Natural Selection and the Improbability of God

[Breydel]

Natural Selection and the Improbability of God
by Richard Dawkins

I suggest that the existence of God is a scientific hypothesis like any other. God's existence or nonexistence is a scientific fact about the universe, discoverable in principle if not in practice. If he exists and chose to reveal it, God himself could clinch the argument, noisily and unequivocally in his favor. And even if God's existence is never proved or disproved with certainty, one way or the other, available evidence and reasoning may yield an estimate of probability far from 50 percent.

The ultimate Boeing 747

The argument from improbability is easily today's most popular argument offered in favor of the existence of God and it is seen, by an amazingly large number of theists, as completely and utterly convincing. It is indeed a very strong and, I suspect, unanswerable argument but in precisely the opposite direction from the theist's intention. The argument from improbability, properly deployed, comes close to proving that God does not exist. The label I give to the statistical demonstration that God almost certainly does not exist is the Ultimate Boeing 747 gambit.

The name comes from Fred Hoyle's amusing image of the Boeing 747 and the scrap yard. Hoyle said that the probability of life originating on Earth is no greater than the chance that a hurricane, sweeping through a scrap yard, would have the luck to assemble a Boeing 747. Others have borrowed the metaphor to refer to the later evolution of complex living bodies, where it has a spurious plausibility. The odds against assembling a fully functioning horse, beetle, or ostrich by randomly shuffling its parts are up there in 747 territory. This, in a nutshell, is the creationist's favorite argument, an argument that could be made only by somebody who doesn't understand the first thing about natural selection: somebody who thinks natural selection is a theory of chance whereas—in the relevant sense of chance—it is the opposite.

The argument from improbability states that complex things could not have come about by chance. But many people define "come about by chance" as a synonym for "come about in the absence of deliberate design." Not surprisingly, therefore, they think improbability is evidence of design. Darwinian natural selection shows how wrong this is with respect to biological improbability. And although Darwinism may not be directly relevant to the inanimate world—cosmology, for example—it raises our consciousness.

The power of accumulation

What is it that makes natural selection succeed as a solution to the problem of improbability, where chance and design both fail at the starting gate? The answer is that natural selection is a cumulative process which breaks the problem of improbability up into small pieces. Each of the small pieces is slightly improbable, but not prohibitively so. When large numbers of these slightly improbable events are stacked up in series, the end product of the accumulation is very, very improbable indeed, improbable enough to be beyond the reach of chance. It is these end products that form the subjects of the creationist's wearisomely recycled argument. The creationist completely misses the point, because he insists on treating the genesis of statistical improbability as a single, one-off event. He doesn't understand the power of accumulation.

In Climbing Mount Improbable, I expressed the point in a parable. One side of the mountain is a sheer cliff, impossible to climb, but on the other side is a gentle slope to the summit. On the summit sits a complex device such as an eye or a bacterial flagellar motor. The absurd notion that such complexity could spontaneously self-assemble is symbolized by leaping from the foot of the cliff to the top in one bound. Evolution, by contrast, goes around the back of the mountain and creeps up the gentle slope to the summit: easy! The principle of climbing the gentle slope as opposed to leaping up the precipice is so simple, one is tempted to marvel that it took so long for a Darwin to arrive on the scene and discover it. Nearly three centuries had elapsed since Newton's annus mirabilis although his achievement seems, on the face of it, harder than Darwin's.

Creationists who attempt to deploy the argument from improbability in their favor always assume that biological adaptation is a question of the jackpot or nothing. Another name for the "jackpot or nothing" fallacy is "Irreducible Complexity" (IC). Either the eye sees or it doesn't. Either the wing flies or it doesn't. There are assumed to be no intermediates. But this is simply wrong. Intermediates abound ... Real life seeks the gentle slopes at the back of Mount Improbable, while creationists are blind to all but the daunting precipice at the front.

The worship of gaps

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 Dietrich 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, one of the truly bad effects of religion is that it teaches us that it is a virtue to be satisfied with not understanding.

There is, then, an unfortunate hook-up between science's methodological need to seek out areas of ignorance in order to target research, and the need of proponents of intelligent design (ID) 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.

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 have. We could easily have had no fossils at all, and the evidence for evolution from other sources, such as molecular genetics and geographical distribution, would still 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 ofthe 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.

Irreducible complexity is not a new idea, but the phrase itself was invented by the creationist Michael Behe in 1996. He is credited (if credited is the word) with moving creationism into a new area of biology: biochemistry and cell biology, which he perhaps saw as 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 bearings? The flagellum is a thread-like propeller, with which the bacterium burrows its way through the water. "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. 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).

Is the bacterial flagellar motor irreducibly complex?

Without a word of justification, Behe simply proclaims the bacterial flagellar motor to be irreducibly complex. Since he offers no argument in favor of his assertion, we may begin by suspecting a failure of his imagination. He further alleges that the 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. Behe was testifying as an expert witness on behalf of a group of creationists who, with "breathtaking inanity" (Judge Jones's immortal phrase), had tried to impose "intelligent design" on the science teaching of a local public school. This wasn't the only embarrassment Behe suffered at the hearing.

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 favorite 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. The TTSS is not used for rotary 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.

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 ofthe 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.

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?

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[Whiteruthenian]

The peak of evolution is a perfect predator – a perfect killer who can eat animal corpses and plants if there is a need to do it. Also it should be able to bear extreme high and extreme low temperatures, so that it would be possible for it not to be dependent on weather and climate. Why haven’t millions of years of natural selection created such a monster (like that one in the film “Alien”)? God knows. A world populated by such creatures would be more interesting than our present world.

…and yes, God definitely knows.

[Breydel]

Originally Posted by Whiteruthenian

The peak of evolution is a perfect predator – a perfect killer who can eat animal corpses and plants if there is a need to do it. Also it should be able to bear extreme high and extreme low temperatures, so that it would be possible for it not to be dependent on weather and climate. Why haven’t millions of years of natural selection created such a monster (like that one in the film “Alien”)? God knows. A world populated by such creatures would be more interesting than our present world.

…and yes, God definitely knows.

there is no such a monster simply because of the fact that there are geographical boundaries with different environmental situations and climates, if he would exist he would have been created by a designer who wouldn't have to play by the natural laws that are coordinating on earth, it isn't about general perfection in total sense but about mutations that get selected and survive because of a local situation, so we can't speak of a global 'pro' obviously