This article is about a form of creationism. For generic arguments from "intelligent design", see Teleological argument. For the movement, see Intelligent design movement. For other uses of the phrase, see Intelligent design (disambiguation).
Intelligent design (ID) is a religious argument for the existence of God, presented by its proponents as "an evidence-based scientific theory about life's origins", though it has been discredited as pseudoscience. Proponents claim that "certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection." ID is a form of creationism that lacks empirical support and offers no testable or tenable hypotheses, so is not science. The leading proponents of ID are associated with the Discovery Institute, a fundamentalist Christian and politically conservative think tank based in the United States.[n 1]
Though the phrase "intelligent design" had featured previously in theological discussions of the design argument, the first publication of the term intelligent design in its present use as an alternative term for creationism was in Of Pandas and People, a 1989 creationist textbook intended for high school biology classes. The term was substituted into drafts of the book, directly replacing references to creation science and creationism, after the 1987 United States Supreme Court's Edwards v. Aguillard decision, which barred the teaching of creation science in public schools on constitutional grounds. From the mid-1990s, the intelligent design movement (IDM), supported by the Discovery Institute, advocated inclusion of intelligent design in public school biology curricula. This led to the 2005 Kitzmiller v. Dover Area School District trial in which U.S. District JudgeJohn E. Jones III found that intelligent design was not science, that it "cannot uncouple itself from its creationist, and thus religious, antecedents," and that the school district's promotion of it therefore violated the Establishment Clause of the First Amendment to the United States Constitution.
ID presents two main arguments against evolutionary explanations: irreducible complexity and specified complexity. These arguments assert that certain features (biological and informational, respectively) are too complex to be the result of natural processes. As a positive argument against evolution, ID proposes an analogy between natural systems and human artifacts, a version of the theologicalargument from design for the existence of God.[n 2] ID proponents then conclude by analogy that the complex features, as defined by ID, are evidence of design.[n 3]
Detailed scientific examination has rebutted the claims that evolutionary explanations are inadequate, and this premise of intelligent design—that evidence against evolution constitutes evidence for design—is a false dichotomy. It is asserted that ID challenges the methodological naturalism inherent in modern science though proponents concede that they have yet to produce a scientific theory.
Origin of the concept
See also: Creation science, Teleological argument, and Watchmaker analogy
By 1910 evolution was not a topic of major religious controversy in America, but in the 1920s the Fundamentalist–Modernist Controversy in theology resulted in Fundamentalist Christian opposition to teaching evolution, and the origins of modern creationism. Teaching of evolution was effectively suspended in U.S. public schools until the 1960s, and when evolution was then reintroduced into the curriculum, there was a series of court cases in which attempts were made to get creationism taught alongside evolution in science classes. Young Earth creationists (YEC) promoted creation science as "an alternative scientific explanation of the world in which we live". This frequently invoked the argument from design to explain complexity in nature as demonstrating the existence of God.
The argument from design, the teleological argument or "argument from intelligent design", has been advanced in theology for centuries. It can be summarised briefly as "Wherever complex design exists, there must have been a designer; nature is complex; therefore nature must have had an intelligent designer."[n 2]Thomas Aquinas presented it in his fifth proof of God's existence as a syllogism. In 1802, William Paley's Natural Theology presented examples of intricate purpose in organisms. His version of the watchmaker analogy argued that, in the same way that a watch has evidently been designed by a craftsman, complexity and adaptation seen in nature must have been designed, and the perfection and diversity of these designs shows the designer to be omnipotent, the Christian God. Like creation science, intelligent design centers on Paley's religious argument from design, but while Paley's natural theology was open to deistic design through God-given laws, intelligent design seeks scientific confirmation of repeated miraculous interventions in the history of life. Creation science prefigured the intelligent design arguments of irreducible complexity, even featuring the bacterial flagellum. In the United States, attempts to introduce creation science in schools led to court rulings that it is religious in nature, and thus cannot be taught in public school science classrooms. Intelligent design is also presented as science, and shares other arguments with creation science but avoids literal Biblical references to such things as the Flood story from the Book of Genesis or using Bible verses to age the Earth.
Barbara Forrest writes that the intelligent design movement began in 1984 with the book The Mystery of Life's Origin: Reassessing Current Theories, co-written by creationist Charles B. Thaxton, a chemist, with two other authors, and published by Jon A. Buell's Foundation for Thought and Ethics. Thaxton held a conference in 1988, "Sources of Information Content in DNA", which attracted creationists such as Stephen C. Meyer.
In March 1986, a review by Meyer used information theory to suggest that messages transmitted by DNA in the cell show "specified complexity" specified by intelligence, and must have originated with an intelligent agent. In November of that year, Thaxton described his reasoning as a more sophisticated form of Paley's argument from design. At the "Sources of Information Content in DNA" conference in 1988, he said that his intelligent cause view was compatible with both metaphysical naturalism and supernaturalism.
Intelligent design avoids identifying or naming the intelligent designer—it merely states that one (or more) must exist—but leaders of the movement have said the designer is the Christian God.[n 4][n 5] Whether this lack of specificity about the designer's identity in public discussions is a genuine feature of the concept, or just a posture taken to avoid alienating those who would separate religion from the teaching of science, has been a matter of great debate between supporters and critics of intelligent design. The Kitzmiller v. Dover Area School District court ruling held the latter to be the case.
Origin of the term
See also: Timeline of intelligent design
Since the Middle Ages, discussion of the religious "argument from design" or "teleological argument" in theology, with its concept of "intelligent design", has persistently referred to the theistic Creator God. Although ID proponents chose this provocative label for their proposed alternative to evolutionary explanations, they have de-emphasized their religious antecedents and denied that ID is natural theology, while still presenting ID as supporting the argument for the existence of God.
While intelligent design proponents have pointed out past examples of the phrase intelligent design that they said were not creationist and faith-based, they have failed to show that these usages had any influence on those who introduced the label in the intelligent design movement.
