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

BOOK 4

CHAPTER 1

THE ESSENCE OF THE CONTROVERSIES ABOUT EVOLUTION

§ 1. The Chief Theories of Evolution.

§ 1 The Chief Theories of Evolution

N Book 3 we have been dealing with facts

beyond any reasonable controversy. We have put them plainly and we hope convincingly before the reader. If we have failed to convince, the fault lies in our writing and not in the facts. Life, we have shown, has appeared not multitudinously and again and again in the world, but at one particular stage in our planet’s history, and from that one beginning it has developed like a branching tree. It has not been multifariously and repeatedly created in its present or kindred forms ; it has unfolded from lowly and simple beginnings, through a vast variety of species, to all the animal, vegetable and other organisms the biologist contemplates to-day. Special creation of each animal and vegetable type is a parable ora myth. Evolution is the shape of life and a fact as well-established now as the roundness of the earth or the relative immensity of the sun. All these three facts have been disputed in the past. To-day controversy about any of them is dead.

Equally dead we shall find is the older and really more plausible belief that life has had numerous origins and, even now, can at times be created afresh. That, it seems, it not so. Life is ome thing. Every living thing is related through a common descent to all the rest of life. There is no reason a priori why this should be so. But all the evidence is that it is so.

In all the three instances we have giventhe round earth, the larger sun, and the evolution of life—men have disputed these great generalizations because they had _ started in life with contrary assumptions and found the shock of the new idea too great. They had intermingled their moral and religious ideas with the notion of a special creation of each kind of animal at a certain date, or with the notion of a flat earth, or with the notion of a small subservient sun going about our planet, and it seemed to them that if these notions were destroyed their very heavens would fall. But new generations have followed them, have accepted the new ideas and found the heavens of religious feeling

§ 2. Method of Treatment.

and moral impulse none the worse for a broadened and enlightened outlook. Today there is no denial of the fact of organic evolution except on the part of manifestly ignorant, prejudiced and superstitious minds.

But here we enter upon a less certain and established region of biological study. In this Fourth Book we are going to discuss how individual development is carried out, and, further, how Evolution has occurred. There we find active and intelligent minds still differing very widely. What are the relations of individual development to the development of the species? ‘There is no question any longer that Evolution has occurred, but our question is now, what has been its method? Or its methods ?

This is a field where the débris and glow of recent controversies are still evident and where wide and often flaming differences of opinion are still found. And, just as in the opening of Book 3 we made it quite plain what fact we had to prove, so here it will enable the reader to understand the full significance of what follows if we give first the broad questions our chapters are designed to illuminate, and point out what is still arguable and what is the present state of the discussion. What are the Theories of Evolution between which we are asked to decide ?

The fact of vital Evolution has gleamed upon intelligent minds at various phases in the world’s history, but the modern revival of biological science had been going on for some time before it rose again to recognition. Linneus (1707-1778) seems to have had no doubts of the fixity of species. It was only towards the close of the eighteenth century and with the increasing study of comparative anatomy and fossils that the fixity of species began to be questioned. |

At first the fact of Evolution was seen piecemeal, as a possible change of one species into another within the boundaries of this or that restricted group of allied forms. It was not apprehended as a process comprehending all living things. Perhaps all the carnivores were genetically related, for example, or all the horned cattle. It was then generally called Transformism. ‘The

261