Jet in Carina WFC3 IR [Courtesy NASA]

Does intelligent design pose a challenge for evolution?

David H. Bailey
Updated 27 November 2022 (c) 2022

Background

The "intelligent design" movement was formed in the mid-1990s by a group of scholars whose objective was to present a significantly more tenable body of scholarship opposed to evolution than that promoted by young-earth creationists such as Henry Morris and John Whitcomb. The leading figures of the intelligent design movement, such as Michael Behe, William Dembski, Phillip Johnson and Jonathan Wells, have respectable academic credentials. They generally accept the overall scientific account and timeline of the creation. However, they still insist that many features of life on Earth are too complex to be explained by natural evolution. They acknowledge limited variations within basic "kinds," but insist that the individual kinds were separately formed or designed by an intelligent entity, utilizing means that may not be subject to human investigation [Behe1996; Behe2007; Dembski1998; Dembski1999; Dembski2002; Dembski2004; Dembski2007; Johnson1993; Johnson2000; Wells2000].

The Discovery Institute, near Seattle, Washington, has provided much of the funding and central direction for the intelligent design movement's activities. One major thrust is to produce material for public school curricula. These efforts came to a head in Dover, Pennsylvania, whose school board in 2005 passed a measure requiring a statement be read in high school biology classes saying, in part:

Because Darwin's Theory is a theory, it continues to be tested as new evidence is discovered. The Theory is not a fact. Gaps in the Theory exist for which there is no evidence. ... Intelligent Design is an explanation of the origin of life that differs from Darwin's view. The reference book, Of Pandas and People, is available for students who might be interested in gaining an understanding of what Intelligent Design actually involves.

A group of parents filed suit, and a widely publicized trial was held. In his strongly worded decision, U.S. District Judge John E. Jones struck down the school district's actions. In spite of this setback, however, the intelligent design movement continues to press forward. In 2013, several members of a Texas state panel (including one person affiliated with the Discovery Institute) questioned material on evolution in high school biology books [Rich2013]. Efforts to water down the teaching of evolution, or to substitute material provided by the Discovery Institute, continue nationwide and even outside the U.S. to the present day.

What exactly is "intelligent design"?

It is important to distinguish here between "intelligent design" as the notion that an intelligent being oversaw or governed the creative process in some general sense (which is a notion that many thinking persons, both scientifically- and theologically-minded, could affirm), and "intelligent design" as the name of the movement described above. In this article (and elsewhere on this site), the second definition of the term (i.e., "intelligent design" as a movement) is used exclusively.

So what exactly is the "intelligent design" movement? On one hand, intelligent design is a refreshing improvement over young-earth creationism, provided one focuses on the writings of its most prominent spokespersons, such as Michael Behe, a microbiologist at Lehigh University. In his 2007 book The Edge of Evolution [Behe2007], Behe acknowledges that life has been on Earth for several billion years [pg. 19], that fish have been around for millions of years [pg. 16], and that "perhaps a trillion" creatures have preceded humans on the planet in the past ten million years [pg. 60]. In general he sees "little question that all species on Earth descended from a common ancestor" [dust jacket]. This stance certainly places Behe in a much more scientifically tenable position than the young-earth creationist school. He and other intelligent design writers principally question whether natural selection and other natural processes could have been the sole driving forces behind evolutionary advance, arguing instead that nature must have been "designed" by some intelligent agent.

But given Behe's approach, one might ask, "What is the point of intelligent design?" If essentially all of the principal assertions of evolutionary biology are granted from the start, and the only question is whether the creation exhibits "design" in some unspecified sense, or whether mutation and natural selection are sufficient by themselves to explain evolution, then there seems little to be gained from intelligent design, scientifically or theologically.

Further, there are significant difficulties even with this more limited agenda. To begin with, the intelligent design writers' search for design in nature is not particularly novel. Similar arguments were advanced by Paley in the 19th century. In any event, their claimed examples of "irreducible complexity" and the like are countered by published research showing how these features could and likely did arise by natural processes. In general, attempting to exhibit "design" in nature as evidence for God is problematic in light of the many features of nature (including numerous features of the human body) that are clearly deficient (see Design). At the least, "design" must be thought of in a high-level sense, not in specific low-level mechanics as argued by intelligent design writers. Indeed, Behe's comments have drawn sharp criticism from some in the evangelical creationist community [Lyons2008].

