University Student in Greifswald and Berlin

In the spring of 1923, Mayr entered the University of Greifswald as a medical student (Fig. 1.8). Recorded in an early notebook, the thought had been continuously in the back of his mind: Could his father's early death not have been prevented by

Fig. 1.8. Ernst Mayr (left) as a medical student in Greifswald, 1924. (Photograph courtesy of E. Mayr.)

a diagnosis of his illness in time? This thought and the family tradition on both his father's and mother's side led him almost automatically to choose a medical profession. He had selected Greifswald on the Baltic Sea not because of its academic reputation but because of the excellent birding areas nearby, and the Darss spit and the islands of Hiddensee and Rügen not far away (1980n). He went birdwatching in the forests and along the beach of the Baltic Sea almost every day, mostly alone or in company with his friends Herbert Kramer (1900-1945), a student of zoology, or Wilhelm Bredahl and Werner Klein, fellow medical students. They banded lapwings and dunlins in the marshy Rosenthal area and found the Red-breasted Flycatcher (Ficedula parva) commonly breeding in the beech forests of the Elisenhain in Eldena (Mayr 1923b), saw the fairly rare Middle Spotted Woodpecker (Picoides medius) and watched Little Gulls (Larus minutus) at the seashore (Mayr and Klein 1924a). Hans Scharnke (1931), a younger schoolmate from Dresden, later published many of Mayr's and Kramer's records together with his own field observations in the Greifswald region. Mayr had a glorious time, summer and winter and felt truly exhilarated on his birding excursions, especially those in the early morning. Some of his discoveries he still remembered with excitement 80 years later, e.g., the nest of a snipe in a bird-rich marsh, nests of both treecreepers (Certhia familiaris and C. brachydactyla) permitting a careful comparison of these sibling species, vast flocks of wintering geese on unused fields, and there were many more! Also, he enjoyed his studies at the university and his complete freedom tempered by a sense of responsibility.

Mayr's considerations about bird study are well reflected by a preserved list of 28 points. This list was probably written during the first half of 1924 (definitely after September 1923; see point 16). Evidently he was particularly occupied at that time with the songs and calls of birds as discussed in the publications of the Saxon ornithologists Rudolf Zimmermann, Bernhard Hoffmann, Bernhard Hantzsch and Alwin Voigt (1921). These were his questions:

(1) Is the call of the European Jay (hiäh) species-specific, or an imitation of that of the buzzard?

(2) Which species of birds can imitate?

(3) How different are the vocalizations of closely related species?

(4) How good is the memory of birds?

(5) Song and mating calls.

(6) One should not claim that species have expanded their range when they had not been observed previously. They might have been overlooked (nocturnal mammals; see Zimmermann).

(7) Conversely, a previously observed species has not necessarily become extinct if it is no longer observed (nutcracker).

(8) One must know the literature before one can make statements about the status of a species.

(9) Which are the latitudinal and altitudinal species borders?

(10) Which species of plants control the distribution of animals?

(11) How far does a nonmigratory bird roam? (see Bacmeister, J. Ornithol. 1917, II).

(12) Test by aviculture whether the two species of treecreepers, the willow tit and the marsh tit, the sprosser and nightingale, etc., can be crossed in captivity (like the horse and donkey).

(13) Investigate the degrees of relationship among species of a single genus, for instance Charadrius dubius and hiaticula.

(14a) Do only such species hybridize in which the female alone raises the young (Capercaillie, etc.)? Or also such others that are very similar in their whole reproductive biology? (14b) How helpful is microscopic analysis of feathers in order to distinguish between juvenile, female, and male plumage?

(15) Investigate the distribution ofMuscicapa hypoleuca, semitorquata, albicollis.

(16) How far north does the osprey range? Migrant ducks from further north or east passing through Moritzburg, were afraid of it on 12 September 1923.

(17) Is it legitimate to make anthropomorphic descriptions of birds, as done by B. Hoffmann?

(18) How independently has the beauty (a relative term!) of bird songs evolved?

(19) Closely related species ofbirds often differ strikingly in the length, structure, and elaboration of their songs (B. Hoffmann).

(20) Different species ofbirds differ strikingly in the tonal quality of their songs.

(21) What is the psychological significance of the various call notes of a species (fear, pleasure, etc.)?

