CHETVERIKOV, SERGEI SERGEEVICH

(b. Moscow, Russia. 6 May 1880: d. Gorki, U.S.S.R., 2 July 1959)

population genetics, evolutionary theory, entomology,

A specialist in butterfly systematics, Chetverikov took up biometrics and genetics after the 1917 revolution. His work at the Institute of Experimental Biology in Moscow during the 1920s led to one of the earliest statements of the evolutionary synthesis (1926) and to the first systematic studies of the genetics of wild populations of Drosophila (1925–1926), Together with R. A. Fisher, J. B. S. Haldane. and Sewall Wright, Chetverikov is now regarded as one of the founders of population genetics and modern evolutionary theory.

Chetverikov was a hybrid of two important Moscow merchant families. His father was Sergei ivanovich Chetverikov (1850–1929), a second-generation entrepreneur who manufactured fine cloth and was active in the Progressive Party. Chetverikov’s mother, Maria Aleksandrovna. came from the Alekseev family, owners of a large firm renowned (or its high quality gold braid and fine gold-laced fabrics. Her brother was Nikolai Alekseev (1852–1893). the mayor of Moscow from 1885 until his death. Her cousin was the famous actor and director Konstantin Alekseev (Stanislavsky), founder of the Moscow Art Theater. Chetverikov’s scientific patron, Nikolai Konstantinovich Kol’tsov, was his distant cousin on his mother’s side.

Chetverikov had three siblings. His older brother Ivan helped his father manage the factory. His younger brother Nikolai (1889–1973) studied mathematics with A. A. Chuprov and became prominent in Soviet mathematical statistics. His younger sister. Maria, left Russia after the revolution with his parents.

Butterflies . After receiving his elementary education at home. Chetverikov attended the Voskresenskii Realschule in Moscow to prepare for a career in engineering. From his geography teacher Vladimir Pavlovich Zykov, a docent at Moscow University, Chetverikov learned about Darwinism and natural history. Around 1895 he began to collect butterflies and decided to become a zoologist. His father opposed this decision, and after his graduation in 1897 sent him to a Technikum in Mittweid, a small town west of Dresden. After less than a year, however, his father relented. In order to qualify for university admission, Chetverikov spent a year and a half in Kiev preparing for the eighteen examinations required to obta in the certificate from the Fifth Kiev Gymnasium.

In September 1900 Chetverikov entered the natural sciences division of the physicomathematical Faculty of Moscow University. At the beginning of his second semester he became involved in demonstrations supporting student protests in Kiev and was briefly under arrest in early 1901. In the fall he decided to repeat his first-year studies, and soon became part of a natural history group headed by the zoologist and anthropologist N. I. Zograf (1851–1922). Over the next four years he received excellent zoological training, specializing in invertebrates and especially Lepidoptera. In 1905, as a result of his participation in student disturbances at Moscow University, he was again arrested and held in the Butyrka prison for two months. He used the time to study for his examinations and passed them in the spring of 1906, earning the degree of candidate of natural sciences (equivalent to a B.S. degree).

Chetverikov was accepted as a graduate student in the department of comparative anatomy of Moscow University, headed by M. A. Menzbir (1855–1935), and spent the period 1907–1909 working on a graduate degree. For his dissertation, Chetverikov undertook a painstaking study of the anatomy of the carapace of Asellus aquaticus L., a widely distributed isopod crustacean. Arguing that the external skeleton of the crustaceans provides some of the most interesting cases of external anatomy in the animal kingdom, Chetverikov described the various parts of the exoskeleton and analyzed their adaptive functional significance in the struggle for existence. Published in German in 1910, the work demonstrated both a commitment to Darwinism and a mastery of the literature, problems, and techniques of invertebrate morphology.

During the period 1900–1920 Chetverikov emerged as one of Russia’s leading butterfly systematists. As an undergraduate, he did work on Lepidoptera for the Imperial Society of Natural History, Anthropology, and Ethnography and its commission on the fauna of Moscow Province, headed by G. A. Kozhevnikov (1866–1933), a zoologist active in conservation. This work led to his first publication, an article on how to collect butterflies (1902), and to two notes adding to the fauna of Moscow Province (1902, 1905). Using the society’s collection of butterflies and other materials, he established that what had previously been regarded as three species were in fact one (1903).

