George Archdall Reid

“ Thus as regards the function of reproduction some cells subserve it more than others; yet many of the cells of all portions of the whole organism are capable of performing it, for almost any fragment of a sponge, if separated from the parent mass and bedded out, is capable of growing into an "individual" and of continuing the race. If we pass in succession to higher species, we find cell-specialization becoming more and more marked; we find cells becoming more and more capable of performing efficiently some one function and less and less capable of performing all other functions. ”

“ In other words, the development of the individual is a short, rapid, blurred recapitulation of the evolution of the species; which, if there is any truth in the theory of evolution, is exactly what was to be expected, and which therefore affords convincing proof of its truth. ”

“ In every species natural selection as a cause of evolution, and atavism as a cause of retrogression, are constantly at war. If the one force predominate we have evolution; if the other, retrogression; if the two forces balance one another, the species in which this occurs undergoes for the time neither evolution nor retrogression. Rapid evolution is accompanied by an increasing tendency to retrogression, because in such a case any ancestor reverted to differs more in structure from the last member of the race than a corresponding ancestor in a race that has been more slowly evolved. ”

“ The decreasing rate of evolution, therefore, must be set down to another cause.
If we mate two ordinary horses there is a fair prospect that some at least of the offspring will be as fine, or even finer, animals than either the sire or the dam. But if we mate a Derby winner with a good mare—a better mare than his dam—we shall find that the majority of his progeny are inferior to himself, and that only very exceptionally does he procreate a son or a daughter that can match him for speed. ”

“ But however slow the multiplicity of essential traits may render evolution, it is difficult at first sight to understand why evolution should be so extremely slow as it generally is. Every plant or animal pair usually gives origin to numerous offspring, sometimes the offspring are numbered by millions (e.g. the offspring of cod-fish) ; yet the number of individuals in each species does not increase as a rule, whence it is clear that nature, by destroying the majority of the offspring, exercises her power of selection with extreme stringency. ”

“ But quite apart from all evidence that evolution has occurred, the conditions of life are such that we may infer from them with mathematical certainty that it must have occurred. It is a matter of common knowledge and experience (1) that in both the animal and vegetable kingdoms every individual differs somewhat from every other individual, but that (2) while the offspring is never an exact copy of the parent, there is yet a tendency for the peculiarities of the parent to reappear in the offspring in a greater or lesser degree. ”

“ Rapid evolution, therefore, rapidly becomes more slow. Why? Evidently because there is a tendency for the offspring to omit more or less of the latest evolution of the race and revert to the ancestry, sometimes the remote ancestry, and therefore in cases in which evolution has been rapid, as with race-horses, this reversion produces wide divergences of structure from the parent, but in cases in which the evolution has been slow, as with lamp-shells, this reversion produces very slight divergences of structure. ”

“ Pushed to its logical conclusion the theory teaches yet more; it teaches, as the only hypothesis scientifically tenable, that life originally arose by a process of evolution from that which was non-living; that under conditions of which we are ignorant, of moisture, or of heat, light, electricity, or other of the protean forms of energy, non-living chemical compounds did in the beginning of life overpass the border space which divides the non-living from the living, and become living beings. ”

“ Therefore if the essential qualities are numerous,—and they always are so in the case of wild animals,—the descendants of numerous ancestors, each one of whom was pre-eminent in one of these qualities, will tend more and more, generation after generation, to approach the general racial mean as regards all these qualities;—which appears to lead to the absurd conclusion, that in the end there will be no evolution at all. ”

“ Now, of two individuals, one of which produces offspring without collaboration with another individual, and the other in collaboration with another and somewhat dissimilar individual, the offspring of the latter must tend to vary more than the offspring of the former, and therefore in the struggle for existence to bring about their ultimate extinction, whereby only the descendants of the individual that reproduced sexually, and which inherited this peculiarity, would be left to continue the race. ”

“ To many, and, surprising as it may seem, even to some medical men, in spite of what ought to be a scientific training, the theory of evolution means nothing more than the theory of the descent of man from the monkey. ”

“ Higher in the scale are such organisms as the amœba; about them we are able to learn much that is important and instructive. They occupy that point in the scale of life at which the plant and animal kingdoms begin to diverge the one from the other, and though excessively minute, are larger than the protogenes, and therefore better observable. Each is a little mass of protoplasm in which may be seen a dot, the nucleus, which is usually situated eccentrically, and which, as modern research seems to have established, is the most important part of the organism. ”

“ Now if the son recapitulates the traits of the parent, the parent the traits of the grandparent, the grandparent the traits of the great-grandparent, and so on, it is evident that the son, the last of the race, must recapitulate the traits of each ancestor up to the remotest, or at least up to the unicellular organism, which for convenience of language we may call the first ancestor. ”

“ Following the above train of thought it may be remarked, that any trait which appears late in the development of the individual, as for instance the horns of deer and the beards of men, must have appeared late in the evolution of the species. ”

“ It is as though, in an endeavour to increase the height of men, we chose the tallest man in the world, eliminated the rest of his species, multiplied him—not by seminal generation, but by some process analogous to the multiplication of plants by slips—into thousands of men and women as tall as himself, chose the tallest individual among the children of these, and repeated the process, and continued to do so through several seminal generations. ”