(23) How differently do different nations represent the vocalizations of the same species ofbirds?

(24) To what extent do females sing? (Hantzsch) Which calls are shared by male and female?

(25) If the song of the male serves to attract females (Hoffmann, p. 93), why do birds sing also long after the period of pairing and frequently even in the autumn? (J. Ornithol. 1917, II, F. Braun)

(26) Can birds really count up to three? (B. Hoffmann, p. 120).

(27) When searching for bird nests, always record how far away from the nest the male was singing.

(28) Find out how many clutches per season the willow tit raises, and search for their nest. Willow tits tend to spend the night in their nest cavity.

Despite the birds, Mayr attended all his medical courses very conscientiously except for his stay at a farm for a couple of weeks during the first semester to help with haying in order to get something to eat (in 1923 the inflation in Germany was rampant and food scarce in the cities). After some difficulties he had found a furnished room in Burgstrasse 17. He had to go down a staircase and cross a yard to get to a toilet. There was, of course, no heat, no warm or running water, only a wash basin (where the water sometimes froze in the winter) and a pitcher with water to fetch somewhere from a faucet. His lunch in the mensa, the student dining hall, consisted mostly of a rather thin soup.

Mayr disliked the student fraternities and their activities like dueling and drinking and turned down their attempts to enroll him. Eventually he joined the Deutsche

Hochschulgilde Sankt Georg. This local Gilde had developed from the Youth Movement: no drinking, but much hiking, singing folksongs, etc. Originally quite unpolitical, the Gilde at some universities became nationalistic in later years and some of them even Nazi.

"My intimate knowledge of the countryside around Greifswald led to a noteworthy incident in my life. A famous professor of paleontology at the university, O. Jaeckel, was an ardent nationalist and at the same time involved in a youth group somewhat like the boy scouts. One of their activities was to have war games. How I came to get involved in this, I no longer remember. However, I was chosen to be the leader of the blue party. The red party had a fort in the middle of the Elisenhain (a forest region, my favorite birding locality) and the assignment of the blue party was to enter the woods on the main road and to take the fort. I saw at once that the whole scheme was set in such a way that the red party (with Professor Jaeckel) had to win. How could I thwart this plan? I knew enough about battles and wars to know how often a battle is won because one army did something totally unexpected by the other. So I decided to surprise the red party. From my birding excursions I knew that there was a small road into the Elisenhain from the opposite direction. A road that could be approached by using service roads through the fields. So I entered the Elisenhain with my blue army from the back and of course had no trouble at all taking the fort by surprise. In the ensuing review the military experts decided that I had not won because I had not followed exactly the instructions. All of my arguments that such a policy would be the ideal education for losing wars were of course rejected. Also I was never again asked to lead an army in such war games. And that was the closest I ever was involved in war."

During short vacations, Mayr explored nearby areas on the Baltic seashore, the Darss spit and the island of Rügen, and on one occasion he visited his older brother Otto in Danzig (Poland today) where the latter was taking an engineering degree. Near Danzighewatched hisfirstCommonRoseFinch (Carpodacus erythri-nus) and heard its distinctive clear whistle. Most importantly, however, he spent several weeks between semesters at the Museum of Natural History in Berlin as a volunteer with Dr. Stresemann. There he also assisted visiting ornithologists like R. C. Murphy from New York and the famous Russian ornithologist M. Menzbier from Moscow. On one occasion, Stresemann assigned to him the identification of a recently received collection of birds from Java. He could have done this himself in less than an hour, but he knew that this assignment would greatly widen Mayr's horizon.

Early scientific views on species and evolution. The roots of Mayr's later contributions to the evolutionary synthesis reach far back to the early 1920s and his seemingly abrupt appearance as an "architect" of the synthetic theory of evolution during the early 1940s had a long history which, however, must be reconstructed from unpublished letters, notebooks and articles in little known journals.

In a letter to Dr. Erwin Stresemann dated 12 May 1924, he reported from Greifswald not only details of his ornithological observations in the field but also reflected on theoretical matters concerning the ecological and historical origin of geographic variation in a bird species and on the evolution of species themselves!

Evidently he had followed up on certain topics discussed with Stresemann during earlier visits to the Berlin museum. Most of this letter is here included because of its historical interest (my translation; letters refer to the notes at the end; see also Haffer 1994b, 1997):

Dear Dr. Stresemann!

