The GOD Delusion (19 page)

By
analogy with the trees of different height, it is easy to imagine
situations in which half an eye would save the life of an animal where
49 per cent of an eye would not. Smooth gradients are provided by
variations in lighting conditions, variations in the distance at which
you catch sight of your prey - or your predators. And, as with wings
and flight surfaces, plausible intermediates are not only easy to
imagine: they are abundant all around the animal kingdom. A flatworm
has an eye that, by any sensible measure, is less than half a human
eye.
Nautilus
(and perhaps its extinct ammonite
cousins who dominated Paleozoic and Mesozoic seas) has an eye that is
intermediate in quality between flatworm and human. Unlike the flatworm
eye, which can detect light and shade but see no image, the
Nautilus
'pinhole camera' eye makes a real image; but it is a blurred
and dim image compared to ours. It would be spurious precision to put
numbers on the improvement, but nobody could sanely deny that these
invertebrate eyes, and many others, are all better than no eye at all,
and all lie on a continuous and shallow slope up Mount Improbable, with
our eyes near a peak - not the highest peak but a high one. In
Climbing
Mount Improbable,
I devoted a whole chapter each to the eye
and the wing, demonstrating how easy it was for them to evolve by slow
(or even, maybe, not all that slow) gradual degrees, and I will leave
the subject here.

So,
we have seen that eyes and wings are certainly not irreducibly complex;
but what is more interesting than these particular examples is the
general lesson we should draw. The fact that so many people have been
dead wrong over these obvious cases should serve to warn us of other
examples that are less obvious, such as the cellular and biochemical
cases now being touted by those creationists who shelter under the
politically expedient euphemism of 'intelligent design theorists'.

We
have a cautionary tale here, and it is telling us this: do not just
declare things to be irreducibly complex; the chances are that you
haven't looked carefully enough at the details, or thought carefully
enough about them. On the other hand, we on the science side must not
be too dogmatically confident. Maybe there is something out there in
nature that really does preclude, by its
genuinely
irreducible
complexity, the smooth gradient of Mount Improbable. The creationists
are right that, if genuinely irreducible complexity could be properly
demonstrated, it would wreck Darwin's theory. Darwin himself said as
much: '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. But I can find no
such case.' Darwin could find no such case, and nor has anybody since
Darwin's time, despite strenuous, indeed desperate, efforts. Many
candidates for this holy grail of creationism have been proposed. None
has stood up to analysis.

In
any case, even though genuinely irreducible complexity would wreck
Darwin's theory if it were ever found, who is to say that it wouldn't
wreck the intelligent design theory as well? Indeed, it already
has
wrecked the intelligent design theory, for, as I keep saying
and will say again, however little we know about God, the one thing we
can be sure of is that he would have to be very very complex and
presumably irreducibly so!

Searching
for particular examples of irreducible complexity is a fundamentally
unscientific way to proceed: a special case of arguing from present
ignorance. It appeals to the same faulty logic as 'the God of the Gaps'
strategy condemned by the theologian Dietrich Bonhoeffer. Creationists
eagerly seek a gap in present-day knowledge or understanding. If an
apparent gap is found, it is
assumed
that God, by
default, must fill it. What worries thoughtful theologians such as
Bonhoeffer is that gaps shrink as science advances, and God is
threatened with eventually having nothing to do and nowhere to hide.
What worries scientists is something else. It is an essential part of
the scientific enterprise to admit ignorance, even to exult in
ignorance as a challenge to future conquests. As my friend Matt Ridley
has written, 'Most scientists are bored by what they have already
discovered. It is ignorance that drives them on.' Mystics exult in
mystery and want it to stay mysterious. Scientists exult
in mystery for a different reason: it gives them something to do. More
generally, as I shall repeat in Chapter 8, one of the truly bad effects
of religion is that it teaches us that it is a virtue to be satisfied
with not understanding.

