The science of life : fully illustrated in tone and line and including many diagrams

BOOK 3

present variety through the modification year by year, and age by age, of simpler and less various ancestral species. In making this declaration we are denying a belief, formerly very prevalent, the belief that animal species, as they are now, came into being suddenly, through some abrupt act of Creation. That belief has now become impossible in the face of an assemblage of countless known and established facts. On the other hand, all these contributing facts build themselves up into the comprehensive vision of Evolution as the fact of facts, the quintessence of the whole display.

But we are not attempting any explanation of this fact of Evolution here. We are not attempting any account here of why species have changed. We will write later of the various theories by which an explanation of this central fact is attempted. We are not discussing here the Theory of Natural Selection, or the Theory of Creative Evolution or any theory at all of how Evolution has been carried on. First the facts and then these more stormy issues may be faced. Here we traverse ground upon which scientific men of every creed and school are now agreed.

We make this distinction between fact and theory here and, so to speak, underline it, because we know there is still a considerable confusion in the public mind between the fact of Evolution and the conflicting theories about how it works. Dishonest Creationists, narrow fanatics, and muddle-headed people attempt to confuse the very wide diversity of opinion among scientific men upon the questions of how and why with their assertion of established fact. Through this confusion it is suggested that the hated fact is still unproven. It is, on the contrary, proven up to the hilt, and here we shall unfold as much of the evidence as is necessary for conviction.

§ 2 The Nature of the Proof

Before we go on to the evidence, however, let us consider what our evidence must show if Evolution is to be accepted as the general process of life.

First, then, all things living, or once living, must fall into a branching plan. Everything in the past must be reasonably shown to be either ancestral to a living thing or else without descendants; there must be no renewal of the process, nothing in the past must be plainly derived from some later form. Every mammal, for example, is held

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to be descended from a reptilian ancestor. Suppose in the early Coal Measures, before ever a reptile existed, we found the skull of a horse or a lion. Then the whole vision of Evolution would vanish. A single human tooth im situ in a coal seam would demolish the entire fabric of modern biology. But never do we find any such anachronisms. The order of descent is always observed.

Next there must be an orderly sequence in fossil forms, so far as they are found. We must see very distinctly that form passes into form. In the days of Darwin such sequences were hard to find. In those days there were probably not a hundredth part of the present multitude of fossils that are now collected and arranged. The Creationists pointed triumphantly to a gapped and fragmentary story, sustained by hypothesis, broken up by “missing links.”” Darwin was challenged to show anywhere in the fossil record the steps by which one species has passed into another. It was then quite a difficult challenge. Today we have an answer, a score of answers, to that challenge, beyond Darwin’s utmost hopes.

Then if animals have been specially created just as they are to fit special conditions, it is reasonable to suppose they are perfectly and completely adjusted to those conditions. There is no reason why any animal should fail to have any structure that might be helpful in its way of life, or possess any structure it has no need for. If a cat lives on birds and a tiger on ground game, is there any reason why a cat should not have wings because a tiger has not? But if the diverse species have been evolved step by step, a certain disharmony is to be expected between inherited structure and reactions, and the full possibilities of the life a creature leads. The second section of our evidence then will be an examination of plant and animal structure to see how far animal and vegetable organs are special to their needs, and how far they have the air of being primarily an inheritance merely fitted to those needs and limited in that fitting by conditions of descent.

And then the way animals and planis are scattered over the world will not be haphazard if Evolution is really the truth of life. If we found a region where an animal might live abundantly and that animal is not there, but somewhere else in the world, then if we are to believe in Creation we have to find Creation very remiss upon the distributive side; but if we believe in Evolution, then it is quite reasonable to suppose that an animal evolved in one part of our planet may