Michael Behe is a professor of biochemistry at Lehigh University and a Senior Fellow at the Discovery Institute Center for Science and Culture. In recent years he has done little or no research, but is best known for a series of books attacking aspects of the theory of evolution. In this summary, we will discuss Behe’s books Darwin’s Black Box (1996) and his latest book Darwin Devolves (2019). We will also review Behe’s role in the 2005 trial in York County, Pennsylvania, after the local school board mandated that anti-evolutionary material be included in a middle-school science curriculum.
Some of this material has been presented in our blog posts on evolution.
Over the past 25 years, Michael Behe has become one of the most prominent critics of the theory of evolution. In 1994, he attacked the idea that whales had evolved from land-dwelling mammals called Mesonychids (an extinct family of carnivorous ungulates). Behe wrote “…if random evolution is true, there must have been a large number of transitional forms between the Mesonychid and the ancient whale. Where are they? It seems like quite a coincidence that of all the intermediate species that must have existed between Mesonychid and whale, only species that are very similar to the end species have been found.” (in Darwinism, Science or Philosophy? 1994. Jon Buell & Virginia Hearn, eds. Published by the Foundation for Thought and Ethics, Houston, Texas).
Here, Behe suffered from extremely bad timing. Over the next few years, several fossils were discovered that clearly showed the transition from land-dwelling mammals to cetaceans (whales). What’s more, the fossils were found in rocks of precisely the age suggested by evolutionists. By now, many transitional fossils have been found, and they show that whales are more closely related to hippopotamids than to mesonychids.
But this setback did not deter Behe – he simply stopped talking about the fossil record and the transition from land-based mammals to whales. Next, he focused on a new idea that he termed irreducible complexity. Behe argued that a scientific examination of genetic biochemistry would lead an objective observer to conclude that an intelligent entity had designed the natural world and in particular humans.
In his books, Behe is rather coy about the nature of the Intelligent Designer, whom he does not identify. This is likely a tactic that has been adopted by the Fellows of the Discovery Institute. Their goal, as set out in detail in their “Wedge” document, is first to overthrow the theory of evolution, and only later to proselytize for Christianity.
However, from Behe’s earlier writings we know that his religious principles (he is a devout Catholic) provide much of the impetus behind his work. For example, in his paper “Randomness or Design in Evolution?” (Ethics & Media 23.6, 1998), Behe cited the comments of Pope Benedict XVI (when he was still Cardinal Ratzinger) that “life is the result of intelligent purpose, not ontologically random events.” Behe noted that the Cardinal “implies that biochemistry … provides particularly strong support for this view.” Behe has stated that “the critical question [for Catholics] is whether life is an unintended accident or the purposeful work of a Creator.” He adds that Catholics are obliged to acknowledge “that modern science has yielded physical evidence which points strongly to an intelligent designer.”
Darwin’s Black Box:
In 1996, Michael Behe published a book Darwin’s Black Box: The Biochemical Challenge to Evolution; the cover of this book is shown in Fig. 2. Behe introduced a pseudoscientific principle called irreducible complexity. This concept first appeared in a chapter of the second edition of Of Pandas and People, where Behe argued that the blood clotting cascade was an irreducibly complex process. The notion of irreducible complexity is the central theme of Darwin’s Black Box.
Behe defines an irreducibly complex system as one “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.” He uses a mousetrap as an example. Behe claims that many biological systems could not possibly result from multi-step genetic mutations, but can only have been produced intact by an intelligent design agent at a single point in time. Many anti-evolutionists claim that “irreducible complexity” provides the strongest evidence in favor of intelligent design and against the theory of evolution.
ID relies centrally on the concept of irreducible complexity, the claim that at least some biological features are so elegant and complex, and so reliant on multiple components working in unison, that they could not possibly have arisen from cumulative incremental random mutations and natural selection. Biochemical systems that Behe suggested were irreducibly complex included the bacterial flagellum (a tail-like rotating propeller used as a molecular motor) of E. coli; the blood-clotting cascade; the adaptive immune system; and cilia (hairlike protuberances from some cells). Another example long promoted by creationists and ID advocates is the eye of sighted animals.