Intelligent design and creationism

Although intelligent design writers and their proponents take pains to distinguish themselves from traditional creationists, there is clear evidence that the intelligent design movement is also rooted in fundamentalism and biblical inerrancy. Each of the four prominent intelligent design scholars mentioned above (except for Michael Behe, who is Catholic) is affiliated with a relatively fundamentalist denomination, and all have acknowledged that their religious beliefs in general, and their inerrant approach to the Bible in particular, are principal motivations for their work. William Dembski, for instance, recently affirmed [Allen2010]:
As a biblical inerrantist, I believe that what the Bible teaches is true and bow to the text, including its teaching about the Flood and its universality. ... I accept that the events described in Genesis 1-11 happened in ordinary space-time, and thus that these chapters are as historical as the rest of the Pentateuch.

The intelligent design textbook Of Pandas and People, mentioned above, is a lightly edited version of an earlier creationist textbook, where, among other things, the word "creation" has been replaced with "intelligent design" [Kitzmiller2005]. The Discovery Institute's Center for Science and Culture, is devoted "to defeat scientific materialism and its destructive moral, cultural, and political legacies" and "to replace materialistic explanations with the theistic understanding that nature and human beings are created by God." To this end, they have outlined a "wedge" strategy, which recommends that they proceed in degrees, first by "teaching the controversy" of evolution, then promoting intelligent design as an alternative theory to evolution, then edging out evolution in favor of Biblical theism [Forrest2004, pg. 25-33].

Although there are exceptions, most intelligent design writers agree with creationist writers that modern evolutionary theory, as it currently stands, is irreconcilable with Christian religion. For example, John G. West of the Discovery Institute says that theistic evolution (the notion that God guided the evolutionary process -- a version that many scientists would affirm) would require "radical revisions in how one views God." West openly criticizes, by name, some scientists and theologians who have spoken for a moderate middle ground [West2007; West2009].

Historical perspectives of intelligent design

It is worth emphasizing that the intelligent design community's focus on "design" is not a particularly novel idea. As briefly mentioned above, similar arguments were raised in the 19th century by William Paley, who, in his book Natural Theology, asked his readers to imagine finding a pocket watch along the road. After even a cursory examination of the watch's intricate structure, Paley argued, one could rationally conclude that it only could have been the result of design by an intelligent being. Paley even included arguments based on chance, and the equivalent of "irreducible complexity" [Ayala2007, pg. 15-26]. Nonetheless, Paley saw God as acting strictly in accord with natural law, not by contravening natural law [Shapiro2009].

It is also worth noting that the early Jewish and Christian writers made no attempt to specify "intelligent design" or "irreducible complexity" as an argument for God [Barr2010a]. For instance, the pre-Christian-era Jewish writer of the Book of the Wisdom of Solomon (a book that is part of the Apocrypha and included in some editions of the Bible), emphasized the magnificence of the creation, but refers to the creator only as the "author of beauty" [NRSV1993, pg. 1517-1518]. Similarly, the Letter of Clement, one of the oldest surviving Christian documents outside the New Testament itself, emphasizes the magnificence and lawfulness of the world, but describes the "Architect and Lord of the universe" mainly as an arbiter of "peace and harmony" among his creations [Barr2010b, pg. 897].

Is intelligent design a testable, falsifiable theory?

Michael Ruse, a philosopher of science who testified in the 1981 Alabama creationism case, describes science as a discipline that (1) is guided by natural law, (2) is explanatory by reference to natural law, (3) is testable against the empirical world, (4) reaches conclusions that are tentative, and (5) is falsifiable [Pennock1999, pg. 5]. So how does intelligent design measure as a scientific theory?

One key weakness of intelligent design, as it currently stands, is that these writers have not yet produced a solid body of quantitative, falsifiable scientific hypotheses that can be tested and scrutinized by the scientific community. For example, exactly what do the intelligent design writers mean by "design"? By contrast, creationists have at least produced a number of testable hypotheses, such as their assertions that the Earth was created in roughly 4000 BCE, and that all fossil layers were deposited during a global flood in roughly 2500 BCE (which hypotheses have been soundly refuted by scientific evidence). Instead, intelligent design writers have mostly focused their efforts on identifying weaknesses in the established evolutionary theory. One difficulty with this approach was noted by Judge John E. Jones in the 2005 Dover, Pennsylvania case: "[Intelligent design] is at bottom premised upon a false dichotomy, namely, that to the extent evolutionary theory is discredited, [intelligent design] is confirmed. ... We do not find this false dichotomy any more availing to justify [intelligent design] today than it was to justify creation science two decades ago." [Jones2005, pg. 71].

