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Further Reading

book contents

flagellum animation
flagellum animation

See also: different pagereview of Michael Behe (2007) The Edge of Evolution.

See also:
different pageAnd God Said: Let There Be Cilia
is a philosophical-theological postscript to Behe's Black Box

See also:

Michael Behe
SARS-CoV-2 was designed says Intelligent Design Theorist Michael Behe.
26 Feb 2021.

Does Irreducible Complexity refute neo-Darwinism?

a review of Michael Behe's 'Darwin's Black Box' by Gert Korthof

26 Apr 1997 (updated 2 May 2011)

Irreducible Complexity is a good test for neo-Darwinism:
it's a potential falsifier of the theory of natural selection.
If particular biochemical systems are irreducibly complex,
then neo-Darwinism is false. However if those systems appear
to be not irreducibly complex after all, then irreducible complexity
shows us at least that neo-Darwinism is a falsifiable theory and passed a risky test.
Michael: thanks for proving neo-Darwinism is a scientific theory!

Darwin's Black Box     The famous philosopher Karl Popper proposed falsifiability of a theory as a criterion to distinguish scientific from non-scientific theories. 'Falsifiability' means that a theory must be able to be refuted by at least some real-life observations. A falsifiable theory is a scientific theory and an unfalsifiable theory is not a scientific theory at all. Potential falsifiers of neo-Darwinism are seldom published by neo-Darwinists. When asked what finding would make him question his belief in evolution, J.B.S. Haldane answered: 'a Precambrian rabbit' (39). There should be more interesting and more risky falsifiers than that! Why don't we read more of them? Too risky? Too difficult? Not interesting enough? Or is neo-Darwinism unfalsifiable? Even when falsifiability is not the only or the best criterion for judging a scientific theory, it is still a powerful criterion. It forces us to specify what things should and should not happen. A good theory should forbid things. The more, the better. If there aren't things that are forbidden, then everything is permitted to happen or to exist. And then we have no scientific theory at all.
Well, biochemist Michael Behe in Darwin's Black Box. The biochemical challenge to evolution (1996) specifies a few things that exist and should not exist according to neo-Darwinism. Behe assumes neo-Darwinism claims :
  1. every organism and every structure in an organism is the result of natural selection. How could there be exceptions? There is no alternative. By consequence whatever structure or organism you specify: neo-Darwinism should be able to explain it (42).
  2. every complex structure must be accessible by small mutational steps. This is basic to the genetical theory of natural selection (46).
  3. every step must be beneficial for the organism, in order to have a reasonable chance to be selected (32).


    These are hard constraints on all possible neo-Darwinistic explanations. Stepwise creation and the beneficial nature of intermediate steps are the most important building blocks of the neo-Darwinist explanation of the adaptations of living organisms. Through Behe's account one starts to realise that these rules are strong constraints indeed. Contrary to what the textbooks seem to tell us, evolution is not easy and surely evolutionary improvement and innovation are not inevitable. The picture that Behe paints is not a distortion of neo-Darwinism. It is neo-Darwinism in a nutshell: "If there is no stepwise path up the mountain, natural selection won't climb it" as evolutionary biologist John Maynard Smith pointed out (9).
    Evolutionary intermediates represented a central preoccupation for Charles Darwin in his case for the theory of evolution. He remarked, for example: '...why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms?' (On the Origin of Species). Although Darwin developed a convincing rationale for their absence, he did realize that the lack of intermediates as proof leaves room for criticism. He noted, for instance:
'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.' (On the Origin of Species) (45).
So, Behe just followed up Darwin's suggestion.

    Behe should not be attacked for claiming to have refuted neo-Darwinism. If these cases trigger new research, new questions and new answers, then Behe indirectly stimulated science. It is now clear that Behe did indeed stimulate scientific thinking (10, 37, 38). However, it is also true that he did not publish his ideas in a peer-reviewed biological or biochemical journal, but in a book for the general public. A book is a way to side-step review by peers. Behe did publish in philosophical journals (14). But Darwinism is a biological theory, not a philosophical theory.

General versus specific

    Please note that Behe did not claim that the Darwinian explanation is wrong in all cases, but that neo-Darwinism cannot explain some cases (such as bacterial flagellum and the blood clotting system). This means that irreducible complexity is not a general falsificator of natural selection or neo-Darwinism, but a specific falsificator for specific cases. Behe did not bother to point out that all other cases are explainable by Darwinism. Please note that Behe did not attack common descent of all life (evolution as a fact) (26). Accepting common descent and rejecting the mechanism of evolution is not a contradiction, because we are talking about two separate theories and the evidence for both theories is different too.
    Furthermore, Behe did not claim that there could never be any functional intermediates on the way to any irreducibly complex system. Irreducible complexity does rule out direct routes, but it does not rule out indirect routes. According to Behe, indirect routes are quite implausible.

The definition of IC

    Irreducible Complexity is defined by Behe as a single system which is composed of several well-matched, interacting parts that contribute to the basic function, and where removal of any one of the parts causes the system to effectively cease functioning.


The Logic of the Concept IC

    Two aspects must be clearly separated: the state of a system and the origin of the system. To call something 'irreducible complex' is a description of the state of the system. It means that all parts of that system are necessary for the functioning of the whole system. According to Behe, each part has no value except within the context of the whole functional unit. The state of being irreducible complex does not say anything about its origin. There are many irreducible systems in your house, the most simple ones are:
They all consist of 3 parts, which are necessary for their function. If one part is removed, the system does not function anymore. However, contrary to Behe, the parts on their own are not completely useless. They can be used for other functions. For example, the wooden part of a clothes peg can be used to stir coffee or as the stick in a lollipop or ice cream. One of the sharp blades of scissors can be used as a knife.
cup of coffee with part of clothes-peg as spoon wooden part of a clothes peg
can be used to stir coffee
ice cream wooden stick or as the stick in a lollipop
or ice cream
What about the origin of these systems? The production of these IC systems is not too difficult. But the construction of a stone arch seems mysterious. Origin of life researcher A.G. Cairns-Smith (1985) asked: how can you build an arch of stones gradually stone by stone? (40)
finished stone arch
finished stone arch
stone arch with temporary support
how it was constructed

The solution is: start with supporting stones and place the final stones on top of it, then remove the supporting stones. Removing one of the stones of the finished arch destroys the whole arch. The stone arch itself cannot be made gradually, but it certainly can be constructed one stone at a time with the help of temporary supporting stones. The first phase of the stone arch is a nonfunctional intermediate, because it does not function as an arch.

