The GOD Delusion (20 page)

'Irreducible
complexity' is not a new idea, but the phrase itself was invented by
the creationist Michael Behe in 1996.
⁶²
He is
credited
(if credited is the word) with moving creationism into a new area of
biology: biochemistry and cell biology, which he saw as perhaps a
happier hunting ground for gaps than eyes or wings. His best approach
to a good example (still a bad one) was the bacterial flagellar motor.

The
flagellar motor of bacteria is a prodigy of nature. It drives the only
known example, outside human technology, of a freely rotating axle.
Wheels for big animals would, I suspect, be genuine examples of
irreducible complexity, and this is probably why they don't exist. How
would the nerves and blood vessels get across the bearing?* The
flagellum is a thread-like propeller, with which the bacterium burrows
its way through the water. I say 'burrows' rather than 'swims' because,
on the bacterial scale of existence, a liquid such as water would not
feel as a liquid feels to us. It would feel more like treacle, or
jelly, or even sand, and the bacterium would seem to burrow or screw
its way through the water rather than swim. Unlike the so-called
flagellum of larger organisms like protozoans, the bacterial flagellum
doesn't just wave about like a whip, or row like an oar. It has a true,
freely rotating axle which turns continuously inside a bearing, driven
by a remarkable little molecular motor. At the molecular level, the
motor uses essentially the same principle as muscle, but in free
rotation rather than in intermittent contraction.t It has been happily
described as a tiny outboard motor (although by engineering standards -
and unusually
for a biological mechanism - it is a spectacularly inefficient one).

*
There is an example in fiction. The children's writer Philip Pullman,
in
His Dark Materials,
imagines a species of
animals, the 'mulefa', that co-exist with trees that produce perfectly
round seedpods with a hole in the centre. These pods the mulefa adopt
as wheels. The wheels, not being part of the body, have no nerves or
blood vessels to get twisted around the 'axle' (a strong claw of horn
or bone). Pullman perceptively notes an additional point: the system
works only because the planet is paved with natural basalt ribbons,
which serve as 'roads'. Wheels are no good over rough country.

Fascinatingly,
the muscle principle is deployed in yet a third mode in
some insects such as flies, bees and bugs, in which the flight muscle
is intrinsically oscillatory, like a reciprocating engine. Whereas
other insects such as locusts send nervous instructions for each wing
stroke (as a bird does), bees send an instruction to switch on (or
switch off) the oscillatory motor. Bacteria have a mechanism which is
neither a simple contractor (like a bird's flight muscle) nor a
reciprocator (like a bee's flight muscle), but a true rotator: in that
respect it is like an electric motor or a Wankel engine.

Without
a word of justification, explanation or amplification, Behe simply
proclaims
the bacterial flagellar motor to be irreducibly complex.
Since he offers no argument in favour of his assertion, we may begin by
suspecting a failure of his imagination. He further alleges that
specialist biological literature has ignored the problem. The falsehood
of this allegation was massively and (to Behe) embarrassingly
documented in the court of Judge John E. Jones in Pennsylvania in 2005,
where Behe was testifying as an expert witness on behalf of a group of
creationists who had tried to impose 'intelligent design' creationism
on the science curriculum of a local public school - a move of
'breathtaking inanity', to quote Judge Jones (phrase and man surely
destined for lasting fame). This wasn't the only embarrassment Behe
suffered at the hearing, as we shall see.

The
key to demonstrating irreducible complexity is to show that none of the
parts could have been useful on its own. They all needed to be in place
before any of them could do any good (Behe's favourite analogy is a
mousetrap). In fact, molecular biologists have no difficulty in finding
parts functioning outside the whole, both for the flagellar motor and
for Behe's other alleged examples of irreducible complexity. The point
is well put by Kenneth Miller of Brown University, for my money the
most persuasive nemesis of 'intelligent design', not least because he
is a devout Christian. I frequently recommend Miller's book,
Finding
Darwin's God,
to religious people who write to me having
been bamboozled by Behe.

