Whitman wrote most of his work on pigeons and orthogenesis between 1900 and 1910, the period of greatest agnosticism and debate about evolutionary mechanisms (see Kellogg, 1907). He therefore upheld orthogenesis as an explicit preference among competing theories. Rejecting Lamarckism, Whitman faced the macromutationism of de Vries and the selectionism of Darwin as chief rivals. And with Darwin's own pigeons reinterpreted as the bulwark of orthogenesis, we can hardly be surprised that Whitman singled out natural selection for special criticism: “To attempt to explain all this as the work of natural selection would lead into an endless tangle of conjecture that would leave even the simplest facts as unapproachable mysteries. Natural selection has probably had most to do with the end stages in the evolution of characters, but little or no direct influence in originating them. The two-barred condition has been reached in the simplest possible way, not by accidental variation or chance mutation, but by progressive modification of a chequered condition previously established” (1919, p. 61). [Page 392]
Whitman's attitude towards natural selection bears closer scrutiny as an aid (still useful today) for clarifying the borderline between two intergrading yet contradictory strategies: (1), using the structuralist and formalist concept of channels in pluralistic reinforcement with natural selection to forge helpful revisions of basic Darwinian theory (the position advocated in this book); or (2) viewing channels as so deep, so unidirectional, and so limiting that such constraints impel evolutionary change from within, leaving selection only to tinker with minor details (a truly anti-Darwinian theory that led the Modern Synthesis to reject orthogenesis completely). I cannot place Whitman on either end of this continuum — for he argued both sides and usually rested with ambivalence at some middle position. But his writings provide our best illustration of this important concept in the logic and historiography of theories.
Whitman's usual account of natural selection grants a distinctly subsidiary role to Darwin's process. By adaptation's dumb luck, the inexorable process of reduction in color may occasionally generate a form with utility. At this point, natural selection may intervene to tinker, rearrange, and even strengthen the valued colors. But selection cannot long prevail, for even a useful concentration of color must eventually move towards orthogenetic effacement: “Even in cases where natural selection has probably played a conspicuous part in modifying and beautifying these marks ... we find that the reducing process has not been brought to a standstill” (1919, p. 62).
Whitman asks us to consider examples from both major components of color — bars and checkers: The bars may be useful as marks of recognition, but they arise by orthogenetic reduction, not natural selection, and Darwinian forces cannot maintain them against the stronger internal push to effacement. (Note the interesting admission at the end of this statement that we have yet to fathom the mechanism of a process powerful enough to overcome selection.)
Standing alone on a pale gray ground, these bars would gain immensely in conspicuity [sic] and utility as ornamental recognition marks. The advantage of all this to the species, whatever it be, would be merely an accident of the situation presented at this particular point in a progressive series of modifications. It is conceivable that the utility of the bars might be great enough to give natural selection a chance to step in and bar [pun intended?] the way to further reduction. But the process of obliteration has certainly gone much farther in many other species. There may be stages in the process, which suggest utility; but when we consider the whole series of stages and note that the process runs on, sweeping away the stages, which we imagine to be most useful, we are left with the conviction that some general principle underlying the course of events has not yet been fathomed (1919, p. 61).
Whitman stresses the same point, in even stronger form, for the few, conspicuous and apparently adaptive checkers of mourning doves. These remaining marks of color are “hanging tough,” stubbornly resisting the orthogenetic [Page 393] washout — but natural selection encountered and preserved this pattern by mere good fortune and must eventually let go:
It is here that we may with some reason suspect the intervention of natural selection. It would, in this case, come in, not as a primary factor to originate a new character, but adventitiously, by invitation, as it were, of favoring predeterminations and environmental conditions.... The ornamental value of these few chequers and their utility as recognition marks would obviously be enhanced by their isolation in a plain ground, just as a few trees, concealed in a large forest, become conspicuous when left standing alone. These chequers, being on the larger feathers, would have the advantage of size, and so their preeminence, attained without the aid of natural selection, would be an open door through which it might enter and contribute to their improvement. The part possibly taken, however, could at most be but a late and inconsiderable share of the total achievement summed up in these spots; and the course of events in at least one of the allied forms . . . indicates that these marks are destined to be washed out (1919, p. 56).
(Note, once again, the literary theme that authors often reveal their basic commitments, probably quite unconsciously, in their choice of words. In this statement, Whitman refers to natural selection as an “intervention” — an externality imposed upon the essential process of orthogenesis.)
Nonetheless, Whitman does acknowledge exceptions. In one case (but only here), he does allow that selection may have reversed, albeit in a minor way, the orthogenetic sequence. He notes that iridescence heightens the value of color in adaptive display. Iridescent spots become unusually conspicuous and potentially useful — so much so, that selection may actually strengthen them against the orthogenetic tide. Thus, when the independent trait of iridescence becomes conjoined with pigmentation, the orthogenetic sequence can be meaningfully impacted by selection. (Whitman properly uses his own criteria, as previously discussed, to gauge the importance of this exception. Juvenile plumages, in this case, develop less conspicuous spotting than adult feathers — so the ontogenetic path belies the orthogenetic sequence): “Iridescence thus appears to be a phenomenon tending to elevate the spots and bring them within the sphere of utility. It seems not only to put a check upon the reduction of pigment, but also to actually turn the tide in the opposite direction, for the reduction in this region is not carried so far in the old as in the young male and female, as we shall presently see. As the acquisition of metallic brilliancy is accompanied by an exceptional love of display in the male, the chief directing factor in its development may well be natural selection” (1919, p. 43).