The history of the concept

Behe's household example of Irreducible Complexity was the mousetrap. Behe's biological examples of an IC system were cilia, flagellum and the blood clotting system. He borrowed the cilia from Michael Denton (1986) (19). Michael Denton came close to inventing Irreducible Complexity. Denton claimed 'intermediates do not exist'. Behe went one step further: 'intermediates cannot exist', which is a stronger claim. Origin of life researcher A.G. Cairns-Smith used in 1985 the idea of the stone arch as a metaphor for the interdependencies in the biochemistry of the cell. The anatomist Mivart listed in 1871 a number of organs that would not (he thought) be advantageous in their initial stages, for example the famous "What use is half a wing?" (41). But Darwin himself had a notion of the idea of 'Irreducible Complexity': "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" (31).
The idea of useless intermediate stages of a useful adaptation is even older than Darwin. William Paley used it as an argument for design and against a natural origin, as S.J. Gould pointed out (33).
book Darwin's Black Box.
The biochemical challenge to evolution.

by Michael J. Behe
The Free Press
ISBN 0-684-82754-9
307 pages
(2006 edition with Afterword Ten Years Later)

Part I: The Box is opened
1. Lilliputian Biology ...3
2. Nuts and Bolts ...26
Part II: Examining the contents of the box
3. Row, Row, Row Your Boat ...51
4. Rube Goldberg in the Blood ...74
5. From Here to There ...98
6. A Dangerous World ...117
7. Road Kill ...140
Part III: What does the box tell us?
8. Publish of Perish ...165
9. Intelligent Design ...187
10. Questions About Design ...209
11. Science, Philosophy, Religion ...232
Appendix: The Chemistry of Life ...255
Notes ...277
Index ...293

Biochemical mousetraps

A potential example of irreducible complexity not given by Behe is the interdependence of DNA and proteins, which results in the notorious difficulty of explaining the origin of life. Maybe all Irreducibly Complex systems are examples of another famous problem: the chicken and egg problem: no chicken without egg, no egg without chicken. A biological example of a potential IC system with two parts is the key-and-lock system such as a hormone and hormone-receptor. There is no point in having an elaborate key if there is no matching lock, and there is no point in having an elaborate lock if there is no matching key. Building a lock-and-key system appears to require at least two changes to happen simultaneously (37).


    According to Phillip Johnson "Darwin himself established the tradition of explaining away the fossil record" and "The central Darwinist concept that later came to be called the "fact of evolution" -descent with modification- was thus from the start protected from empirical testing" (6). This amounts to saying Darwinists made Darwinism unfalsifiable. However, Michael Behe unintentionally shows clearly why Phillip Johnson is wrong in claiming that Darwin and Darwinists created a nonfalsifiable theory! Darwinism is risky! However, if scientists claim (as a reaction to Behe) that neo-Darwinism is true and therefore cannot be refuted, then Johnson as yet is right.
    It is not right to call 'Irreducible Complexity' just a gap in our knowledge, because a gap in our knowledge can be neutral to a theory, whereas a potential falsificator is contra evidence for a theory. A falsificator is stronger than an unexplained phenomenon.
    Did Behe falsify neo-Darwinism? Above we saw that irreducible complexity is not a general falsificator, but a falsificator for specific cases. Therefore, a general refutation of neo-Darwinism is out of the scope of irreducible complexity. Furthermore, a mousetrap will not do: it is irreducible by definition. Behe needs an empirical demonstration that a specific biochemical system is irreducible. He must show that all 200 parts of the cilium are necessary! Only then, one can establish that the removal of one component destroys the function of the system. To do that, one must know exactly how many parts the system has. Behe is not precise about that: "a cilium contains over two hundred different kinds of proteins" (p.72, my emphasis). Without a precise list of parts, he never can determine whether the cilium is irreducibly complex.
    Furthermore, he must show that these parts do not have a second function. For, it they have a second function, they are maintained by natural selection. And this circumvents the requirement for usefulness of each intermediate step of proteins involved in the first function (motor function of the cilium or flagellum). For example, flagella are also essential for viability of the single-cell African parasite trypanosome, because they are essential for trypanosome cell division (36). Empirical evidence has the last word, not mousetraps (7). If Behe fails to come up with a case of irreducible complexity, that withstands all criticism, then neo-Darwinism survived another failed falsification. Precisely that is the right sort of positive evidence for a theory. It is evidence that counts. Actually the best possible confirmation for any scientific theory!
    Finally: the fact that Behe proposes 'design' as an alternative explanation, does not affect in the fact that 'Irreducible Complexity' is an interesting falsificator. 'Irreducible Complexity' itself is not a religious concept. Behe was smart enough to make his central concept non-religious. Behe's religious motives are also irrelevant for the evaluation of the correctness of 'Irreducible Complexity'. Even if Behe's hybrid hypothesis 'design and/or evolution' (4) is unfalsifiable, this does not affect the value of 'Irreducible Complexity' as a potential falsificator of the neo-Darwinian mechanism. Indeed, the value of 'Irreducible Complexity' as a falsificator is logically and factually independent of any alternative hypothesis.