In
the case of the bacterial rotary engine, Miller calls our attention to
a mechanism called the Type Three Secretory System or TTSS.
⁶³
The TTSS is not used for rotatory movement. It is one of several
systems used by parasitic bacteria for pumping toxic substances through
their cell walls to poison their host organism. On our human scale, we
might think of pouring or squirting a liquid through a hole; but, once
again, on the bacterial scale things look different. Each molecule of
secreted substance is a large protein with a definite,
three-dimensional structure on the same scale as the TTSS's own: more
like a solid sculpture than a liquid. Each molecule is individually
propelled through a carefully shaped mechanism, like an automated slot
machine dispensing, say, toys or bottles,
rather than a simple hole through which a substance might 'flow'. The
goods-dispenser itself is made of a rather small number of protein
molecules, each one comparable in size and complexity to the molecules
being dispensed through it. Interestingly, these bacterial slot
machines are often similar across bacteria that are not closely
related. The genes for making them have probably been 'copied and
pasted' from other bacteria: something that bacteria are remarkably
adept at doing, and a fascinating topic in its own right, but I must
press on.

The
protein molecules that form the structure of the TTSS are very similar
to components of the flagellar motor. To the evolutionist it is clear
that TTSS components were commandeered for a new, but not wholly
unrelated, function when the flagellar motor evolved. Given that the
TTSS is tugging molecules through itself, it is not surprising that it
uses a rudimentary version of the principle used by the flagellar
motor, which tugs the molecules of the axle round and round. Evidently,
crucial components of the flagellar motor were already in place and
working before the flagellar motor evolved. Commandeering existing
mechanisms is an obvious way in which an apparently irreducibly complex
piece of apparatus could climb Mount Improbable.

A
lot more work needs to be done, of course, and I'm sure it will be.
Such work would never be done if scientists were satisfied with a lazy
default such as 'intelligent design theory' would encourage. Here is
the message that an imaginary 'intelligent design theorist' might
broadcast to scientists: 'If you don't understand how something works,
never mind: just give up and say God did it. You don't know how the
nerve impulse works? Good! You don't understand how memories are laid
down in the brain? Excellent! Is photosynthesis a bafflingly complex
process? Wonderful! Please don't go to work on the problem, just give
up, and appeal to God. Dear scientist, don't
work
on
your mysteries. Bring us your mysteries, for we can use them. Don't
squander precious ignorance by researching it away. We need those
glorious gaps as a last refuge for God.' St Augustine said it quite
openly: 'There is another form of temptation, even more fraught with
danger. This is the disease of curiosity. It is this which drives us to
try and discover the secrets of nature, those secrets which are beyond
our understanding, which can
avail us nothing and which man should not wish to learn' (quoted in
Freeman 2002).

Another
of Behe's favourite alleged examples of 'irreducible complexity' is the
immune system. Let Judge Jones himself take up the story:

In
fact, on cross-examination, Professor Behe was questioned concerning
his 1996 claim that science would never find an evolutionary
explanation for the immune system. He was presented with fifty-eight
peer-reviewed publications, nine books, and several immunology textbook
chapters about the evolution of the immune system; however, he simply
insisted that this was still not sufficient evidence of evolution, and
that it was not 'good enough.'

Behe,
under cross-examination by Eric Rothschild, chief counsel for the
plaintiffs, was forced to admit that he hadn't read most of those
fifty-eight peer-reviewed papers. Hardly surprising, for immunology is
hard work. Less forgivable is that Behe dismissed such research as
'unfruitful'. It certainly is unfruitful if your aim is to make
propaganda among gullible laypeople and politicians, rather than to
discover important truths about the real world. After listening to
Behe, Rothschild eloquently summed up what every honest person in that
courtroom must have felt:

Thankfully,
there are scientists who do search for answers to the question of the
origin of the immune system . . . It's our defense against debilitating
and fatal diseases. The scientists who wrote those books and articles
toil in obscurity, without book royalties or speaking engagements.
Their efforts help us combat and cure serious medical conditions. By
contrast, Professor Behe and the entire intelligent design movement are
doing nothing to advance scientific or medical knowledge and are
telling future generations of scientists, don't bother.
⁶⁴

As
the American geneticist Jerry Coyne put it in his review of Behe's
book: 'If the history of science shows us anything, it is that we
get nowhere by labelling our ignorance "God".' Or, in the words of an
eloquent blogger, commenting on an article on intelligent design in the
Guardian
by Coyne and me,