Variations on the phrase appeared in Young Earth creationist publications: a 1967 book co-written by Percival Davis referred to "design according to which basic organisms were created". In 1970, A. E. Wilder-Smith published The Creation of Life: A Cybernetic Approach to Evolution which defended Paley's design argument with computer calculations of the improbability of genetic sequences, which he said could not be explained by evolution but required "the abhorred necessity of divine intelligent activity behind nature", and that "the same problem would be expected to beset the relationship between the designer behind nature and the intelligently designed part of nature known as man." In a 1984 article as well as in his affidavit to Edwards v. Aguillard, Dean H. Kenyon defended creation science by stating that "biomolecular systems require intelligent design and engineering know-how", citing Wilder-Smith. Creationist Richard B. Bliss used the phrase "creative design" in Origins: Two Models: Evolution, Creation (1976), and in Origins: Creation or Evolution (1988) wrote that "while evolutionists are trying to find non-intelligent ways for life to occur, the creationist insists that an intelligent design must have been there in the first place." The first systematic use of the term, defined in a glossary and claimed to be other than creationism, was in Of Pandas and People, co-authored by Davis and Kenyon.
Of Pandas and People
Main article: Of Pandas and People
The most common modern use of the words "intelligent design" as a term intended to describe a field of inquiry began after the United States Supreme Court ruled in 1987 in the case of Edwards v. Aguillard that it is unconstitutional for a state to require the teaching of creationism in public school science curricula.
A Discovery Institute report says that Charles B. Thaxton, editor of Pandas, had picked the phrase up from a NASA scientist, and thought, "That's just what I need, it's a good engineering term." In drafts of the book, over one hundred uses of the root word "creation", such as "creationism" and "Creation Science", were changed, almost without exception, to "intelligent design", while "creationists" was changed to "design proponents" or, in one instance, "cdesign proponentsists" [sic]. In June 1988, Thaxton held a conference titled "Sources of Information Content in DNA" in Tacoma, Washington, and in December decided to use the label "intelligent design" for his new creationist movement. Stephen C. Meyer was at the conference, and later recalled that "The term intelligent design came up..."
Of Pandas and People was published in 1989, and in addition to including all the current arguments for ID, was the first book to make systematic use of the terms "intelligent design" and "design proponents" as well as the phrase "design theory", defining the term intelligent design in a glossary and representing it as not being creationism. It thus represents the start of the modern intelligent design movement. "Intelligent design" was the most prominent of around fifteen new terms it introduced as a new lexicon of creationist terminology to oppose evolution without using religious language. It was the first place where the phrase "intelligent design" appeared in its primary present use, as stated both by its publisher Jon A. Buell, and by William A. Dembski in his expert witness report for Kitzmiller v. Dover Area School District.
The National Center for Science Education (NCSE) has criticized the book for presenting all of the basic arguments of intelligent design proponents and being actively promoted for use in public schools before any research had been done to support these arguments. Although presented as a scientific textbook, philosopher of science Michael Ruse considers the contents "worthless and dishonest". An American Civil Liberties Union lawyer described it as a political tool aimed at students who did not "know science or understand the controversy over evolution and creationism". One of the authors of the science framework used by California schools, Kevin Padian, condemned it for its "sub-text", "intolerance for honest science" and "incompetence".
Main article: Irreducible complexity
The term "irreducible complexity" was introduced by biochemist Michael Behe in his 1996 book Darwin's Black Box, though he had already described the concept in his contributions to the 1993 revised edition of Of Pandas and People. Behe defines it as "a single system which is 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".
Behe uses the analogy of a mousetrap to illustrate this concept. A mousetrap consists of several interacting pieces—the base, the catch, the spring and the hammer—all of which must be in place for the mousetrap to work. Removal of any one piece destroys the function of the mousetrap. Intelligent design advocates assert that natural selection could not create irreducibly complex systems, because the selectable function is present only when all parts are assembled. Behe argued that irreducibly complex biological mechanisms include the bacterial flagellum of E. coli, the blood clotting cascade, cilia, and the adaptive immune system.
Critics point out that the irreducible complexity argument assumes that the necessary parts of a system have always been necessary and therefore could not have been added sequentially. They argue that something that is at first merely advantageous can later become necessary as other components change. Furthermore, they argue, evolution often proceeds by altering preexisting parts or by removing them from a system, rather than by adding them. This is sometimes called the "scaffolding objection" by an analogy with scaffolding, which can support an "irreducibly complex" building until it is complete and able to stand on its own.[n 6] Behe has acknowledged using "sloppy prose", and that his "argument against Darwinism does not add up to a logical proof."[n 7] Irreducible complexity has remained a popular argument among advocates of intelligent design; in the Dover trial, the court held 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."
Main article: Specified complexity
In 1986, Charles B. Thaxton, a physical chemist and creationist, used the term "specified complexity" from information theory when claiming that messages transmitted by DNA in the cell were specified by intelligence, and must have originated with an intelligent agent. The intelligent design concept of "specified complexity" was developed in the 1990s by mathematician, philosopher, and theologian William A. Dembski. Dembski states that when something exhibits specified complexity (i.e., is both complex and "specified", simultaneously), one can infer that it was produced by an intelligent cause (i.e., that it was designed) rather than being the result of natural processes. He provides the following examples: "A single letter of the alphabet is specified without being complex. A long sentence of random letters is complex without being specified. A Shakespearean sonnet is both complex and specified." He states that details of living things can be similarly characterized, especially the "patterns" of molecular sequences in functional biological molecules such as DNA.