Assessment of intelligent design's scientific claims

Nonetheless, many are convinced that intelligent design writers have identified substantive technical issues that draw into question certain aspects of evolutionary theory. Since these issues are very frequently raised in these discussions, here is a brief summary of the some issues raised by the intelligent design writers and the consensus response of the scientific world:
  1. Irreducibly complex systems. Michael Behe has argued that certain biological systems, such as bacterial flagella, blood clotting machinery, and the immune system, are "irreducibly complex": they consist of multiple subsystems, the removal of any one of which would render the system nonfunctional. He argues that such systems must have been designed by an intelligent entity, because none of the components could have evolved in the absence of the others.

    Rejoinder: Scientists counter that systems labeled as "irreducibly complex" by Behe can arise by natural evolution -- individual parts may arise separately, each useful in different context, and then later be combined into a larger system. With regards to Behe's example of the bacterial flagella, researchers recently found that its DNA sequence is almost identical to that of a "needle" that certain bacteria use to insert toxins [Jones2008; Miller2003; Miller2004; Pallen2006]. In a similar way, scientists have found that most of the proteins involved in the human blood clotting system are genetically similar and most likely are the result of gene duplication [Fairbanks2007, pg. 150-156]. With regards to the Behe's claim that the vertebrate immune system is irreducibly complex, journalist Lauri Lebo's account of the proceedings in the 2005 trial on intelligent design in Dover, Pennsylvania provides an amusing illustration of the difficulties involved, as the prosecuting attorney produced stacks of articles and books documenting the evolution of the immune system in great detail [Lebo2008, pg. 153-154]. Facts such as these ultimately convinced conservative Judge John E. Jones, who presided over the Dover trial, to write in his decision, "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." [Jones2005, pg. 78-79].

  2. Probability. Creationists and intelligent design writers have often employed impressive-sounding arguments from probability theory suggesting that certain biomolecular compounds, for instance, could not possibly have arisen from "random" evolution. For example, several of these writers argued that the probability of a biomolecule such as human alpha globin, which is a sequence of 141 amino acids, forming at random from scratch is so remote that it could not be expected to have occurred even once in the history of the universe.

    Rejoinder: Such calculations may sound impressive to a lay audience, but to a researcher familiar with the many potential pitfalls of arguments based on probability and statistics, they are deeply flawed. To begin with, these writers presume completely unrealistic probabilistic models, such as when they attempt to reckon the probability of selecting human alpha-globin "at random," based on an all-at-once random assemblage of atoms. But available evidence from many published studies indicates that human alpha-globin arose as the end product of a long sequence of intermediate steps, each of which was biologically useful in an earlier context [Hardison2012]. Such reckonings also implicitly presume that every instance, say of the space of 141-long amino acid sequences, is equally likely to actually occur in the organism in question, so that the probability of any particular instance is merely the reciprocal of the total number of theoretical possibilities. But no justification is given for this sweeping assumption -- some amino acid sequences might be relatively more likely to emerge, while vast numbers of other sequences might not be biologically possible at all. Furthermore, most anti-evolution probability arguments (certainly including the alpha-globin example) fail to recognize that the process of natural biological evolution is not really a "random" process -- the all-important process of natural selection, acting in a competitive landscape and with numerous complicated environmental pressures, is anything but random. There are other major fallacies as well -- for full details, see Probability.

  3. Information theory. William Dembski has invoked probability and information theory (the mathematical theory of information content) in arguments against Darwinism. Rejoinder: Knowledgeable researchers who have examined Dembski's works in detail have identified serious errors of reasoning and are not convinced that he has identified any such weaknesses in evolutionary theory [Perakh2004, pg. 27-28; Perakh2005; Shallit2002]. Computational biologist Wesley Elsberry, after a thorough analysis of Dembski's claims, wrote:
    We have argued that Dembski's justification for "intelligent design" is flawed in many respects. His concepts of complexity and information are either orthogonal or opposite to the use of these terms in the literature. His concept of specification is problematic and ill-defined. ... [H]is claims about the limitations of natural causes and computation are incorrect. We conclude that there is no reason to accept his claims.

