It is an explanation of evolution which it is the merit of Darwin to have devised;—or perhaps we ought already to say in the light of the fatal results brought about by the wide unreasoning acceptance of it, it is the demerit of Darwin to have devised;—an explanation based partly on certain observed facts, but more largely on a certain logical elaboration of argument for which the observed facts are assumed to be sufficient base.
The more relevant of these facts are the production by parents of too many young and the slight differing of these young among themselves in most of their characters, physical and mental. The production of too many young leads, according to the natural selectionists, to a life and death struggle for existence among them, and the slight differences among them lead to a decision in this struggle on a basis of the slight advantages or disadvantages of these differences. The two logical conclusions seem to be inevitable on the basis of the two facts.
On the structure so far reared, however, other blocks are placed. The selectionists believe that by the laws of heredity, although the young of a different parent or pair of parents do differ among themselves, they resemble their own parents more closely than they resemble other individuals of their kind of species. So that the young produced by the survivors in the struggle for existence, although again slightly differing from their parents and each other, will, by the laws of heredity, tend to reproduce in their make-up the advantageous variations which were possessed by their parents and which gave these parents success in the struggle for life.
More than that: some of these young will tend to possess those advantageous differences—this by the laws of variation as antidote needed just here for the laws of heredity—in even more marked degree than existed in the parents, while others will possess them in less degree and still others in about the same degree. Hence, the particular young showing the increased differences will be the individuals of this generation to survive in the struggle. These will then leave behind them new young again tending to possess in varying degree those advantageous variations from the old or species type that make them especially “fit for the conditions under which they must live.”
Thus there will result, in a series of many generations, a gradual shifting of the character of the species to the type characterized by an ever increasing and perfecting of the original advantageous differences. This is “species transformation,” or the “origin of species” by natural selection. It is evolution on a basis of life and death struggle; extinction of the unfit; and survival of the fit, fitter or fittest. And just as with the different individuals inside the species, so with the different varying species. Each struggles with the other and the one or ones with the advantageous differences win at the expense of the others.
There is no doubt of the fascinating plausibility and seeming reality and sufficiency of this explanation. It makes a strong appeal to the logical mind; to the theory-spinning brain. You can understand it, prove it, expand it, improve on it, and, all this almost without ever seeing an animal or a plant, or knowing anything of its actual life and relations to the world it lives in. No wonder it fascinated and seized a world demanding a logical explanation for the theory of evolution. No wonder that this explanation of Darwin, offered at the same time with a clear elucidation of the evolution theory itself to a world just ready for both, came to be the one all-sufficient explanation, came to be a scientific dogma of the most dogmatic type.
Now for real thorough-going dogmatism there is nothing like scientific dogmatism, there is no dogmatist like a scientific dogmatist. There are many scientific men who pretend to know absolutely that many things cannot possibly be because they have never seen them, heard them, felt them or measured them. It is because of these men, who are not many, but loud, that we scientific men as a class have a reputation among many people of being narrow-minded and bigoted; and I hasten to admit that many of us are. Not all that is called science is proved; and most certainly not all that is called non-science is disproved, or because as yet unproved is to be tossed lightly or sneeringly aside. The scientific man who declares what cannot possibly be, exposes himself as a boaster and a charlatan, for by such declaration he, by implication, claims to know all the order of nature, which certainly no man does know. No man knows all that is or may be; hence no man knows what is not or may not be.
It was Weismann’s new facts and new theories about heredity that did much to overthrow Lamarckism and make it possible to expand rational Darwinism into irrational ultra-Darwinism and then claim for it such an insolently dominating place among the explanations of evolution. And now it is the still newer and far less theoretical and more concrete knowledge of heredity that has dethroned Neo-Darwinism, made impossible and absurd the German claims of the Allmacht of natural selection as evolution explanation, and revealed to us how little we really know of the potent causes and controls of evolution—if we may call that revelation which reveals darkness where before was apparent light. The factors of evolution that today we are more certain of than any others are the unknown factors, the causes we do not know, the methods we do not understand.
If this seems to be a humiliating confession to come from a biologist and professed student of evolution, it is one in which all honest scholars must join. If the Germans will not, they are not honest.