Dembski defines complex specified information (CSI) as anything with a less than 1 in 10150 chance of occurring by (natural) chance. Critics say that this renders the argument a tautology: complex specified information cannot occur naturally because Dembski has defined it thus, so the real question becomes whether or not CSI actually exists in nature.[n 8]
The conceptual soundness of Dembski's specified complexity/CSI argument has been discredited in the scientific and mathematical communities. Specified complexity has yet to be shown to have wide applications in other fields, as Dembski asserts. John Wilkins and Wesley R. Elsberry characterize Dembski's "explanatory filter" as eliminative because it eliminates explanations sequentially: first regularity, then chance, finally defaulting to design. They argue that this procedure is flawed as a model for scientific inference because the asymmetric way it treats the different possible explanations renders it prone to making false conclusions.
Richard Dawkins, another critic of intelligent design, argues in The God Delusion (2006) that allowing for an intelligent designer to account for unlikely complexity only postpones the problem, as such a designer would need to be at least as complex. Other scientists have argued that evolution through selection is better able to explain the observed complexity, as is evident from the use of selective evolution to design certain electronic, aeronautic and automotive systems that are considered problems too complex for human "intelligent designers".
Main article: Fine-tuned Universe
Intelligent design proponents have also occasionally appealed to broader teleological arguments outside of biology, most notably an argument based on the fine-tuning of universal constants that make matter and life possible and which are argued not to be solely attributable to chance. These include the values of fundamental physical constants, the relative strength of nuclear forces, electromagnetism, and gravity between fundamental particles, as well as the ratios of masses of such particles. Intelligent design proponent and Center for Science and Culture fellow Guillermo Gonzalez argues that if any of these values were even slightly different, the universe would be dramatically different, making it impossible for many chemical elements and features of the Universe, such as galaxies, to form. Thus, proponents argue, an intelligent designer of life was needed to ensure that the requisite features were present to achieve that particular outcome.
Scientists have generally responded that these arguments are poorly supported by existing evidence.Victor J. Stenger and other critics say both intelligent design and the weak form of the anthropic principle are essentially a tautology; in his view, these arguments amount to the claim that life is able to exist because the Universe is able to support life. The claim of the improbability of a life-supporting universe has also been criticized as an argument by lack of imagination for assuming no other forms of life are possible. Life as we know it might not exist if things were different, but a different sort of life might exist in its place. A number of critics also suggest that many of the stated variables appear to be interconnected and that calculations made by mathematicians and physicists suggest that the emergence of a universe similar to ours is quite probable.
Main article: Intelligent designer
The contemporary intelligent design movement formulates its arguments in secular terms and intentionally avoids identifying the intelligent agent (or agents) they posit. Although they do not state that God is the designer, the designer is often implicitly hypothesized to have intervened in a way that only a god could intervene. Dembski, in The Design Inference (1998), speculates that an alien culture could fulfill these requirements. Of Pandas and People proposes that SETI illustrates an appeal to intelligent design in science. In 2000, philosopher of science Robert T. Pennock suggested the RaëlianUFO religion as a real-life example of an extraterrestrial intelligent designer view that "make[s] many of the same bad arguments against evolutionary theory as creationists". The authoritative description of intelligent design,[n 9] however, explicitly states that the Universe displays features of having been designed. Acknowledging the paradox, Dembski concludes that "no intelligent agent who is strictly physical could have presided over the origin of the universe or the origin of life." The leading proponents have made statements to their supporters that they believe the designer to be the Christian God, to the exclusion of all other religions.
Beyond the debate over whether intelligent design is scientific, a number of critics argue that existing evidence makes the design hypothesis appear unlikely, irrespective of its status in the world of science. For example, Jerry Coyne asks why a designer would "give us a pathway for making vitamin C, but then destroy it by disabling one of its enzymes" (see pseudogene) and why a designer would not "stock oceanic islands with reptiles, mammals, amphibians, and freshwater fish, despite the suitability of such islands for these species". Coyne also points to the fact that "the flora and fauna on those islands resemble that of the nearest mainland, even when the environments are very different" as evidence that species were not placed there by a designer. Previously, in Darwin's Black Box, Behe had argued that we are simply incapable of understanding the designer's motives, so such questions cannot be answered definitively. Odd designs could, for example, "...have been placed there by the designer for a reason—for artistic reasons, for variety, to show off, for some as-yet-undetected practical purpose, or for some unguessable reason—or they might not." Coyne responds that in light of the evidence, "either life resulted not from intelligent design, but from evolution; or the intelligent designer is a cosmic prankster who designed everything to make it look as though it had evolved."
Intelligent design proponents such as Paul Nelson avoid the problem of poor design in nature by insisting that we have simply failed to understand the perfection of the design. Behe cites Paley as his inspiration, but he differs from Paley's expectation of a perfect Creation and proposes that designers do not necessarily produce the best design they can. Behe suggests that, like a parent not wanting to spoil a child with extravagant toys, the designer can have multiple motives for not giving priority to excellence in engineering. He says that "Another problem with the argument from imperfection is that it critically depends on a psychoanalysis of the unidentified designer. Yet the reasons that a designer would or would not do anything are virtually impossible to know unless the designer tells you specifically what those reasons are." This reliance on inexplicable motives of the designer makes intelligent design scientifically untestable. Retired UC Berkeley law professor, author and intelligent design advocate Phillip E. Johnson puts forward a core definition that the designer creates for a purpose, giving the example that in his view AIDS was created to punish immorality and is not caused by HIV, but such motives cannot be tested by scientific methods.
Asserting the need for a designer of complexity also raises the question "What designed the designer?" Intelligent design proponents say that the question is irrelevant to or outside the scope of intelligent design.[n 10] Richard Wein counters that "...scientific explanations often create new unanswered questions. But, in assessing the value of an explanation, these questions are not irrelevant. They must be balanced against the improvements in our understanding which the explanation provides. Invoking an unexplained being to explain the origin of other beings (ourselves) is little more than question-begging. The new question raised by the explanation is as problematic as the question which the explanation purports to answer." Richard Dawkins sees the assertion that the designer does not need to be explained as a thought-terminating cliché. In the absence of observable, measurable evidence, the very question "What designed the designer?" leads to an infinite regression from which intelligent design proponents can only escape by resorting to religious creationism or logical contradiction.