Undermining the falsificator

    Unfortunately, but honestly, Behe later stated: "Demonstration that a system is irreducibly complex is not a proof that there is absolutely no gradual route to its production" (21), thereby undermining the beauty and power of his falsificator. But Behe did more to undermine his falsificator of Darwinism. In an article in the journal Biology and Philosophy (29) Behe stated "A weak point of Darwinian theory is its resistance to falsification. What experimental evidence could possibly be found that would falsify the contention that complex molecular machines evolved by a Darwinian mechanism? I can think of none". I can think of none? This is an extremely amazing claim. Behe forgets his own biochemical mousetraps! What was the point of writing Darwin's Black Box? What was the point of the concept 'irreducible complexity'? What was the point of the bacterial flagellum and the blood clotting system, if not refuting their Darwinian origin?
      Recently, it has been shown how a seemingly irreducible complex system could originate by a step-by-step Darwinian process (37,38). The system consists of two key-and-lock systems: the aldosterone and cortisol receptor system. It has been shown that these particular hormone-receptor systems evolved from a duplicated receptor-gene. The two copies differentiated by 2 point mutations and so an exclusive aldosterone sensitive and an exclusive cortisol sensitive receptor resulted. The two pairs now have different physiological functions. Experimentally, it has been shown that an evolutionary path exists from ancestor system to the recent aldosterone and cortisol system through 2 useful intermediate steps. Therefore, it has been shown that two seemingly irreducible complex key-and-lock systems evolved in a Darwinian way and that a designer was not necessary to explain them.
Another famous irreducible complex system, the flagellum, has been refuted by a detailed step by step evolutionary model, which is beautifully explained in this animation at YouTube:

flagellum animation
The Evolution of the Flagellum

(click on link to open animation in new window)

"When attempting to understand evolution, we traditionally rely on analysing evolutionary outcomes, despite the fact that unseen intermediates determine its course. A handful of recent studies has begun to explore these intermediate evolutionary forms, which can be reconstructed in the laboratory. With this first view on empirical evolutionary landscapes, we can now finally start asking why particular evolutionary paths are taken." (45).

Common Descent

To my surprise Behe stated: "I believe the evidence strongly supports common descent" (p.176) and he has repeated this in later publications (26). Behe did not bother to present the evidence for common descent. Is he interested at all in the evidence for common descent? Does he know or understand the evidence? Behe does not seem to realise the consequences of his statement.
Common descent of life means that all life is descended from the first form of life.
Common descent of life means that all life on Earth is physically, historically and genetically connected. It is one unbroken chain of ancestors and descendants.
Common descent of life means that there is only one tree of life.
Common descent of life means that gaps in the fossil record are gaps in the record, and not in the tree of life.
Common descent of life means that whatever the mechanism, every organism inherited its genes and all its so-called 'irreducibly complex' systems from the previous generation and so on until first life. Every intervention would be a violation of common descent.

2 May 2011


To my surprise Behe rejects macro-evolution: "Many people have followed Darwin in proposing that huge changes can be broken down into plausible, small steps over great periods of time. Persuasive evidence to support that position, however, has not been forthcoming." (p.15). How can one reject macro-evolution while at the same time accepting common descent? Common descent implies macro-evolution.

Behe is a theistic evolutionist

Behe accepts that evolution occurred and accepts common descent, however he thinks that evolution was 'guided by God' (15). That makes him a theistic evolutionist. However, Behe does not give a rigorous definition of 'guided evolution', so I don't know whether 'guided evolution' is the same as 'supernatural intervention' or contradicting common descent.

Unhistorical nature of Design

"The irreducibly complex biochemical systems that I have discussed in this book did not have to be produced recently. It is entirely possible (...) that they were designed billions of years ago and have been passed down to the present...
One can postulate that the designs for systems that were to be used later, such as blood clotting, were present but not 'turned on'." (page 227,228).
I overlooked this passage when I first read Behe's book, but I found it in Kenneth Miller's review (11). The problem with Behe's reasoning is that population genetics predicts that genes which are not "turned on", accumulate random mutations because they escape natural selection. They surely do so over "billions of years". Behe should explain what keeps them intact. Do we need a designer again to turn those silent genes on? When? Where? How? It is easy to suggest all these things as Behe does, but he did not work out the details as he himself demands again and again of Darwinists. Remarkably, Fred Hoyle (12) also proposes that genes where kept silent for millions of years until needed. The difference is that Hoyle's genes came from space! But Hoyle runs into the same problems (see review of John Maynard Smith (9) ).
    A fundamental difference between evolution and creation/design is that evolution needs precursors and creation/design does not need precursors. The creation/design view is clearly opposed to evolution and neo-Darwinism: completely specified genes waiting millions of years before they are turned on. Genes without any history, without any signs of their origin, without any relation to precursor genes. To be honest: Behe stated that the design hypothesis does not depend on 'when' in the history of the Earth. This is a disadvantage. It strikes me that 'design' is so unhistorical. For example: because the blood clotting system doesn't need to be based on pre-existing parts, it could be created anytime in the history of the Earth. 'Intelligent Design Theory' has nothing to say about when for example humans should appear in the fossil record. Therefore humans could appear before the first mammals; birds could appear before reptiles and land vertebrates could appear before fishes, etc. Because the Design theory is unhistorical, it is unsuitable for the study of life, since life itself is closely connected to the history of the Earth. It is not a coincident that Michael Behe has been educated in an unhistorical science (biochemistry). Biology has a significant historical component.

Unbiological nature of Design

Behe did not search for flagella in related species, neither did he search for simpler flagella. Yet, there are simpler variants of flagella as can be seen from the illustrations below:

bacterial flagellum A: cross section of a bacterial flagellum (44),(47)
much simpler flagella in related species B: The much simpler flagella that are found in related species of bacteria (44),(47)
The existence of simpler flagella means that it is in principle possible to evolve complex flagella from simpler flagella. A professional biologist always investigates related species when he wants to know the origin of a biological structure.

