|Behe, Biochemistry, and
the Invisible Hand
by Niall Shanks and Karl Joplin
Abstract: In this essay we take
creationist biochemist Michael Behe to task for failing to make an
evidentially grounded case for the supernatural intelligent design of
biochemical systems. In our earlier work on Behe we showed that there
were dimensions to biochemical complexity—redundant
complexity—that he appeared to have ignored. Behe has recently
replied to that work. We show here that his latest arguments contain
Michael Behe has argued that biochemists
have uncovered a kind of biochemical complexity that could only result
from intelligent design.1 We have criticized his reasoning in two
essays.2 Behe has recently responded to our first essay in ways that are
simultaneously interesting enough and misleading enough to warrant
further analysis.3 Since Behe’s work takes place in the context of the
intelligent design branch of the creationist movement, we will begin
with some comments on the very enterprise of explaining biochemical
phenomena through appeals to supernatural intelligent design. We will
then address some specific issues that have arisen in the context of our
Behe and the Invisible Hand of God
Behe has argued that biochemical systems
exhibit a species of complexity—irreducible complexity—that he
believes cannot possibly arise from natural processes but must have
arisen from deliberate, intelligent design. Behe tells us that an
irreducibly complex system is one consisting of several well-matched,
interacting parts, with all the parts contributing to the achievement of
function, and doing so in such a way that the removal of any one of the
parts causes the system to cease functioning.4
Like William Paley before him, he
compares the complexity observed in biological systems to that of
mechanical contrivances. For Paley the mechanical metaphor was that of a
pocket watch, for Behe it is the mousetrap. Mousetraps have several
interconnected parts (spring, base, hammer, catch, holding bar), and all
are necessary for the achievement of function—catching mice.
If organisms are artifacts, it is natural
to both assume they were designed (more or less intelligently), and if
they are designed then we should identify the designer and the methods
and materials used. Perhaps we organisms are the result of an experiment
by space aliens from a galaxy far, far away. . . . But, as Behe notes,
“Most people, like me, will find these scenarios entirely
unsatisfactory, but they are available for those who wish to avoid
unpleasant theological implications.”5 Hovering unmentioned over the
text is the suggestion that a supernatural, undesigned designer could
provide a suitable invisible hand, not to mention the necessary
expertise in biochemistry.
Behe, like others in the intelligent
design movement, is cagey about identifying the intelligent designer,
contenting himself with the following comments:
Inferences to design do not require that
we have a candidate for the role of designer. We can determine that a
system was designed by examining the system itself, and we can hold the
conviction of design much more strongly than a conviction about the
identity of the designer. In several of the examples above, the identity
of the designer is not obvious. . . .
Nonetheless, we know that all of these things were designed
because of the ordering of independent components to achieve some end.6
We do not think Behe’s caginess is
satisfactory. We think it is incumbent upon him to say more.
To see why, imagine you are strolling
across a heath and you stumble upon an old pocket watch. Knowing
antecedently that watches are artifacts, you know it is the fruit of
intelligent human design, though being ignorant of horological history
you know not how or by whom. The hand of the human designer is a
mystery. And perhaps your interest in the matter ends here. It is a nice
watch, and whoever made it did a good job.
But suppose you are inquisitive. You will
then want answers to what we shall term the intelligent design
questions. These are: 1) What is it? 2) Who made it? 3) When was it
made? 4) How was it made? 5) For what purpose was it made? All of these
questions can be asked about the fruits of design, be they watches, crop
circles, stone tools, or signals from outer space.
For example, a little research at the
museum of the National Association of Watch and Clock Collectors
suggests that your watch might be a quarter repeater, made by
Abraham-Louis Breguet, in 1814, in Paris, France. Studies of the watch
itself reveal that it is a quarter repeater on gongs with push pendant,
ruby cylinder escapement, gilt finish, serial number 2371 (so it must
once have been owned by Napoleon’s sister, Caroline).
Careful studies into the anatomy of the
watch itself reveal a silver engine turned dial with Breguet secret
signatures. The watch bears the mark of Breguet. Research into the
records of Breguet Atelier lists twenty artisans who were paid to make
parts for this watch. Finally, through careful investigations into the
history of technology, you are able to uncover the nature of the
materials and methods employed by Breguet and his band of helpers.
