evolve to become a handicapping feature, but through sexual selection the feature is passed through generations to again become useful in a completely different context. In this new context it may seem impossible to us that it was naturally selected to its purpose.

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

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 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."

Behe's own Criticisms

In his "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.

The Designer and Irreducible Complexity

Intelligent design proponents attribute to an intelligent designer those biologcial structures they believe are irreducibly complex and where a natural explanation is absent or insufficient to account for them. Eugenie Scott, along with Glenn Branch and other critics, has argued that many points raised by intelligent design proponents are arguments from ignorance. Critics view irreducible complexity as a special case of the "complexity indicates design" claim and thus see it as a argument from ignorance and God of the gaps argument.

Claimed significance

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.

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."

Irreducible complexity is at root 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 that current evolutionary theory and intelligent design are the only two valid models to explain life.

See also

• Intelligent design
• Specified complexity

External links

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

In support

• Michael J. Behe home page
• Institute for Creation Research
• Irreducible Complexity Revisited
• Behe's Reply to his Critics
• Dr. Thomas Gold opines about new scientific ideas.
• Argument: 'Irreducible complexity'
• Origins - Intelligent Design

In opposition

• "Unlocking the Mystery of Life" - The bacterial motor video review
• Behe, Biochemistry, and the Invisible Hand
• Facilitated Variation
• Darwin vs. Intelligent Design (again), by H. Allen Orr (review of Darwin's Black Box)
• 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.)
  • Discussion of the Bombardier Beetle at Talk.origins
• TalkDesign.org (sister site to talk.origins 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 reducibly complex mousetrap (graphics-intensive, requires JavaScript)
• 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)
• Unlocking cell secrets bolsters evolutionists (Chicago Tribune)

Notes and references

• Behe, Michael (1996). Darwin's Black Box. New York: The Free Press. ISBN 0684834936
• Denton, Michael (1986). Evolution: A Theory in Crisis. Adler & Adler.
• Mcnab, Robert M. (2004). Type III flagellar protein export and flagellar assembly Biochim Biophys Acta. 1694(1-3):207-17. Review. PMID: 15546667
• Ruben, J.A.; Jones, T.D.; Geist, N.R.; & Hillenius, W.J. (November 14, 1997). Lung Structure and Ventilation in Theropod Dinosaurs and Early Birds. Science 278 (5341) 1267–1270.
• Sunderland, Luther D. (March 1976). Miraculous Design in Woodpeckers. Creation Research Society Quarterly.
• Testing Darwin Discover Magazine Vol. 26 No. 02 | February 2005