Behe Responds to the Author
The Sterility of Darwinism
by Michael J. Behe
v. Intelligent Design (Again) H. Allen Orr's discussion of
Darwin's Black Box: Boston Review, Dec/Jan 97.
Allen Orr Responds Boston Review, Feb/Mar 97.
As it struggles to
comprehend nature, science sometimes has to completely re-think
how the world works. For example, Newton's laws apply to everyday
objects but can't handle nature's tiny building blocks. Propelled
by this discovery, quantum mechanics overthrew Newton's theory.
Revolutions in biology have included the cell theory of life in
the 19th century, as well as the slow realization in this century
that cells are composites of enormously complex molecular systems.
Newton's theory remains very useful, and we can still learn many
things by studying whole animals or cells. When explaining the
nuts and bolts of the world, however, those views must yield to
more basic descriptions. A mechanical engineer can't contradict
a physicist on fundamental principles of matter. And evolutionary
biology can't overrule biochemistry1 on fundamental
principles of life. It's not a question of pride--that's just
the way the world works.
Curiously, some people seem offended by the way the world works.
In his review of my book, Darwin's Black Box: The Biochemical
Challenge to Evolution, evolutionary biologist H. Allen Orr
unexpectedly attempts to claim priority for his field. He grouses
that pre-med students are required to take biochemistry but not
evolutionary biology. He plaintively asks "Why is everyone
an expert witness when the topic is Darwinism but not when it's
biochemistry?" The obvious reply is that the evolution of
biochemical systems is itself biochemistry. When a protein sequence
changes, when DNA mutates, those are biochemical changes. Since
inherited changes are caused by molecular changes, it is biochemists--not
evolutionary biologists--who will ultimately decide whether Darwin's
mechanism of natural selection can explain life. No offense--that's
just the way the world works.
Orr hankers for the respect accorded physicists, and thinks evolutionary
biologists can finally lay aside their "physics envy"
because "we biologists have discovered the structure of DNA,
broken the genetic code, sequenced the entire genome of some species
. . ." Orr is like a podiatrist claiming credit for progress
in brain surgery. Biochemistry made those dramatic advances; evolutionary
biology played no part. I mean no disrespect, but this is not
a minor academic turf war--the point is crucial. Anyone who wants
to address questions about life's basic mechanisms has to do so
from a molecular perspective. Orr does not.
Declining the opportunity to address my biochemical arguments,
Orr questions the concept of irreducible complexity on logical
grounds. He agrees with me that "You cannot . . . gradually
improve a mousetrap by adding one part and then the next. A trap
having half its parts doesn't function half as well as a real
trap; it doesn't function at all." So Orr understands the
point of my mousetrap analogy--but then mysteriously forgets it.
He later writes, "Some part (A) initially does some job (and
not very well, perhaps). Another part (B) later gets added, because
it helps A." Some part initially does some job? Which part
of the mousetrap is he talking about? A mouse has nothing to fear
from a "trap" that consists of just an unattached holding
bar, or spring, or platform, with no other parts.
I do sympathize with Orr's muddling of the analysis. The concept
of irreducible complexity is new, and can be difficult to grasp
for people who have always assumed without demonstration that
small, continuous changes could produce virtually any biological
structure. Perhaps in the future that assumption will not have
such a strong hold on the minds of evolutionary biologists.
Having completed his logical analysis, Orr turns to the topic
of gene duplication: "So how does Behe explain duplicate
genes? He doesn't." But I do. I discuss them on pages 89-90
of my book, concluding "The sequence similarities are there
for all to see. . . . By itself, however, the hypothesis of gene
duplication . . . says nothing about how any particular protein
or protein system was first produced." For example, the DNA
in each of the antibody-producing cells of your body is very similar
to that of the others, but not identical. The similarities are
due to common descent; that is, all the cells in your body descended
from one fertilized egg cell. The differences, however, are not
due to Darwinian natural selection. Rather, there is a very clever,
built-in program to rearrange antibody genes. Billions of different
kinds of antibody genes are "intentionally" produced
by your body from a pre-existing stock of just a few hundred gene
pieces. Perhaps because of his unfamiliarity with molecular systems,
Orr has trouble seeing that similarity in gene sequences may indicate
common ancestry, but is not itself evidence that a system was
constructed by natural selection.