You may even conclude that the watch is
so beautiful it was intended to be a work of art as well as a
timekeeper. But most importantly, you do not have to pursue the
intelligent design questions for watches (or mousetraps) because they
are known antecedently to be artifacts, and hence to be the fruits of
intelligent human design, even if the identities and methods of the
designers remain obscure. For artifacts such as watches and mousetraps,
Behe is right, “The inference to design can be held with all the
firmness that is possible in this world, without knowing anything about
Suppose now you are strolling across the
same heath and you come across a human cell. Microscopic examination
reveals that it, like the watch, is a complex system with many
interacting parts. But there is a crucial difference. Because for all of
the use of mechanical metaphors to make sense of intracellular processes
and structures, it is not known antecedently that the cell is the fruit
of intelligent design.
Saying biochemical systems are like
familiar artifacts such as mousetraps or watches, or behave as if they
were machines or designed artifacts, does not make them so. And in fact,
from the standpoint of complexity of organization and dynamic
interaction, they are utterly unlike anything in everyday human
experience of designed artifacts. Mechanical metaphors and analogies may
render biochemical systems familiar and more tractable to thought, but
they do not transform these systems into artifacts. As Rosenblueth and
Wiener have noted, “The price of metaphor is eternal vigilance.”8
The claim that biochemical systems are
intelligently designed systems is a claim that needs evidential
justification. The very issue of design itself—an issue we did not
have to confront for watches—is an issue that must be confronted here.
About the only way to provide hard evidence that these systems are in
fact the fruit of intelligent design is to provide a lot of high-quality
evidence to support specific and unambiguous answers to the intelligent
design questions. Settling the very issue of the intelligent design of
biochemical systems is thus inextricably intertwined with the provision
of evidentially grounded answers to the intelligent design questions
precisely because it is not known antecedently that biochemical systems
result from deliberate design by a nonhuman agent (or agents) of
As Behe himself has noted,9 it is
possible for humans to intelligently design human proteins, and even
novel proteins that have never been seen before. We speculate that one
day it will be possible for a clever biochemist to intelligently design
a functioning cell indistinguishable from a human cell. Even if this
were so, it would not demonstrate that our cells were the results of
intelligent design. Moreover, whether a given cell was extracted from a
human subject, or intelligently designed in the laboratory, could be
settled only through analysis of its causal history. The judgment would
be in favor of human intelligent design, if the trail led back to the
laboratory, to identifiable human designers with the biochemical and
biological wherewithal to accomplish the feat. The judgment would favor
intelligent design precisely if the design questions could be
appropriately answered and justified.
Behe has tried to argue that irreducible
complexity is a mark of supernatural intelligent design. Here, Behe
makes himself a hostage to fortune because the history of science is
littered with the corpses of phenomena believed to be inexplicable by
natural means. For example, the complex motion of the heart was believed
by Fracastorius to be a mystery known only unto God. William Harvey
unraveled the mystery. Likewise, crop circles were believed by many to
be the fruits of extraterrestrial or supernatural agency, yet human
ingenuity with planks of wood and lengths of rope turned out to be the
And we have been mistaken about the very
signs of intelligent design before. When Anthony Hewish and Jocelyn Bell
discovered the first pulsar in 1967 (an astronomical object emitting
bursts of microwaves every 1.33730109 seconds), they wondered whether it
was a beacon—a sort of cosmic lighthouse—signaling the existence of
an alien intelligence. The objects were even referred to as LGMs
(“Little Green Men”).10
The intelligent design theory of pulsars
dropped from sight partly because plausible answers to the intelligent
design questions were not forthcoming (e.g., Why broadcast in such a
messy part of the electromagnetic spectrum? Why expend so much energy?
And, as more objects were discovered, why send signals to Earth from so
many different places using similar frequencies?). And also because it
was discovered that there were natural, unintelligent explanations for
the same phenomenon—rapidly rotating neutron stars.11
Behe’s design inference in fact
exhibits an appeal to ignorance. He cannot see how irreducible
complexity could have arisen in a natural, unguided manner, so it must
have arisen in an unnatural, supernatural manner, though we know not
how, by whom, when, or for what purpose. But within the cell we have
nothing analogous to the Breguet secret signatures. And, moreover, the
examples of irreducible complexity in biochemical processes will not
suffice as evidence either. Irreducible complexity is a phenomenon for
which there exist naturalistic, unguided evolutionary explanations. We
will discuss one below in connection with some of Behe’s favorite
The upshot is that the very features of
biochemical systems that Behe points to cannot simply be viewed as
either the trademark, or even the fingerprints, of an intelligent
designer. For these features, the inference to design cannot be
separated from the provision of evidence about the designer and its
methods. Behe has made an extraordinary claim, and its validation will
require extraordinary evidence. Behe makes no attempt to meet this
essential, evidential requirement.