Vitamin C as an example of Irreducible Complexity

Irreducible Complexity means that removal of a component destroys the function, because there are no redundant components available to take over. These non-redundant systems are "best explained as the result of deliberate intelligent design." (14).
Redundant complexity means that removal of a component does not destroy the function, because there are redundant components that can compensate for the lost function. In a reply to criticism (14) Behe mentions that humans cannot produce vitamin C (ascorbic acid), because the gene that is responsible for the last step in the synthesis of vitamin C is not functional in humans. It is functional in other animals. Since vitamin C is made by no other pathway (16), it is a case of non-redundant (or irreducible) complexity. It doesn't matter if the mutation is actually present. It is the construction of the pathway that makes it redundant or not. Behe successfully refuted the claim that all biochemical systems have redundant components. Indeed all genetic diseases – more than thousand have now been found in humans – are examples of non-redundant or irreducible biochemical systems. All genetic diseases apparently have no compensating pathways. This is another way of looking at genetic diseases, but otherwise not remarkable. What is remarkable is what follows from Behe's logic:
  1. some biochemical systems are redundant (reducible)
  2. some biochemical systems are non-redundant (irreducible)
  3. all non-redundant (irreducibly) complex systems are best explained by deliberate intelligent design
  4. the vitamin C pathway is a non-redundant (irreducible) system
  5. the vitamin C pathway is best explained by deliberate intelligent design
In fact it follows that all genetic diseases are examples of deliberate intelligent design. At the bottom of this lurks a fundamental dilemma: What is 'intelligent': a redundant, reducible system that is mutation-tolerant, or a non-redundant, irreducible system that is easily damaged by mutations? You can't have it both ways.
Finally: why did the Designer create a vitamin-C pseudogene (17) in humans and intact vitamin-C genes in other animals? A beautiful animation of this can be found at YouTube (recommended!).

Muscular Dystrophy as an example of Hidden Redundant Complexity

By Hidden Redundant Complexity I mean that a copy of a gene exists, but is not expressed. This may result in a genetic disease. For example Duchenne Muscular Dystrophy (a devastating muscular disorder) is caused by a mutation in the dystrophin gene. So this seems to be a case of nonredundant or irreducible complexity, because the defect is not compensated. However there is a fully functional fetal version of the gene (utrophin) that is active in the fetus, but not in the adult. There is evidence (18) that this fetal gene could cure Duchenne patients if only the gene was expressed after birth! So in fact this is a case of hidden redundant or reducible complexity, because a 'redundant' copy of the gene is present. Wouldn't it be easy for an Intelligent Designer to implement a switch mechanism that turned on a (fetal) copy of a gene in case a (adult) gene is damaged? (23). It is tragic that children have to die because an intact gene that could save their lives is not turned on! And why did the designer not install a backup copy of the dystrophin gene in the first place?

Implementing design in DNA

If a human designer implements his design in wood and if his product must be permanent then he should prevent rot. If a human designer uses iron to implement his design he should prevent oxidation if his creation must be permanent. He had better use gold instead or eliminate oxygen from the atmosphere. If a human designer implements his design in DNA he should know that DNA is mutable. If he wants a permanent product then DNA is not the best choice. Beforehand it is known that mutations arise with a predictable frequency. That follows from the laws of physics and chemistry. And that is what we observe. So far the design language. In scientific language we say that mutations create, modify or destroy genes. DNA is stable enough to permit long term inheritance, but unstable enough to permit evolution.

Unethical design

In chapter 3 Behe concludes that the cilium is irreducibly complex (p65) and that Darwinian theory has given no explanation for the cilium or flagellum (p73). In other words: the cilium is intelligently designed.
I discovered that Trypanosoma brucei, the cause of sleeping sickness in humans, has a cilium. This single-celled parasite is passed to humans through the bite of the tsetse fly. If left untreated, the infection progresses to death within months or years. Pharmaceutical industry is not interested in production of the medicines because African countries are too poor to buy them.
Stage II sleeping sickness involves the nervous system. Gambian sleeping sickness, in particular, has a clearly delineated phase in which the predominant symptoms involve the brain. The patient's speech becomes slurred, mental processes slow, and the patient sits and stares for long periods of time, or sleeps. Other symptoms resemble Parkinson's disease, including imbalance when walking, slow and shuffling gait, trembling of the limbs, involuntary movements, muscle tightness, and increasing mental confusion. Untreated, these symptoms eventually lead to coma and then to death (20).
Now why would an Intelligent Designer give such a destructive parasite a beautifully designed irreducibly complex cilium? And why would an Intelligent Designer create such a cruel parasite in the first place? Of course this is not a disproof of a Designer, it is only a disproof of a benevolent Designer. If Irreducible complexity leads to a designer then it is a designer who allows or creates suffering (22). It is not my idea to introduce ethics in the discussion of the evolution-creation controversy. It was already present in the tradition of British natural theology:
"the Power, Wisdom, and Goodness of God, as manifested in his Creation" (27)
salmonella flagellumsalmonella flagellum Salmonella with 'intelligently designed flagellum' causes food poisoning and 500 deaths a year in America (source). (source illustrations).

    Other examples of un-ethical intelligent design are: Salmonella bacterium with flagellum (see illustrations above) which causes salmonellosis (food poisoning) in humans (43); in Legionella the presence of flagella is necessary for infection, resulting in a potentially fatal form of pneumonia and an estimated 800 - 2700 deaths per year in the USA; the requirement for vitamins and genetic diseases such as muscular dystrophy, which I mentioned above. Vitamin A deficiency in developing countries results in the premature death of about a million children a year and leaves another five million children permanently blind. The dependence on an external source (diet) of essential vitamins is clearly not an ethical design of the human genome. The intelligent designer could have easily included the appropriate genes in the human genome, thereby preventing pain, suffering and death of millions of innocent children. That would be a morally useful form of 'guided evolution'. That would be a morally useful form of 'supernatural intervention'. But that does not happen.