To test natural selection requires much more evidence than mere
sequence similarity: it requires experimentation. In all of the
scientific literature, however, no experimental evidence can be
found that natural selection can produce irreducibly complex biochemical
systems. To rebut my arguments Orr could simply have cited papers
in the science literature where the systems I discuss have been
explained. He didn't do that because explanations are nowhere
to be found.
What has biochemistry found that must be explained? Machines--literally,
machines made of molecules. Let's look at just one example. The
flagellum is an outboard motor that many bacteria use to swim.
It consists of a rotary propeller, motor, and stationary framework.
Yet this short description can't do justice to the machine's full
complexity. Writing of the flagellum in Cell,2 Lucy Shapiro
of Stanford University marvels, "To carry out the feat of
coordinating the ordered expression of about 50 genes, delivering
the protein products of these genes to the construction site,
and moving the correct parts to the upper floors while adhering
to the design specification with a high degree of accuracy, the
cell requires impressive organizational skills." Without
any one of a number of parts, the flagellum does not merely work
less efficiently; it does not work at all. Like a mousetrap it
is irreducibly complex and therefore cannot have arisen gradually.
The rotary nature of the flagellum has been recognized for about
25 years. During that time not a single paper has been published
in the biochemical literature even attempting to show how such
a machine might have developed by natural selection. Darwin's
theory is completely barren when it comes to explaining the origin
of the flagellum or any other complex biochemical system.
The sterility of Darwinism indicates that it is the wrong framework
for understanding the basis of life. As I argue in my book, an
alternative hypothesis is both natural and obvious: systems such
as the flagellum were intentionally designed by an intelligent
agent. Just as in the everyday world we immediately conclude design
when we see a complex, interactive system such as a mousetrap,
there is no reason to withhold the same conclusion from interactive
molecular systems. This conclusion may have theological implications
that make some people uncomfortable; nonetheless it is the job
of science to follow the data wherever they lead, no matter how
One last charge must be met: Orr maintains that the theory of
intelligent design is not falsifiable. He's wrong. To falsify
design theory a scientist need only experimentally demonstrate
that a bacterial flagellum, or any other comparably complex system,
could arise by natural selection. If that happened I would conclude
that neither flagella nor any system of similar or lesser complexity
had to have been designed. In short, biochemical design would
be neatly disproved.
Let's turn the tables on Orr. Is natural selection falsifiable?
He writes, "We have no guarantee that we can reconstruct
the history of a biochemical pathway. But even if we can't, its
irreducible complexity cannot count against its gradual evolution.
. . ." This is a dangerously antiscientific attitude. In
effect he is saying, "I just know that phenomenally complex
biochemical systems arose gradually by natural selection, but
don't ask me how." With such an outlook, Orr runs the risk
of clinging to ideas that are forever insulated from contact with
the outside world.
After reading Robert Berwick's criticism of Climbing Mount Improbable,
I find myself in the odd position of sympathizing with Richard
Dawkins. Although his book is a juicy target for debunking, Berwick
chides Dawkins for all the wrong reasons. Berwick points out that
natural selection is sometimes not a complete explanation for
some biological feature. For example, he writes that polioviruses
have shapes like geodesic domes not because selection made them
that way, but because the symmetrical shape is required by physical
law. Well, fine. But there are many tasks a virus faces that are
not explained at all by simple physical laws: The virus has to
attach to a cell surface, inject its genetic material into the
cell, hijack the cell's machinery, make copies of the poliovirus
DNA, and re-package the genetic material. In response the body's
immune system launches a counterattack to ferret out and destroy
the virus. None of these processes is explained by simple physical
constraints. Berwick seems mesmerized by the simple crystal that
covers nature's watch, and ignores the complex ticking gears of
the mechanism within. Dawkins's writing should be roundly criticized
for failing to answer the question he has set himself: what is
the origin of biological complexity? But, to his credit, Dawkins
at least knows the important question. Berwick doesn't.
1. By biochemistry I mean all sciences that investigate
life at the molecular level, including molecular biology, much
of embryology, immunology, genetics, etc. return to text
Shapiro, "The Bacterial Flagellum: From Genetic Network to
Complex Architecture," Cell 80 (1995): 525-27. return to
Copyright © 1997 Michael Behe. All rights
reserved. International copyright secured.