  4. Biological novelty. A key premise of intelligent design theory is that whereas minor changes may occur within an established kind, "random" or "undirected" evolution can never produce anything fundamentally new [Dembski1999, pg. 113]. Rejoinder: Biologists counter with examples such as a 1974 experiment, wherein a gene in the bacterium E. coli that is responsible for metabolizing lactose was removed. Within 24 hours the bacteria had re-evolved a capability to utilize lactose, by means of a similar but distinct three-part biochemical pathway [Miller1999, pg. 145-147]. An even more remarkable case is Richard Lenski's multi-decade experiment, in which one colony of E. coli bacteria, after 33,000 generations, suddenly developed the ability to utilize citrate, by means of a combination of two mutations [Pennisi2013]. Perhaps the best-known examples, however, are the recent evolution of new strains of tuberculosis that are resistant to all known anti-TB drugs, and drug-resistant strains of HIV that in many cases evolve within the body of a single patient [Coyne2009, pg. 130-131]. This is discussed in more detail at Novelty.

  5. Design. The intelligent design community has strongly advanced the notion that many features of nature exhibit "design." Rejoinder: This design hypothesis presents severe problems, technical and theological, not only in light of the many troublesome features of nature, such as pain, disease and violence, but also from the undeniable fact that millions of species that once roamed the Earth have become extinct. For example, paleontologists have identified 22 distinct species of elephants that arose and became extinct during the past six million years. Why did it take so many tries to "design" modern elephants? [Miller1999, pg. 97]. For that matter, numerous features of the human body present difficulties for the "design" hypothesis. Many persons suffer from back ailments, due to a skeletal design that is clearly adapted from four-footed ancestors [Miller1999, pg. 101]. Almost all mammals generate their own vitamin C, but while we have the same biochemical machinery, it doesn't work because mutations have inactivated at least one key step [Fairbanks2007, pg. 53-54; Miller2008, pg. 97-98]. Numerous other examples could be mentioned, but the conclusion is the same -- at the least, design must be viewed in high-level terms, not in low-level mechanics. This is discussed in more detail at Design.

Do intelligent design writers publish in peer-reviewed scientific publications?

Intelligent design writers have published their arguments dissenting from conventional evolutionary science in books and in online articles, but, as far as anyone can determine, not in any recognized peer-reviewed scientific journal.

This lack of peer-reviewed publications presents a severe obstacle to intelligent design being taken seriously in the scientific world. After all, if intelligent design writers (individually or collectively) believe that any of their technical issues have significant merit on purely scientific grounds, why do they not compose them into well-researched and well-analyzed articles and submit these articles to recognized peer-reviewed scientific journals? After all, as emphasized in a recent commentary in Science, signed by numerous prominent scientists, after brief mention of the prevailing theories of geology, big bang cosmology and evolution, "Even as these are overwhelmingly accepted by the scientific community, fame still awaits anyone who could show these theories to be wrong." [Gleick2010].

Criticism of intelligent design from the religious community

The intelligent design movement has even drawn criticism from religious writers. For example, Carl Wieland, a writer for Creation Ministries International, criticized the intelligent design movement for its lack of candor as to its true intent [Wieland2002]:
They generally refuse to be drawn on the sequence of events, or the exact history of life on Earth or its duration, apart from saying, in effect, that it 'doesn't matter.' However, this is seen by the average evolutionist as either absurd or disingenuously evasive -- the arena in which they are seeking to be regarded as full players is one which directly involves historical issues. In other words, if the origins debate is not about a 'story of the past,' what is it about?