[...] Now I would like to ask you to undertake several studies. You told me in Berlin that [A. B.] Meyer mentioned in his Birds of Celebes [A] that everything in ornithology will soon be accomplished with the help of mathematical formulas. How about you setting up principles of an ornithological mathematics? This wouldsave usfrom a quaternary nomenclature (which appears necessary from a purely theoretical point of view). (1) Intensity index. Compare Parus atricapillus rhenanus and subrhenanus, Motacilla flava rayi and thunbergi, Carduelis l. linaria and cabaret. (2) a geographical, respectively climatic, factor (desert, steppe, polar climate, island, humid coastline, etc.), (3) the individual variation needs to be taken into account, and (4) the nomenclature of intermediate forms (Fig. 1.9)

Five strongly differentiated forms are to be expected in this region where one has to distinguish between the intermediate forms between 1 and 2, 2 and 3, 3 and 4, 5 and 6 on one hand and between 4 and 5 on the other hand. For instance, the transition from 5 to 6 will be gradual so that a [b, c, etc.] will be rather uniform. However, hybridization will take place between 4 and 5 and therefore a strong individual variation will occur (see Long-tailed Tit [B]). Therefore intermediate forms between 5 and 6 have to be labeled 6-5, by contrast those between 4 and 5 should be designated 4 x 5, etc [C]. Isolation needs to be taken into consideration too. If a form does not continuously receive fresh blood [gene flow] from the parent form, it will enter into a totally aberrant evolution. This, however, probably cannot be expressed mathematically. So many subspecies have been described within recent years that the time is ripe to write a "general Hartert" (or "The Theory of Geographical Variation and of the Species") [emphasis added].

The facts mentioned above will have to be discussed as well as modifying factors, i.e., active factors (climate, etc., partly based on Görnitz [D]) and passive factors (color, size, biology, etc.). In addition the following topics need to be treated: (1) How is it possible that members of the same Formenkreis overlap their ranges without hybridizing? and: (2) May similar and geographically representative species nevertheless be members of different Formenkreise? An example: If Ficedula hypoleuca and F. albicollis would exclude each other geographically, they would surely be included in the same species. Conversely, someone may say: I can no longer recognize the forms of the Yellow Wagtail only as subspecies, although they mostly exclude one another geographically; just as the delimitation of genera is more or less a matter of taste. Furthermorethephylogenetic connections ofthedifferentspeciesmustbeclari-fied. With the help of mutations and several representative forms like Sprosser [Luscinialuscinia] and the Short-toed Tree-creeper (C[erthia] brachydactyla)

Fig. 1.9. Dynamic-historical interpretation of the origin of geographical variation in a bird species as sketched schematically by the medical student Ernst Mayr in a letter to Dr. E. Stresemann (Berlin) dated 12 May 1924 (redrawn and terms translated). Arrows indicate range expansion of populations from a high plateau ("center of origin"). An intermediate form (Zwischenform) results from secondary contact of populations circumventing barriers like mountains and the sea. Various ecologically different regions and their respective subspecies are indicated as follows: 1. High plateau, 2. Steppe, 3. Swampy plain, 4.-5. Agricultural lowlands, 6. Hilly region; a-g symbolize stages in a cline between the subspecies inhabiting areas 5 and 6

Fig. 1.9. Dynamic-historical interpretation of the origin of geographical variation in a bird species as sketched schematically by the medical student Ernst Mayr in a letter to Dr. E. Stresemann (Berlin) dated 12 May 1924 (redrawn and terms translated). Arrows indicate range expansion of populations from a high plateau ("center of origin"). An intermediate form (Zwischenform) results from secondary contact of populations circumventing barriers like mountains and the sea. Various ecologically different regions and their respective subspecies are indicated as follows: 1. High plateau, 2. Steppe, 3. Swampy plain, 4.-5. Agricultural lowlands, 6. Hilly region; a-g symbolize stages in a cline between the subspecies inhabiting areas 5 and 6

a theory may be elaborated [E]. This is necessary to replace Kleinschmidt's dogma which does not advance science [F]. I am an adherent ofLamarckism (despite the theory of genetics, Baur's modifications, etc.). Each organism has a large number of equal possibilities of development and this explains the phenomena of convergence.