We reviewed in detail the notion of irreducible complexity in our blog posts on evolution. Here we will briefly summarize the situation with respect to the bacterial flagellum. Behe pointed out that 40 different proteins were required to produce a bacterial flagellum. He claimed that the first 39 of these proteins would have served no useful purpose; consequently the bacterial flagellum could not possibly have been produced by a sequence of “numerous, successive, slight modifications of a precursor system.”
The bacterial flagellum has been the subject of many studies. Different strains of bacteria have flagella that are composed of distinctly different proteins. In some bacteria, several of the proteins involved in flagellum function are very similar to amino acid sequences that allow bacteria to secrete toxins; this suggests that this subset of proteins could provide a different function.
In 2016, Behe issued a challenge to his critics, in particular to molecular biologist Kenneth Miller. Behe asked “…why doesn’t [Miller] just take an appropriate bacterial species, knock out the genes for its flagellum, place the bacterium under selective pressure (for mobility, say), and experimentally produce a flagellum – or any equally complex system – in the laboratory? … If he did that my claims would be utterly falsified.” Behe did not realize that this experiment had already been carried out and published in 2015.
In this study, experimenters deleted a gene that governs flagellum synthesis in soil-based bacteria, and they produced two independent strains of bacteria without flagella. They then depleted nutrients in the starting colony, imposing a strong selection for mutations that would allow the bacteria to re-evolve motility. Over the ensuing 96 hours the researchers observed a regeneration of flagellar motility for each of the two independent strains of modified bacteria.
The researchers discovered an evolutionary pathway involving two successive point mutations to genes that initially served different purposes. The first mutation led to increased production of a protein normally associated with regulation of nitrogen uptake and assimilation, but now with a single amino acid substitution. The modified protein began to exert control over the regulatory network for flagellum synthesis, at the cost of disruption to the nitrogen uptake. The bacteria with both mutations regained flagella and full motility, at the expense of nitrogen assimilation. This was a clear demonstration that the flagellum system is not irreducibly complex. The mechanism (adapting genes developed for one purpose to serve a different purpose in response to a change in the environment) is precisely what was predicted by evolutionary theory.
In 1996, Allen Orr reviewed Darwin’s Black Box in the Boston Review in 1996. Orr summarized: “Behe’s colossal mistake is that, in rejecting these possibilities, he concludes that no Darwinian solution remains. But one does. It is this: An irreducibly complex system can be built gradually by adding parts that, while initially just advantageous, become – because of later changes – essential. The logic is very simple. Some part (A) initially does some job (and not very well, perhaps). Another part (B) later gets added because it helps A. This new part isn’t essential, it merely improves things. But later on, A (or something else) may change in such a way that B now becomes indispensable. This process continues as further parts get folded into the system. And at the end of the day, many parts may all be required.”
“The point is there’s no guarantee that improvements will remain mere improvements. Indeed because later changes build on previous ones, there’s every reason to think that earlier refinements might become necessary. The transformation of air bladders into lungs that allowed animals to breathe atmospheric oxygen was initially just advantageous: such beasts could explore open niches – like dry land – that were unavailable to their lung-less peers. But as evolution built on this adaptation (modifying limbs for walking, for instance), we grew thoroughly terrestrial and lungs, consequently, are no longer luxuries: they are essential. The punch-line is, I think, obvious: although this process is thoroughly Darwinian, we are often left with a system that is irreducibly complex. I’m afraid there’s no room for compromise here: Behe’s key claim that all the components of an irreducibly complex system ‘have to be there from the beginning’ is dead wrong.”
