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The article was written purely from one perspective. I have edited adjectives and added some rebuttals that were glossed over, while leaving the original arguments in place so that both sides can be more full seen. |
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{{Intelligent Design}}
'''Irreducible complexity''' ('''IC''') is a
*{{cite book |last= Smith |first= Jonathan C. |title= Pseudoscience and Extraordinary Claims of the Paranormal: A Critical Thinker's Toolkit |page= 307 |isbn= 1-40518-122-2 |ref= harv}}
*{{cite book |last= Shermer |first= Michael |title= The Skeptic Encyclopedia of Pseudoscience |publisher= ABC-CLIO |___location= Santa Barbara |year= 2002 |isbn= 1-57607-653-9 |page= 450 |ref= harv}}
*{{cite book |last= Shulman |first= Seth |title= Undermining Science |publisher= University of California Press |___location= Berkeley |year= 2008 |isbn= 0-520-25626-3 |page=139}}
*{{cite book |last= Pigliucci |first= Massimo |title= Nonsense on Stilts |publisher= University of Chicago Press |___location= Chicago |year= 2010 |isbn= 0-226-66786-3 |pages=177, 180–183}}</ref> Central to the [[creationism|creationist]] concept of [[intelligent design]], IC is rejected by the
[[Michael Behe]], a professor of biochemistry at Lehigh University, first argued that irreducible complexity made evolution purely through natural selection of random mutations impossible.<ref>*{{cite book |last= Behe |first= Michael |title= Darwin's Black Box |publisher= Free Press |___location= New York |year= 1996 |isbn= 978-0-684-82754-4}}</ref> However,
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."<ref name="dover_behe_ruling"/>
==Definitions==
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[[Georges Cuvier]] applied his principle of the ''correlation of parts'' to describe an animal from fragmentary remains. For Cuvier, this was related to another principle of his, the ''conditions of existence'', which excluded the possibility of [[transmutation of species]].<ref>See especially chapters VI and VII of {{cite book|author=William Coleman |title=Georges Cuvier, Zoologist: A Study in the History of Evolution Theory |___location=Cambridge, Massachusetts |publisher=Harvard University Press |year=1964}} See also the discussion of these principles in the Wikipedia article on Cuvier.</ref>
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."<ref>[[Charles Darwin|Darwin, Charles]] (1859). ''[[The Origin of Species|On the Origin of Species]]''. London: John Murray. [http://darwin-online.org.uk/content/frameset?itemID=F373&viewtype=side&pageseq=207 page 189, Chapter VI]</ref> 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. By
In the late 19th century, in a dispute between supporters of the adequacy of [[natural selection]] and those who held for [[inheritance of acquired characteristics]], one of the arguments made repeatedly by [[Herbert Spencer]], and followed by others, depended on what Spencer referred to as ''co-adaptation'' of ''co-operative'' parts, as in: "We come now to Professor [[August Weismann|Weismann]]'s endeavour to disprove my second thesis — that it is impossible to explain by natural selection alone the co-adaptation of co-operative parts. It is thirty years since this was set forth in "The Principles of Biology." In §166, I instanced the enormous horns of the extinct [[Irish elk]], and contended that in this and in kindred cases, where for the efficient use of some one enlarged part many other parts have to be simultaneously enlarged, it is out of the question to suppose that they can have all spontaneously varied in the required proportions."<ref>Page 594 in: {{cite journal|author=Herbert Spencer|title=Weismannism Once More|journal=[[The Contemporary Review]]|date= October 1894|volume=66 |pages=592–608}} Another essay of his treating this concept is: {{cite journal|author=Herbert Spencer |title=The Inadequacy of "Natural Selection" |journal=The Contemporary Review |volume= 63 |year=1893 |pages= 153–166}} (Part I: February) and pages 439-456 (Part II: March). These essays were reprinted in {{cite book|author=Herbert Spencer|title=The Works of Herbert Spencer|year=1891|place=London|publisher=Williams and Norgate|volume=17}} (also Osnabrück: Otto Zeller, 1967). See also part III, Chapter XII, §166, pages 449-457 in: {{cite book |author=Herbert Spencer |title= Principles of Biology |year= 1864 |place=London |publisher=Williams and Norgate|volume=I}} And: {{cite journal|journal=[[The Nineteenth Century (periodical)|The Nineteenth Century]] |author=Herbert Spencer|title=The Factors of Organic Evolution |volume=19 |year=1886 |pages=570–589}} (Part I: April) and pages 749-770 (Part II: May). "Factors" was reprinted in pages 389-466 of {{cite book|author=Herbert Spencer|title=The Works of Herbert Spencer|volume=13|___location=London|publisher=Williams and Norgate|year=1891}} (also Osnabrück: Otto Zeller, 1967)= volume 1 of ''Essays: Scientific, Political, and Speculative''.