Main article: Intelligent design movement
The intelligent design movement is a direct outgrowth of the creationism of the 1980s. The scientific and academic communities, along with a U.S. federal court, view intelligent design as either a form of creationism or as a direct descendant that is closely intertwined with traditional creationism; and several authors explicitly refer to it as "intelligent design creationism".[n 11]
The movement is headquartered in the Center for Science and Culture, established in 1996 as the creationist wing of the Discovery Institute to promote a religious agenda[n 12] calling for broad social, academic and political changes. The Discovery Institute's intelligent design campaigns have been staged primarily in the United States, although efforts have been made in other countries to promote intelligent design. Leaders of the movement say intelligent design exposes the limitations of scientific orthodoxy and of the secular philosophy of naturalism. Intelligent design proponents allege that science should not be limited to naturalism and should not demand the adoption of a naturalistic philosophy that dismisses out-of-hand any explanation that includes a supernatural cause. The overall goal of the movement is to "reverse the stifling dominance of the materialist worldview" represented by the theory of evolution in favor of "a science consonant with Christian and theistic convictions".[n 12]
Phillip E. Johnson stated that the goal of intelligent design is to cast creationism as a scientific concept.[n 4][n 13] All leading intelligent design proponents are fellows or staff of the Discovery Institute and its Center for Science and Culture. Nearly all intelligent design concepts and the associated movement are the products of the Discovery Institute, which guides the movement and follows its wedge strategy while conducting its "Teach the Controversy" campaign and their other related programs.
Leading intelligent design proponents have made conflicting statements regarding intelligent design. In statements directed at the general public, they say intelligent design is not religious; when addressing conservative Christian supporters, they state that intelligent design has its foundation in the Bible.[n 13] Recognizing the need for support, the Institute affirms its Christian, evangelistic orientation:
Alongside a focus on influential opinion-makers, we also seek to build up a popular base of support among our natural constituency, namely, Christians. We will do this primarily through apologetics seminars. We intend these to encourage and equip believers with new scientific evidences that support the faith, as well as to "popularize" our ideas in the broader culture.[n 12]
Barbara Forrest, an expert who has written extensively on the movement, describes this as being due to the Discovery Institute's obfuscating its agenda as a matter of policy. She has written that the movement's "activities betray an aggressive, systematic agenda for promoting not only intelligent design creationism, but the religious worldview that undergirds it."
Religion and leading proponents
Although arguments for intelligent design by the intelligent design movement are formulated in secular terms and intentionally avoid positing the identity of the designer,[n 14] the majority of principal intelligent design advocates are publicly religious Christians who have stated that, in their view, the designer proposed in intelligent design is the Christian conception of God. Stuart Burgess, Phillip E. Johnson, William A. Dembski, and Stephen C. Meyer are evangelical Protestants; Michael Behe is a Roman Catholic; and Jonathan Wells is a member of the Unification Church. Non-Christian proponents include David Klinghoffer, who is Jewish,Michael Denton and David Berlinski, who are agnostic, and Muzaffar Iqbal, a Pakistani-CanadianMuslim. Phillip E. Johnson has stated that cultivating ambiguity by employing secular language in arguments that are carefully crafted to avoid overtones of theistic creationism is a necessary first step for ultimately reintroducing the Christian concept of God as the designer. Johnson explicitly calls for intelligent design proponents to obfuscate their religious motivations so as to avoid having intelligent design identified "as just another way of packaging the Christian evangelical message."[n 15] Johnson emphasizes that "...the first thing that has to be done is to get the Bible out of the discussion. ...This is not to say that the biblical issues are unimportant; the point is rather that the time to address them will be after we have separated materialist prejudice from scientific fact."
The strategy of deliberately disguising the religious intent of intelligent design has been described by William A. Dembski in The Design Inference. In this work, Dembski lists a god or an "alien life force" as two possible options for the identity of the designer; however, in his book Intelligent Design: The Bridge Between Science and Theology (1999), Dembski states:
Christ is indispensable to any scientific theory, even if its practitioners don't have a clue about him. The pragmatics of a scientific theory can, to be sure, be pursued without recourse to Christ. But the conceptual soundness of the theory can in the end only be located in Christ.
Dembski also stated, "ID is part of God's general revelation [...] Not only does intelligent design rid us of this ideology [ materialism ], which suffocates the human spirit, but, in my personal experience, I've found that it opens the path for people to come to Christ." Both Johnson and Dembski cite the Bible's Gospel of John as the foundation of intelligent design.[n 13]
Barbara Forrest contends such statements reveal that leading proponents see intelligent design as essentially religious in nature, not merely a scientific concept that has implications with which their personal religious beliefs happen to coincide.[n 16] She writes that the leading proponents of intelligent design are closely allied with the ultra-conservative Christian Reconstructionism movement. She lists connections of (current and former) Discovery Institute Fellows Phillip E. Johnson, Charles B. Thaxton, Michael Behe, Richard Weikart, Jonathan Wells and Francis J. Beckwith to leading Christian Reconstructionist organizations, and the extent of the funding provided the Institute by Howard Ahmanson, Jr., a leading figure in the Reconstructionist movement.
Reaction from other creationist groups
Not all creationist organizations have embraced the intelligent design movement. According to Thomas Dixon, "Religious leaders have come out against ID too. An open letter affirming the compatibility of Christian faith and the teaching of evolution, first produced in response to controversies in Wisconsin in 2004, has now been signed by over ten thousand clergy from different Christian denominations across America. In 2006, the director of the Vatican Observatory, the Jesuit astronomer George Coyne, condemned ID as a kind of 'crude creationism' which reduced God to a mere engineer."Hugh Ross of Reasons to Believe, a proponent of Old Earth creationism, believes that the efforts of intelligent design proponents to divorce the concept from Biblical Christianity make its hypothesis too vague. In 2002, he wrote: "Winning the argument for design without identifying the designer yields, at best, a sketchy origins model. Such a model makes little if any positive impact on the community of scientists and other scholars. [...] ...the time is right for a direct approach, a single leap into the origins fray. Introducing a biblically based, scientifically verifiable creation model represents such a leap."