Admissions
of ignorance and temporary mystification are vital to good science. It
is therefore unfortunate, to say the least, that the main strategy of
creation propagandists is the negative one of seeking out gaps in
scientific knowledge and claiming to fill them with 'intelligent
design' by default. The following is hypothetical but entirely typical.
A creationist speaking: 'The elbow joint of the lesser spotted weasel
frog is irreducibly complex. No part of it would do any good at all
until the whole was assembled. Bet you can't think of a way in which
the weasel frog's elbow could have evolved by slow gradual degrees.' If
the scientist fails to give an immediate and comprehensive answer, the
creationist draws a
default
conclusion: 'Right
then, the alternative theory, "intelligent design", wins by default.'
Notice the biased logic: if theory A fails in some particular, theory B
must be right. Needless to say, the argument is not applied the other
way around. We are encouraged to leap to the default theory without
even looking to see whether it fails in the very same particular as the
theory it is alleged to replace. Intelligent design - ID - is granted a
Get Out Of Jail Free card, a charmed immunity to the rigorous demands
made of evolution.

But
my present point is that the creationist ploy undermines the
scientist's natural - indeed necessary - rejoicing in (temporary)
uncertainty. For purely political reasons, today's scientist might
hesitate before saying: 'Hm, interesting point. I wonder how the weasel
frog's ancestors
did
evolve their elbow joint. I'm
not a specialist in weasel frogs, I'll have to go to the University
Library and take a look. Might make an interesting project for a
graduate student.' The moment a scientist said something like that -
and long before the student began the project - the default conclusion
would become a headline in a creationist pamphlet: 'Weasel frog could
only have been designed by God.'

There
is, then, an unfortunate hook-up between science's methodological need
to seek out areas of ignorance in order to target research, and ID's
need to seek out areas of ignorance in order to claim victory by
default. It is precisely the fact that ID has no
evidence of its own, but thrives like a weed in gaps left by scientific
knowledge, that sits uneasily with science's need to identify and
proclaim the very same gaps as a prelude to researching them. In this
respect, science finds itself in alliance with sophisticated
theologians like Bonhoeffer, united against the common enemies of
naive, populist theology and the gap theology of intelligent design.

The
creationists' love affair with 'gaps' in the fossil record symbolizes
their whole gap theology. I once introduced a chapter on the so-called
Cambrian Explosion with the sentence, 'It is as though the fossils were
planted there without any evolutionary history.' Again, this was a
rhetorical overture, intended to whet the reader's appetite for the
full explanation that was to follow. Sad hindsight tells me now how
predictable it was that my patient explanation would be excised and my
overture itself gleefully quoted out of context. Creationists adore
'gaps' in the fossil record, just as they adore gaps generally.

Many
evolutionary transitions are elegantly documented by more or less
continuous series of gradually changing intermediate fossils. Some are
not, and these are the famous 'gaps'. Michael Shermer has wittily
pointed out that if a new fossil discovery neatly bisects a 'gap', the
creationist will declare that there are now twice as many gaps! But in
any case, note yet again the unwarranted use of a default. If there are
no fossils to document a postulated evolutionary transition, the
default assumption is that there was no evolutionary transition,
therefore God must have intervened.

It
is utterly illogical to demand complete documentation of every step of
any narrative, whether in evolution or any other science. You might as
well demand, before convicting somebody of murder, a complete cinematic
record of the murderer's every step leading up to the crime, with no
missing frames. Only a tiny fraction of corpses fossilize, and we are
lucky to have as many intermediate fossils as we do. We could easily
have had no fossils at all, and still the evidence for evolution from
other sources, such as molecular genetics and geographical
distribution, would be overwhelmingly strong. On the other hand,
evolution makes the strong prediction that if a
single
fossil
turned up in the
wrong
geological stratum, the
theory would be blown out of the water. When challenged by a zealous
Popperian to say how evolution could ever be falsified, J. B. S.
Haldane famously growled: 'Fossil rabbits in the Precambrian.' No such
anachronistic fossils have ever been authentically found, despite
discredited creationist legends of human skulls in the Coal Measures
and human footprints interspersed with dinosaurs'.