An attempt should also be made to find out for all bird species where they originated based on certain characteristics (Berajah [G]). The comparative morphology of immature plumages would probably play a decisive role in such an endeavor. That form whose immature plumage most resembles the adult plumage, perhaps represents the ancestral type. In searching for the center of origin one must avoid the mistake (as happened before, particularly in ethnography) and select that region from where the least amount of material is available. One thought has not yet been incorporated into the ornithological theory of colonization which (perhaps more than justified) is prevalent in ethnography, namely the thought that a center of origin sends out again and again entire waves of animals. According to what I have read so far ornithologists seem to think that the centers of expansion are always located along the periphery of the distributional range. However, they may equally well have been located in ecologically favorable areas [within the ranges].

Another interesting question is the rate of differentiation ("Polish Serin" [H]). Supporters of the mutation theory should answer this question: In which way does the established form disappear from its range? Possibly the mutant is more strongly expansive. The peculiar phenomena of convergence which caused so many errors in systematics need to be taken thoroughly into consideration. Very many ornithologists would appreciate a comprehensive treatment of these problems. Surely such a study would suit you. [...] With ornithological greetings. Sincerely yours, Ernst Mayr.

Notes:

[A] In cases of clinal or stepped clinal geographical variation, A. B. Meyer and L. W. Wiglesworth (1898) and L. Wiglesworth (1898) had proposed to assign subspecies names only to the endpoints and to selected intermediate stages in the character progression.

[B] This is a reference to the hybridization between the white-headed and stripe-headed forms of the Long-tailed Tit (Aegithalos caudatus) in central Europe.

[C] Mayr distinguished here between primary and secondary intergradation.

[D] Görnitz (1923: 498) had concluded "that the majority of the geographical subspecies are not due to the effect of natural selection but originated through the effect of climatic factors."

[E] This is a reference to two pairs of sibling species (Luscinia luscinia/L. mega-rhynchos and Certhia brachydactyla/C. familiaris) whose members probably originated in geographical isolation from their respective common ancestors and are today in secondary contact along a narrow (nightingales) or broad (treecreepers) zone of overlap in central Europe.

[F] The Protestant pastor and ornithologist Otto Kleinschmidt (1870-1954) had proposed a typological species concept ("Formenkreis") and the independent origin (creation) of all animal species.

[G] In his excellently illustrated monograph series "Berajah" (1905-1936) Kleinschmidt had discussed geographical variation and range expansion of numerous species.

[H] Several subspecies of the Serin (Serinus serinus) had been described from regions (Germany, Poland), which this bird had colonized only during the last century. In his dissertation on "The expansion of the Serin" Mayr (1926e) was able to prove that the Serin finch does not differ in these latter areas taxonomically from the populations in the Mediterranean region.

When I sent a copy of the above letter to Ernst Mayr in 1992, he was totally surprised and answered (transl.):

"I am terribly amused at my forwardness with Stresemann. No doubt this is part of the reason why in the Stresemann family I was always referred to as the fresh ('freche') young Mayr. I admire the patience with which Stresemann tolerated me and my letters. He must have appreciated my genuine deep interest in science. I had completely forgotten all about this letter and even reading and re-reading it now does not trigger any remembrance."

The three-volume magnum opus of the renowned ornithologist Ernst Hartert on the birds of the Palearctic fauna (1903-1922) had just been completed. However, Hartert was mainly a practical taxonomist. The above letter of the 19-year-old Ernst Mayr shows his early interest in theoretical analyses of taxonomic data and his ability to synthesize critically the results derived from studies in widely different fields, capacities which characterize many of his publications in later decades. It is evident that already in the spring of 1924 he was familiar not only with writings of the leading ornithologists Stresemann, Hartert, Kleinschmidt, etc., but also with the basic concepts of evolution, genetics and systematics through a close reading of textbooks and specialized articles, as shown by his reference to Erwin Baur's "modifications" and the theory of inheritance of acquired characters. His concern with genetics probably goes back to the volume on human heredity (Menschliche Erblichkeitslehre, 1923) by E. Baur, E. Fischer and F. Lenz which greatly impressed the student in Greifswald (notebook). Mayr's course in genetics was rather traditional consisting largely in exercises demonstrating the "Mendelian Laws"; the emphasis was on mutation and physiological genetics. The connection between genetics and evolution was not dealt with at all.