These statements might lead a modern evolutionist to view Whitman's orthogenesis as irrelevant to current debates (if not risible in any context). But if Whitman did not come to praise Darwin, he did not write to bury the founding father either. Within his chosen context of primacy for the orthogenetic pathway, Whitman sought a maximal and fruitful interaction with [Page 394] Darwinism. I know no other orthogeneticist who remained so open to the prospect of a pluralistic consensus (for, in contrast with Whitman, most scientists of this school entered the fray with strong anti-Darwinian inclinations). As one indication of his more conciliatory stance, Whitman followed the usual attitude of naturalists in accepting adaptation as a central phenomenon. He speaks of the most remarkable phenomenon of the organic world, namely adaptation” (1919, p. 40). He also recognized that orthogenesis cannot be construed as inherently adaptive, whereas Darwin's force actively creates utility. He admits the conundrum that orthogenesis, while true by observation, does not explain the progressive and adaptive character of life — and he realizes that evolutionary biology needs an account, as yet unavailable, for a probable bias towards adaptation in the stages of orthogenetic channels: “But how comes it to pass that these advances are, on the whole, adaptive and progressively so? Recapitulation can only conserve what is given. If it moves on within a progressive way, there must be some way of limiting germinal variations to lines of accumulative improv
ement. Here we find ourselves confronted with the difficulty which has long led investigation and theory, and the solution is yet a long way ahead” (1919, p. 180).
Beyond this central acknowledgment, two features of Whitman's thinking open his particular version of orthogenesis to a broad synthesis with Darwinism.
1. Like Eimer, Whitman developed an interpretation of orthogenesis that could fuse external pushes with internal channels. Eimer also sought a fusion with functionalist views (see pp. 360–365), but he opted for a Lamarckian push as his external source, and explicitly relegated Darwin to an insignificant periphery among sources of adaptation. But Whitman rejected Lamarckism and located his external push in natural selection.
Whitman directly criticized Eimer for his negative view of Darwinism, and for subjecting the entire theory of orthogenesis to undeserved derision thereby:
Among the rival theories of natural selection two are especially noteworthy. One of these is now generally known as orthogenesis. Theodor Eimer was one of the early champions of this theory . . . Eimer's intemperate ferocity toward the views of Darwin and Weismann, coupled with an equally intemperate advocacy of the notion that organic evolution depends upon the inheritance of acquired characters, was enough to prejudice the whole case of orthogenesis. Moreover, the controversial setting given to the idea of definitely directed variation, without the aid of utility and natural selection, made it difficult to escape the conclusion that orthogenesis was only a new form of the old teleology, from the paralyzing domination of which Darwin and Lyell and their followers had rescued science. Thus, handicapped, the theory of orthogenesis has found little favor (1919, p. 9).
2. Eimer was a polemicist by dint of personality. Whitman, as a great administrator, displayed an opposite temperament in his inclination to seek compromise among good ideas. Whitman believed that major systems, as [Page 395] devised and supported by such brilliant men as Darwin and de Vries, must inevitably hold at least partial value — and he sought a fruitful union of these systems with his own favored theory of orthogenesis. “Natural selection, orthogenesis, and mutation appear to present fundamental contradictions, but I believe that each stands for truth, and that reconciliation is not distant” (1919, p. 10).
We all know that the theories of de Vries and Darwin eventually reached peace through a recognition that micromutations could act as the source of isotropic Darwinian variation. We regard this fusion as the basis for the Modern Synthesis. A similar and vital task has only begun in our time, but we now live in an age struggling for further union — to join the success of this Modern Synthesis with neglected structuralist and formalist themes of developmental constraint and channeled variation (see Chapters 10 and 11 for my effort in this direction). Whitman surely erred in interpreting a channel of variation — a pathway of potential evolution in either direction — as a one-way street of inevitable change. (The reinterpretation of orthogenetic “one way streets” as “channels” of preferred variability establishes a key “translation” for updating this older and valuable literature into relevance for our modern debates. I also strongly suspect, in opposition to both Darwin and Whitman, that ancestral pigeons were neither two-barred nor checkered, but both. After all, ancestors exist as populations, not archetypes. Both states persist in continuous gradation within many modern populations of pigeons — and this entire channel may well have been expressed among variable adults in ancestral populations.)