Likewise, two of the most prominent YEC organizations in the world have attempted to distinguish their views from those of the intelligent design movement. Henry M. Morris of the Institute for Creation Research (ICR) wrote, in 1999, that ID, "even if well-meaning and effectively articulated, will not work! It has often been tried in the past and has failed, and it will fail today. The reason it won't work is because it is not the Biblical method." According to Morris: "The evidence of intelligent design ... must be either followed by or accompanied by a sound presentation of true Biblical creationism if it is to be meaningful and lasting." In 2002, Carl Wieland, then of Answers in Genesis (AiG), criticized design advocates who, though well-intentioned, "'left the Bible out of it'" and thereby unwittingly aided and abetted the modern rejection of the Bible. Wieland explained that "AiG's major 'strategy' is to boldly, but humbly, call the church back to its Biblical foundations ... [so] we neither count ourselves a part of this movement nor campaign against it."
The unequivocal consensus in the scientific community is that intelligent design is not science and has no place in a science curriculum. The U.S. National Academy of Sciences has stated that "creationism, intelligent design, and other claims of supernatural intervention in the origin of life or of species are not science because they are not testable by the methods of science." The U.S. National Science Teachers Association and the American Association for the Advancement of Science have termed it pseudoscience. Others in the scientific community have denounced its tactics, accusing the ID movement of manufacturing false attacks against evolution, of engaging in misinformation and misrepresentation about science, and marginalizing those who teach it. More recently, in September 2012, Bill Nye warned that creationist views threaten science education and innovations in the United States.
In 2001, the Discovery Institute published advertisements under the heading "A Scientific Dissent From Darwinism", with the claim that listed scientists had signed this statement expressing skepticism:
We are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life. Careful examination of the evidence for Darwinian theory should be encouraged.
The ambiguous statement did not exclude other known evolutionary mechanisms, and most signatories were not scientists in relevant fields, but starting in 2004 the Institute claimed the increasing number of signatures indicated mounting doubts about evolution among scientists. The statement formed a key component of Discovery Institute campaigns to present intelligent design as scientifically valid by claiming that evolution lacks broad scientific support, with Institute members continued to cite the list through at least 2011. As part of a strategy to counter these claims, scientists organised Project Steve, which gained more signatories named Steve (or variants) than the Institute's petition, and a counter-petition, "A Scientific Support for Darwinism", which quickly gained similar numbers of signatories.
Several surveys were conducted prior to the December 2005 decision in Kitzmiller v. Dover School District, which sought to determine the level of support for intelligent design among certain groups. According to a 2005 Harris poll, 10% of adults in the United States viewed human beings as "so complex that they required a powerful force or intelligent being to help create them." Although Zogby polls commissioned by the Discovery Institute show more support, these polls suffer from considerable flaws, such as having a very low response rate (248 out of 16,000), being conducted on behalf of an organization with an expressed interest in the outcome of the poll, and containing leading questions.
The 2017 Gallup creationism survey found that 38% of adults in the United States hold the view that "God created humans in their present form at one time within the last 10,000 years" when asked for their views on the origin and development of human beings, which was noted as being at the lowest level in 35 years. Previously, a series of Gallup polls in the United States from 1982 through 2014 on "Evolution, Creationism, Intelligent Design" found support for "human beings have developed over millions of years from less advanced formed of life, but God guided the process" of between 31% and 40%, support for "God created human beings in pretty much their present form at one time within the last 10,000 years or so" varied from 40% to 47%, and support for "human beings have developed over millions of years from less advanced forms of life, but God had no part in the process" varied from 9% to 19%. The polls also noted answers to a series of more detailed questions.
Allegations of discrimination against ID proponents
Main article: Expelled: No Intelligence Allowed
There have been allegations that ID proponents have met discrimination, such as being refused tenure or being harshly criticized on the Internet. In the documentary filmExpelled: No Intelligence Allowed, released in 2008, host Ben Stein presents five such cases. The film contends that the mainstream science establishment, in a "scientific conspiracy to keep God out of the nation's laboratories and classrooms", suppresses academics who believe they see evidence of intelligent design in nature or criticize evidence of evolution. Investigation into these allegations turned up alternative explanations for perceived persecution.[n 17]
The film portrays intelligent design as motivated by science, rather than religion, though it does not give a detailed definition of the phrase or attempt to explain it on a scientific level. Other than briefly addressing issues of irreducible complexity, Expelled examines it as a political issue. The scientific theory of evolution is portrayed by the film as contributing to fascism, the Holocaust, communism, atheism, and eugenics.
Expelled has been used in private screenings to legislators as part of the Discovery Institute intelligent design campaign for Academic Freedom bills. Review screenings were restricted to churches and Christian groups, and at a special pre-release showing, one of the interviewees, PZ Myers, was refused admission. The American Association for the Advancement of Science describes the film as dishonest and divisive propaganda aimed at introducing religious ideas into public school science classrooms, and the Anti-Defamation League has denounced the film's allegation that evolutionary theory influenced the Holocaust. The film includes interviews with scientists and academics who were misled into taking part by misrepresentation of the topic and title of the film. Skeptic Michael Shermer describes his experience of being repeatedly asked the same question without context as "surreal".