Michael Behe’s attacks on evolution have made no inroads with the mainstream scientific community. Several critiques of his intelligent-design model have been published, and in the next section we will discuss several of the refuting points that were raised at the Kitzmiller vs. Dover trial. In fact, Behe’s own colleagues in the Lehigh University biology department have published a disclaimer on the department’s Web site. It reads: “While we respect Prof. Behe’s right to express his views, they are his alone and are in no way endorsed by the department. It is our collective position that intelligent design has no basis in science, has not been tested experimentally, and should not be regarded as scientific.”
2. Behe and Kitzmiller vs. Dover:
Over the past century, several states have attempted to modify the standards for science instruction as a means of introducing creationist viewpoints into the biology curriculum. The most recent of these led to a trial in York County, Pennsylvania in 2005 (Kitzmiller et al. vs. Dover Area School District et al.). That school board mandated that ninth-grade science classes had to be presented with “an explanation of the origin of life that differs from Darwin’s view.” The creationist book Of Pandas and People was mentioned as a suitable textbook, and the president of the Dover Board of Education donated 60 copies of this book to the middle school. A group of parents and teachers subsequently sued the school board on the grounds that the new standards were motivated by religion rather than science.
When the trial was announced, Fellows of the Center for Science and Culture at Seattle’s anti-evolution Discovery Institute (DI) expressed eagerness to provide testimony in favor of intelligent design. DI Fellows Michael Behe, William Dembski, Stephen Meyer and John Angus Campbell were scheduled to testify for the defense, which was organized by the Thomas More Center, a conservative Christian non-profit law firm. However, at the last minute all of these people except for Behe withdrew from the case.
This left Michael Behe and Scott Minnich (an associate professor of biology at the University of Idaho) as the only scientists who testified on behalf of the (anti-evolution) defense in this trial. Behe was the central witness in defense of the notion of intelligent design.
The “ID” proponents fared very badly at the Kitzmiller vs. Dover trial. First, Barbara Forrest compared different versions of the anti-evolution textbook Of Pandas And People. She showed that later versions of that book had replaced all references to “The Creator” with “Intelligent Design.” This clearly demonstrated a religious motivation behind the book.
Behe claimed that ‘intelligent design’ was a legitimate scientific theory. However, under cross-examination Behe admitted that “there are no peer reviewed articles by anyone advocating for intelligent design supported by pertinent experiments or calculations which provide detailed rigorous accounts of how intelligent design of any biological system occurred.” Furthermore, Behe admitted that “his definition of ‘theory’ as applied to intelligent design was so loose that astrology would also qualify.”
At the trial Behe reviewed in detail his hypothesis, the subject of Darwin’s Black Box, that certain features found in nature were “irreducibly complex.” As in his book, Behe compared irreducible complexity using the analogy of a mousetrap, a device that works only after several critical elements are joined together. And Behe argued that features such as the bacterial flagellum, the blood-clotting cascade, and the immune system were compelling examples supporting his hypothesis of irreducible complexity.
Several mainstream scientists refuted Behe’s testimony. They pointed out that in several instances, Behe’s claims had been tested and falsified. Furthermore, they attacked Behe’s assertion that the examples he cited would lead an unbiased scientist to conclude that they were the result of intelligent design.
The testimony of Behe and the mainstream scientists made a strong impact on the judge, John Jones, an appointee of George W. Bush and a regular churchgoer. In a 139-page ruling, Judge John Jones stated that “The overwhelming evidence at trial established that ID is a religious view, a mere re-labeling of creationism, and not a scientific theory.” Jones concluded that “the secular purposes claimed by the Board amount to a pretext for the Board’s real purpose, which was to promote religion in the public school classroom, in violation of the Establishment Clause.”
The outcome of the trial was a major setback for ID proponents. In addition, Jones’ ruling made numerous references to the testimony of Behe and other scientists, including the following points:
- “Consider, to illustrate, that Professor Behe remarkably and unmistakably claims that the plausibility of the argument for ID depends upon the extent to which one believes in the existence of God.”