Heavily occupied with the manuscript for his large volume on Aves and many other projects, Stresemann was not able to follow up on Mayr's suggestions. However, he was so much impressed by his enthusiasm and knowledge that he wrote to his fatherly friend Ernst Hartert a few weeks later (12 July 1924):

"I have discovered [...] a rising star, a young Studiosus med[icinae] by the rare name of Mayr, of fabulous systematic instinct. Unfortunately, he will probably have to wither away as a medical doctor. If only one could always place the right man in the right position!" (transl.)

At this moment, neither Stresemann nor Hartert could have imagined that this young man, less than 8 years hence, would be proposed to be Hartert's successor at Lord Walter Rothschild's private museum in Tring (see p. 96, footnote) and actually became the curator of the Rothschild Collection at the American Museum of Natural History.

In 1925, Mayr entered the following remarks into his notebook:

"Theses regarding the dispute between Darwinism and Lamarckism.

1. The controversy in evolutionary theory today does not concern the question of selection. Selection is also acknowledged by the Lamarckian.

2. The controversy relates to the cause of variability (which Darwin accepts as given).

3. Varieties [heritable] originate according to De Vries by random mutations. The mode of life of an organism is determined by the structures thus originating. This seems to be the view of some evolutionists, particularly of experimental zoologists and geneticists.

4. The Lamarckian, on the other hand, claims that new variants originate under the influence of the mode of life [Lamarck] or of the environment [Geoffroy].

5. The Lamarckian has the right to interpret the laws and findings of genetics in his sense; this refers both to mutations and Dauermodifications; cumulative aftereffect-Alverdes.

6. While the experimental biologist states that mutations are undirected (random), the Lamarckian asserts mutations on the way to an adaptation are directed7. It would make no sense to believe that the destabilization of the germ plasm (caused by a mutation) would be without influence on subsequent mutations-Orthogenesis.

7. Changed conditions of the environment influence the reaction of the body plasma [soma] (modification of the phenotype). If this influence continues for a lengthy period, the germ plasm will also be influenced, the modifications become heritable, they become Dauermodifications, which after return to the normal environment will disappear only after many generations (cumulative aftereffect). We must assume such Dauermodifications in many geographical races.

8. There are no proper arguments against Lamarck's claim that organs deteriorate by lack of use. It is in line with the economy of the organism that of the available 'fund' (Hesse) [resources] particularly those organs will be endowed which are very much in use (Roux, the Struggle of Parts in the Organism). On the other hand, it is reasonable that in the organs which are used most actively corresponding to the degree of use, mutations will occur, the maintenance of which will be controlled by selection.

9. The Lamarckian theory [in its modern version] is not teleological."

Additional entries in his notebook read (transl.): "Darwin distinguished between sudden and gradual changes too." "The genetico-darwinists always claim that a very small mutation is sufficient gradually to prevail through natural selection. However, there are sufficient examples that at least a predisposition for mutations is triggered by biological processes." "Certain doubts appeared whether everything can be explained by mutations as, e.g., Baur hints at. These mutations have been derived from experiments. It is questionable that this is a secure basis, because the conditions during experimental work often are not normal, or better, not natural. There is another path, because we encounter frequently natural experiments of speciation that originated under natural conditions. An example is Stresemann's 'mutations', [...] and borderline cases of the doctrine of Formenkreise."

Mayr (1980n: 413) later stated, "I have no recollection of when I first learned about evolution." However, it is true that he had an early interest in evolution and genetics if only coincidental to his enthusiasm for birds. Even though he was inscribed as a medical student in Greifswald, he was first and foremost an ornithologist.

Wide-ranging biological interests are documented by a notebook of 1925 with hints to what Mayr considered open problems and topics suitable for possible future research (transl.):

7 "I am here in agreement with Professor Buchner in Greifswald with whom I discussed this point."

