Creation or Evolution? A Philosophical Inquiry

by George Ticknor Curtis

"Species," "races," and "varieties"—Sexual division—Causation.

The two friendly disputants have again met. Sophereus begins their further colloquy, in an effort to reach a common understanding of certain terms, so that they may not be speaking of different things.

Sophereus. I have more than once referred to the fact that Nature does not permit crosses between the true species of animals, in breeding, and that we have no reason to suppose it ever did. This is a very important fact to be considered in weighing the claims of your theory of evolution. I have been looking into Darwin, and I find it somewhat uncertain in what sense he uses the terms "species," "races," and "varieties." In his "Descent of Man," he devotes a good deal of space to the discussion of the various classifications made by different naturalists under these respective terms; and there is no small danger of confusion arising from the use of these terms unless they are defined. The possibility of the process of evolution, as a means of accounting for the existence of any known animal, depends in some degree upon the animals among which, by sexual generation, the supposed transition from one kind of animal to another kind has taken place. Darwin speaks of the difficulty of defining "species"; and yet it is obvious (is it not?) that the theory of the graduation of different forms into one another depends for its possibility upon the forms which have admitted of interbreeding. While, therefore, the term "species" is in one sense arbitrary, as used by different naturalists, and there is no definition of it common to them all, it is still necessary to have a clear idea of the limits within which crosses can take place in breeding, because there are such limits in nature. Thus, in the case of man, as known to us in history and by observation, there are different families, which are classed as "races." Darwin speaks of the weighty arguments which naturalists have, or may have, for "raising the races of man to the dignity of species." Whether this would be anything more than a matter of scientific nomenclature, is perhaps unnecessary to consider. Whether we call the "races" of men "species," or speak of them as families of one race, we know as a fact that interbreeding can take place among them all, and that between man and any other animal it can not take place. The same thing is true of the equine and the bovine races and their several varieties. Whether, in speaking of the different families or races of men, we consider them all as one "species," or as different species—and so of the varieties of the equine or the bovine races—the important fact is, that there are limits within which interbreeding can take place, and out of which it can not take place. Do you admit or deny that the barriers against sexual generation between animals of essentially different types, which are established in nature, are important facts in judging of the hypothesis of animal evolution?

Kosmicos. Take care that you have an accurate idea of what the theory of evolution is. Apply it, for example, to the origin of man, as an animal, proceeding "by a series of forms graduating insensibly from some ape-like creature to man as he now exists." This expresses the whole theory as applied to one animal, man, without going behind his ape-like progenitors. It does not suppose a crossing between the ape-like creature and some other creature that was not an ape. It supposes a gradual development of the ape-like creature into the man as he now exists; and, of course, the interbreeding took place between the males and the females of that ape-like race and their descendants—the descendants, through a long series of forms, being gradually modified into men, by the operation of the laws of natural and sexual selection, which I need not again explain to you.

Sophereus. Very well, I have always so understood the theory. But then I have also understood it to be a part of the same theory that there is important auxiliary proof of the supposed process of evolution to be derived from what is known to take place in the interbreeding of different races or families of the same animal. Whatever value there may be in this last fact, as auxiliary evidence of the supposed process of evolution, there must have been a time, in the development of the long series of forms proceeding from the ape-like progenitor, when an animal had been produced which could propagate nothing but its own type, and between which and the surrounding other animals no propagation could take place, if we are to judge by what all nature teaches us. You may say that the laws of natural and sexual selection would still go on operating among the numerous individuals of this animal which had become in itself a completed product, and that to their descendants would be transmitted newly acquired organs and powers, new habits of life, and all else that natural and sexual selection can be imagined to have brought about. But at some time, somewhere in the series, you reach an animal of a distinct character, in which natural and sexual selection have done all that they can do; in which there can be no propagation of offspring but those of a distinct and peculiar type, and the invincible barrier against a sexual union with any other type becomes established. For this reason, we must recognize the limits of possible interbreeding. It is best for us, therefore, to come to some understanding of the sense in which we shall use the term "species." For I shall press upon you this consideration—that animals differ absolutely from each other; that there can be no interbreeding between animals which so differ; and yet that, without interbreeding between animals having distinct organizations, natural and sexual selection had not the force necessary to produce, in any length of time, such a being as man out of such a being as the ape.

Kosmicos. I will let Darwin answer you, in a passage which I will read. "Whether primeval man," he observes, "when he possessed but few arts, and those of the rudest kind, and when his power of language was extremely imperfect, would have deserved to be called man, must depend on the definition which we employ. In a long series of forms graduating insensibly from some ape-like creature to man as he now exists, it would be impossible to fix on any definite time when the term 'man' ought to be used. But this is a matter of very little importance." That is to say, in the long series of forms descending from the ape-like creature, we can not fix on any one of the modified descendants which we can pronounce to be separated from the family of apes, and to have become the new family, man, because to do this requires a definition of man. Man as he now exists we know, but the primeval man we do not know. He may have been an animal capable of sexual union with some of his kindred who stood nearest to him, but yet remained apes, or he may not. It is not important what he was, or whether we can find the time when he ceased to belong to the family of apes and became the primeval man. The hypothesis of his descent remains good, notwithstanding we can not find that time, because it is supported by a great multitude of facts.