Is design a scientific explanation?

hybrid design
"Either God is everywhere present in nature,
or He is nowhere" (28)

Now let's have a look at the 'design'-explanation itself. According to Behe Irreducible Complexity must be determined on a case by case basis. That's fair. However this implies that only irreducibly complex things can show evidence of design, not everything. Cilia have been designed; cell membranes arose spontaneously; the beak of the finch evolved by mutation and natural selection. Design theory is a hybrid theory. Organisms are hybrids of design and evolution (see illustration)! Could it be that design is another word for 'we-do-not-yet-know-a-natural-explanation'? What is Behe going to do in his lab when he definitively established that a biochemical system is Irreducibly Complex? If it is designed then further research into the origin must be impossible by definition. Further research, if anything, could only find natural mechanisms. And to find natural causes of a 'designed' system means that it isn't designed anymore. Behe's definition of "intelligent design" summarises it perfectly:
By "intelligent design" I mean to imply design beyond the laws of nature." (13). (my emphasis).
He means beyond the fine tuning of the laws of nature. Beyond the laws of nature is beyond biological science. So design is beyond biological science. Michael Ruse (2005) asked Behe "Do you mean that the Intelligent Designer suspends the laws of physics through working a miracle?", Behe replied "YES"." (35) Design is a miracle.

Design is like vitalism

According to vitalism the difference between living and nonliving matter is that life has a 'vital force' which is absent from matter. That's why life cannot arise from non-life according to vitalism. The belief that living creatures contain molecules that cannot be made from nonliving precursors, or that living matter contains "vital force", died out in the nineteenth century (24). The refutation of vitalism was the synthesis of urea from inorganic substances by Friedrich Wöhler in 1828 and the synthesis of acetic acid from carbon disulfide by Adolph Kolbe in 1845. Just like nineteenth century scientists believed that 'organic' substances cannot be formed by dead substances, Michael Behe believes that 'irreducible' complex systems cannot be formed by a natural process such as evolution. Behe's 'intelligent designer' is an occult and immaterial force, just as vitalism was an occult and immaterial force. Biologists have come to despise vitalism and everything similar for good reasons (34).

Design is mentalism

Mentalistic explanations are explanations using psychological concepts such as intention, purpose and motive. The history of biology is a struggle to eliminate mentalism. To Behe's credit Irreducible Complexity itself is not a mentalistic concept. However the concept of 'Irreducible Complexity' is strongly connected with the concept 'Intelligent Designer'. The concept of an Intelligent Designer certainly is a mentalistic concept, because it is a person with a mind, motives and intentions (25). So Behe tried to introduce into biology something that biologists eliminated more than a century ago. Obviously a regression.

Design is essentialism

Essentialism means biological species (organisms, genes) have an essence and variations are unimportant. Ernst Mayr (30) pointed out that biologists before Darwin were essentialists. This was under the influence of physics and chemistry. All atoms of oxygen are the same. There are no variations. But biologists after Darwin recognised that species and individuals have no essence and that variations are crucial. Mayr called this new way of thinking 'population thinking'. Design thinking is essentialism because it beliefs that the created Genesis kinds ('basic types') are important and that variations are limited and unimportant. Typically in design thinking, variations and mutations are interpreted as degeneration of the 'original' type. In population thinking variations are the raw material for natural selection and evolution.

Design is scientifically a dead end

'Design' is a sterile hypothesis. 'Design' is scientifically a dead end, because it discourages research into the possible natural mechanisms that could have produced design-like features. Design is a lazy explanation. It stops research. And since there is no independent scientific method to know more about the hypothetical designer, we had better study nature directly as it is. So 'design' is a superfluous concept in science. Compare 'design' with evolution: evolutionists cannot repeat 3 billion years of evolution in the lab, but they can subject a laboratory population of fish, flies or bacteria to selection, vary selection intensity, vary mutation rates, etc and study the outcomes. So evolutionary research is experimental. How can an 'Intelligent Design Theorist' do laboratory experiments with God's powers?

God in the laboratory

Despite the fact that evolution is a historical process, evolutionary mechanisms are operating now in nature and in the lab. Is the designer operating now and not only during the six creation days? Then that should also be demonstrable in nature and in the lab. Additionally: how do we perform the control experiments where the God-factor is excluded? If design is beyond the laws of nature, then demonstrating the designer's actions in the laboratory is impossible by definition. Then 'intelligent design' cannot be science.


  1. Irreducible complexity was an interesting falsificator of the Darwinian mechanism until Behe started to undermine it
  2. Irreducible complexity describes the state of a system, not its origin
  3. Behe admitted that Design involves miracles. Miracles are "science stoppers".
  4. Prime examples of Irreducible Complexity are genetic diseases (muscular dystrophy) and infectious diseases (sleeping sickness)