Why
is God considered an explanation for anything? It's not - it's a
failure to explain, a shrug of the shoulders, an 'I dunno' dressed up
in spirituality and ritual. If someone credits something to God,
generally what it means is that they haven't a clue, so they're
attributing it to an unreachable, unknowable sky-fairy. Ask for an
explanation of where that bloke came from, and odds are you'll get a
vague, pseudo-philosophical reply about having always existed, or being
outside nature. Which, of course, explains nothing.
⁶⁵

Darwinism
raises our consciousness in other ways. Evolved organs, elegant and
efficient as they often are, also demonstrate revealing flaws - exactly
as you'd expect if they have an evolutionary history, and exactly as
you would not expect if they were designed. I have discussed examples
in other books: the recurrent laryngeal nerve, for one, which betrays
its evolutionary history in a massive and wasteful detour on its way to
its destination. Many of our human ailments, from lower back pain to
hernias, prolapsed uteruses and our susceptibility to sinus infections,
result directly from the fact that we now walk upright with a body that
was shaped over hundreds of millions of years to walk on all fours. Our
consciousness is also raised by the cruelty and wastefulness of natural
selection. Predators seem beautifully 'designed' to catch prey animals,
while the prey animals seem equally beautifully 'designed' to escape
them. Whose side is God on?
⁶⁶

THE
ANTHROPIC PRINCIPLE: PLANETARY VERSION

Gap
theologians who may have given up on eyes and wings, flagellar motors
and immune systems, often pin their remaining hopes on the origin of
life. The root of evolution in non-biological chemistry
somehow seems to present a bigger gap than any particular transition
during subsequent evolution. And in one sense it is a bigger gap. That
one sense is quite specific, and it offers no comfort to the religious
apologist. The origin of life only had to happen once. We therefore can
allow it to have been an extremely improbable event, many orders of
magnitude more improbable than most people realize, as I shall show.
Subsequent evolutionary steps are duplicated, in more or less similar
ways, throughout millions and millions of species independently, and
continually and repeatedly throughout geological time. Therefore, to
explain the evolution of complex life, we cannot resort to the same
kind of statistical reasoning as we are able to apply to the origin of
life. The events that constitute run-of-the-mill evolution, as distinct
from its singular origin (and perhaps a few special cases), cannot have
been very improbable.

This
distinction may seem puzzling, and I must explain it further, using the
so-called anthropic principle. The anthropic principle was named by the
British mathematician Brandon Carter in 1974 and expanded by the
physicists John Barrow and Frank Tipler in their book on the subject.
⁶⁷
The anthropic argument is usually applied to the cosmos, and I'll come
to that. But I'll introduce the idea on a smaller, planetary scale. We
exist here on Earth. Therefore Earth must be the kind of planet that is
capable of generating and supporting us, however unusual, even unique,
that kind of planet might be. For example, our kind of life cannot
survive without liquid water. Indeed, exobiologists searching for
evidence of extraterrestrial life are scanning the heavens, in
practice, for signs of water. Around a typical star like our sun, there
is a so-called Goldilocks zone - not too hot and not too cold, but just
right - for planets with liquid water. A thin band of orbits lies
between those that are too far from the star, where water freezes, and
too close, where it boils.

Presumably,
too, a life-friendly orbit has to be nearly circular. A fiercely
elliptical orbit, like that of the newly discovered tenth planet
informally known as Xena, would at best allow the planet to whizz
briefly through the Goldilocks zone once every few (Earth) decades or
centuries. Xena itself doesn't get into the Goldilocks zone at all,
even at its closest approach to the sun, which it reaches once
every 560 Earth years. The temperature of Halley's Comet varies between
about 47°C at perihelion and minus 270°C at aphelion.
Earth's orbit, like those of all the planets, is technically an ellipse
(it is closest to the sun in January and furthest away in July*); but a
circle is a special case of an ellipse, and Earth's orbit is so close
to circular that it never strays out of the Goldilocks zone. Earth's
situation in the solar system is propitious in other ways that singled
it out for the evolution of life. The massive gravitational vacuum
cleaner of Jupiter is well placed to intercept asteroids that might
otherwise threaten us with lethal collision. Earth's single relatively
large moon serves to stabilize our axis of rotation,
⁶⁸
and helps to foster life in various other ways. Our sun is unusual in
not being a binary, locked in mutual orbit with a companion star. It is
possible for binary stars to have planets, but their orbits are likely
to be too chaotically variable to encourage the evolution of life.