The goal
of creationists has always been to replace the teaching of evolution with
the narrative given in the first eleven chapters of
Genesis. When the courts stymied this effort,
creationists tried a new strategy: cloaking
themselves in the mantle of science. This produced
the oxymoronic 'scientific creationism', arguing that
the very facts of biology and geology show that the
Earth is young, all species were created suddenly and
simultaneously, and mass extinctions were caused by a
great world-wide flood. The resemblance between this
theory and the book of Genesis was, of course, purely
coincidental. Scientific creationism, however, also
came to grief. Virtually all creation 'scientists'
were religious fundamentalists without biological
expertise, and American courts clearly spied clerical
collars beneath the lab coats.
In Darwin's Black Box, Michael Behe offers a
new and more sophisticated version of scientific
creationism. Unlike his predecessors, Behe is a
genuine scientist, a biochemist from Lehigh
University in Pennsylvania. The book jacket asserts
that he is not a creationist, but believes in the
scientific method. His argument, however, is a
recycled version of the creationist notion that
'complex design' implies an intelligent designer. But
where William Paley illustrated this logic with a
watch, Behe uses biochemistry. His intended audience
of lay readers may be impressed by the elaborate
descriptions of molecular biology and long lists of
references, but Behe's 'scientific' alternative to
evolution ultimately becomes a confusing and
untestable farrago of contradictory ideas.
Behe's thesis is that organisms harbour molecular
pathways so elaborate and interconnected that they
cannot be explained by gradual evolution from simpler
precursors. His examples of such pathways, described
with admirable clarity, include blood- clotting, the
immune system and intracellular transport. These
share what he calls "irreducible
complexity": they would not function if any
single component were removed. Because Darwinism
requires that a pathway be useful at every stage of
its evolution, Behe claims that such irreducibly
complex pathways could not evolve in steps. Their
existence therefore implies conscious design and an
intelligent designer. (Like all scientific
creationists, Behe keeps quiet about the identity of
the Great Designer, but the author's professed Roman
Catholicism offers one clue.) Evolutionists are said
to resist this idea of design because of our dogged
but unreasonable dislike of supernatural
explanations. Behe, however, is free from this
constraint. With paternal pride, he declares that his
discovery of biochemical design "must be ranked
as one of the greatest achievements in the history of
science", rivalling "those of Newton and
Einstein, Lavoisier and Schrodinger, Pasteur, and
Darwin".
There is no doubt that the pathways described by Behe
are dauntingly complex, and their evolution will be
hard to unravel. Unlike anatomical structures, the
evolution of which can be traced with fossils,
biochemical evolution must be reconstructed from
highly evolved living organisms, and we may forever
be unable to envisage the first proto-pathways. It is
not valid, however, to assume that, because one man
cannot imagine such pathways, they could not have
existed. Moreover, a J.B.S. Haklane pointed out:
"My own suspicion is that the universe is not
only queerer than we suppose, but queerer than we can
suppose." We face not only the absence of data,
but also the awful fact that we ourselves are evolved
creatures with limited cognition and imagination.
The answer to Behe's argument lies in realizing that
biochemical pathways did not evolve by the sequential
addition of steps to pathways that became functional
only at the end. Instead, they have been rigged up
with pieces co-opted from other pathways, duplicated
genes and early multifunctional enzymes. Thrombin,
for example, is one of the key proteins in blood-
clotting, but also acts in cell division, and is
related to the digestive enzyme trypsin. Who knows
which function came first? Behe makes a few
half-hearted attempts to build up such pathways, but
quickly abandons the enterprise and cries
"design".
