The case against evolution

by George Barry O'Toole

But we came from there.”

In this predicament it will not do, as we shall see presently, to adopt Mr. McCann’s expedient of balancing anatomical differences against anatomical resemblances. To do so is to court certain and ignominious defeat. We must, therefore, examine the argument dispassionately. If it be solid, we must accept it and give it general application. If it be unsound, we must detect its flaws and expose them. Intellectual honesty allows us no alternative!

Moreover, in weighing the argument from organic homology we must not lose sight of the two important considerations previously stressed: (1) that the inference of common ancestry in the case of homologous forms is based, not upon this or that particular likeness, but upon an entire group of coördinated resemblances; (2) that the resemblances involved are not exterior similarities, but deep-seated structural uniformities perfectly compatible with diversities of a superficial and functional character. “Nothing,” says Dr. W. W. Keen, “could be more unlike externally than the flipper of a whale and the arm of a man. Yet you find in the flipper the shoulderblade, humerus, radius, ulna, and a hand with the bones of four fingers masked in a mitten of skin.” (Science, June 9, 1922, p. 605.)

In fact, the resemblances may, in certain instances, be so deeply submerged that they no longer appear in the adult organism at all and are only in evidence during a transitory phase of the embryological process. In such cases, the embryo or larva exhibits, at a particular stage, traces of a uniformity completely obliterated from the adult form. In short, though frequently presented as a distinct argument, embryological similarity, together with all else of value that can still be salvaged from the wreck of the Müller-Haeckel Law of Embryonic Recapitulation, is, at bottom, identical with the general evolutionary argument from homology. In the latter argument we are directed to look beneath the modified surface of the adult organism for surviving vestiges of the ancestral type. In the former, we are bidden to go deeper still, to the extent, that is, of descending into the very embryological process itself, in order to discover lingering traces of the ancestral likeness, which, though now utterly deleted from the transformed adult, are yet partially persistent in certain embryonic phases.

In sectioning a larval specimen of the fly-like termite-guest known as Termitoxenia Heimi, Father Wasmann came across a typical exemplification of this embryological atavism. In the adult insect, a pair of oar-like appendages replace the wings characteristic of the Diptera (flies). These appendages are organs of exudation, which elaborate a secretion whereof the termites are very fond, and thereby render their possessors welcome guests in the nests of their hosts. The appendages, therefore, though now undoubtedly inherited characters, are the specific means by which these inquilines are adapted to their peculiar environment and mode of life among the termites. Moreover, the organs in question not only differ from wings functionally, but, in the adult, they bear no structural resemblance whatever to the wings of flies. Nevertheless, on examining his sections of the above-mentioned specimen, Wasmann found a developmental stage of brief duration during which wing veins appeared in the posterior branches of the embryonic appendages. Now, assuming that Wasmann’s technique was faultless, his specimen normal, and his interpretation correct, it is rather difficult to avoid his conclusion that we have here, in this transitory larval phase, the last surviving vestige of ancestral wings now wholly obliterated from the adult type, that, consequently, this wingless termite guest is genetically related to the winged Diptera, and that we must see in the appendages aboriginal wings diverted from their primitive function and respecialized for the quite different purpose of serving as organs of exudation, (cf. “Modern Biology,” p. 385.) Indeed, phenomena of this kind seem to admit of no other explanation than the atavistic one. It should be remembered, however, that Wasmann does not appear to have verified the observation in more than one specimen, and that a larger number of representative specimens would have to be accurately sectioned, strained, examined and interpreted, before any reliable conclusion could be drawn.[5]

Such, in its most general aspect, is the atavistic solution of the problem presented by the homology of types. In it, similarity and diversity are harmoniously reconciled, in the sense that they affect, respectively, different structural, or different developmental, levels. It is futile, therefore, to look for contradictions where they do not exist. In a word, the attempt to create opposition between a group of basic and correlated uniformities, on the one hand, and some particular external difference, on the other, is not only abortive, but absolutely irrelevant as well. The reason is obvious. Only when likeness is associated with unlikeness is it an argument for Transmutation. Likeness alone would demonstrate Immutability by indicating a process of pure inheritance as distinguished from the process of variation. Hence evolutionists do not merely concede the coëxistence of diversity with similarity, they gladly welcome this fact as vitally necessary to their contention.

