Systematics And The Origin Of Species

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Fig.5.1. Title page of E. Mayr's book (1942e) on species and speciation that became a cornerstone of the evolutionary synthesis journals. Afterwards he took notes on articles dealing with species and speciation or with problems of systematics and evolution. He had also participated in the seminars at the zoology department of Columbia University (L. C. Dunn) since about 1932 (see p. 132) and had been in close communication with Dobzhansky since 1935. When he received the request, it was "simply" a matter of organizing this material and writing (pers. comm.).6 The manuscript was finishedin early 1942 and L. C. Dunn delivered it to the Press in March of that year. The book appeared toward the end of 1942; A. H. Miller received his review copy on December 15. Mayr's Preface began:

"During the past 50 years animal taxonomy has undergone a revolution as fundamental as that which occurred in genetics after the discovery of Mendel's laws [...], the change from the static species concept of Linnaeus to the dynamic species concept of the modern systematist."

The book was not intended to show that the data of the systematists are consistent with the newly developed principles of genetics which in fact they are. Mayr felt that he had little to add to what Dobzhansky (1937; and S. Wright through Dobzhansky) had said on genetics. As I mentioned above, the real objective of the volume was to explain a whole set of phenomena well known to systematists (naturalists) but not to geneticists, particularly species and speciation and the role of geography in the evolution of species and populations. It should be noted that certain topics treated in this book were later modified by Mayr himself. The book was a continuation of the thinking expressed in Dobzhansky's book (1937) and dealt with many aspects of species and speciation which the latter had neglected or discussed only briefly. Mayr's volume was also written in response to Goldschmidt's (1940) ideas on saltational speciation through systemic macromutations:

"Even though personally I got along very well with Goldschmidt, I was thoroughly furious at his book [1940], and much of my first draft of Systematics and the Origin of Species was written in angry reaction to Goldschmidt's total neglect of such overwhelming and convincing evidence" for the concept of geographic speciation (1980n, p. 421). "Goldschmidt [1940] confuses the sympatric with the allopatric gap [between species] and this is the reason why he denies speciation through geographical variation. He shows very clearly what all of us, of course, have always known that sympatric gaps are bridgeless gaps because otherwise we would have hybrid flocks. He then proceeds to state that all gaps between species are bridgeless even those between allopatric species. This conclusion is not only not justified but actually contradicted by his own material and quotations" (Mayr in a letter to E. Anderson, 21 January 1941). In 1952, when both Mayr and Goldschmidt were teaching courses at the University of Washington (p. 260), Mayr once asked him how a new "hopeful monster" would react to the other (normal) members of the population. He was quite nonplused and finally said "Well, I never thought of it that way." And Mayr (1982d: 381) later: "There are literally scores of

6 Mayr also registered the publications in various other fields like general ornithology, anthropology, genetics, behavior, and paleontology to broaden his general knowledge. "My reading in those days was quite enormous, because I was equally interested in many animal groups and almost all aspects of biology."

cases in the history of science where a pioneer in posing a problem arrived at the wrong solution but where opposition to this solution led to the right solution," e.g., Goldschmidt-Mayr or Lyell-Darwin.

On Richard Goldschmidt (1878-1958) Mayr reported: "So far as I remember, I never met Goldschmidt when I was a student at the University of Berlin. Presumably, during that time (in 1925-1926) when I took courses at Dahlem he was absent in Japan. When I first met him in the States, I don't know. I do know that in the 1930s he visited me several times at the American Museum of Natural History, and that on those occasions I showed him all the marvelous examples of geographic variation as displayed by the South Sea island birds, particularly those of the Solomon Islands. Obviously, I did not convince him because he refers to this only in a parenthetical footnote in his 1940 volume on The Material Basis of Evolution.

Our relationship was quite cordial in spite of our scientific disagreement, and this is illustrated by the following anecdote. Probably in 1936 Goldschmidt visited me on a Saturday in the museum, and he was so much interested in my demonstrations that it came close to my lunchtime. He accepted mine and Gretel's invitation to a simple lunch (lentils and frankfurters), came to my apartment in northern Manhattan, and we had an altogether delightful time together.