Stephen M. Barr, a University of Delaware physicist and columnist for the inter-denominational publication First Things, recently summarized the impact of intelligent design in these terms [Barr2010a]:

It is time to take stock: What has the intelligent design movement achieved? As science, nothing. The goal of science is to increase our understanding of the natural world, and there is not a single phenomenon that we understand better today or are likely to understand better in the future through the efforts of ID theorists. If we are to look for ID achievements, then, it must be in the realm of natural theology. And there, I think, the movement must be judged not only a failure, but a debacle.
Very few religious skeptics have been made more open to religious belief because of ID arguments. These arguments not only have failed to persuade, they have done positive harm by convincing many people that the concept of an intelligent designer is bound up with a rejection of mainstream science. ...
None of this is to say that the conclusions the ID movement draws about how life came to be and how it evolves are intrinsically unreasonable or necessarily wrong. Nor is it to deny that the ID movement has been treated atrociously and that it has been lied about by many scientists. The question I am raising is whether this quixotic attempt by a small and lightly armed band to overthrow "Darwinism" and bring about a new scientific revolution has accomplished anything good. It has had no effect on scientific thought. Its main consequence has been to strengthen the general perception that science and religion are at war. ...
I suspect that some religious people have embraced the ID movement's arguments because they want "scientific" answers to the scientific atheists, and they know of no others. But there are plenty of ways to make a case for the reasonableness of religious belief that can be persuasive to many in the scientific world. Such a case has been made by a growing number of research scientists who are Christian believers, such as John Polkinghorne, Owen Gingerich, Francis Collins, Peter E. Hodgson, Michal Heller, Kenneth R. Miller, and Marco Bersanelli. I have addressed many audiences myself using arguments similar to theirs and have had scientists whom I know to be of firm atheist convictions tell me that they came away with more respect for the religious position. Religion has a significant number of friends (and potential friends) in the scientific world. The ID movement is not creating new ones.

Conclusion

The creationist and intelligent design movements were founded out of deeply felt concerns that modern science in general, and evolutionary theory in particular, are a challenge to the Bible and Judeo-Christian religion. Many of their adherents are deeply religious people and commendably practice their religion in daily life. Their general notion that a supreme Being oversaw or governed the creation in some high-level sense is one that many scientists, religious or not-so-religious, can accept.

However, with regards to the technical arguments raised by these communities, the consensus of the vast majority of scientists who have examined these issues is that their arguments are overwhelmingly refuted by well-known evidence. Virtually all of these issues were settled long ago in the scientific literature. And the latest evidence, such as DNA sequence data (produced thanks to a dramatic drop in the cost of DNA sequencing technology) all but scream "common ancestry between species," sharply contradicting the claim of independent creation of individual species -- there is no other reasonable way to interpret these data (see Evolution evidence) and DNA).

In any event, the creationist-intelligent design arguments have not been published in reputable peer-reviewed scientific journals, so they cannot be taken seriously by the scientific community. If any of these writers have solid arguments that could withstand peer review, they are welcome to compose these arguments in a soberly written, well-organized technical paper, and submit it to a prominent journal in the evolutionary science field.

One overriding difficulty with both the creationist and intelligent design movements is that invoking a Creator or Designer whenever one encounters a difficult question is a "thinking stopper." Such an approach places numerous grand questions of our existence off-limits to human investigation, buried in the inscrutable mind of a mysterious supreme Being: "Why was the Earth (or the universe in general) designed the way it was?" "How did the design and creative processes proceed?" "What physical laws were employed?" "Why those particular laws?" "What prompted the creation?" "Have other earths or universes been designed or created?" "Where are they?" Surely there is a more fruitful avenue for finding a harmony between science and religion than just saying "God created and/or designed it that way" and then deeming it either unnecessary or inappropriate to inquire further -- reveling in ignorance instead of thirsting for knowledge.

It is ironic, in a way, that the creationist and intelligent design movements seek to "prove" the hand of God in creation by seeking scientific evidence that certain aspects of the creation could not possibly have occurred by natural processes. By placing God on the anvil of scientific verification or refutation, these writers are implicitly affirming the scientific materialist worldview of the critics who are their most implacable foes -- see Atheists. Further, these movements inevitably lead to such theological disasters as "God the Great Deceiver" theology, wherein God is thought to have constructed the world with an appearance of ancient evolutionary development [to mislead diligent seekers of truth?] (see Deceiver), and "God of the gaps" theology, wherein God is sought in the ever-shrinking gaps of what is currently unexplained in science [tantamount to theological suicide?] (see God of the gaps).

For these reasons, neither creationism nor intelligent design can be recommended for those seeking rational harmony between science and religion, to say the least! Other approaches, which acknowledge basic scientific precepts, and do not attempt to combat the world of science, are recommended instead -- see Harmony for a high-level discussion of these issues.