- “As no evidence in the record indicates that any other scientific proposition’s validity rests on belief in God, nor is the Court aware of any such scientific propositions, Professor Behe’s assertion constitutes substantial evidence that in his view, as is commensurate with other prominent ID leaders, ID is a religious and not a scientific proposition.”
- “First, defense expert Professor Fuller agreed that ID aspires to ‘change the ground rules’ of science and lead defense expert Professor Behe admitted that his broadened definition of science, which encompasses ID, would also embrace astrology. Moreover, defense expert Professor Minnich acknowledged that for ID to be considered science, the ground rules of science have to be broadened to allow consideration of supernatural forces.”
- “What is more, defense experts concede that ID is not a theory as that term is defined by the NAS and admit that ID is at best ‘fringe science’ which has achieved no acceptance in the scientific community.”
- “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.”
- “ID proponents primarily argue for design through negative arguments against evolution, as illustrated by Professor Behe’s argument that ‘irreducibly complex’ systems cannot be produced through Darwinian, or any natural, mechanisms. However, … arguments against evolution are not arguments for design. Expert testimony revealed that just because scientists cannot explain today how biological systems evolved does not mean that they cannot, and will not, be able to explain them tomorrow. As Dr. Padian aptly noted, ‘absence of evidence is not evidence of absence.’… Irreducible complexity is a negative argument against evolution, not proof of design, a point conceded by defense expert Professor Minnich.”
- “Professor Behe’s concept of irreducible complexity depends on ignoring ways in which evolution is known to occur. Although Professor Behe is adamant in his definition of irreducible complexity when he says a precursor ‘missing a part is by definition nonfunctional,’ what he obviously means is that it will not function in the same way the system functions when all the parts are present. For example in the case of the bacterial flagellum, removal of a part may prevent it from acting as a rotary motor. However, Professor Behe excludes, by definition, the possibility that a precursor to the bacterial flagellum functioned not as a rotary motor, but in some other way, for example as a secretory system.”
- “In fact, 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.”
Prof. Behe appears to be sincere in his belief that investigation of different species and certain complex functions leads to the conclusion that they were ‘intelligently designed.’ However, his religious convictions lead him to advance proposals that are rejected by the mainstream scientific community, and to various assertions that have been falsified. Neil de Grasse Tyson contrasted skeptics and deniers, saying that “a skeptic will question claims, then embrace the evidence. A denier will question claims, then reject the evidence.”
Thus when Behe is presented with evidence supporting the evolution of the immune system, he rejects it as “not good enough.” Similarly, creationists frequently (and falsely) claim that there are no fossils representing transitional forms from one species to another. When presented with transitional fossils, they reject them as being insufficient to show every step involved in the transition.
3. Darwin Devolves:
In 2019, Michael Behe published his latest book, Darwin Devolves: The New Science About DNA That Challenges Evolution. Here Behe argues that mutation and natural selection can only increase diversification at the species and genus levels by degrading genes. He claims that “natural selection itself acts as a powerful de-volutionary force, increasing helpful broken and degraded genes in the population.” According to Behe, mutation and natural selection are thus self-limiting; left to their own devices, these processes will eventually wind down and prevent further change. Behe then claims that meaningful innovation capable of producing new functions and new species is possible only through “purposeful design” by an “intelligent agent.”
Unfortunately, in this book Behe continues his habit of ignoring or rejecting any evidence that contradicts predetermined conclusions. Thus, he spends a good deal of time in his book analyzing results from Richard Lenski’s famous long-term evolutionary study of more than 65,000 E. coli generations placed in a limited-nutrient environment. As Lents, Swamidass and Lenski point out in their review of Darwin Devolves in Science, Behe emphasizes “the many mutations that arose that degraded function—an expected mode of adaptation to a simple laboratory environment, by the way—while dismissing improved functions and deriding one new one as a ‘sideshow’.”