Main article: Intelligent design and science
Advocates of intelligent design seek to keep God and the Bible out of the discussion, and present intelligent design in the language of science as though it were a scientific hypothesis.[n 14] For a theory to qualify as scientific,[n 18][n 19] it is expected to be:
- Parsimonious (sparing in its proposed entities or explanations; see Occam's razor)
- Useful (describes and explains observed phenomena, and can be used in a predictive manner)
- Empirically testable and falsifiable (potentially confirmable or disprovable by experiment or observation)
- Based on multiple observations (often in the form of controlled, repeated experiments)
- Correctable and dynamic (modified in the light of observations that do not support it)
- Progressive (refines previous theories)
- Provisional or tentative (is open to experimental checking, and does not assert certainty)
For any theory, hypothesis or conjecture to be considered scientific, it must meet most, and ideally all, of these criteria. The fewer criteria are met, the less scientific it is; and if it meets only a few or none at all, then it cannot be treated as scientific in any meaningful sense of the word. Typical objections to defining intelligent design as science are that it lacks consistency, violates the principle of parsimony,[n 20] is not scientifically useful,[n 21] is not falsifiable,[n 22] is not empirically testable,[n 23] and is not correctable, dynamic, progressive or provisional.[n 24][n 25][n 26]
Intelligent design proponents seek to change this fundamental basis of science by eliminating "methodological naturalism" from science and replacing it with what the leader of the intelligent design movement, Phillip E. Johnson, calls "theistic realism".[n 27] Intelligent design proponents argue that naturalistic explanations fail to explain certain phenomena and that supernatural explanations provide a very simple and intuitive explanation for the origins of life and the universe.[n 28] Many intelligent design followers believe that "scientism" is itself a religion that promotes secularism and materialism in an attempt to erase theism from public life, and they view their work in the promotion of intelligent design as a way to return religion to a central role in education and other public spheres.
The failure to follow the procedures of scientific discourse and the failure to submit work to the scientific community that withstands scrutiny have weighed against intelligent design being accepted as valid science. The intelligent design movement has not published a properly peer-reviewed article supporting ID in a scientific journal, and has failed to publish supporting peer-reviewed research or data. The only article published in a peer-reviewed scientific journal that made a case for intelligent design was quickly withdrawn by the publisher for having circumvented the journal's peer-review standards. The Discovery Institute says that a number of intelligent design articles have been published in peer-reviewed journals, but critics, largely members of the scientific community, reject this claim and state intelligent design proponents have set up their own journals with peer review that lack impartiality and rigor,[n 29] consisting entirely of intelligent design supporters.[n 30]
Further criticism stems from the fact that the phrase intelligent design makes use of an assumption of the quality of an observable intelligence, a concept that has no scientific consensus definition. The characteristics of intelligence are assumed by intelligent design proponents to be observable without specifying what the criteria for the measurement of intelligence should be. Critics say that the design detection methods proposed by intelligent design proponents are radically different from conventional design detection, undermining the key elements that make it possible as legitimate science. Intelligent design proponents, they say, are proposing both searching for a designer without knowing anything about that designer's abilities, parameters, or intentions (which scientists do know when searching for the results of human intelligence), as well as denying the very distinction between natural/artificial design that allows scientists to compare complex designed artifacts against the background of the sorts of complexity found in nature.[n 31]
This article is about the concept in intelligent design. For the concept in systems theory, see Emergence.
Irreducible complexity (IC) is the idea that certain biological systems cannot evolve by successive small modifications to pre-existing functional systems through natural selection. Irreducible complexity is central to the creationist concept of intelligent design, but it is rejected by the scientific community, which regards intelligent design as pseudoscience. Irreducible complexity is one of two main arguments used by intelligent design proponents, the other being specified complexity.
The theological argument from design was presented in creation science with assertions that evolution could not explain complex molecular mechanisms, and in 1993 Michael Behe, a professor of biochemistry at Lehigh University, presented these arguments in a revised version of Of Pandas and People. In his 1996 book Darwin's Black Box he called this irreducible complexity and said it made evolution through natural selection of random mutations impossible. This was based on the mistaken assumption that evolution relies on improvement of existing functions, ignoring how complex adaptations originate from changes in function, and disregarding published research.Evolutionary biologists have published rebuttals showing how systems discussed by Behe can evolve, and examples documented through comparative genomics show that complex molecular systems are formed by the addition of components as revealed by different temporal origins of their proteins.
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."
Michael Behe defined irreducible complexity in natural selection in his book Darwin's Black Box:
... a single system which is composed of several well-matched, 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.
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 A. 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.
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 appear 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 one can trace it back at least as far as Cicero's De Natura Deorum ii.34, written in 45 BC.
Up to the 18th century
Galen (1st and 2nd centuries AD) wrote about the large number of parts of the body and their relationships, which observation was cited as evidence for creation. The idea that the interdependence between parts would have implications for the origins of living things was raised by writers starting with Pierre Gassendi in the mid-17th century and by John Wilkins (1614-1672), who wrote (citing Galen), "Now to imagine, that all these things, according to their several kinds, could be brought into this regular frame and order, to which such an infinite number of Intentions are required, without the contrivance of some wise Agent, must needs be irrational in the highest degree." In the late 17th-century, Thomas Burnet referred to "a multitude of pieces aptly joyn'd" to argue against the eternity of life. In the early 18th century, Nicolas Malebranche wrote "An organized body contains an infinity of parts that mutually depend upon one another in relation to particular ends, all of which must be actually formed in order to work as a whole", arguing in favor of preformation, rather than epigenesis, of the individual; and a similar argument about the origins of the individual was made by other 18th-century students of natural history. In his 1790 book, The Critique of Judgment, Kant is said by Guyer to argue that "we cannot conceive how a whole that comes into being only gradually from its parts can nevertheless be the cause of the properties of those parts".
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.
Georges Cuvier applied his principle of the correlation of parts to describe an animal from fragmentary remains. For Cuvier, this related to another principle of his, the conditions of existence, which excluded the possibility of transmutation of species.
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 (1859), 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. By showing how simple unintelligent forces can ratchet up designs of extraordinary complexity without invoking outside design, Darwin showed that an intelligent designer was not the necessary conclusion to draw from complexity in nature. The argument from irreducible complexity attempts to demonstrate that certain biological features cannot be purely the product of Darwinian evolution.