The next thing was that I went up to New Haven together with my friend Herman Spieth to attend Goldschmidt's Silliman Lectures. Of course, I did not approve at all of his saltationist origin of species through hopeful monsters, but it was interesting to hear him present his ideas. As we were talking together after one of his lectures, Herman asked him about the origin of birds from reptiles. He clearly, unequivocally said, 'Well, the first bird hatched out of a reptilian egg.' He was that much of a saltationist.

This experience, and particularly his rather cavalier treatment of my work in his 1940 volume, made me rather angry. I considered it almost unscientific to suppress this splendid evidence for geographic speciation. And, as I have said on other occasions, part of my Systematics and the Origin of Species was written in a mood of anger over Goldschmidt's behavior.

He was a typical Geheimrat—as the modern sociologists call it, a mandarin. He was fully aware of his position in life and had little patience with ignorance and poor manners. Interestingly, the fact that we disagreed scientifically did not disturb our relationship. I am told that he was quite upset when coming to the University of California at Berkeley about the secondary role he played there. Having been the director of a Kaiser Wilhelm Institute, practically being the Pope of German biology, it was a terrible let down for him to be only one professor in a large department.

He had a peculiar tendency always to come out with unorthodox biological theories. This was true not only for speciation, but also for sex determination, for gene action, and I don't know what other subjects. Invariably almost everybody opposed him, and as history shows, he was almost always completely wrong. However, he himself was fully convinced that he was right, and he would say, 'Well, this will probably not be adopted in my lifetime, but I am perfectly sure that eventually it will be shown that I am right.' There is a very good biography of Goldschmidt by Curt Stern [National Academy of Sciences USA, Biographical Memoirs 39 (1967): 141-192]. On the other hand, Goldschmidt's autobiographical reminiscences Portraits from Memory (1958), are not reliable. Those German biologists who were his friends are usually praised too highly, and those who were his enemies, particularly if they were known to have been anti-Semitic, were presented usually as being very poor zoologists also. This is definitely in some cases misleading as, for instance, in the case of Ludwig Plate" (1862-1937).

As mentioned above, Mayr's specific contribution to the evolutionary synthesis was the analysis of the origin of organic diversity (speciation), i.e., the causes of divergence and discontinuity: "To fight for the inclusion of speciation, the origin of diversity, was my major task and contribution to the evolutionary synthesis." Species and speciation formed the center of his research. In contrast to his emphasis on the geographic ("horizontal") component of evolution, earlier evolutionary biologists and geneticists had studied almost exclusively adaptive ("vertical") changes within populations along individual phyletic lineages. The reductionist approach of the geneticists concentrated on the genotypic level of organisms and considered evolution as changes in the genetic composition of populations, whereas the naturalists (systematists and paleontologists) considered the phenotype, the entire organism, as the target of selection and defined evolution as descent with modification (anagenesis) and multiplication of species (cladogene-sis). The Evolutionary SynthesisinNorth Americaledtoamoregeneral acceptance of natural selection as a mechanism of evolutionary change and eliminated non-Darwinian theories like neo-Lamarckism and orthogenesis. Cooperation between systematics, genetics and paleontology was established through the major publications of Dobzhansky, Mayr, Huxley, Simpson, Stebbins, and several authors in Europe (e.g., Rensch). Mayr (1980f: 1) summarized their conclusions: "(1) Gradual evolution can be explained in terms of small genetic changes ('mutations') and recombination, (2) the ordering of this genetic variation by natural selection, and (3) the observed evolutionary phenomena, particularly macroevolutionary processes and speciation, can be explained in a manner that is consistent with the known genetic mechanisms."