  1. I moved a section of the review to Unscientific Postscript (with notes 1,5,8).
  2. "The Sterility of Darwinism" by Michael J. Behe.
  3. "Behe Responds to Postings in Talk Origins Newsgroup"
  4. Jerry A. Coyne's review in Nature, 19 Sept 1996, pp227-228.
  5. Massimo Pigliucci (2002) Denying Evolution. Creationism, scientism, and the nature of science.
  6. Phillip Johnson: Darwin on Trial,1993. (p151)
  7. This is explained by Robert Pennock(1999) in Tower of Babel and by Dave Ussery.
  8. -
  9. John Maynard Smith in Nature, 403, 594-595 (2000). See: Note 12.
  10. "A Classification of Possible Routes of Darwinian Evolution" by Richard H. Thornhill, David W. Ussery. Journal of Theoretical Biology, Vol. 203, No. 2, Mar 2000, pp. 111-116 (abstract), which is a very important scientific discussion of Irreducible Complexity. This journal is an important mainstream journal in biology. [added 17 Mar 2000]. A reply to Thornhill & Ussery. [added 1 Jul 2000].
  11. Darwin's Black Box reviewed by Kenneth R. Miller, Professor of Biology, University of Colorado.
  12. Fred Hoyle(1999): Mathematics of Evolution. (review).
  13. Michael Behe, Discovery Institute, 31 July 2000, "Philosophical Objections to Intelligent Design: Response to Critics".
  14. Michael Behe(2000): "Self-Organization and Irreducibly Complex Systems: A Reply to Shanks and Joplin". Philosophy of Science 67. (this article was kindly send to me by Enezio E. De Almeida Filho).
  15. Michael Behe(2000): "Intelligent Design Is Not Creationism", letter to Science magazine, 7 july 2000
  16. Of course the inability to produce vitamin C is easily compensated for by vitamin C in food. So if vitamin C in food is included in the definition of 'complex system' we have a redundant system. Consequently there is no high selection pressure for an intact vitamin C gene for all animals with easy access to vitamin C (= Darwinist explanation).
  17. Grauer & Li(2000) Fundamentals of molecular evolution, p275. A pseudogene is damaged gene that is not functioning but still present.
  18. Interview with Kay Davies.
  19. Michael Denton(1986) Evolution: A Theory in Crisis, p108: "There is no hint anywhere of any sort of structure halfway to the complex molecular organization of these fascinating microhairs [cilia] through which evolution might have occurred."
  20. Sleeping Sickness is one of many internet sources. [added 24 Jun 2001].
  21. Michael Behe(2001): Darwin's Breakdown: Irreducible Complexity and Design at the Foundation of Life, p94 in: Signs of Intelligence. [added 24 Jun 2001].
  22. IDT's complain that these statements are theology. However the creation story is the only alternative for evolution to compare with. Furthermore the introduction of the Intelligent Designer (a person) as an explanation inevitably introduces responsibility for the design. Natural Selection (an impersonal force) can't be blamed for its actions.[16 Jul 2001].
  23. Exactly this is done in ß-thalassaemia disaease: a fetal haemoglobin gene is switched on in adults.
  24. Brian Silver(1998): The Ascent of Science, p268.
  25. A good example of 'mentalism' is Walter Remine, see review (I called it 'designer psychology').
  26. This is repeated by Behe: "since I dispute the mechanism of natural selection, not common descent." in Reply to My Critics, Biology and Philosophy 16, p697, 2001.
  27. Bridgewater Treatises, Chalmers(1835), p9; quoted by Helena Cronin(1991).
  28. Aubrey Moore (1891), 12th edition of Lux Mundi, p73.
  29. Biology and Philosophy 16, p. 698, 2001. Online version of the article (pdf of 45 pages; page numbers are not identical to those in B and P).
  30. Ernst Mayr (1991) One Long Argument. Charles Darwin and the Genesis of Modern Evolutionary Thought. Harvard University Press.
  31. Charles Darwin (1859) The origin of species, chapter 6 - Difficulties on Theory.
  32. Every step must be either beneficial or neutral, but too many neutral steps would not be acceptable. Neutral mutations are not selected by definition.
  33. Stephen J. Gould (2002) The Structure of Evolutionary Theory, p.267.
  34. See also the paragraph 'Vitalism and Mechanism' of evolutionary biologist George Williams (1996) Plan & Purpose in Nature, p.65. About Francis Crick: His atheism was rooted and militant. Ridley introduces it where it determined Crick's choice of problems: molecular biology in the late 1940s to dispel the last traces of vitalism, ..." see: Nature 26 October 2006 p.917.
  35. Michael Ruse (2005) The Evolution-Creation Struggle, p.255
  36. Scott M. Landfear (2006) "When the tail wags the dog". Nature. Summary: "Flagella are whip-like structures that power the movement of certain cells. Analysis of a single-cell parasite, the African trypanosome, reveals that flagella are also essential for viability in this organism".
  37. Christoph Adami (2006) "Reducible Complexity", Science 7 Apr 2006 pp 61-63.
  38. Jamie T. Bridgham, Sean M. Carroll, Joseph W. Thornton (2006) "Evolution of Hormone-Receptor Complexity by Molecular Exploitation" Science 7 Apr 2006 pp 97-101.
  39. Nick Lane (2005) Power, Sex, Suicide page 271.
  40. A.G. Cairns-Smith (1985) Seven Clues to the Origin of Life pp.58-59.
  41. G.J. Mivart (1871) The Genesis of Species, quoted by Mark Ridely (2004) page 13.
  42. However, some structures or properties are the inevitable consequences of the selection of other structures or properties of the organism (spandrels, exaptation).
  43. Salmonella spp.
  44. Massimo Pigliucci (2002) Denying Evolution. Creationism, Scientism, and the Nature of Science, p.241. The source of the figure is not mentioned. But see note 47.
  45. Frank J. Poelwijk, et al (2007) 'Empirical fitness landscapes reveal accessible evolutionary paths', Nature 445, 383-386 (25 January 2007)
  46. There are exceptions to the requirement of micro mutations; usefull macromutations cannot be excluded. See: G. Theissen (2009) 'Saltational evolution: hopeful monsters are here to stay', Theory in Biosciences. [13 Feb 2010]
  47. According to Thomas Waschke: "The figures in Chapter "Unbiological nature of Design" are Fig. 5.1 (source there) and 5.2 (p. 141 and p. 142) in: Miller, K.R. (2007) Finding Darwin's God. A Scientist's Search for Common Ground Between God and Evolution [1999] New York; London; Toronto; Sydney, Harper Perennial. The figures show *cilia* (sometimes, if they're longer, even also called 'flagella'), but they are restricted to eukaryotes. So your legend "cross section of a bacterial flagellum" must read "Detailed cross-section of a eukaryotic cilium". [21 Jan 2022]