Sophereus. I have never seen any facts which I can regard as giving direct support to the theory. But, waiving this want of evidence, doubtless it is not important to find the time, chronologically, when the modified descendants, supposed to have proceeded from the ape-like creature, became the primeval man; but it is of the utmost importance to have some satisfactory grounds for believing that there ever was such an occurrence as the development of the animal man, primeval or modern man, out of such an animal as the ape. And therefore, without reference to the sense in which naturalists use the term "species," I shall give you the sense in which I use it. I use it to designate the animals which are distinct from each other, as the man, the horse, the ape, and the dog are all distinct from each other. Speaking of man as one true species, I include all the races of men. Speaking of the apes as another species, I include all the families of apes. Speaking of the bovine, the equine, or the canine species, I include in each their respective varieties. Now, as crosses in interbreeding can take place between the different varieties or families of these several species, and can not take place between the species themselves—between those which I thus class as species—the limits of such crosses become important facts in considering the theory of evolution, because they narrow the inquiry to the possibility of effecting a propagation of one species out of another species. Take any animal which has become a completed and final product—a peculiar and distinct creature—whether made so by aboriginal creation or produced by what you call evolution. The reproductive faculty of the males and the females of this distinct and peculiar animal is limited to the generative reproduction of individuals of the same type, by a sexual union of two individuals of that type. Their progeny, in successive generations, may be marked by adventitious and slowly acquired peculiarities; but unless there can be found some instance or instances in which the process of modification has resulted in an animal which we must regard as an 'essentially new creature—a new species—what becomes of the auxiliary evidence which is supposed to be derived from the effects of interbreeding between those individuals which can interbreed? I lose all hold upon the theory of evolution, unless I can have some proof that natural and sexual selection have overcome the barriers against a sexual union among animals which are divided into males and females of the several species, each of which is placed under a law of procreation and gestation peculiar to itself, and never produces any type but its own.

Kosmicos. You wander from the principle of evolution. I have to be perpetually restating it. Observe, then, that there are multitudes of facts which warrant the belief that, starting with any one kind of animal organism, however peculiar and distinct, the struggle for existence among the enormous number of individuals of that animal becomes most intense, and a furious battle is constantly going on. The best-appointed males, in the fierceness of the strife for possession of the females, develop new organs and powers, or their original organs and powers are greatly enhanced. Their descendants share in these modifications; and the modifications go on in a geometrical ratio of increase through millions of years, until at some time there is developed an animal which differs absolutely from its remote progenitors which were away back in the remote past, and which began the struggle for individual life and the continuation of their species or their race in a condition of things which left the fittest survivors the sole or nearly the sole propagators of new individuals. This struggle for existence may have begun—probably it did begin—before the separation of the sexes, when the organism was unisexual or even asexual. That is to say, there may have been, and there probably was, an organism which multiplied with enormous rapidity, without the bisexual method of reproduction. The vast multitude of such individuals would lead to the destruction of the weakest; the strong survivors would continue to give rise to other individuals, modified from the original type, until at length, by force of this perpetual exertion and struggle and the survival of the fittest, modifications of the method of reproduction would ensue, and the bisexual division would be developed and perpetuated.

Sophereus. I confess I did not expect to hear you go quite so far. I will yield all the potency to natural and sexual selection that can be fairly claimed for them as modifying agencies operating after the sexual division has come about; but I have, I repeat, seen no facts which justify the hypothesis that they have led to distinct organisms between which no propagation can take place. But now you expect me to accept the startling conclusion that at some time the asexual or the unisexual method of reproduction passed into the bisexual, without any formative will or design of a creating power, and without any act of direct creation. We know what Plato imagined as the origin of the sexual division, and that he could not get along without the intervention of the gods. What modern naturalist has done any better? I have examined Darwin's works pretty diligently, and I can not get from them any solution of the origin of the bisexual division. I am left to reason upon it as I best can. We know, then, that in the higher animal organisms the individuals of each species are divided into the related forms of male and female, and that for each species there exists the one invariable method of the sexual union, and a law of gestation peculiar to itself. One hypothesis is that this system was produced by the operation of natural causes, like those which are supposed to have differentiated the various kinds of organisms; the other hypothesis is that it was introduced with special design, by an act of some creative will. If we view the phenomena of the sexual division and the sexual genesis in the highest animal in which they obtain, we find that they lead to certain social results, which plainly indicate that in this animal they exist for a great and comprehensive moral purpose, which far transcends all that can be imagined as the moral purpose for which they exist in the other animals. To a comparatively very limited extent, certain social consequences flow from the law of sexual division and genesis among the other animals. But there is no animal in which the moral and social effects of this law are to be compared to those which it produces in the human race. Not only does the same law of multiplication obtain among the human race; not only does it lead to love of the offspring far more durable and powerful than in the case of any other animal; not only is it the origin of a society far more complex, more lasting, and more varied in its conditions than any that can be discovered in the associations of other animals which appear to have some social habits and to form themselves into communities, but in the human race alone, so far as we have any means of knowledge, has the passion of sexual love become refined into a sentiment. You may remember the passage in the "Paradise Lost" in which Raphael, in his conversation with Adam, touches so finely the distinction between sexual love in the human race and in all the other animals. The angel reminds Adam that he shares with the brutes the physical enjoyment which leads to propagation; and then tells him that there was implanted in his nature a higher and different capacity of enjoyment in love. The conclusion is:—

"... for this cause