</ref><ref>One example of a response was in Section III(γ) pages 32-42 of {{cite book|author=August Weismann |chapter=The Selection theory |pages=19–65 |title=Darwin and Modern Science: Essays in Commemoration of the Centenary of the Birth of Charles Darwin and of the Fiftieth Anniversary of the Publication of The Origin of Species|editor=[[Albert Charles Seward]]|___location=Cambridge |publisher=Cambridge University Press |year=1909}} See also Chapter VII, §12(1), pages 237-238 in: {{cite book|author=[[J. Arthur Thomson]]|title=Heredity|place=London|publisher=John Murray|year=1908}} Both of these referred to what has become known as the [[Baldwin effect]]. An analysis of both sides of the issue is: {{cite book |author=[[George John Romanes]] |title=Darwin and After Darwin: Post-Darwinian Questions, Heredity, Utility |volume=II |chapter=III: Characters as Hereditary and Acquired (continued) |pages=60–102 |place=London |publisher=Longman, Green |year=1895}}</ref> Darwin responded to Spencer's objections in chapter XXV of ''[[The Variation of Animals and Plants under Domestication]]''.<ref>{{cite book|title=The Variation of Animals and Plants under Domestication|author=Charles Darwin|year=1868|___location=London|publisher=John Murray|chapter=XXV. Laws of Variation ''continued'' - Correlated Variability|volume=2|pages=321–338|url=http://darwin-online.org.uk/content/frameset?keywords=co%20ordinated&pageseq=236&itemID=F877.2&viewtype=text}} especially page 333 and following.</ref> The history of this concept in the dispute has been characterized: "An older and more religious tradition of idealist thinkers were committed to the explanation of complex adaptive contrivances by intelligent design. ... Another line of thinkers, unified by the recurrent publications of Herbert Spencer, also saw [[co-adaptation]] as a composed, irreducible whole, but sought to explain it by the inheritance of acquired characteristics."<ref>Pages 67-68 in: {{cite journal|author=[[Mark Ridley (zoologist)|Mark Ridley]]|title=Coadapatation and the Inadequacy of Natural Selection|journal=British Journal for the History of Science |volume=15|issue=1 |date=March 1982 |pages=45–68 |doi=10.1017/S0007087400018938}}</ref>
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In 1974, [[young Earth creationism|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."<ref>{{cite book |author=[[Henry M. Morris|Morris, Henry]] |title=Scientific creationism |publisher=Creation-Life Publishers |___location=San Diego, Calif |year=1974 |page=59 |isbn=0-89051-003-2 |edition=2nd}}</ref>
A book-length study of a concept similar to irreducible complexity,
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 ...?"<ref>{{cite book |author1=Keough, Mark J. |author2=Geisler, Norman L. |title=The Creator in the courtroom "Scopes II": the 1981 Arkansas creation-evolution trial |publisher=Mott Media |___location=Milford, Mich |year=1982 |page=146 |isbn=0-88062-020-X |url=http://www.antievolution.org/projects/mclean/new_site/docs/geislerbook.htm#Chapter%20Seven}}</ref>
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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."<ref>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)]]</ref> (The judge ruled that "intelligent design is not science and is essentially religious in nature".)<ref>[[s:Kitzmiller v. Dover Area School District/6:Curriculum, Conclusion#H. Conclusion|Kitzmiller v. Dover Area School District 6: Conclusion, section H]]</ref>
According to the theory of evolution, genetic variations occur without specific design or intent. The environment "selects" the variants that have the highest fitness
===The mousetrap example===
[[File:Mausefalle 300px.jpg|thumb|200px|[[Michael Behe]] believes that many aspects of life show evidence of design, using the [[mousetrap]] in an analogy disputed by others.<ref name=trap>[http://udel.edu/~mcdonald/mousetrap.html A reducibly complex mousetrap] (graphics-intensive, requires [[JavaScript]])</ref>]]
Behe uses the mousetrap as an illustrative example of this concept. A mousetrap consists of five interacting pieces: the base, the catch, the spring, the hammer, and the hold-down bar. All of these must be in place for the mousetrap to work, as the removal of any one piece destroys the function of the mousetrap. Likewise, he asserts that 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
In his 2008 book ''[[Only A Theory]]'', biologist [[Kenneth R. Miller]] challenges Behe's claim that the mousetrap is irreducibly complex. Miller
Other systems identified by Miller that include mousetrap components include the following:<ref name= Only/>
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*remove the hold-down bar for use as a toothpick (single element system)
The
Thus the development of the mousetrap, said to consist of five different parts which had no function on their own, has been reduced to one step: the assembly from parts that are already present, performing other functions.