“ Bernards, Newfoundlands, mastiffs, boarhounds, do not very greatly exceed wild dogs or wolves in size, nor do our most intelligent dogs greatly surpass them in intelligence; but our smallest dogs, some of them little bigger than rats, are very much smaller, and some of our tame breeds are exceedingly stupid. Clearly as regards dogs, we have been able to produce little evolution, but great retrogression. In some breeds there has undoubtedly been evolution in this or that respect—in the St. Bernard of size, in the mastiff of strength, in the greyhound of speed, in the bulldog of courage ”

“ Such a speck of living protoplasm as the amoeba is known to biologists as a cell; and of such cells or variations of them the structures of all plants and animals are built up, a plant or animal composed of a single cell being known as a unicellular organism, whereas a plant or animal composed of a plurality of associated cells is known as a multicellular organism. Since such unicellular organisms as the amœba are fairly observable, we may conveniently begin the study of life at that stage of evolution which they have reached. ”

“ The above considerations may afford an explanation of another set of facts, viz. that cultivated plants and domesticated animals are much more variable than the wild varieties of the same species. In a state of nature plants and animals exist under conditions which, normally, are uniform during long ages; owing to which, and to the circumstance that in a state of nature many traits are essential to survival, evolution is slow, and therefore the traits of wild animals and plants acquire a certain fixity, because if any recent ancestor be reverted to in any particular, the change is not great ”

“ It may be objected however, and it often is objected, that natural selection is not the same thing as artificial selection; but the objection cannot be sustained, for in effect it is the same thing, artificial selection being merely natural selection with man as the governing agent. Man, for instance, has caused the evolution of speed in the greyhound and in the race-horse by breeding, on the whole, from the swiftest animals of each species ”

“ On consideration it is apparent that of two individuals the one that produces offspring that vary within certain limits more from itself is the better placed as regards the ultimate survival of its descendants, other things equal, than the other individual which produces offspring that vary less, assuming of course, what must on the average happen, namely, that some of the offspring vary favourably as compared to the parent and some unfavourably. ”

“ We have seen that evolution depends on three factors: (1) that offspring in general inherit (i.e. recapitulate) the traits of their parents; (2) that offspring vary somewhat from their parents; (3) that there is invariably a struggle for existence, during which natural selection causes evolution by preserving favourable and eliminating unfavourable variations. ”

“ In those plants which multiply by means of suckers or are multiplied by means of cuttings, the cells whence the individual is derived are to be regarded as little differentiated and specialized, like the cells of the sponge, cell-differentiation and specialization not having proceeded nearly so far among plants as among animals; for the highest plants are inferior in this respect to animals low in the scale. As a result, while plants high in the scale are able to reproduce otherwise than by means of germ cells, animals comparatively very low in the scale are not so able. ”

“ It has already been pointed out, that the conditions of life are usually such as to cause the number of traits necessary for survival to be numerous, and that this again causes the process of evolution to be slow, though it is no bar to it as some biologists have supposed. ”

“ But the race-horse surpasses the ordinary horse not so much because it is more powerful, but because it is better shaped for speed, just as the racing boat surpasses in speed the ordinary rowing boat for the same reason. We can hardly conclude that the evolution of the race-horse is now slow because he has nearly reached the perfection of shape for speed, for another of the equidæ, the wild ass, a smaller animal, is said to be swifter. ”

“ Moxon appears to think that, if a struggle for existence leading to evolution ever did occur, it has now ceased so far at least as man is concerned, and the struggle has become one against mere existence, whatever that may mean, and he adds—"Darwin, Huxley, and even Haeckel will in time learn that over-scrutinizing insufficient evidence does not make it more complete." ”

“ The reduction towards the specific mean which interbreeding tends to bring about in the qualities of individuals as exhibited in their descendants, has caused some biologists to insist that isolation is a necessary antecedent to evolution. [2] But if we bear in mind the fact (to be more fully discussed in a future page) that evolution proceeds not on lines of traits, however favourable, which occur infrequently or abnormally, but on lines of traits common to all the individuals of the whole species, that is, in which every individual rises above or falls below the specific average ”

“ Again, atavism is not the only cause of retrogression. Evolution may be a cause of apparent retrogression, as in the case of certain insects, which, living as they do in storm-swept islands, are exposed when flying to the danger of being carried to sea. In them natural selection, reversed selection as it is called in such cases, has co-operated with atavism to deprive them of the power of flight. ”

“ But if, owing to any circumstance, such as a deficiency of food supply, a portion of the species separated from the rest, and migrated permanently to forest land, then the two divisions of the species, being unable to interbreed, and differently conditioned as to the environment, would develop on divergent lines of evolution. ”

“ The young hornless deer and the young beardless man should therefore correspond to very recent stages in the evolution of their respective species. Whence if there is any truth in my theory of retrogression by atavism, it follows that comparatively hornless deer and comparatively beardless men ought to be comparatively frequent, for the ancestor reverted to would in either case be comparatively recent. As regards the beard, we know that comparatively beardless men are common in a well-bearded race such as the Anglo-Saxon. ”

“ Therefore, if this theory of retrogression be correct, it may afford us a not unimportant insight into the past life-history of species, and enable us to decide what retrogressive changes are due to atavism and what to natural selection. For instance, man as we know has descended from a hairy ancestor: if his present partially hairless condition is due to atavism, then since he has reverted in this respect to a remote hairless ancestry, his embryo will not be hairy, nor will he in cases of atavism be hairy. ”

“ The improvements in our cultivated plants are the result of centuries of stringent selection; and here again it cannot be doubted, that if the process by which they were evolved were reversed, were we to propagate only from the most inferior plants, that the rate of retrogression would be much more rapid than was the rate of evolution. ”