The Invisible Hand of the Laws of
How could a complex system such as an
economy, with many interacting parts, manifest stability and order? As
the economic collapse of the former Soviet Union has shown, the attempt
to intelligently design economic order through centralized planning was
a huge failure. The older tradition of laissez faire capitalism had a
very different answer to the origins of economic order.
Commenting on the origins of adaptative
order in economic systems, Stephen Jay Gould has pointed out:
To achieve the goal of a maximally
ordered economy in the laissez faire system, you do not regulate from
above by passing explicit laws for order. You do something that, at
first glance, seems utterly opposed to your goal: You simply allow
individuals to struggle in an unfettered way for personal profit. In
this struggle the inefficient are weeded out and the best balance each
other to form an equilibrium to everyone’s benefit.12
Adam Smith, one of the architects of
classical economic theory, explained how an individual agent in a
laissez faire economy makes his contribution to the emergence of order
in the following way:
He generally indeed neither intends to
promote the public interest, nor knows how much he is promoting it. . .
. He intends only his own gain, and he is in this, as in many other
cases, led by an invisible hand to promote an end which was no part of
his intention [our italics].13
The invisible hand that produces the
economic order is in the interaction dynamics of a group of individuals
attempting to maximize personal profits and gains, and who have no
broader view of the public interest. Economic order emerges as an
unintended, undesigned consequence of the operation of this invisible
Could another invisible hand, this time
the invisible hand of chemical interaction dynamics, explain the
emergence of a system manifesting irreducible complexity? In our initial
commentary on Behe’s claims, we argued that this was indeed the case.14 We there presented and discussed a chemical system known as the
Belousov-Zhabotinski (BZ) reaction. The BZ reaction, we argued,
manifested irreducible complexity as a consequence of self-organization.
It did not require an intelligent designer.
The BZ system self-organizes into an
orderly sequence of reactions, with the products of one reaction in the
sequence forming the substrates for the next, and which eventually
cycles round so that the products of the last reaction in the sequence
form the substrates for the first reaction, thus beginning the process
all over again. Thus, the system will cycle or oscillate until chemical
equilibrium is achieved, at which point the system can be reactivated by
the provision of further “food” molecules from outside.
That the reaction manifests
self-organization means nothing more than that the invisible hand of the
chemical interactions between molecules brings about highly ordered
behavior of the system as a whole in the form of regular temporal
oscillations (and the formation of elaborate spatial patterns under
certain circumstances). The explanation of this behavior does not
require the intervention of a deus ex machina, either physical or
metaphysical. The oscillations are typically observed in the form of
color changes—for example from red to blue to red . . . and so on. The
system behaves like a chemical clock—a sort of Breguet repeater in a
We argued that the BZ system manifested
irreducible complexity because it satisfies all the requirements of the
mousetrap model of irreducible complexity. Behe tells us that there are
three steps to be satisfied. The system must have a function. Behe tells
us, “The function of the system is determined from the system’s
internal logic.”15 In the light of this, the function of the BZ
reaction—determined by the logic of the chemical interaction dynamics
internal to the system—is to oscillate.
The next requirement is that the system
consist of several components.16 The BZ system consists of several key
reactions. Behe does not appear to dispute this part of our example.
Finally we must ask whether all the components so identified are
required for the achievement of function. The key components of the BZ
reaction are all needed for the oscillatory cycle to exist. The
disruption of any of these key reactions results in the catastrophic
failure of the system. Apparently, the unguided laws of chemistry will
generate irreducibly complex systems.