The Intelligent Design argument focuses on the functionality to catch mice. It skips over the case that many, if not all, parts are already available in their own right, at the time that the need for a mousetrap arises.
===Consequences of irreducible complexity===
Supporters of intelligent design 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
Behe's original examples of irreducibly complex mechanisms included the bacterial [[flagellum]] of ''[[Escherichia coli|E. coli]]'', [[coagulation|the blood clotting cascade]], [[cilia]], and the [[adaptive immune system]].
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<blockquote>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.</blockquote>
==Stated examples==
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The process of blood clotting or [[coagulation]] cascade in vertebrates is a complex biological pathway which is given as an example of apparent irreducible complexity.<ref>Action, George [http://www.talkorigins.org/origins/postmonth/feb97.html "Behe and the Blood Clotting Cascade"]</ref>
The irreducible complexity argument
The "improbability argument"
===Eye===
{{Main|Evolution of the eye}}
[[File:Stages in the evolution of the eye.png|thumb|300px|Stages in the evolution of the eye<br/>(a) A pigment spot<br/>(b) A simple pigment cup<br/>(c) The simple optic cup found in [[abalone]]<br/>(d) The complex lensed eye of the marine snail and the octopus]]
The [[eye]] is an 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.<ref name="aig">[[Jonathan Sarfati|Sarfati, Jonathan]] (2000). [http://www.answersingenesis.org/home/area/re2/chapter10.asp Argument: 'Irreducible complexity'], from ''[[Refuting Evolution]]'' ([[Answers in Genesis]]).</ref>{{failed verification|redirects to http://www.answersingenesis.org/get-answers/topic/design-features, an unauthored blog|date=June 2012}}
[[File:Evolution eye.svg|thumb|left|200px|The eyes of vertebrates (left) and invertebrates such as the [[octopus]] (right) developed independently: vertebrates evolved an inverted [[retina]] with a [[blind spot (vision)|blind spot]] over their [[optic disc]], whereas octopuses avoided this with a non-inverted retina.]]
Since Darwin's day,
===Flagella===
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The [[flagella]] of certain bacteria constitute a [[molecular motor]] requiring the interaction of about 40 different protein parts. Behe presents this as a prime example of an irreducibly complex structure defined as "a single system 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", and argues that since "an irreducibly complex system that is missing a part is by definition nonfunctional", it could not have evolved gradually through [[natural selection]].<ref name="Flagellum Unspun"/>
'''Reducible complexity'''.