However, Whitman's notion that selection does not encounter a full range of isotropic variation, but must work instead with material strongly biased by internal constraint, may supply a key theme for an even higher synthesis of external and internal forces — a theory that will preserve a Darwinian core, but finally and properly incorporate the formalist themes, advocated as central to evolutionary understanding by many of the finest biologists from the very beginning of our profession. Whitman succinctly stated the basis of this synthesis, but we are only now beginning to learn enough about genetics and development to vindicate his hunches: “Natural selection waits for opportunities to be supplied, not by multifarious variation or orderless mutation, but by continuous evolutional processes advancing in definite directions” (1919, p. 13).* [Page 396]
Saltation as a Theory of Internal Impetus:
A Second Formalist Strategy for Pushing Darwinism
to a Causal Periphery
WILLIAM BATESON: THE DOCUMENTATION OF INHERENT DISCONTINUITY
Darwin, as noted earlier, viewed his own accomplishment as dual and distinguishable: establishing the fact of evolution by copious data, and devising a theory, natural selection, to explain the mechanism of change. Darwin also stated that the first achievement must be ranked as more fundamental, for the deepest and most disturbing implications flow from the simple fact of genealogical continuity itself, whatever the philosophically radical character of natural selection as a cause of change.
William Bateson, speaking at the major Darwinian centennial celebration of 1909, made the same point — and the same assessment of the two achievements:
Darwin's work has the property of greatness in that it may be admired for more aspects than one. For some the perception of the principle of natural selection stands out as his most wonderful achievement to which all the rest is subordinate. Others, among whom I would range myself, look up to him rather as the first who plainly distinguished, collected, and comprehensively studied that new class of evidence from which hereafter a true understanding of the process of evolution may be developed. We each prefer our own standpoint of admiration; but I think that it will be in their wider aspect that his labors will most command the veneration of posterity . . . We shall honor most in him not the rounded merit of finite accomplishment, but the creative power by which he inaugurated a line of discovery endless in variety and extension (Bateson, 1909, p. 85).
Bateson's and Darwin's motives, however, could scarcely have been more different. Darwin, while ranking his joys, took great pride in both achievements. But Bateson viewed natural selection as an insignificant force and a methodological disaster. In downpeddling natural selection, Bateson presented his argument as an attempt to save Darwin's wider viewpoint from its own worst error, thus preserving the centennial season as a time of triumph.
William Bateson (1861-1926), son of a classical scholar who served as master of St. John's College, Cambridge, shared with Charles Darwin both the enormous advantages of birth and the potential impediment of a slow educational start. Darwin's father reproached him in 1825: “You care for nothing but shooting, dogs, and rat-catching, and you will be a disgrace to yourself and all your family.” Bateson, at a similar stage in his education, was branded as “a vague and aimless boy” by his headmaster at Rugby. Yet Bateson finally focused his interests on zoology and morphology, studying with Sedgwick and Weldon at Cambridge, and from 1883 to 1884 (in an interesting [Page 397] reversal at a time when most aspiring American scholars traveled to Europe for postgraduate work) with W. K. Brooks, the finest American zoologist of his time, at Johns Hopkins.
I generally shun psychological or intellectual biography in this book (both for limitations of space and authorial competence), but I have long been fascinated by the structural principle that groups of ideas seem to cohere just as morphological parts often correlate — with possession of one trait implying a set of logically or mechanically appended consequences. The rationale for this book depends, in large part, on such a structural isomorphism between nucleating centers of mutually implicating ideas and the integrity of organic Bauplan, for my notion of a Darwinian essence, construed as a minimal but distinctive set of interpenetrating and almost necessarily correlated concepts, builds the organizational framework of this book.
Whatever the validity of this general framework, I think we will all admit that ideas do coagulate in implicating sets, and that fascination with one — and we get hooked for the damnedest of impenetrable reasons — attracts us to the oth
ers as well. The Darwinian set implies a basic intrigue with functional and adaptational arguments and includes preferences for gradualism of change, separability of parts, and efficiency of competition. An opposing set — an aggregation that exerted a far lesser, but still identifiable, pull upon Darwin himself (see pp. 330–341), and that motivates the formalist “nucleating center” of this chapter — includes fascination with structurally based correlation, evolution by internally generated sources of variation, and suspicion of adaptational scenarios as primary explanations for basic organic design.
For whatever reasons, and from his earliest days in zoology, Bateson felt drawn to the structuralist set* (and to consequent disfavor for Darwinian mechanisms). He quoted and admired the literature on distrust of functional and teleological arguments, from Bacon to Voltaire. Bateson's wife remarked in her memoir (1928, p. 13): “I think he never travelled without a copy of Candide in his pocket.” In 1888, at the beginning of his career, he wrote to his sister: “My brain boils with evolution.” But note the main theme that emerged from this cauldron — the necessary breadth and extent of the network of correlations enjoined by any primary change, with inevitable swamping of the primary trigger by the sequelae (a keen foreshadowing of [Page 398] my personal favorite among modern structuralist themes, as embodied in the concept of exaptation — see Chapter 11):
My brain boils with evolution. It is becoming a perfect nightmare to me. I believe now that it is an axiomatic truth that no variation, however small, can occur in any part without other variation occurring in correlation to it in all other parts; or, rather, that no system, in which a variation of one part had occurred without such correlated variation in all other parts, could continue to be a system. This follows from what one knows of the nature of an “individual,” whatever that may be ... Further, any variation must always consist chiefly of the secondary correlated variations and to an infinitely small degree of an original primary variation (in Bateson, 1928, p. 39).
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