Yet Behe has objected to our example. It
is instructive to examine his reasoning. Commenting on the BZ system, he
notes, “Although it does have interacting parts that are required for
the reaction, the system lacks the crucial feature—the components are
not well-matched”(our italics).17 He tells us that only systems,
“that require well-matched components are irreducibly complex.”18 He
As an illustration, contrast the greater
complexity of a mechanical mousetrap with the much lesser complexity of
a lever and fulcrum. Together a lever and fulcrum form an interactive
system which can be used to move weights. Nonetheless, the parts of the
system have a wide variety of shapes and sizes and still function.
Because the system is not well-matched, it could easily be formed by
chance [our italics].19
To be irreducibly complex, then, involves
well-matched components, and this means components that cannot easily
form into a complex system by chance.
Noting that the distinction between
systems with well-matched components and those without is not very
sharp, Behe adds:
. . . no law of physics automatically
rules out the chance origin of even the most intricate IC [irreducibly
complex] system. As complexity increases, however, the odds become so
abysmally low that we reject chance as an explanation.20
Behe is thus arguing that the BZ reaction
does not have well-matched components, and this means that the
self-organization of the components of the system into an oscillating
complex system could easily occur by chance! If it was truly irreducibly
complex, the probability that the molecular components would
self-organize to form an integrated, complex system just by chance would
be abysmally low.
And now Behe’s error becomes quite
apparent. We agree with Behe that the probability that irreducibly
complex systems self-assemble just by chance is abysmally low. But the
probability that the BZ system self-organizes and oscillates just by
chance is also abysmally low. However, it does not occur just by chance.
It occurs as the result of chemical mechanisms operating in accord with
the laws of chemistry—the unaided, unguided, but lawlike invisible
hand of the chemical interactions internal to the system. Ignorance,
sometimes wilful ignorance, of the organizing power of natural
mechanisms operating in accord with laws of nature, is an old
Similarly, ignorance of the lawlike
invisible hand of gravitational interactions led medieval design
theorists to postulate the invisible hand of God as the source of the
order we observe in celestial motion. And, as Darwin showed, we do not
require the invisible hand of God to explain the adaptations we find in
organisms. Natural selection, acting on heritable variation in
populations of organisms, sculpts the beaks of finches just as surely as
it shapes other features of organisms. You cannot conclude that complex
structures and processes must occur just by chance if they are not the
result of intelligent design.
Behe bolsters his attack on the BZ
reaction with a truly bizarre argument derived from the fact that the
reagents in the BZ reaction have a wide variety of uses—in Behe’s
terminology, they have low specificity. For example, one ingredient,
sodium bromate, is a general purpose oxidizing agent, and ingredients
other than the ones we mentioned can be substituted. In our reaction, we
mentioned the use of cerium ions, but iron or manganese ions will work
just as well. He points out that the reaction is easy to set up and runs
over a wide range of concentrations.21
If this is the case, then mousetraps are
not irreducibly complex either. The steel used in their construction has
a wide range of uses, as does the wood used for the base. You can
substitute plastic for wood, and any number of metals for the spring and
hammer. Mousetraps are easy to make (which is why they are cheap) and
will work with metals manifesting a wide range of tensile strengths. But
the fact that they are easy to make does not mean they assemble just by
chance. Mousetraps need a maker just as much as the BZ system needs
chemical mechanisms governed by the laws of chemistry. Either the BZ
system is an irreducibly complex system, or the complexity of mousetraps
is not a model for irreducible complexity. Take your pick, for you
cannot have it both ways.
This matter is made all the more acute
because crucial components of Behe’s own examples of irreducible
complexity have multiple uses and lack substrate specificity (interact
with a wide variety of substrates). For example, plasminogen (a
component of the irreducibly complex blood-clotting cascade) has been
documented to play a role in a wide variety of physiological processes,
ranging from tissue remodeling, cell migration, embryonic development,
and angiogenesis, as well as wound healing.22 And though Behe tells us
that plasmin (the activated form of plasminogen), “. . . acts as
scissors specifically to cut up fibrin clots,”23 we learn in one of
the very papers he cites that, “Plasmin has a relatively low substrate
specificity and is known to degrade several common extracellular-matrix
glycoproteins in vitro.”24
Redundant Complexity (Again)
Behe’s discussion of our concept of
redundant complexity really takes us to the heart of the matter.25 In
our initial analysis of Behe’s work we proposed that many real
biochemical systems exhibited redundant complexity rather than
irreducible complexity. Behe’s characterization of our view of
redundant complexity is fair and accurate. He explains our view of
redundancy as follows:
By this they mean that biochemical
pathways overlap and are interconnected, so that removal of one or even
several components does not completely destroy the function. In support
of their position they cite a diverse array of biological examples. . .