Chetverikov’s third-year essay described and discussed seasonal and irregular radical fluctuations in the appearance of various Lepidoptera species, based on observations near his family’s dacha in the summer of 1903. It was published in 1905 as “Volnyzhizni” (Waves of life), a title drawn from William Henry Hudson’s The Naturalist in La Plata (1892). This essay was one of the first works to draw attention to the implications of fluctuating population size in nature.

In his student years Chetverikov became involved in the collecting work of the ornithologist and biogeographer Petr P. Sushkin (1868–1928), then a privatdocent at the university. On the basis of material from Sushkin’s 1902 expedition to Minusinsk and the western Sayan mountains, Chetverikov published two notes in German, one naming a new species (1903) and the other establishing four new species and two subspecies (1904). In 1904 he participated in Sushkin’s expedition to the Tarbagatai mountain range. Subsequently, with Sushkin and Sushkin’s young wife Anna Ivanovna, he participated in expeditions to the Minusinsk region, the western Sayans, and Lake Zaisan. As a graduate student, he classified the butterfly material collected on Leo S. Berg’s expedition to the Aral Sea in 1900–1902 (1907), and on Sushkin’s various expeditions. In 1910, when Sushkin left Moscow to become a professor at Kharkov University, Anna Ivanovna divorced him to marry Chetverikov.

Political disputes at Moscow University beginning in 1909 caused Kol’tsov to move his teaching to the Shaniavskii Municipal University and to the zoology department of the physicomathematical faculty of the Beztuzhev Advanced Courses for Women. On 12 November 1909 Chetverikov joined him as his laboratory assistant in the zoology department of the Beztuzhev courses, organizing an insect room and opening his own specialized course in entomology. In 1911 he published an account of the Lepidoptera collected on B. M. Zhitkov’s 1908 expedition to the lamal Peninsula. In 1913 he traveled to the Crimea and subsequently reported on its butterflies (1915). In 1916 he published a long article on butterflies for an anthology, edited by Kol’tsov, of observations of seasonal variation in the flora and fauna of the Moscow area.

Chetverikov’s professional expertise led to scientific recognition. In 1913 he was elected to the Moscow Society of Naturalists. The next year he founded the Moscow Entomological Society and became editor of its journal At its opening meeting on 1 March 1914, Chetverikov presented his first major theoretical paper, “Osnovnoi faktor evoliutsii nasekomykh” (The fundamental factor of insect evolution, 1915; American translation, 1920). Noting that the early fossil insects are among the largest known, he asked why insects have evolved toward smaller forms, in contrast to vertebrates, which have evolved toward larger ones. On the basis of calculations of the relative strengths of internal and external skeletons of different sizes, he argued that the “fundamental cause” of the evolution of insects was their outer chitinous skeleton.

… thanks to which they were in a position, by continuously diminishing the size of their body, to conquer for themselves an entirely independent place among the other terrestrial animals, and not only to conquer it, but to proliferate in an endless variety of forms and thereby acquire a tremendous importance in the general economy of nature. Thus, their smallness became their strength. (1915, p. 24)

On 11 October 1916 Chetverikov was elected to the Russian Entomological Society of St. Peterburg.

During the civil war (1918–1922), the exigencies of the time led most Russian scientists to take on multiple jobs. Chetverikov managed to become preparator and temporary director of the zoological section of the State Polytechnical Museum in Moscow, where he worked part-time from 1920 to 1924. He published two popular manuals on how to collect butterflies (1919, 1925) and a study of the Lepidoptera from the Minusinsk region. The Zoological Museum of the Academy of Sciences declared his collection of butterflies to be one of the best in the country and urged that special measures be taken to ensure its preservation. He was invited to write the article on butterflies for the Great Soviet Encyclopedia (1926); it was his last publication on butterflies for thirty years.

The Kol’tsov Institute . Chetverikov would later characterize the decade 1919–1929 as the most productive and interesting period of his creative life. During these years, in connection with new teaching and research responsibilities. Chetverikov moved from butterfly systematics into biometry and genetics, developing a highly original view of the evolutionary process that led to pathbreaking studies of the genetics of natural populations.

After 1917, when the Beztuzhev Advanced Courses for Women became the Second Moscow University, Chetverikov was promoted from laboratory assistant to a lecturer in Kol’tsov’s department. On 1 November 1919 the two Moscow universities were united and Chetverikov became a lecturer there, teaching a course on general entomology. In addition, he opened a new course, “Introduction to The oretical Systematics,” which he taught from 1919 to 1929. Initially the course treated the nature of species, interspecific and intraspecific variation, and quantitative methods. Through his brother Nikolai, Chetverikov had become interested in biometrics, and the course applied statistical and biometric techniques to the analysis of variation in species and populations. Then in 1921, Kol’tsov invited Chetverikov to join the staff of his Institute of Experimental Biology.