Evolutionists will find two other problems with
Behe's arguments. First, there is ample evidence for
the evolution of morphology and anatomy from studies
of palaeontology, embryology, biogeography and
vestigial organs. Such evolution must, of course, be
based on the evolution of molecules and biochemical
pathways. Second, we have plenty of direct evidence
for the evolution of molecules. This includes the
remarkable congruence between phylogenies based on
anatomy and those based on DNA or protein sequence
(bat haemoglobin, for example, is far more similar to
that of whales than of birds), the relatedness of
genes through gene duplication (including those
involved in the immune system and blood-clotting),
and the existence of vestigial 'pseudogenes' that
were useful in ancestors. (Unlike most mammals,
humans cannot synthesize vitamin C, we still carry
the gene for the final step in this pathway, but
deletions have rendered it non-functional.)
Behe's response to these problems constitutes the
major weakness of his theory. He chews on the idea of
morphological evolution, but cannot bring himself to
swallow it. He finds the idea of common descent of
all organisms "fairly convincing", and
admits that microevolution occurs within species, but
sees no evidence for transitions between major forms.
(How one can admit common descent but deny
macroevolution is one of the fascinating questions
Behe leaves unanswered.) Finally, in a tactic unique
in the creationist literature, he admits that both
evolution and creation might occur at the molecular
level. Such a hybrid theory, however, yields sterile
offspring, such as Behe's idea that the first
'designed' cell could include the DNA for all future
evolutionary change, including that producing eyes
and the immune system.
Responding to observations of non-functional genes
and inefficient molecular processes, Behe theorizes
that he Great Designer, like his counterparts in
Paris and Milan, has goals beyond functionality:
"Features that strike us as odd in a design
might have been placed there by the designer for a
reason -- for artistic reasons, for variety, to show
off, for some as-yet-undetectable practical purpose,
or for some unguessable reason -- or they might
not." One should add the "puckish
reason": to confuse future biologists by making
things look as though they evolved.
If one accepts Behe's idea that both evolution and
creation can operate together, and that the
Designer's goals are unfathomable, then one confronts
an airtight theory that can't be proved wrong. I can
imagine evidence that would falsify evolution (a
hominid fossil in the Precambrian would do nicely),
but none that could falsify Behe's composite theory.
Even if, after immense effort, we are able to
understand the evolution of a complex biochemical
pathway, Behe could simply claim that evidence for
design resides in the other unexplained pathways.
Because we will never explain everything, there will
always be evidence for design. This regressive ad hoc
creationism may seem clever, but it is certainly not
science. As the theologian Dietrich Bonhoeffer
pointed out, it is also bad religion: "If in
fact the frontiers of knowledge are being pushed
farther and farther back (and that is bound to be the
case), then God is being pushed back with them, and
is therefore continually in retreat."
In the end, Darwin's Black Box is a work of
advocacy whose creationist ancestry is revealed by
both its rhetoric and its failure to deal honestly
with the evidence for evolution. There is the usual
selective quotation of evolutionists (including, to
my horror, a remark of my own, both altered and taken
out of context), ridicule of scientists, and a folksy
'us-against-them' style reflecting the populist roots
of creationism. The book will no doubt be widely
cited by Biblical creationists who will tout its
message of design wile ignoring its timid acceptance
of evolution and its view of the creator as Cosmic
Prankster.
If the history of science shows us anything, it is
that we get nowhere by labelling our ignorance 'God'.
Lord Kelvin declared that the primaeval Earth had
cooled down too quickly to permit the great age
required by Darwinism. How could he imagine that
radioactivity would be discovered four decades later
and prove the missing source of heat? Duane Gish, the
doyen of American creationists, once argued for the
separate creation of mammals and reptiles, based on
their jaw structure. Each has a jaw joint made from a
different pair of bones, and Gish could not imagine
how the transitional form could chew while its jaw
was being unhinged and rearticulated. In 1958,
however, Fuzz Crompton described a mammal-like
reptile with a double jaw joint that included both
pairs of bones. The evolution of biochemical pathways
is certainly queerer than Professor Behe can suppose.
Jerry Coyne is in the Department of Ecology
and Evolution, University of Chicago, Chicago, Illinois
60637, USA.