. Their initial illustration is the metabolic pathways for the synthesis
of glucose-6-phosphate. They point out that the molecule can be made by
“several different isoforms or variants of hexokinase, and all are
present, as a result of gene duplication, in varying proportions in
different tissues.” What’s more, “Knock out one enzyme isoform and
the other isoforms in the tissue can take over its function.”26
And Behe agrees with us that biochemical
systems can indeed exhibit redundant complexity.27
Our original purpose in introducing the
concept of redundant complexity was twofold. First, this sort of
redundancy is a hallmark of evolutionary processes. Gene duplication,
for example, is one of the ways in which the number of genes in a genome
can be increased, with the result that one of the genes can continue the
original function, while the other is freed up to be coopted in
evolutionary time to serve new, and novel functions. The redundancy we
observe today in effect represents the biochemical and molecular
footprints of evolutionary processes in action. Second, we felt that
Behe’s analysis of biochemical complexity had obscured the
significance of this important evidence.
But Behe observes, “The observation
that some biochemical systems are redundant does not entail that all
are. And in fact, some are not redundant.”28 Behe goes on to give some
interesting and examples to make his case. Let’s suppose he is right.
This merely raises the question of the origins of this irreducible
complexity. Although we did not explicitly address this question in our
original commentary, we have subsequently.29
In terms of redundant complexity we have
the tools to provide a naturalistic, evolutionary explanation of the
source of irreducible complexity. Behe’s metaphor for an irreducibly
complex system was that of the mousetrap. We think a better metaphor is
found in the architectural image of a free-standing arch. This image was
first suggested by A.G. Cairns-Smith, a biochemist interested in the
origins of biochemical complexity.30 Cairns-Smith’s own interests were
in the origins of life, but the complexity problem he confronted was
essentially identical to that raised a decade later by Behe—though
couched in different terminology. It is instructive to examine
Cairns-Smith’s reasoning a bit more closely.
Cairns-Smith’s complexity problem was
discussed under the heading of the unity of biochemistry, but it is
clearly very similar to Behe’s problem. Cairns-Smith comments:
For example, proteins are needed to make
catalysts, yet catalysts are needed to make proteins. Nucleic acids are
needed to make proteins, yet proteins are needed to make nucleic acids.
Proteins and lipids are needed to make membranes, yet membranes are
needed to provide protection for all the chemical processes going on in
the cell. . . . The interlocking is tight and critical. At the center
everything depends on everything.31
Cairns-Smith thinks this complexity must
be explained. However, unlike Behe, Cairns-Smith thinks a natural,
rather than a supernatural, explanation will suffice.
Consider a free-standing arch of stones.
It manifests irreducible complexity in that the keystone at the top of
the arch is supported by all the other stones in the arch, yet these
stones themselves cannot stand without the keystone. In other words, the
arch stands because all the component stones depend on each other. Take
away a stone, and the arch collapses.