'''Evolution from Type Three Secretion Systems'''. Scientists regard this argument as having been disproved in the light of research dating back to 1996 as well as more recent findings.<ref name="Flagellum Unspun">Miller, Kenneth R. [http://www.millerandlevine.com/km/evol/design2/article.html The Flagellum Unspun: The Collapse of "Irreducible Complexity"] with reply here [http://www.designinference.com/documents/2003.02.Miller_Response.htm]</ref><ref>{{cite journal |last1=Pallen |first1=M.J. |last2=Matzke |first2=N.J. |year=2006 |title=From ''The Origin of Species'' to the origin of bacterial flagella |journal=Nature Reviews Microbiology |volume=4 |issue= 10|pages=784–790 |publisher= |doi=10.1038/nrmicro1493 |url= |accessdate= |pmid=16953248}}</ref> They point out that the basal body of the flagella has been found to be similar to the [[Type three secretion system|Type III secretion system]] (TTSS), a needle-like structure that pathogenic germs such as ''[[Salmonella]]'' and ''[[Yersinia pestis]]'' use to inject [[toxin]]s 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.<ref>[http://www.youtube.com/watch?v=RQQ7ubVIqo4 Kenneth Miller's The Collapse of Intelligent Design: Section 5 Bacterial Flagellum] (Case Western Reserve University, 2006 January 3)</ref> The TTSS system
Dembski has argued that phylogenetically, the TTSS is found in a narrow range of bacteria which makes it seem to him to be a late innovation, whereas flagella are widespread throughout many bacterial groups, and he argues that it was an early innovation.<ref>[http://www.evolutionnews.org/2010/01/spinning_tales_about_the_bacte031141.html Spinning Tales About the Bacterial Flagellum]</ref><ref>Dembski, [http://www.designinference.com/documents/2005.09.Expert_Rebuttal_Dembski.pdf Rebuttal to Reports by Opposing Expert Witnesses, p. 52]</ref> Against Dembski's argument, different flagella use completely different mechanisms, and publications
==Response of the scientific community==
Like intelligent design, the concept it seeks to support, irreducible complexity has
===Reducibility of "irreducible" systems===
Researchers have proposed
Niall Shanks and Karl H. Joplin, both of [[East Tennessee State University]], have claim that systems satisfying Behe's characterization of irreducible biochemical complexity can arise naturally and spontaneously as the result of self-organizing chemical processes.<ref name="Redundant Complexity">{{cite journal |doi=10.1086/392687 |author1=Shanks, Niall |author2=Joplin, Karl H. |title=Redundant Complexity: A Critical Analysis of Intelligent Design in Biochemistry |journal=Philosophy of Science |year= 1999 |pages= 268–282 |volume= 66 |issue= 2, June |publisher=The University of Chicago Press |jstor=188646}}</ref><!--not working <ref>Niall Shanks and Karl H. Joplin. [http://www.asa3.org/ASA/topics/Apologetics/POS6-99ShenksJoplin.html Redundant Complexity:A Critical Analysis of Intelligent Design in Biochemistry.] East Tennessee State University.</ref>--> 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.▼
▲Niall Shanks and Karl H. Joplin, both of [[East Tennessee State University]], have
In addition, research published in the peer-reviewed journal [[Nature (journal)|''Nature'']] has shown that computer simulations of evolution demonstrate that it is possible for complex features to evolve naturally.<ref>{{cite journal |author= [[Richard Lenski|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|bibcode= 2003Natur.423..139L}}</ref>
In an attempt to debunk the mousetrap analogy, some have compared a mousetrap with a cat. 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, evolutionists assert that the mousetrap (which is not alive) offers better evidence, in terms of irreducible complexity, for intelligent design than the cat; yet proceed to 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.<ref name=trap/><ref name=Only/> But again, Behe's book and website answer this. Conceptual similarities do not prove actual, real precursors. And adjustments to the perifieral anatomy of the cat (ears and tail) are irrelevant to the "irreducible complexity" argument.▼
▲
Evolution
A team led by [[Joseph Thornton (biologist)|Joseph Thornton]], assistant professor of biology at the [[University of Oregon]]'s Center for Ecology and Evolutionary Biology, using techniques for resurrecting ancient genes, reconstructed the evolution of an apparently irreducibly complex molecular system. The April 7, 2006 issue of ''Science'' published this research.<ref name="thornton2006">{{cite journal |vauthors=Bridgham JT, Carroll SM, Thornton JW |title=Evolution of hormone-receptor complexity by molecular exploitation |journal=Science |volume=312 |issue=5770 |pages=97–101 |date=April 2006 |pmid=16601189 |doi=10.1126/science.1123348 |bibcode= 2006Sci...312...97B}}</ref><ref>[http://www.discovery.org/scripts/viewDB/filesDB-download.php?command=download&id=746 Press release] University of Oregon, April 4, 2006.</ref>
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