Further Reading

  • Behe page of Lehigh University (2 Nov 06).
  • Non-conservative Mutations are Well Tolerated in the Globular Region of Yeast Histone H4 by Seema Agarwal, Michael J. Behe, Journal of Molecular Biology Volume 255 Number 3, January 26 1996 p 401-411.
  • Irreducible Complexity or Irreproducible Irreducibility? by Keith Robison.
  • Complexity--Yes! Irreducible--Maybe! Unexplainable--No! A Creationist Criticism of Irreducible Complexity by Terry M. Gray.
  • A review by Robert Dorit Biology, Yale University in the American Scientist, 1997.
  • Behe's Empty Box. A collection of many reviews and criticisms of Behe's book by John Catalano.
  • A Biochemist's Response to "The Biochemical Challenge to Evolution" by Dave Ussery. First version: December, 1997. Last update: 10 August, 2000.
  • Molecular Machines: Experimental Support for the Design Inference. An online summary of Darwin's Black Box by Behe himself.
  • The God of Science: The Case for Intelligent Design. a 'review' by Michael Behe of Robert Pennock's Tower of Babel. This 'review' does not really discuss Pennock's book, but is very useful to learn more about Behe's own position. [ Sep 15 1999]
  • A reducibly complex mousetrap by John McDonald. Contains drawings of five-part down to one-part mousetraps! [ 19 Dec 2001]
  • Ian Musgrave Evolution of the Bacterial Flagella. (Senior Lecturer, Dept. Clinical and Experimental Pharmacology, University of Adelaide, Australia).
  • Michael Behe: "Embryology and Evolution", Science Volume 281, Number 5375, Issue of 17 Jul 1998, pp347-351. (this is a letter to the editor).
  • Irreducible Complexity Demystified by Pete Dunkelberg, (biologist) posted at the Talkreason site. [ 19 Apr 2003]
  • N. J. Matzke (2003) Evolution in (Brownian) space: a model for the origin of the bacterial flagellum Preprint Version 1.0 (last updated November 10, 2003). The article is an attempt to put forward a reasonably detailed model for the evolutionary origin of the bacterial flagellum.
  • Mark Perakh (2004) "Irreducible Contradiction", chapter two of: Unintelligent Design, pp.111-140. This chapter is about Michael Behe. Perakh comes to the surprsing conclusion that "If a machine, be it mechanical or biomechanical, is very complex, it points to its unintelligent origin" and "the best designs are always the simplest designs". [ 19 May 2004]
  • Niall Shanks (2004) "God, the Devil, and Darwin: A critique of intelligent design theory". The fifth chapter "The Biochemical Case for Intelligent Design" covers Michael Behe's claim that natural selection cannot produce irreducible complexity. [ 6 Sep 2004 ]
  • Matt Young, Taner Edis (2004) Why Intelligent Design Fails. The following chapters discuss Michael Behe: Chapter 2: "Grand Designs and Facile Analogies: Exposing Behe's Mousetrap and Dembski's Arrow" (Matt Young); Chapter 4: Darwin's Transparent Box: The Biochemical Evidence for Evolution (David Ussery); Chapter 5: "Evolutionary Paths to Irreducible Systems: The Avian Flight Apparatus" (Alan D. Gishlick); Chapter 6: "Evolution of the Bacterial Flagellum" (Ian Musgrave). [ 6 Sep 2004 ]
  • Michael J. Behe and David W. Snoke (2004) Simulating evolution by gene duplication of protein features that require multiple amino acid residues, Published online before print August 31, 2004, Protein Science 13 (2004):2651-64. This is the first ID article in a peer-reviewed journal. [ 31 Oct 04 ]. It is refuted by:
  • Ian F. Musgrave, Steve Reuland, Reed A. Cartwright (2004) Theory is as Theory Does is a critique of Behe and Snoke (2004). [ 31 Oct 04 ]
  • Clive Trotman (2004) The Feathered Onion - Creation of Life in the Universe. Trotman devotes a whole chapter to irreducible complexity of life. [ 19 Dec 04 ]
  • Michael J. Behe (2004) "A Catholic Scientist Looks at Darwinism", p133-151, in: William Dembski (editor) Uncommon Dissent. Intellectuals who find Darwinism unconvincing. ISI Books paperback 366 pages.
  • Kenneth Miller (2004) "The flagellum unspun: The collapse of 'irreducible complexity' in Debating Design: From Darwin to DNA, ed M. Ruse, W. Dembski (2004).
  • M. D. Lynch (2005) "Simple evolutionary pathways to complex proteins", Protein Science 14 (2005):2217-25. Summary: "A recent paper in this journal has challenged the idea that complex adaptive features of proteins can be explained by known molecular, genetic, and evolutionary mechanisms. It is shown here that the conclusions of this prior work are an artifact of unwarranted biological assumptions, inappropriate mathematical modeling, and faulty logic. Numerous simple pathways exist by which adaptive multi-residue functions can evolve on time scales of a million years (or much less) in populations of only moderate size. Thus, the classical evolutionary trajectory of descent with modification is adequate to explain the diversification of protein functions. [ 2 June 2006 ]
  • Mark Perakh (2005) Beyond suboptimality: Why irreducible complexity does not imply intelligent design. [ 26 Feb 2005 ]
  • Andrea Bottaro (2005) Behe's meaningless complexity posted by Andrea Bottaro on June 2, 2005 03:10 PM on The Panda's Thumb. This article is a very readable response to Behe's response to 'The Revenge of Calvin and Hobbes'. [ 5 Jun 2005 ]
  • Mark Perakh Does Irreducible Complexity Imply Intelligent Design? Skeptical Inquirer Nov 2005.
  • "The recent evisceration of Behe's views by the plaintiff's attorneys at Kitzmiller vs DASD trial and in the Judge Jones's decision have vividly shown Behe's inability to say anything of substance in defense of his IC concept." See also Science 6 Januari 2006: "ID is not science. We find that ID fails on three different levels, any one of which is sufficient to preclude a determination that ID is science." [ 6 Jan 2006 ]