- Convergence versus phylogenetic relationship in birds: (1) significance of food, bill, etc. (2) significance of subsoil and climate (pigmentation), (3) significance of mode of life (sense organs, legs, claws, wings, etc.);

- Biology and relationship; nest building, feeding, voice, courtship, sociology, birds and plants, diurnal and nocturnal mode of life, migration instinct, number of broods and eggs, molt, wintering areas, direction of migration, proportion of males and females during migration, care of young, ecology, race formation, variability, differences of males and females in size and coloration;

- Influence of age, temperature, weakness, irritants, poison, etc. on the determination of sex (in plants);

- Fragrance of flowers: (1) Which flowers of our flora are fragrant? (2) During which months and at what time of the day are they visited by which insects? (3) Definition of fragrance (4) Repellents (mercaptane, ether), (5) Organs producing odor, (6) Elimination of all optical markers, e.g., cut off flowers.

Originally, it was necessary to study five semesters before one could take the cand. med. examinations. Mayr had planned to stay in Greifswald for three semesters and do the next two semesters at Tübingen University. While he was in his second semester, a new regulation permitted taking the cand. med. only after four semesters. Therefore he decided he should finish in Greifswald. In February 1925, Mayr passed his pre-clinical examinations with straight "A"s in all six subjects, a rare achievement. When he again visited Berlin and his "beloved Zoological Museum" (entry in an early notebook), Dr. Stresemann persuaded him to switch to zoology and to major in ornithology, partly by promising to place him on an expedition to the tropics later on. This was a temptation Mayr could not resist, particularly because by that time, certain doubts had been growing in his mind regarding medical practice as his lifelong occupation. Within the field of medicine, he could see himself only as a researcher in one of the basic medical sciences (early notebook). Stresemann gave him at once the topic for his dissertation: "The range expansion of the Serin finch Serinus serinus in Europe." He started work during his last semester in Greifswald, now registered as a student of zoology. In the fall, he transferred to the University of Berlin where, in October 1925, he participated in the annual meeting of the DOG (see the group photograph in Haffer et al. 2000:431). Stresemann remarked in a letter to O. Kleinschmidt on 19 August 1926, "I am placing great expectations in his further scientific development." Without Mayr's chance observation of the pair of rare ducks at Moritzburg, which led to his encounter with Dr. Stresemann, he probably would have become and "withered away" as a medical doctor (p. 30) somewhere in Germany, perhaps known only to the local community of birdwatchers.

The biweekly meetings of the DOG comprised a lecture, usually with slides, or, alternately, a special session (Fachsitzung) when recent literature was reviewed. Most of the new books and monographs were introduced by Stresemann himself, others by his graduate students. When Mayr was asked to discuss a recently published avifauna of a region in Bavaria, authored by a most distinguished local ornithologist, the medical doctor J. Gengler, he simply presented a long list of all the mistakes he had found in the book, for his work on the Serin finch had made him quite familiar with the faunistic literature. When he finally sat down after his review, the president of the DOG, Herr F. von Lucanus, and other members protested against such a young student criticizing the master. Heinroth and Stre-semann had to quiet the troubled waters, but Dr. Stresemann later took him aside and advised him always to say something favorable at the beginning (advice that Mayr passed on to his students in later years).

The graduate students had noticed that Stresemann occasionally reviewed a book that he had had no time to read. However, while introducing the author and the title of the book, he studied the table of contents and made a few remarks on it. Meanwhile he opened a few pages that appeared interesting. Reading a page "diagonally" with one glance, he then picked out several important sentences, especially those that he could criticize. Someone who had studied the book from cover to cover could not have done better. Mayr continued (pers. comm.):

"I was an equally quick reader as Stresemann, and bold as I was already in those days, I bragged to my fellow graduate students that I could do the same. When I was assigned again a book for review, (probably) Kattinger seized it immediately, before I could take a look at it. He sat next to me during the following session and gave me the book the moment that Stresemann called me up. My heart was beating to my neck but, strictly following his example, I managed to do the review and Stresemann didn't notice anything. We never confessed to him."

The student home in Borsig Street run by the widow of a Protestant minister was rather primitive to say the least. There was no real vacancy when Mayr arrived but he and 6 or 7 others were permitted to sleep in dormitory-style "housing" directly under the slanting roof in the attic. Each student had a camp bed separated from the next one by a hanging sheet. Several months later he got his own room, but it was alive with bedbugs so that he could hardly sleep. When he complained, he got another room and the first one was fumigated. He stayed in this place until his PhD examination and during one semester shared the room with his younger brother Hans who studied law. Since they always got along splendidly, this was a very enjoyable time.

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