Behe also ignores a number of evolutionary mechanisms that do not involve broken genes. He does not mention duplication, where a gene is accidentally copied twice and the copies diverge in useful ways. Nor does he consider examples where new functions arise simply by changing when genes are turned on or off. He also does not mention cases where ancient genes acquired from viruses are re-purposed; and he ignores instances where changes in DNA sequences alter proteins without breaking them.
A particularly serious error is that Behe continues to ignore the experimentally established important role of exaptation. This is the process by which genes originally developed for one function are subsequently re-purposed to play innovative roles in complex new functions. This is not an oversight – exaptation is a powerful mechanism by which new functions can arise through evolution; it provides a strong argument against intelligent design. In their review, Lents, Swamidass and Lenski point out that the feathers of birds, gas bladders of fish, and ossicles of mammals (small bones of the inner ear) all have exaptive origins.
By ignoring contrary evidence, Behe grossly overstates his case. Random mutation does often, but certainly not “overwhelmingly,” result in degraded genes. Behe appears to neglect the sizable frequency of neutral or only slightly deleterious mutations, which very often serve as stepping stones in a sequence of mutations that lead eventually, over one or another among myriad evolutionary paths, to innovative functionality.
Mutations that break or degrade genes do sometimes, but hardly “always,” lead to short-term adaptive improvements that make species vulnerable to environmental changes over the longer term. Although 99% of all species that ever existed on Earth are now extinct, nevertheless many species have continued to evolve and to thrive, and many new species have been produced. The scientific evidence is completely consistent with the claim that such evolution results from natural processes involving common descent fueled by occasionally innovative sequences of mutation and natural selection.
In conclusion, Michael Behe has published three books criticizing the theory of evolution. His arguments have received a great deal of publicity, and his work is widely cited by evolution deniers. On the other hand, Behe’s work has been almost universally panned by mainstream biologists and chemists. There have been several devastating critiques of his basic arguments: namely, that he cherry-picks evidence that supports his theories and ignores events that contradict his predetermined conclusions; his examples of irreducible complexity have been discredited; and his recent claim that natural selection acts as a powerful “de-volutionary force” has also been widely debunked.
Behe does essentially no original research, and he publishes books rather than submit his scientific arguments to peer-refereed journals. Although he attempts to respond to his critics, the mainstream scientific community sees his arguments as seriously flawed and unconvincing. This was particularly evident in Behe’s presentation at the “Kitzmiller v. Dover” trial.
Wikipedia, Michael Behe
Michael Behe, Blind Evolution or Intelligent Design? Address at the American Museum of Natural History, April 23, 2002:
Michael Behe, Randomness or Design in Evolution? Ethics & Media 23.6, 1998.
Intelligent Design Gets Even Dumber: Jerry Coyne, review of Darwin Devolves by Michael Behe, Washington Post, Mar 8, 2019:
A Biochemist’s Crusade to Overturn Evolution Misrepresents Theory and Ignores Evidence: Nathan H Lents, J. Joshua Swamidass and Richard E. Lenski, review of Darwin Devolves by Michael Behe, Science, Feb 7, 2019: https://blogs.sciencemag.org/books/2019/02/07/darwin-devolves/
John Catalano, Behe’s Empty Box: [this is a detailed review of Behe’s arguments, together with many links to relevant material from both creationists and mainstream scientists]:
- Allen Orr, Darwin vs. Intelligent Design (Again), Boston Review, Dec. 1996.
Is the Hippopotamus the Closest Living Relative to the Whale?
Wikipedia, The Wedge Strategy:
National Center for Science Education, The Wedge Document:
Barbara Forrest and Paul Gross, Creationism’s Trojan Horse: The Wedge of Intelligent Design, Oxford University Press, 2004:
Michael Behe, Darwin’s Black Box: The Biochemical Challenge to Evolution (Free Press, 1996)
J.T. Londergan and S. Vigdor, Debunking Denial, Evolution:
Michael Behe, Darwin Devolves: The New Science About DNA That Challenges Evolution (HarperOne, 2019)