Since 1900 Kol’tsov had planned a research institute of laboratory biology, in 1916 he was finally able to obtain sufficient philanthropic funding, and he set up the Institute of Experimental Biology in a house in the Moscow merchant quarter. After the revolution, the loss of the institute’s endowment forced a change in its research program: no longer able to afford expensive imported laboratory equipment and forced to cultivate new patrons. Kol’tsov obtained support from the Commissariat of Agriculture (for animal breeding studies) and the Commissariat of Public Health (for work on blood chemistry and eugenics). As a butterfly taxonomist without experience in agricultural or experimental research, Chetverikov did not figure in these plans.

In 1919, when word reached Russia of the remarkable developments in genetics by William Bateson (on poultry), W. E. Castle (on guinea pigs), and T. H. Morgan and his school (on Drosophila), Kol’tsov undertook studies, with V. N. Lebedev, on the inheritance of coat color in guinea pigs, and set his student Aleksandr Serebrovskii to work on the genetics of poultry. The same year, under Kol’tsov’s direction, Dmitrii Romashov attempted to produce mutations in Drosophila through the use of X rays, but the experiments were unsuccessful, owing largely to the institute staff’s inexperience with insects in general and with Drosophila in particular. It seems likely that Chetverikov was invited to join the institute in 1921 because he was the one figure in Kol’tsov’s network who knew a great deal about insects.

Upon his appointment to the Institute of Experimental Biology (IEB) Chetverikov began to work with a number of Kol’tsov’s graduate and undergraduate students. The original group (1921–1922) consisted of his wife, Anna Ivanovna; Nikolai Vladimirovich Timoféeff-Ressovsky (1900–1981); Elena Aleksandrovna Fiedler (1898–1973), who subsequently married Timoféeff-Ressovsky and adopted his name; Dmitrii Dmitrievich Romashov (1899–1963); Sergei Romanovich Tsarapkin (1892–1960); and Aleksandr Nikolaevich Promptov (1898–1948), an ornithologist. In the next two years, five bright undergraduates from Moscow University joined the group: Boris L’vovich Astaurov (1904–1974);Elizaveta Ivanovna Balkashina (1899–1981), who subsequently married Romashov; Nikolai Konstantinovich Beliaev (1899–1937); Sergei Mikhailovich Gershenzon (1906-); and Petr FomichRokiiskii (1903–1977).

Originally the group focused on general zoological questions of systematics, evolution, biometrics, and genetics. In August 1922 Hermann J. Muller visited Kol’tsov’s institute and its Anikovo genetics station, headed by Serebrovskii, and brought with him Drosophila cultures containing the famous mutants that had been the basis for the researches of the Morgan school. After consultations it was decided that the flies would go to Chetverikov’s group, and that, in addition to pursuing their own research, all members would work together with the Drosophila.

From 1922 to 1924 most of the group’s work was directed at mastering the theory and practice of Morganist genetics. The summers were spent at the IEB’s hydrobiological station at Zvenigorod, headed by the hydrobiologist S. N. Skadovskii, which had been commissioned by Glavryba (the central administration of fisheries) to inventory the fauna of lakes in the region. During the winters the group worked with Drosophila in the laboratory at the IEB and held informal seminars at the apartments of group members. The discussion format was set by Chetverikov, who perused newly arrived issues of Western scientific journals for articles on genetics and assigned them to seminar members to report on. In this way, Chetverikov and his students learned genetics.

Around 1925 Chetverikov dropped his entomology course at Moscow University and opened its first genetics course. At about the same time, he organized his seminar on a more formal basis. It became known as the So-or, an acronym for sovmestnoe oranie (literally, “concerted cacophony” or, more loosely. “Screeching society”) it is sometimes referred to as the “genetic so-or” or the Droz-So-or (for Drosophilists). In order to keep the group small and its discussions focused, its membership was restricted, although the institute’s senior staff attended when they could. Candidates for membership were admitted only by a unanimous vote of the group.

