Chance, Natural Selection and God
Probability theory plays an important part in creationist argumentation. Creationists point out the vast improbability of any complicated organism, like those that make up life on Earth, originating 'purely by chance.' That is certainly a strong argument, but if it is intended to target the theory of evolution, it misses the mark seriously.
The power of the Darwinian theory of natural selection is precisely that it is non-random. It not only acknowledges, but postulates that no really complex organism can originate by 'blind chance.' This is the essence of Darwin's theory, and what distinguishes it from theories that have been advanced as alternatives.
Darwinian selection requires the existence of something we can call replicators. A replicator is something, say a molecule (or set of molecules), that creates copies of itself by using other molecules in its environment as raw material. In any environment where a replicator exists, Darwinian selection will start to occur as a necessary consequence, as long as two other premises are present: that the replication is not necessarily 100% perfect, and that the resources (raw material for further replication) are scarce. Both these premises will be met in a real world.
Some mistakes in replication will occur. These copying errors - which we can call mutations - are random in one sense and one sense only: there is nothing in the error-making process that will favor copying errors of a kind that are more positive for the survival of the mutants. Mutations itself are neutral towards value for survival.
Now, once we have a mutant, natural selection will start to work on the mutants. If the mutant is just as good in making copies of itself as the original, we should expect mutants and non-mutants to coexist, if the mutant by chance happens to bring further replicas of itself into the world. If the mutant is less likely to be able to propagate copies of itself in the gene pool than the non-mutant, the mutant will go extinct, or it will at least become a negligible proportion of surviving replicators. In some very, very few instances the mutation will be an improvement. By improvement I mean one thing and one thing only: it will be more successful in making copies of itself and add them to the population. A mutant will leave off more offspring than a non-mutant. By statistical necessity (unless a freak accident kills them) will the mutants be propagated in what we can now call the gene pool of replicators. For every generation, the proportion of the population that is mutants will increase, at the cost of non-mutants. Undoubtedly, the non-mutant will go extinct.
What examples can we imagine of mutations that are beneficial to survival? Obviously, a mutant that breeds faster in its lifetime will leave more offspring. A mutant with a longer productive life will leave more offspring. If a replicator mutant was able to break down other replicators and use their raw material for its own reproduction, that would be a very positive mutation in a world of scarce resources, and we would have the first predator. In time, replicators could start growing small, simple "survival machines" of non-replicating materials around itself, perhaps to help it move around in the environment, and to protect itself against predators and a hostile environment. We would have what would later be a cell, and it would grow in sophistication as many small, random changes were introduced by mutations, and natural selection favored the best survival-machines.
If this 'game of life' went on for sufficiently long, who knows if not some of those survival machines would even be sophisticated enough to question where they came from? They would be totally ignorant (at first, that is) about the vicious arms races and hard competition between components of the replicators that made them in the first place. Some of them might even postulate that the question was uninteresting, and that they had of course always existed. Others may have looked to the fact that they themselves produced various artifacts for various purposes, and would speculate that perhaps some other, super-powerful being had indeed created them originally. And both those answers would, as we have seen, be wrong.
There is only a very small part of this 'grand view of life,' as Darwin called it, which requires chance. The first is, of course, the actual mutation. The fact that mutations occur is well known. We even know how often mutations occur in different parts of our own replicators, our DNA. No calculation can be made to determine how many of those mutations are positive, since there is no intrinsic 'positiveness' about the mutation itself that makes it positive. Only in interaction with its environment, when natural selection starts to operate on the mutant in the gene pool, will we receive the answer: survival or death.
The second phase - chronologically the first - where chance plays a part is when the original replicator came about. The first replicator had to originate by chance, since there was and is no natural selection present to work on a non-replicator. The first replicator was certainly not DNA based. DNA is much too complicated to originate by chance. Since none of the events that took place actually left any trace, except that the game of life indeed started, the exact how remains speculation. It might have been a very simple form of carbon-based life as we know it. It might also be something entirely different, like clay crystals, and these may eventually have started to use a predecessor of DNA as part of their survival machines. Or something entirely different. And since there is no way to know how many different replicators can possibly exist, or how they can come about, there is absolutely no way to calculate the odds of it happening. This of course refutes the totally absurd probability calculations of people like Hoyle, who indeed "calculates" the odds of something happening that no serious biologist has seriously postulated ever happened!
We know with reasonable certainty that life is not very common. On Earth, there is no reason to assume life originated more than once. It is, as far as we can see, not found on any other planet in our system. We can say that intelligent life with an advanced civilization (as we know it) is unlikely to exist in the immediate neighborhood, or we would have seen their radio communication in some form or another. So we could expect biogenesis to be something that occurs only, say, once in a billion billion years per planet. If this were the case, it would explain what we currently see: life here, no known life elsewhere, and it did take quite some time to develop here.
The crucial fact is that nowhere does the theory of evolution propose that something extremely improbable, comparable to spontaneously creating a complex organ, really happened. "Extreme saltationists" (you'd be hard pressed to find one alive today, though) have proposed it, that a "super-mutation" originally originated complex organs, for example the eye, from "nothing." The chance of this happening is so small that no modern biologist, and certainly no Darwinist, even considers taking this seriously. To the degree creationists debate with this position, and they do, they are either making up a straw man, or they attack a position so old and so marginal it only has historical interest.
But there is a large and significant group of people who postulate that beings of immense complexity indeed can arise from random chance, or alternatively that they always existed (which is not more likely at all). This group of people is called theists, of which Christianity is one branch. Being very happy to apply various forms of the flawed 'watchmaker argument' against the idea of life originating by natural processes, theists are very unhappy if the argument is turned around and applied to their god.
Creationists and other evolutionists alike would ridicule an evolutionist that argued that something as complicated as a human being originated by pure chance. The idea would be labeled absurd, and it would be absurd. Yet, those who believe in the Christian God do believe this, or a total equivalent. They do believe that something immensely more powerful and complex originated spontaneously, or has always existed, and that this being did not need any cause, any originator or watchmaker.
And I seriously doubt that Christians will argue that God evolved through natural selection of a long range of successively more powerful and 'fit' gods. Darwin has given us the only known mechanism in the universe that can explain how complex life could originate from simple beginnings without a monumental leap of improbability. Nobody can explain how, why, where and when any god originated, except by accepting the fact that 'god' was something postulated as a perfectly reasonable explanation by intelligent survival machines who just happened to be ignorant about the force of natural selection that made them.
Source and recommended reading:Dawkins, Richard. 1986. The Blind Watchmaker. London: Longman.
- Jan
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Faith, n. Belief without evidence in what is told by one who speaks without knowledge, of things without parallel. [Ambrose Bierce, The Devil´s Dictionary, 1911]