Postulate a Design, say “Here was something in the making,” and the process is explicable, especially if fairly rapid so as to bridge over the dangerously weak stages of imperfection. Postulate Natural Selection, and it is manifestly impossible. Now Natural Selection wants that to happen not only with every kind of bird, but with every kind of living creature.
(4) The fourth a priori argument against Natural Selection:
When two or more progenital agents are required, Natural Selection, acting by blind chance alone, loses effect in geometrical proportion with each generation.
This argument is rather more difficult to follow than the first two, but it is worth understanding, because it is particularly strong, and because it was among the first rude blows against the Darwinian theory. Nägeli brought it out with crushing force as long ago as 1884—it is a commonplace with everyone—except Mr. Wells, who imagines (a great compliment!) that I made it up.
Where two or more progenitors are necessary, rare accidental advantages rapidly disappear in a few generations if the process be left to chance, as Natural Selection demands.
Suppose two progenitors required—as is the case with all animals—there are, of course, many cases in which the total number of factors necessary for the production of progeny is more than two and the argument far stronger, e.g. the pollen of one flower, the pistil of another flower, and the insect which acts as go-between. Take any proportion you like of slightly favoured specimens. Suppose out of a hundred individual males ten show in varying degrees the slight differentiation which gives them a survival-value under changing conditions of environment. It will not be anything like ten out of a hundred, and we have already seen that a single advantage is useless. But we can afford to give this nonsense every advantage in argument, so we will consider only one clear advantage and allow one-tenth of the males to have it. Now, suppose a similar number of females showing in varying degrees this slight valuable differentiation. Upon the mechanical theory of Natural Selection, the chances in favour of progeny inheriting that differentiation in the next generation are not one-tenth, but only one-tenth of one-tenth, i.e. one-hundredth. The chances of favoured progeny in the third generation are not one-hundredth, but one in ten thousand. In the fourth, the chances are already only one in a hundred million—which we may call zero.
The reason is clear. Here are a hundred male land birds compelled by change of environment to take to the water. Ten of them show an infinitesimal rudimentary webbing between the toes of their feet, and that is a first infinitesimal advantage in swimming. Ten hens are of the same kind. Left to mere chance there is no reason why a season’s mating should allocate the web-footed male to the web-footed female. Each one of the ten males has nine chances to one of paring with a non-advantaged mate, and only one chance of mating with a hen similar to himself and possessing, as he does, this infinitesimal advantageous differentiation. On the average you would have only one couple in each hundred handing on in full even that first tiny advantage to their progeny with a corresponding tiny survival-value. In the case of eighteen others it would be halved, and in the case of a hundred and eighty-one, it would be absent. It is so with each generation. Each little infinitesimal advantage can only be fully handed on to a fraction which is the square of the last, and in even diminished form to a fraction smaller in proportion to the flock in the third generation than in the second. Long before you got anything like an even rudimentary webbed foot the tiny advantage would have been absorbed. The advantage, left to chance, sinks into the common stock.
There is no getting away from this conclusion by saying, “Oh! we’re not talking of individuals, we’re talking of great masses.” The masses are made up of individuals, and the mathematical argument is exactly the same whether you are dealing with a hundred or ten million.
These four a priori arguments against the theory of Natural Selection as the agent of differentiation in species are as conclusive as arithmetic can make them, and there is really no need for any others—though many others have been urged—e.g. the mathematical chances against one special advantageous variation appearing by pure accident at exactly the time it was needed.
But, as I have said, apart from these a priori and sufficient arguments, there are conclusive arguments drawn from actual evidence, and all this evidence is in favour of this Fixed Type. A fixed type would be an impossibility under Natural Selection: it goes with a Creator and with Design; and certainly it is true of the real world.