Among the architects of the synthetic theory of evolution Mayr and Rensch had conducted extensive research in avian systematics and zoogeography (as had their teacher Erwin Stresemann) and Huxley had studied the behavior of birds for several years (Junker 2003). One may ask the question whether birds were particularly suited for such a generalizing approach. The answer is probably "yes": Birds demonstrate geographical variation better than most other animal groups. More importantly, there was so much information about birds available, far more than for any other group of organisms. Nevertheless, Alden H. Miller in California, with virtually the same facts at his disposition, wrote a very formalistic monograph on "Speciation in the avian genus Junco" (1941) and missed many if not most of Mayr's general questions, even though his basic ideas were similar (see Mayr's review of Miller's work [1942d]). Abroad synthetical overview on the relevant data from many different biological disciplines was required, and this was supplied by Mayr (1942e).

Reviewers of Systematics and the Origin of Species (see 1942e for references) were enthusiastic about the wide scope of the book, the clear and logical presentation of the topics of the "new systematics" and geographical speciation illustrated by the author's own taxonomic work and the findings of modern genetics and other fields of science. The reviewers emphasized the book's general biological-evolutionary significance when stating, e.g.,

"Dr. Mayr's lucid and stimulating book [...] should be read and understood by every individual who would be called a systematist. The subject is approached from the broad viewpoint of a general biologist who not only understands the principles of genetics, ecology, morphology, physiology, and geographical distribution, but who is able to apply these to problems of systematics" (Ownbey);

"This work is of great value in bringing about a better understanding of the contributions of systematics to evolutionary theory and in facilitating the synthesis of the results of different lines of investigation into a unified and logical picture" (NN);

"No systematist can afford to overlook any point that Dr. Mayr raises. The author has presented a scientific synthesis" (Zirkle);

"A broad groundwork of sound generalization is laid for the construction of a modern philosophy of speciation; systematics and other branches of zoology are coming to a rapprochement" (Hubbs), a "synthetic exposition of modern research in zoology" (Jepsen), "an attempt at a general synthesis," although limited to animals (Sturtevant). "Very helpful to American students of speciation will be the data and interpretations of European systematists; Mayr's familiarity with the far-flung systematic literature is amazing" (Hubbs); similarly also Emerson, Schmidt, and Ripley.

Critical comments concern the claim that speciation is almost exclusively geographic (allopatric), a less detailed treatment of aquatic animals, and the lack of examples from plants. Therefore Mayr entitled his follow-up work Animal Species and Evolution (1963b).

Lack, Miller, Ripley, Griscom, and Kramer noted with pride the advanced state of their special field of interest and the leading role ornithologists have played in developing the methods of "new systematics." Their application of trinominal nomenclature led to the study of geographical variation and later to the concept of geographical speciation. Besides the book pointed the way toward more intensive utilization of museum material for general studies.

Mayr himself wrote in retrospect (in 1982) in his autobiographical notes: "When rereading my 1942 book 40 years later I cannot conceal how impressed I am by the maturity of much of my discussion. I open up many important evolutionary problems and the solutions I propose are by and large the ones that are still considered valid today. In view of the fact that I had rather slight contacts with other evolutionists at that period I was at first puzzled as to how I could have reached such maturity. I then recollected that after all I had been a working taxonomist for

15 years and that I had read voluminously. Even though I did not maintain a 'Notebook on Transmutation of Species,' as Darwin did, I nevertheless had kept massive excerpts from the literature always with comments of my own. Unfortunately all this has now disappeared; I probably threw it out when I moved from New York to Cambridge.

What is also evident to a careful student is that in various major issues I tended to diverge from both Simpson and Dobzhansky, as much as all three of us stood on the common ground of the Evolutionary Synthesis. My emphasis on populations and horizontal evolution is altogether absent in Simpson. My emphasis on the essential completion of the building-up of isolating mechanisms during geographical isolation is not shared by Dobzhansky. And there are various other differences. Even though I still express one or two reservations concerning the power of natural selection, I nevertheless was a far more consistent selectionist than Dobzhansky, who had been strongly influenced in his thinking by Sewall Wright."

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