However, Cairns-Smith notes, not all the
stones, nor all the functional biological structures must be there from
It is clear that not all such functions
were hit on at once. Some would have been later discoveries. If new
uses may be found for old structures, so, too, can old needs be met by
more recently evolved structures. There is plenty of scope for the
accidental discovery of new ways of doing things that depend on two or
more structures that are already there. . . . This is typical at all
levels of organization, from organs to molecules.32
There is plenty of scope for accidental
discoveries of effective new combinations of subsystems. It seems
inevitable that every so often an older way of doing things will be
displaced by a newer way that depends on a new set of subsystems. It
is then that seemingly paradoxical collaborations may come about.33
Why does he think these collaborations
Referring back to the stone arch,
Cairns-Smith comments, “This might seem to be a paradoxical structure
if you had been told that it arose from a succession of small
modifications, that it had been built one stone at a time.”34 This is
especially true if, as in biochemistry, the arch is multidimensional,
with central “stones” each touching more than the two stones touched
by the keystone in our arch.35
Nevertheless, it is possible to construct
an arch in gradual stages. You cannot, of course, gradually build a
self-supporting, free-standing arch using only the component stones,
piling them up, one at a time. But if you have scaffolding—and a pile
of rocks will suffice to support the growing structure—you can build
the arch one stone at a time until the keystone is in place, and the
structure becomes self-supporting. When this occurs, the (now redundant)
scaffolding can be removed to leave the irreducibly complex,
The study of developmental processes
suggests that an important biological role is indeed played by removable
scaffolding, in the formation of all manner of elaborate structures
including body parts and neural pathways. For example, developmental
scaffolding, in the form of an initial superabundance of cells, can be
removed by programmed cell death (apoptosis), and this process plays a
crucial role in the developmental sculpting of such structures as
fingers and toes.36
Behe concedes the existence of
redundantly complex biochemical systems. This is an important concession
because natural evolutionary processes give rise to the redundant
complexity we observe in biochemical systems. These redundancies then
provide, in concert with extant functional systems and structures, the
biochemical and molecular scaffolding to support the gradual evolution
of systems that ultimately manifest irreducible complexity when the
scaffolding is removed or reduced. The resulting biochemical arches may
then achieve functions as integrated wholes that could not be achieved
by the parts acting independently. Natural selection will result in some
of these biochemical arches being retained for further evolutionary
elaboration, while others will be eliminated by the same mechanism.
In his reply, Behe himself comes close to
achieving our crucial insight. Discussing our work, he writes, “They
then go on to argue that biochemical systems are ‘redundantly
complex’—that is, contain components that can be removed without
entirely eliminating function.”37 He is right. And irreducibly complex
systems can be viewed simply as limiting cases of redundantly complex
systems. Reduce redundancy to the point where further reduction results
in loss of function and the system is now irreducibly complex.
As noted above, gene duplication is one
route to redundant complexity, but how could redundancy be reduced to
give rise to irreducible complexity? One way is through the
transformation of functional genes into pseudogenes—nonfunctional
members of gene families. “Pseudogenes are DNA sequences that were
derived from functional genes but have been rendered nonfunctional by
mutations that prevent their proper expression. Since they are subject
to no functional constraints, they are expected to evolve at a high
rate.”38 If a functional gene becomes a pseudogene, its product will
no longer be available to the biochemical pathways in which it formerly
The transformation of a gene to a
pseudogene will not have catastrophic consequences if the biochemical
pathways in which its product formerly participated are redundantly
complex—other products can take over the role of the missing product.
Perhaps not as efficiently, but efficiency is something that can be
improved by selection. In this way, redundant scaffolding can be
reduced, ultimately to the point where a system or pathway is
irreducibly complex. There may be strong selection against further
reductions at this point of evolution. But not necessarily, as we shall
Behe’s Examples Revisited
Now that we have an evolutionary
framework within which we can explain the origins of irreducibly complex
systems, we can usefully re-examine Behe’s examples. Behe cites as an
example of an irreducibly complex system, the synthetic pathway that
makes vitamin C in other mammals, but which in humans (and certain other
animal species) is disrupted by the lack of a functional gene for L-gulono-gamma-lactone
oxidase. As he notes, in humans a pseudogene is present.39 The vitamin C
mousetrap ceases to function in humans when a functional component is
lost. But this is hardly a shocking observation. The pathway in humans
has simply been disrupted by a continuation of the same sorts of process
that reduce redundancy to yield irreducibly complex systems in the first
From an evolutionary standpoint, this
example looks like a case of “Use it or lose it.” As Nesse and
Our ancestral shift to a high-fruit diet,
rich in vitamin C, had the incidental consequence about forty million
years ago of allowing the degeneration of the biochemical machinery for
making this vitamin. Our frugivorous close relatives share our
requirement for dietary vitamin C.40
In this case, loss of a functional
pathway was preceded by adaptation to a niche rich in vitamin C.
Mutational events called
“deletions”—whereby bases are deleted from genes (often a single
base or a few bases, but sometimes several thousand)—occur naturally,
and can result in dysfunction. A special kind of deletion, however, is
artificially induced in a knockout experiment. In a knockout experiment,
a gene is deliberately deleted from a genome, and hence all the causal
roles played by that gene are halted. We have here a tale of two
In our original article we pointed to the
gene coding for the protein p53. Lab mice have been created in which
this gene has been knocked out. In support of our claims about the
existence of redundancy in biochemical systems, we pointed out that,
though this protein was involved in a number of important biochemical
and biological processes, its removal did not result in a catastrophic
disruption of the developmental process. There was redundancy, and other
proteins could conspire to do the work of the missing protein.