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 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."
Darwin responded to Spencer's objections in chapter XXV of The Variation of Animals and Plants under Domestication (1868). 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."
St. George Jackson Mivart raised the objection to natural selection that "Complex and simultaneous co-ordinations … until so far developed as to effect the requisite junctions, are useless" which "amounts to the concept of "irreducible complexity" as defined by … Michael Behe".
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. 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."
In 1974 the young Earth creationistHenry 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."
In 1975 Thomas H. Frazzetta published a book-length study of a concept similar to irreducible complexity, explained by gradual, step-wise, non-teleological evolution. Frazzetta wrote:
"A complex adaptation is one constructed of several components that must blend together operationally to make the adaptation "work". It is analogous to a machine whose performance depends upon careful cooperation among its parts. In the case of the machine, no single part can greatly be altered without changing the performance of the entire machine."
The machine that he chose as an analog is the Peaucellier–Lipkin linkage, and one biological system given extended description was the jaw apparatus of a python. The conclusion of this investigation, rather than that evolution of a complex adaptation was impossible, "awed by the adaptations of living things, to be stunned by their complexity and suitability", was "to accept the inescapable but not humiliating fact that much of mankind can be seen in a tree or a lizard."
In 1981, Ariel Roth, in defense of the creation-science position in the trial McLean v. Arkansas, said of "complex integrated structures": "This system would not be functional until all the parts were there ... How did these parts survive during evolution ...?"
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 called centering - used to build an arch then removed afterwards: "Surely there was 'scaffolding'. Before the multitudinous components of present biochemistry could come to lean together they had to lean on something else." However, neither Muller or Cairns-Smith claimed their ideas as evidence of something supernatural.
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". The author asked the reader to "imagine the effects of natural selection on those organisms that fortuitously evolved the flagella ... without the concommitant [sic] control mechanisms".
An early concept of irreducibly complex systems comes from Ludwig von Bertalanffy (1901-1972), an 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. 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. 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.
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 (alone among the predecessors) 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 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." (The judge ruled 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.
The mousetrap example
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 observes that various subsets of the five components can be devised to form cooperative units, ones that have different functions from the mousetrap and so, in biological terms, could form functional spandrels before being adapted to the new function of catching mice. In an example taken from his high school experience, Miller recalls that one of his classmates
...struck upon the brilliant idea of using an old, broken mousetrap as a spitball catapult, and it worked brilliantly.... It had worked perfectly as something other than a mousetrap.... my rowdy friend had pulled a couple of parts --probably the hold-down bar and catch-- off the trap to make it easier to conceal and more effective as a catapult... [leaving] the base, the spring, and the hammer. Not much of a mousetrap, but a helluva spitball launcher.... I realized why [Behe's] mousetrap analogy had bothered me. It was wrong. The mousetrap is not irreducibly complex after all.
Other systems identified by Miller that include mousetrap components include the following:
- use the spitball launcher as a tie clip (same three-part system with different function)
- remove the spring from the spitball launcher/tie clip to create a two-part key chain (base + hammer)
- glue the spitball launcher/tie clip to a sheet of wood to create a clipboard (launcher + glue + wood)
- remove the hold-down bar for use as a toothpick (single element system)
The point of the reduction is that - in biology - most or all of the components were already at hand, by the time it became necessary to build a mousetrap. As such, it required far fewer steps to develop a mousetrap than to design all the components from scratch.
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.
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 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.
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. In explicating his definition of "irreducible complexity" he notes 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 by TalkOrigins. 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..."
Behe and others have suggested a number of biological features that they believe may be irreducibly complex.
Blood clotting cascade
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.
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.Natural selection can lead to complex biochemical systems being built up from simpler systems, or to existing functional systems being recombined as a new system with a different function. For example, one of the clotting factors that Behe listed as a part of the clotting cascade (Factor XII, also called Hageman factor) 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. Behe has responded to critics of his clotting cascade arguments by suggesting that homology is evidence for evolution, but not for natural selection.
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 ten.
Main article: Evolution of the eye
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 pointed out 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.[not in citation given]
In an often misquoted passage from On 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 (see fallacy of quoting out of context). 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.
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.
Current evidence does suggest possible evolutionary lineages for the origins of the anatomical features of the eye. One likely chain of development is that the eyes originated as simple patches of photoreceptor cells that could detect the presence or absence of light, but not its direction. When, via random mutation across the population, the photosensitive cells happened to have developed on a small depression, it endowed the organism with a better sense of the light's source. This small change gave the organism an advantage over those without the mutation. This genetic trait would then be "selected for" as those with the trait would have an increased chance of survival, and therefore progeny, over those without the trait. Individuals with deeper depressions would be able to discern changes in light over a wider field than those individuals with shallower depressions. As ever deeper depressions were advantageous to the organism, gradually, this depression would become a pit into which light would strike certain cells depending on its angle. The organism slowly gained increasingly precise visual information. And again, this gradual process continued as individuals having a slightly shrunken aperture of the eye had an advantage over those without the mutation as an aperture increases how collimated the light is at any one specific group of photoreceptors. As this trait developed, the eye became effectively a pinhole camera which allowed the organism to dimly make out shapes—the nautilus is a modern example of an animal with such an eye. Finally, via this same selection process, a 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. 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. Behe asserts that this is only an explanation of the gross anatomical steps, however, and not an explanation of the changes in discrete biochemical systems that would have needed to take place.
Behe maintains that 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, and that the proposed series of infinitesimal steps to get from patches of photoreceptors to a fully functional eye would actually be considered great, complex leaps in evolution if viewed on the molecular scale. Other intelligent design proponents claim that the evolution of the entire visual system would be difficult rather than the eye alone.
Main article: Evolution of flagella
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.
