Reply to Michael J. Behe

K. John Morrow, Jr.

This is the author's comment to a response to his original paper.


I AM PLEASED TO HAVE an opportunity to respond to Dr. Behe's criticism of
my paper, as it gives me an opportunity to elaborate on some aspects of my
talk and clarify what I believe are misstatements or misinterpretations of
my position. As Dr. Behe has accused me of raising straw men, I could
perhaps point to a few of his own. This discussion could perhaps be
subtitled, "My straw man can beat up your straw man "
The thrust of Dr. Behe's criticism is that in arguing the validity of
Darwinian evolutionary theory, a comparison of the various hypotheses of
immune diversity is (1) irrelevant and (2) begs the issue of where the
immune system came from, for which he thinks there is at present no
adequate answer. Let me address these issues one at a time.
In the first place, I chose this topic because it is restricted enough and
sufficiently well investigated to be understandable in the framework of a
short presentation. I did not wish to deal with the evolution of the
immune system, since it is an extremely complex topic that does not lend
itself to a didactic exposition. But since Dr. Behe has brought this up I
will be happy to do so.
But first, let us consider his criticism that my analysis of the various
hypotheses of immune diversity constitutes a straw man, which I use to
buttress my own narrow and unsubstantiated belief in evolutionary dogma.
Perhaps we can best do this by turning the argument around.
Say the germ line theory had proven to be true, and say that a mammal
contained a huge amount of genetic information coding for millions and
millions of different antibody types. Most of this information would never
be marshaled, either in the individual's lifetime or the lifetime of the
entire species. Say, further, that it were discovered that mammals carried
genes that coded for man-made compounds that had been synthesized only
this year, and that bore absolutely no resemblance to any naturally
occurring compound. Do you think that a creationist would argue that such
a system constituted scientific evidence for purpose in biology? And do
you think, moreover, he would argue that the existence of genes of no
selective value to the individual (or perhaps to the entire species) would
suggest that mechanisms other than Darwinian evolution and natural
selection guide the development of complex biological system? I leave it
to the reader to decide this question.
Dr. Behe points out quite correctly that the enigma of immune diversity
was solved using molecular techniques that were not available when the
question was formulated. It was not resolved through a deductive process
carried out by monks speculating in the confines of their cells in a
lonely mountainside monastery. I agree with the statement that immune
diversity was never a topic of theological conjecture. My point was that
in the early years of the twentieth century there were several competing
theories to account for how antibodies were produced. The theory of
natural selection predicted that the germ line hypothesis could not
possibly have been right, at least in its simplest formulation. This is a
characteristic of a good scientific theory; it makes predictions,
generates experiments, and drives the field forward.
Dr. Behe accuses me of presenting a biological mechanism and then
arbitrarily stating that God wouldn't use it, and therefore God does not
exist. Au contraire. My point was that what we know about the immune
system gives us no reason to propose any kind of divine purpose or
conscious will in shaping it. Clearly God may exist and he may use any
means he wishes to shape the universe. Perversely, he may have created the
universe ten minutes ago, and everything in it may be placed there simply
to confuse and distract us. I certainly don't believe in such a wicked
god, and neither does Dr. Behe or anyone else who defends Christian
theology. The divine purpose that we are considering here finds its roots
in biblical accounts of God and his powers. This God is a knowing, loving
deity.
But Dr. Behe's obstruction is typical of anyone who clings steadfastly to
the notion that living systems were shaped by a knowledgeable, rational,
purposeful consciousness. When one presents a biological system that
doesn't tit these criteria, Dr. Behe can always say, "You are trying to
put ideas in God's head. Neither you nor anyone else knows what God was
thinking when he created living systems."
If there is a rational purpose to life and if Darwinian evolution is
inadequate to explain it, then the divine hand that shaped it must have
created us in his image and his thought processes must be similar to our
own. This is what the God of Christianity is all about. He is not
arbitrary. He is not wicked. He is not capricious.
My point is that an inspection of the history of biology shows that, over
and over again, theories of life requiring a teleological basis have been