Behe acknowledges this case, but draws
his reader’s attention to the blood-clotting cascade originally
discussed in his book:
Yet contrast this case [p53] with that of
mice in which the gene for either fibrinogen, tissue factor, or
prothrombin has been knocked out. . . . The loss of any one of those
proteins prevents clot formation—the clotting cascade is broken. Thus
Shanks and Joplin’s concept of redundant complexity does not apply to
all biochemical systems.41
Again, suppose this point is right. What
is its relevance when the role of redundant complexity lies in its
ability to account, in natural, evolutionary terms, for the origins of
irreducible complexity? And origins, as Behe points out, is the central
issue. Loss of functional genes reduces redundancy to yield an
irreducibly complex system. All Behe’s example shows is that further
losses at this point can catastrophically disrupt the system.
We also think, however, that Behe has
oversold the irreducible complexity of the blood-clotting cascade. The
cascade itself has features that manifest redundant complexity. The real
situation is thus more complex than Behe’s carefully massaged
description would lead you to believe. Plasminogen deficient (Plg-/-)—hence
plasmin deficient—mice have been studied. As noted earlier, plasmin is
needed for clot degradation (it cuts up the fibrin), yet:
Plasmin is probably one member of a team
of carefully regulated and specialized matrix-degrading enzymes,
including serine-, metallo-, and other classes of proteases, which
together serve in matrix remodeling and cellular reorganization of wound
fields. . . . However, despite slow progress in wound repair, wounds in
Plg-/- mice eventually resolve with an outcome that is generally
comparable to that of control mice. Thus an interesting and unresolved
question is what protease(s) contributes to fibrin clearance in the
absence of Plg?42
Behe cited this very paper, so we must
assume that he, too, knows that parts of his clotting-cascade are
redundantly complex. In this case, healing delayed is not healing
Evolution and Biochemical Novelty
Behe says that he accepts much that has
been uncovered through the study of organismal evolution:
I find the idea of common descent (that
all organisms share a common ancestor) fairly convincing, and have no
particular reason to doubt it. I greatly respect the work of my
colleagues who study the development and behavior of organisms within
an evolutionary framework, and I think that evolutionary biologists
have contributed enormously to our understanding of the world.43
But he adds, “I do not believe it
explains molecular life.”44
Behe accepts evolution at the organismal
level, yet denies it at the level of biochemistry. Yet, though the basic
pattern of metabolism is common to all species, biochemical evolution
has occurred, and in ways that reflect the evolution of organic
diversity. The various mammalian species, for example, are not exactly
the same molecular animal dressed up in different organismal clothes.
Thus, as noted by Caldwell, there are several pathways whose occurrence
is restricted to primate species (e.g., the aromatization of quinic
acid; C-Glucuronidation of pyrazolones; and carbamate acyl
glucuronidation, among others).45 Since there has been life on Earth for
more than 3 billion years, the original design event must have been at
least that long ago. But primates appear late in life’s
history—about 65 million years ago.46 If these unique primate pathways
are not the fruits of biochemical evolution, then are we to believe they
are the result of subsequent intelligent redesign of primate
biochemistry? And if so, when, by whom, and for what purpose?
Since primates are not the only evolved
organisms to display biochemical novelty, we suspect Behe will have to
introduce, on an ad hoc basis, many such redesign events. The situation
is not unlike that which confronted the catastrophist geologists of the
eighteenth century who had to postulate a multiplicity of floods and
re-creations of life to explain the fossil record in the stratified
geological column, with Noah’s flood being the last!
It seems, then, that it is simply wrong
to suggest that there is no possible unguided, naturalistic explanation
of irreducible complexity. Self-organization is one route, and redundant
complexity is another. If Behe wishes to disagree, he would do well to
formulate precise and unambiguous answers to the intelligent design
questions we have proposed, and then to justify his answers about the
identity, methods, and materials of his hypothetical designer with the
provision of high-quality evidence. Scientists do not rule out of court
all talk of supernatural beings, but they do require high-quality
evidence before they will take such talk seriously. After all, as Carl
Sagan said, extraordinary claims require extraordinary evidence.