Reducible complexity. In contrast to Behe's claims, many proteins can be deleted or mutated and the flagellum still works, even though sometimes at reduced efficiency. In fact, the composition of flagella is surprisingly diverse across bacteria with many proteins only found in some species but not others. Hence the flagellar apparatus is clearly very flexible in evolutionary terms and perfectly able to lose or gain protein components. Further studies have shown that, contrary to claims of "irreducible complexity", flagella and related protein transport mechanisms show evidence of evolution through Darwinian processes, providing case studies in how complex systems can evolve from simpler components. Multiple processes were involved in the evolution of the flagellum, including horizontal gene transfer.
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. 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 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. The TTSS system negates Behe's claim that taking away any one of the flagellum's parts would prevent the system from functioning. On this basis, Kenneth Miller notes that, "The parts of this supposedly irreducibly complex system actually have functions of their own." Studies have also shown that similar parts of the flagellum in different bacterial species can have different functions despite showing evidence of common descent, and that certain parts of the flagellum can be removed without completely eliminating its functionality.
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. Against Dembski's argument, different flagella use completely different mechanisms, and publications show a plausible path in which bacterial flagella could have evolved from a secretion system.
The cilium construction of axoneme microtubules movement by the sliding of dynein protein was cited by Behe as an example of irreducible complexity. He further said that the advances in knowledge in the subsequent 10 years had shown that the complexity of intraflagellar transport for two hundred components cilium and many other cellular structures is substantially greater than was known earlier.
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".
Reducibility of "irreducible" systems
Researchers have proposed potentially viable evolutionary pathways for allegedly irreducibly complex systems such as blood clotting, the immune system and the flagellum - the three examples Behe proposed. John H. McDonald even showed his example of a mousetrap to be reducible. If irreducible complexity is an insurmountable obstacle to evolution, it should not be possible to conceive of such pathways.
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"—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.
A computer model of the co-evolution of proteins binding to DNA in the peer-reviewed journal Nucleic Acids Research consisted of several parts (DNA binders and DNA binding sites) which contribute to the basic function; removal of either one leads immediately to the death of the organism. This model fits the definition of irreducible complexity exactly, yet it evolves. (The program can be run from Ev program.)
In addition, research published in the peer-reviewed journal Nature has shown that computer simulations of evolution demonstrate that it is possible for complex features to evolve naturally.
One can 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 could not 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 humans build them easily enough, one stone at a time, by building over centering that is removed afterward. Similarly, naturally occurring arches of stone form by the weathering away of 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.
A team led by 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.
Irreducible complexity may not actually exist in nature, and the examples given by Behe and others may not in fact represent irreducible complexity, but can be explained in terms of simpler precursors. The theory of facilitated variation challenges irreducible complexity. 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, presented this theory in 2005. 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
Main article: Exaptation
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) provide 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). Furthermore, recent research shows that viruses play a heretofore unexpected 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. In the Dover trial an expert witness for the plaintiffs, Ken Miller, demonstrated this possibility using Behe's mousetrap analogy. By removing several parts, Miller made the object unusable as a mousetrap, but he pointed out that it was now a perfectly functional, if unstylish, tie clip.
Methods by which irreducible complexity may evolve
Further information: Evolvability
Irreducible complexity can be seen as equivalent to an "uncrossable valley" in a fitness landscape. A number of mathematical models of evolution have explored the circumstances under which such valleys can, nevertheless, be crossed.
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 former executive director of the National Center for Science Education) have argued that the concept of irreducible complexity and, more generally, intelligent design is not falsifiable and, therefore, not scientific.
Behe argues that the theory that irreducibly complex systems could not have 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".
Other evidence that irreducible complexity is not a problem for evolution comes from the field of computer science, which routinely uses computer analogues of the processes of evolution in order 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 automatically produce human-competitive designs—but no human designer is required.
Argument from ignorance
Intelligent design proponents attribute to an intelligent designer those biological structures they believe are irreducibly complex and therefore they say a natural explanation is insufficient to account for them. 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 as a God-of-the-gaps argument.
Eugenie Scott, along with Glenn Branch and other critics, has argued that many points raised by intelligent-design proponents are arguments from ignorance. Behe has been accused by critics  of using an "argument by lack of imagination".
Irreducible complexity is at its core an argument against evolution. If truly irreducible systems are found, the argument goes, then intelligent design must be 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.
In the Dover trial
While testifying during the 2005 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
- ^ ab"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." Ruling, Judge John E. Jones III, Kitzmiller v. Dover Area School District
- ^"True in this latest creationist variant, advocates of so-called intelligent design ... use more slick, pseudoscientific language. They talk about things like "irreducible complexity" Shulman, Seth (2006). Undermining science: suppression and distortion in the Bush Administration. Berkeley: University of California Press. p. 13. ISBN 0-520-24702-7. "for most members of the mainstream scientific community, ID is not a scientific theory, but a creationist pseudoscience."
David Mu (Fall 2005). "Trojan Horse or Legitimate Science: Deconstructing the Debate over Intelligent Design"(PDF). Harvard Science Review. 19 (1). Archived from the original(PDF) on 2007-07-24.
Perakh M (Summer 2005). "Why Intelligent Design Isn't Intelligent — Review of: Unintelligent Design". Cell Biol Educ. 4 (2): 121–2. doi:10.1187/cbe.05-02-0071. PMC 1103713.
Mark D. Decker. College of Biological Sciences, General Biology Program, University of Minnesota Frequently Asked Questions About the Texas Science Textbook Adoption ControversyArchived 2010-09-30 at the Wayback Machine. "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."
See also list of scientific societies explicitly rejecting intelligent design
- ^Ker Than (September 23, 2005). "Why scientists dismiss 'intelligent design' - LiveScience". msnbc.com. Retrieved 2010-05-17.
(a) A pigment spot
(b) A simple pigment cup
(c) The simple optic cup found in abalone
(d) The complex lensed eye of the marine snail and the octopus