  • Mark P Styczynski, Curt R Fischer and Gregory N Stephanopoulos (2006) The intelligent design of evolution, Molecular Systems Biology doi:10.1038/msb4100065 Published online: 2 May 2006
  • Frank J. Poelwijk, Daniel J. Kiviet, Sander J. Tans (2006) Evolutionary Potential of a Duplicated Repressor-Operator Pair: Simulating Pathways Using Mutation Data, PLoS Computational Biology, 26 May 2006. [ 30 May 2006 ]
    • "Gene duplication followed by functional divergence is now seen as a general mechanism for acquiring new functions. ... We show that the landscape allows evolutionary paths toward independent repressor-operator interactions, exhibiting a step-by-step increasing fitness, starting as early as the first or second mutation. ... Our results contrast with the notion that a number of neutral or even deleterious mutations have to accumulate before a new function can develop."
  • James Downard (2006) Secondary Addiction: Anne Coulter on Evolution contains a lot about (misunderstandings of) IC and Behe. [ 30 Jun 2006 ]
  • Mark J. Pallen and Nicholas J. Matzke (2006) From The Origin of Species to the origin of bacterial flagella. Nature Reviews Microbiology | AOP, published online 5 September 2006. PubMed | Here is the pdf. [ 9 Sep 2006 ]
    • Summary: "In the recent Dover trial, and elsewhere, the 'Intelligent Design' movement has championed the bacterial flagellum as an irreducibly complex system that, it is claimed, could not have evolved through natural selection. Here we explore the arguments in favour of viewing bacterial flagella as evolved, rather than designed, entities. We dismiss the need for any great conceptual leaps in creating a model of flagellar evolution and speculate as to how an experimental programme focused on this topic might look".
  • Irreducible Complexity as an Evolutionary Prediction posted on Panda's Thumb October 23, 2006. [ 24 Oct 2006 ]
    • "Muller's definition of "interlocking complexity" is exactly the same as the definition of 'irreducible complexity' - a system of mutually independent parts that requires all those parts to be present for the system to work. However, Muller's claim is that this is an EXPECTED result of evolution. Behe took the same definition, and claimed it was IMPOSSIBLE as a result of evolution."
  • Douglas Theobald (20060 The Mullerian Two-Step: Add a part, make it necessary or, Why Behe's "Irreducible Complexity" is Silly (TalkOrigins). This is the most concise explanation of "Irreducible Complexity". [ 19 Nov 2006 ]
  • The Evolution of the Flagellum animation on You Tube: "Here I present a theory first published in 2003 by Nicholas Matzke. This theory is derived from a wealth of data regarding protein homologies. It shows that a fully functional flagellum could evolve through multiple functional intermediates. Each step involves the modification of only a single protein." October 06, 2006
  • Michael J. Behe (2007) The Edge of Evolution: The Search for the Limits of Darwinism, Hardcover: 336 pages Publisher: Free Press (June 5, 2007). (info, 'Q & A' gives a nice summary, Simon & Schuster). See also: Introduction page and my review.
  • W. Doolittle, O. Zhaxybayeva (2007) Evolution: Reducible Complexity - The Case for Bacterial Flagella. Current Biology, 3 July 2007 Volume 17, Issue 13, Pages R510-R512
  • Barbara C. Forrest, Paul R. Gros (2007) Biochemistry by design, Trends in Biochemical Sciences, Volume 32, Issue 7, July 2007, Pages 322-331
  • My review of Michael Behe (2007) The Edge of Evolution. 22 Jul 2007.
  • Renyi Liu, Howard Ochman (2007) 'Stepwise formation of the bacterial flagellar system', Open Access article PNAS | April 24, 2007 | vol. 104 | no. 17 | 7116-7121
  • Abigail Clements et al (2009) 'The reducible complexity of a mitochondrial molecular machine', PNAS, August 26, 2009. Abstract.
  • Evolution of complexity in a protein ring ©NatureGregory C. Finnigan et al (2012) Evolution of increased complexity in a molecular machine, Nature, 481, 360–364 (19 January 2012). Important research that refutes the claim that mutation and natural selection cannot produce irreducible complexity.
  • Helen Pearson (2012) Prehistoric proteins: Raising the dead, Nature 483, 390–393 (21 March 2012).
    To dissect evolution, Joe Thornton resurrects proteins that have been extinct for many millions of years. His findings rebut creationists and challenge polluters. "Such studies solidly refute all parts of the intelligent design argument," wrote Christoph Adami, an evolutionary biologist at the Keck Graduate Institute of Applied Life Sciences in Claremont, California, in an article entitled 'Reducible complexity'7. But Behe dismissed the result. The receptor and ligand are not irreducibly complex, he says, and evolution did not give them any truly new function. "I think his results are quite consistent with my own view that Darwinian processes are poor ones to explain the complexity found in life," Behe told Nature.".
  • Behe's latest book Darwin Devolves is reviewed in Science, 8 Feb 2019: "Ultimately, Darwin Devolves fails to challenge modern evolutionary science because, once again, Behe does not fully engage with it. He misrepresents theory and avoids evidence that challenges him.".
  • Behe's latest book A Mousetrap for Darwin. Michael J. Behe answers his critics. Nov 2020.

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