We would like to thank Hugh LaFollette
(Philosophy) and Foster Levy (Biological Sciences) of East Tennessee
State University, Massimo Pigliucci (Botany) University of Tenessee–Knoxville,
and George Gale (Philosophy) of the University of Missouri-Kansas City
for helpful discussions and comments on earlier versions of this essay.
1. See Michael J. Behe,
Darwin’s Black Box: The Biochemical Challenge to Evolution, (New York:
The Free Press, 1996).
2. See Niall Shanks and
Karl H. Joplin, “Redundant Complexity: A Critical Analysis of
Intelligent Design in Biochemistry,” Philosophy of Science 66, (1999):
268–82. See also Niall Shanks and Karl H. Joplin, “Of Mousetraps and
Men: Behe on Biochemistry,” forthcoming in Reports of the National
Center for Science Education (2000).
3. See Michael J. Behe,
“Self-Organization and Irreducible Complexity: A Reply to Shanks and
Joplin,” Philosophy of Science 67 (2000): 155–62.
4. See Behe, Darwin’s
Black Box, 39.
5. Ibid., 249.
6. Ibid., 196.
7. Ibid., 107.
8. Quoted in Richard Lewontin,
Helix: Gene, Organism and Environment (Cambridge, Mass.: Harvard
University Press, 2000), 4.
9. See Behe, Darwin’s Black
10. See Robert Dixon, Dynamic Astronomy
(New Jersey: Prentice-Hall, 1980), 402.
11. See Isaac Asimov, The Universe: From
Flat Earth to Quasar (Baltimore: Penguin, 1971), 306–8.
12. See Stephen J. Gould,
Piggies (New York: W.W. Norton, 1993), 149.
14. See Shanks and Joplin, “Redundant
15. See Behe, Darwin’s Black
16. Ibid., 42.
17. See Behe, “Self-Organization and
Irreducible Complexity,” 157.
18. Ibid., 157.
20. Ibid., 157–58.
21. Ibid., 158–59.
22. See Thomas H. Bugge, Keith W.
Kombrinck, Matthew J. Flick, Cynthia C. Daugherty, Mary J. Danton, Jay
L. Degan, “Loss of Fibrinogen Rescues Mice for the Pleiotropic Effects
of Plasminogen Deficiency,” Cell 87 (1996): 709–19.
23. See Behe, Darwin’s Black
24. See Bugge, et al., “Loss of
Fibrinogen Rescues Mice,” 709.
25. See Behe, “Self-Organization and
Irreducible Complexity,” 160–61.
26. Ibid., p. 160.
29. See Shanks and Joplin, “Of
Moustraps and Men.”
30. See Alexander G. Cairns-Smith,
Clues to the Origin of Life: A Scientific Detective Story (Cambridge:
Cambridge University Press, 1986), 59–60.
31. Ibid., 39.
32. Ibid., 59.
35. Ibid., 60.
36. See Neil A. Campbell,
York: Benjamin Cummings, 1996), 980. See also Ricki Lewis, “Apoptosis
Activity: Cell Death Establishes Itself as a Lively Research Field,”
The Scientist 9 (1995): 15.
37. Ibid., 156.
38. Wen-Hsiung Li, Molecular Evolution
(Sunderland, Mass.: Sinauer Associates, 1997), 187.
39. See Behe, “Self-Organization and
Irreducible Complexity,” 160.
40. See Randolph M. Nesse and George C.
Williams, Why We Get Sick: The New Science of Darwinian Medicine (New
York: Random House, 1994), 130.
41. See Behe, “Self-Organization and
Irreducible Complexity,” 161.
42. See Bugge, et al. “Loss of Fibrogen
Rescues Mice,” 717.
43. See Behe, Darwin’s Black
45. See John Caldwell, “Species
Differences in Metabolism and their Toxicological Significance,”
Toxicology Letters 64/65 (1992): 651–59.
46. See Monroe W. Strickberger,
(Boston: Jones and Bartlett, 1990).
Niall Shanks is Professor of Philosophy
and Adjunct Professor of Biological Sciences at East Tennessee State
University. E-mail: email@example.com.
Karl H. Joplin is Associate Professor of Biological Sciences at East
Tennessee State University. E-mail: firstname.lastname@example.org.