Now it is precisely this point which Mr. McCann, like many other critics of evolution, fails utterly to apprehend. Consequently, his efforts to extricate the human foot from the toils of simian homology are entirely unavailing. To offset the force of the argument in question, it is by no means sufficient, as he apparently imagines, to point to the fact that, unlike the hallux of the ape, the great toe in man is non-opposable (cf. “God—or Gorilla,” pp. 183, 184, and legends under cuts opposite pp. 184 and 318). The evolutionist will reply at once that the non-opposability of man’s great toe is correlated with the specialization of the human foot for progression only, as distinguished from prehension; while, in the ape, whose foot has retained both the progressive and the prehensile function, the hallux is naturally opposable in adaptation to the animal’s arboreal habits. He will then call attention to the undeniable fact that, despite these adaptational differences, the bones in the foot of a Troglodyte ape are, bone for bone, the counterparts of the bones in the human foot and not of those in the human hand. He will readily concede, that, so far as function and adaptedness go, this simian foot is a “hand,” but he will not fail to point out that it is, at the same time, a heeled hand equipped with a calcaneum, a talus, a navicular, a cuboid, and all other structural elements requisite to ally it to the human foot and distinguish it from the human hand. In fact, Mr. McCann’s own photographs of the gorilla skeleton show these features quite distinctly, though he himself, for some reason or other, fails to speak of them. It is to be feared, however, that his adversaries may not take a charitable view of his reticence concerning the simian heel, but may be inclined to characterize his silence as “discreet,” all the more so, that he himself has uncomplimentarily credited them with similar discretions in their treatment of unmanageable facts. In short, Mr. McCann’s case against homology resembles the Homeric hero, Achilles, in being vulnerable at the “heel.” At all events, the homology itself is an undeniable fact, and it is vain to tilt against this fact in the name of adaptational adjustments like “opposability” and “non-opposability.” Since, therefore, our author has failed to prove that this feature is too radical to be classed as an adaptive modification, our only hope of exempting the human skeleton from the application of the argument in question is to show that argument itself is inconsequential.

Mr. McCann’s predicament resembles that of the unlucky disputant, who having allowed a questionable major to pass unchallenged, strives to retrieve his mistake by picking flaws in a flawless minor. As Dwight has well said of the human body, “it differs in degree only from that of apes and monkeys,” and “if we compare the individual bones with those of apes we cannot fail to see the correspondence.” (“Thoughts of a Catholic Anatomist,” p. 149.) In short, there exists no valid anatomical consideration whatever to justify us in subtracting the human frame from the extension of the general conclusion deduced from homology. Whosoever, therefore, sees in the homology of organic forms conclusive evidence of descent from a common ancestor, cannot, without grave inconsistency, reject the doctrine of the bestial origin of man. He may still, it is true, exclude the human mind or soul from the evolutionary account of origins, but, if homology is, in any sense, a sound argument for common descent, the evolutionary origin of the human body is a foregone conclusion, and none of the anatomical “differences in degree” will avail to spare us the humiliation of sharing with the ape a common family-tree. It remains for us, then, to reëxamine the argument critically for the purpose of determining as precisely as possible its adequacy as a genuine demonstration.

To begin with, it must be frankly acknowledged that here the theory of transformism is, to all appearances, upon very strong ground. Its first strategic advantage over the theory of immutability consists in the fact that, unlike the latter, its attitude towards the problem is positive and not negative. When challenged to explain the structural uniformities observed in organic Nature, the theory of immutability is mute, because it knows of no second causes or natural agencies adequate to account for the facts. It can only account for homology by ascribing the phenomenon exclusively to the unity of the First Cause, and, while this may, of course, be the true and sole explanation, to assume it is tantamount to removing the problem altogether from the province of natural science. Hence it is not to be wondered at that scientists prefer the theory of transformism, which by assigning intermediate causes between the First Cause and the ultimate effects, vindicates the problem of organic origins for natural science, in assuming the phenomena to be proximately explicable by means of natural agencies. Asked whether he believes that God created the now exclusively arboreal Sloth (Bradypus) in a tree, the most uncompromising defender of fixism will hesitate to reply in the affirmative. Yet, in this case, what is nowadays, at least, an inherited preadaptation, dedicates the animal irrevocably to tree-life, and makes its survival upon the ground impossible.

Analogous preadaptations occur in conjunction with the phenomena of parasitism, symbiosis and commensalism, all of which offer instances of otherwise disparate and unrelated organisms that are inseparably bound together, in some apparently capricious and fortuitous respect, by a preadaptation of the one to the other. Parasites, guests, or symbiotes, as the case may be, they are now indissolubly wedded to some determinate species of host by reason of an appropriate and congenital adjustment. For all that, however, the association seems to be a contingent one, and it appears incredible that the associates were always united, as at present, by bonds of reciprocal advantage, mutual dependence, or one-sided exploitation. Yet the basis of the relationship is in each case a now inherited adaptation, which, if it does not represent the primitive condition of the race, must at some time have been acquired. For phenomena such as these, orthogenesis, which makes an organ the exclusive product of internal factors, conceiving it as a preformed mechanism that subsequently selects a suitable function, has no satisfactory explanation. Lamarckism, which asserts the priority of function and makes the environment mold the organ, is equally inacceptable, in that it flouts experience and ignores the now demonstrated existence of internal hereditary factors. But, if between these two extremes some evolutionary via media could be found, one must confess that it would offer the only conceivable “natural explanation” of preadaptation.[6] All this, of course, is pure speculation, but it serves to show that here, at any rate, the theory of Transformism occupies a position from which it cannot easily be dislodged.