Hugo DeVries, of Amsterdam, believes he has found the answer to this difficulty. Outside of his botanical garden an American species of Evening Primrose had run wild. In looking over a number of these plants he found, every here and there, certain peculiar members of the species. They differed noticeably to the practiced eye from the rest of the group. When they were planted and crossed with each other, and the resulting seeds were again planted, the peculiarity remained constant in all the members of the collection. Here then we have a true variation, not large in amount, but at the same time quite definite, and which from the first remains true. Here are the beginnings, says DeVries, of new species. They are true from the first; they can live among other members of the species and still come true; they do not need isolation, at least in Wagner's geographical sense. These forms DeVries calls mutations. It is his thought that a species may run along uniformly for a long time when, from some cause which he has not determined as yet, instability comes into the species and it varies in quite a number of directions. Each of these variations may be the starting point of a new species. DeVries believes that he has at least half a dozen mutants of his new Evening Primrose.
This theory of Mutation has been eagerly seized upon by many botanists. The zoölogists have not accepted it quite so enthusiastically. If this is the chief method by which species transform, it seems strange that we do not find more mutations than we do. Perhaps we do not look carefully enough; perhaps we shall find them a little later. Just at present it seems premature to believe that all evolution is by mutation, although quite possibly some of it is. The main apparent advantage of mutation is that it hastens the time in which a new species may arise.
There are certain difficulties which run back into the problem, and which must first be reasonably solved before a clear understanding of the idea of evolution is possible. The first of these is as to the nature of life. What is life? The reply of the biologist will probably be that so far as its material side is concerned, it must be answered in terms of physics and chemistry. As to any side not material, if it have any such side, science says that the chemist can have nothing to say. The chemist may have an opinion of his own based on some other ground than his chemistry, but so far as he is a chemist, he has no opinion. The chemical side of life is being very carefully and very fully investigated. We are certainly being brought nearer to the borders of the living substance. We are rapidly gaining fuller knowledge of the physical and chemical processes which constitute life, or with which life is always associated. If we gain this knowledge we shall be in better position to solve many of our other problems. Even then there is a problem which preceded and which will possibly always defy solution. How did life originate? Has it developed out of chemical and physical activities which we know as heat, light or electricity? If so, what were the conditions under which it developed? If we understand the nature of life, and the conditions under which it developed, we may be able to produce it at will.
A few scientists may hope dimly that this will be attained. I suspect a great majority believe it to be impossible, and that the question as to whether life evolved upon this planet, or this planet became infected with life through meteoric dust from some other center, will forever remain an unsolved problem.
CHAPTER X
The Future Evolution of Man
The disturbance of mind created by the publication of Charles Darwin's "Origin of Species" would have amounted to nothing if the theory had been applied to the lower animals alone. Few people would have disputed that a cow and a buffalo had descended from the same ancestor, or that monkeys and apes were of a common blood. The whole theory would have been looked upon by those outside the biological world as entirely an academic question, in which they had little concern, and less interest. But within this century the scientist has so persuaded the world of the unity underlying the activities of the universe, that so soon as a principle is established men begin to run it out to the very end. Everyone knows perfectly well that if it could be proved that the dog and the horse had a common ancestor, still more if it could be made apparent that the dog and the frog and fish had sprung from the same stock, then there could be no question of what would be the final application of the theory. Man himself could be no exception to the law. So the battle dropped at once upon this most interesting point, and around this center the contest has waged.
What is the origin of man? Who are his ancestors? As soon as we ask the question there is no doubt whatever as to the answer, if we accept the principle of evolution. Our only means of judging relationship between animals is by the similarity of their structure. As soon as we come to examine the other creatures even in the most cursory fashion, there is only one group which in any close degree resembles the human species. Our nearest relatives among living animals must undoubtedly be the apes. Some little distance farther away stand the monkeys, and, structurally speaking, there is more difference between a monkey and an ape than there is between an ape and man. The gap between man and his relatives of this group, known as the primates, is a mental, not a physical one. While his brain and his mind have developed far beyond theirs, the rest of his body is comparatively close to that of an ape.
Probably no one can face the possibility of his being descended from creatures not unlike the ape, without feeling a stirring sense of repugnance. The least aristocratic of us hesitates to name in the line of his ancestry creatures so unlike himself as the members of this group. It seems to us impossible that we should have descended from creatures as lowly as they. If evolution is true, these are among our near ancestors. Back of the group of primates lies a far less developed set of insectivorous animals, behind them the reptiles, behind them the fishes. When we get back this far we are less certain but most probably the worms take up the story. So our ancestry runs back to the very beginning, when it originated in the one-celled animals which are also the ancestors of all the rest of the animal world. If we are inclined to deny our ancestors in the trees, what shall we say of our forefathers in the seas?