Russel Wallace : Alfred Russell Wallace (sic)
[[p. 491]] In 1872, Mr. Gulick sent me his paper on "Diversity of Evolution under One Set of External Conditions," requesting me, if I thought fit, to communicate it to the Linnean Society. As the paper contained a body of very interesting facts observed by the author, I had no hesitation in recommending its acceptance by the Society, although I did not agree with the conclusions Mr. Gulick drew from his facts.
Last year Mr. Gulick send me the manuscript of his present paper, informing me that it was the result of long-continued study of the subject, and asking me to forward it to the Linnean Society. I did so, writing to the Secretary that I had not read the paper through, and did not undertake the responsibility of recommending it for acceptance.
Having now read the paper in print, I find very little in it that I can agree with. I can discover in it no additional facts beyond those which were set before us in the former paper sixteen years ago, while there is an enormous body of theoretical statements, many of which seem to me erroneous, and a highly complex classification of the conditions under which the separation or isolation of individuals of a species takes place, with a new and cumbrous terminology, neither of which, in my opinion, adds to our knowledge or comprehension of the matter at issue.
As in almost every page of this long paper I find statements which seem to me to be either disputable or positively erroneous, any extended criticism of it is out of the question; but I wish to call attention to one or two points of vital importance. Mr. Gulick's alleged discovery is, "the law of cumulative divergence through cumulative segregation" (p. 212). He maintains that any initial variation, if isolated by any of the causes he has enumerated, but remaining under identically the same environment, will increase till it becomes in time a specific or even a generic divergence, and this without any action whatever of natural selection. Now if this is a fact it is a most important and fundamental fact, equal in its far-reaching significance to natural selection itself. I accordingly read the paper with continual expectation of finding some evidence of this momentous principle, but in vain. There is a most elaborate discussion and endless refined subdivisions of the varied modes in which the individuals constituting a species may be kept apart and prevented from intercrossing, but no attempt whatever to prove that the result of such complete or partial isolation is "cumulative divergence." The only passage which may perhaps be considered such an attempt at proof is that on p. 219, where he supposes an experiment to be made, and then gives us what he thinks "experienced breeders" will assure us would be the result. In this experiment, however, there is to be constant selection and reassortment of each brood, yet he asserts that "there is no selection in the sense in which natural selection is selection"; by which he appears to mean that the selection is by "separation" not by "extermination." This, however, seems to me to be a distinction without a difference.
Again, in the various illustrations of how "cumulative segregation" is brought about, natural selection must always come into play--as in the case of a change in digestive powers, and consequent adoption of a different food (p. 223), leading to partial isolation; and such cases are exactly what is contemplated by Darwin in his brief statement of the effects of "divergence of character" ("Origin," pp. 86-90), while the concurrence of "isolation" as a factor is fully recognized at pp. 81-83 of the same work (6th edition).
It appears to me that throughout his paper Mr. Gulick omits the consideration of the inevitable agency of natural selection, arising from the fact of only a very small proportion of the offspring produced each year possibly surviving. Thus when, at p. 214, he states that "the fact of divergence in any case is not a sufficient ground for assuming that the diverging form has an advantage over the type from which it diverges," he omits from all consideration the fact that at each step of the divergence there was necessarily selection of the fit and the less fit to survive; and that if, as a fact, the two extremes have survived, and not the intermediate steps which led to one or both of them, it is a proof that both had an advantage over the original less specialized form. Darwin explains this in his section on "Extinction caused by Natural Selection" (p. 85). On the whole, I fail to see that Mr. Gulick has established any new principle, either as a substitute for, or in addition to, natural selection as set forth by Darwin. Others, however, may think differently; and I shall be glad if any naturalists who have studied Darwin's works will point out, definitely, in what way this paper extends our knowledge of the mode in which species have originated.
The earlier Gulick paper of 1872 referred to here may be found in my webpages at http://post.queensu.ca/~forsdyke/gulick.htm. It describes studies with tree snails in the Sandwich Islands where John Gulick (1832-1923) spent much of his life as a missionary. Here he clearly describes what we would now call "peripatric speciation." Darwin had noted how easily a small isolate might become established on an island. Snails, literally, move at a snail's pace, and even within an island Gulick observed many such isolates, each characteristic of a particular valley. He ponders:
The advantages of snails for evolutionary studies were recognized by many evolutionists (e.g. S. J. Gould), who were able to find their fossilized shells in geological formations that could be dated. With help from his London-based ally, George Romanes, Gulick published a greatly expanded version of his original 1872 text in the Journal of the Linnean Society in 1888; it is this work of which Wallace's Nature letter is so critical. Like Romanes, Gulick declared that isolation must come first. Then, different phenotypic characters--that may have arisen either spontaneously with or without the further encouragement of natural selection--would be preserved from the blending effects that must occur when there is no reproductive isolation. Aghast, Wallace declares:
Wallace's quote from page 214 of Gulick's 1888 text in complete form reads:
Both Gulick and Romanes identified as the holy grail of speciation "the cause of this segregate generation," which Romanes referred to as some abstract "peculiarity of the reproductive system." Gulick joined Romanes in responding in the literature to Wallace's attacks. In 1905, back in the USA after a lifetime on Pacific islands including Japan, he published a treatise entitled "Evolution Racial and Habitudinal" for the Publications series of the Carnegie Institution. In the 1930s his son Addison, a biochemist, took up the paternal torch and reargued the case, but to little avail. Addison Gulick's biography of his father, published by the University of Chicago Press in 1932, is one of the great biographies of all time, and includes some very moving correspondence between the elder Gulick and the younger Romanes on the latter's religious doubts. If, with hindsight, we had to fault John Gulick, perhaps it should be for his pedantic terminology. It was Wallace, not Gulick, who came up with the term "physiological complements" (see Forsdyke, The Origin of Species, Revisited, 2001).