found, in the light of modern molecular investigations, to be unnecessary.
This realization certainly doesn't argue that God does not exist, but
simply that it is unnecessary to propose a divine purpose to explain how
living creatures came to their present state of development. But this is
precisely where Dr. Behe and I differ. He says that the most important
materialistic, mechanistic principle of biology, the theory of evolution,
is inadequate to explain the diversity of living systems, and therefore we
must evoke divine purpose, and a divine purpose that intervenes on a
step-by-step basis.
But to return to Dr. Behe's second criticism of my argument, are there
really unresolvable questions concerning how the immune system could have
evolved solely through natural selection? Most of Behe's specific points
go back to the notion that the evolution of complex systems is impossible
because none of the individual components has selective value independent
of a complete, integrated whole. But this is a straw-man argument, which
implies that unless the system is working flawlessly it won't work at all.
Clearly in Dr. Behe's universe there is no Model T on the way from the
horse and buggy to the Mercedes.
For instance, Behe says that an antibody molecule by itself would have no
selective value for an organism, and therefore it is impossible that the
immune system arose through a gradual process of evolution and natural
selection. He then goes on to mention that a specific protein, known as
complement, must be present in order for immunoglobulin molecules to exert
toxicity against foreign invaders; he suggests that without a fully
developed complement system antibodies would be of no selective value. But
this statement ignores the fact that various primitive complement-like
molecules have been identified in invertebrates, which function in a
nonspecific manner to protect the organism from foreign invaders. In fact,
complement-like molecules have been found in a variety of protostome and
deuterostome invertebrates. These molecules are used for triggering
phagocytosis (a process by which pathogens are devoured), possibly through
the intervention of other molecules known as lectins.
Behe seems oblivious to the evidence that antibodies are members of a
class of molecules, the immunoglobulin super family, many of whose members
are involved in cell-cell recognition and signaling. In fact, super family
molecules of the class known as b-microglobulin exist on the brain of the
squid. It has been suggested that the immunoglobulin superclass evolved
from a common precursor responsible for mediation of cell signals. Members
of the Ig super family are found in the membranes of neurons, indicating
that molecules that communicate signals use a common basic plan, modified
for individual tasks. Thus a common molecular precursor has been revamped
over and over again in the course of evolution. The ancestral
immunoglobulin molecule no doubt functioned as a crude recognition
molecule, allowing some degree of reactivity against foreign pathogens.
From this vantage point we can think of the immune system as being one
component of a broad-ranging communication network, occurring throughout
the phylogenetic tree and throughout different organ systems within
individuals.
It is not known how an internal recognition system became modified in the
course of evolution so as to "turn outward" and recognize foreign
proteins. But it does not take a great leap of the imagination to conceive
of a primitive species that would use immunoglobulin-like molecules for
recognition of foreign proteins through a mechanism of broad specificity,
eventually developing through natural selection a panel of recognition
signals, and then later evolving a broader and broader collection of
molecules through gene duplication. Eventually mutations destabilizing
some of these recognition genes might appear. These unstable regions might
generate a wider range of molecules with a weak affinity for pathogenic
organisms.
One can imagine what an advantage an organism would have with this crude
proto-recognition system for the identification of foreign marauders, even
if it were initially extremely inefficient.
A reasonable idea does not constitute a proof. I have suggested these
possibilities simply to illustrate how artificial Behe's argument is, and
to emphasize that there is nothing arcane or mysterious about the
evolution through intermediate steps to a highly sophisticated biological
mechanism. I would have to admit that we really do not know precisely
how the immune system came to be. But Dr. Behe's objection to a Darwinian
evolutionary interpretation is precisely what troubles me about the
anti-evolutionist stance; because we don't have an ironclad proof of every
precise feature of the evolution of the immune system in hand, Behe
suggests that we just abandon the whole enterprise and accept a fuzzy and
ill-defined teleology as a scientific explanation.
This strikes me as a profoundly unscientific approach that is foreordained
to failure.