Gaps,
by default in the mind of the creationist, are filled by God. The same
applies to all apparent precipices on the massif of Mount Improbable,
where the graded slope is not immediately obvious or is otherwise
overlooked. Areas where there is a lack of data, or a lack of
understanding, are automatically assumed to belong, by default, to God.
The speedy resort to a dramatic proclamation of 'irreducible
complexity' represents a failure of the imagination. Some biological
organ, if not an eye then a bacterial flagellar motor or a biochemical
pathway, is
decreed
without further argument to be
irreducibly complex. No attempt is made to
demonstrate
irreducible
complexity. Notwithstanding the cautionary tales of eyes, wings and
many other things, each new candidate for the dubious accolade is
assumed to be transparently, self-evidently irreducibly complex, its
status asserted by fiat. But think about it. Since irreducible
complexity is being deployed as an argument for design, it should no
more be asserted by fiat than design itself. You might as well simply
assert that the weasel frog (bombardier beetle, etc.) demonstrates
design, without further argument or justification. That is no way to do
science.

The
logic turns out to be no more convincing than this: 'I [insert own
name] am personally unable to think of any way in which [insert
biological phenomenon] could have been built up step by step. Therefore
it is irreducibly complex. That means it is designed.' Put it like
that, and you immediately see that it is vulnerable to some scientist
coming along and finding an intermediate; or at least imagining a
plausible intermediate. Even if no scientists do come up with an
explanation, it is plain bad logic to assume that 'design' will fare
any better. The reasoning that underlies 'intelligent design' theory is
lazy and defeatist - classic 'God of the Gaps' reasoning. I have
previously dubbed it the Argument from Personal Incredulity.

Imagine
that you are watching a really great magic trick. The celebrated
conjuring duo Penn and Teller have a routine in which they
simultaneously appear to shoot each other with pistols, and each
appears to catch the bullet in his teeth. Elaborate precautions are
taken to scratch identifying marks on the bullets before they are put
in the guns, the whole procedure is witnessed at close range by
volunteers from the audience who have experience of firearms, and
apparently all possibilities for trickery are eliminated. Teller's
marked bullet ends up in Penn's mouth and Penn's marked bullet ends up
in Teller's. I [Richard Dawkins] am utterly unable to think of any way
in which this could be a trick. The Argument from Personal Incredulity
screams from the depths of my prescientific brain centres, and almost
compels me to say, 'It must be a miracle. There is no scientific
explanation. It's got to be supernatural.' But the still small voice of
scientific education speaks a different message. Penn and Teller are
world-class illusionists. There is a perfectly good explanation. It is
just that I am too naive, or too unobservant, or too unimaginative, to
think of it. That is the proper response to a conjuring trick. It is
also the proper response to a biological phenomenon that appears to be
irreducibly complex. Those people who leap from personal bafflement at
a natural phenomenon straight to a hasty invocation of the supernatural
are no better than the fools who see a conjuror bending a spoon and
leap to the conclusion that it is 'paranormal'.

In
his book
Seven Clues to the Origin of Life,
the
Scottish chemist A. G. Cairns-Smith makes an additional point, using
the analogy of an arch. A free-standing arch of rough-hewn stones and
no mortar can be a stable structure, but it is irreducibly complex: it
collapses if any one stone is removed. How, then, was it built in the
first place? One way is to pile a solid heap of stones, then carefully
remove stones one by one. More generally, there are many structures
that are irreducible in the sense that they cannot survive the
subtraction of any part, but which were built with the aid of
scaffolding that was subsequently subtracted and is no longer visible.
Once the structure is completed, the scaffolding can be removed safely
and the structure remains standing. In evolution, too, the organ or
structure you are looking at may have had scaffolding in an ancestor
which has since been removed.