The 1926 Paper . In the fall of 1925, Chetverikov completed a paper that has come to be regarded as one of the founding documents of the evolutionary synthesis. It was published the next year in Zhurnal eksperimental’ noi biologii. edited by kol’tsov, under the title “O nekotorykh momentakh evoliutsionnogo protsessa s tochki zreniia sovremennoi genetiki” (On certain aspects of the evolutionary process from the viewpoint of modern genetics). Chetverikov defined the paper’s goal as “clarifying certain questions on evolution in connection with our current genetic concepts” (1961. p. 169).

The first section of the paper, dealing with mutations in nature, seeks to establish the relevance of genetics to evolutionary theory. At the time, such relevance was far from obvious: many genetic variations appear in the laboratory setting and under domestication, but natural populations appear remarkably uniform phenotypically. Lamarckians argued that such variations were probably produced by changed conditions of existence and an inheritance of acquired characteristics, Orthogeneticists who believed that there were no’ random’ variations regarded their appearance as part of an internally unfolding process of species development.

Chetverikov pointed out that, contrary to what would be expected if Lamarckians were right, at the present time “we are not only completely unable to produce desirable mutations artificially, but are even unable to influence the frequency of their occurrence” (1961. p. 170). Furthermore, contrary to what might be expected if the orthogeneticists were right, most mutations observed in the laboratory are harmful. This fact, he wrote, explains why we do not observe such variations in the wild, for’ in the severe struggle for survival, which reigns in nature, the majority of these less viable mutations, originating among normal individuals, must perish very quickly, usually not leaving any descendants’ (1961. p. 171).

Chetverikov also argued against the widely held view advocated by Leningrad’s leading geneticist, lurii A. Filipchenko, that microevolution and macroevolution are qualitatively different. Observing that’ along with ‘harmful’ freakish mutations, there is also a series of ‘neutral’ ones, not having any biological significances and therefore not subject to selection” he emphasized that “some of these ‘biologically neutral’ mutations occurring randomly in the normal populations of some species or other sometimes correspond to the’ normal’ features of neighboring species or even genera and families” (1961, p. 172). Drawing on his expertise in insect taxonomy, he gave a string of examples from the systematics of Diptera and Lepidoptera, emphasizing that “alongside the least salient traits, such as the color of the body, such important characters of Drosophila are changed as venation, wing structure, etc., which are fundamental in the modern systematics of insects for distinguishing the higher systematic categories” (1961, p. 173).

The second section of the paper relates biometrics to the problem of the species. Chetverikov’s species concept is that of a Paarungsgemeinschaft (freely crossing community). Drawing on G. H. Hardy’s law of equilibrium under free crossing (1908) and Karl Pearson’s law of stabilizing crossing (1904), Chetverikov pointed out that new variations would not be “swamped” through crossing, as Fleeming Jenkin had argued. To the contrary, in the absence of selection, mutation, or migration, new variations would be maintained in a sufficiently large population at a constant frequency by the process of free crossing.

This fact led Chetverikov to two important deductions. The first was that “a species, like a sponge, soaks up heterozygous [recessive] mutations, while remaining from first to last externally (phenotypically) homogeneous” (1961, p. 178). Thesecond, harkening back to Chetverikov’s 1905 essay on “waves of life,” concerned the effect of population size on the phenotypic expression of mutations. Chetverikov calculated that “on the one hand, the more numerous the population, the greater are the chances for origin of new mutations in it… the less numerous… the greater is the probability of manifestation in it in homozygous form of mutations absorbed by it earlier” (1961, p. 178), because the probability of homozygous expression through inbreeding is greatly increased. This led him to conclude that

isolation entirely automatically leads to a differentiation within a species, to the fact that the colonies of one species, isolated from each other, begin, with time, to manifest differences in individual characters, which may be detected either by direct morphological study, or by biometric evaluation of their means and variabilities. And so, isolation, under the conditions of a process of continuous accumulation of mutations becomes, by itself, a cause of intraspecific (and consequently, eventually, also of interspecific) differentiation. (1961. p. 179)

Chetverikov argued that this “genetic” effect of isolation helped to explain the geographical races and insular faunas described by A. P. Semenov-Tian-Shanskii, J. T. Gulick, A. Garrett, A. G. Mayer, and H. E. Crampton.

The third section of Chetverikov’s paper, “Natural Selection,” analyzes the role of selection under conditions of free crossing with genotypical variability. He based his analysis on a table prepared by H. T. J. Norton in R. C. Punnett’s Mimicry in Butterflies (1915), a book Chetverikov knew because of his work on Lepidoptera systematics. The table gives numbers indicating the relationship between different selection intensities, the frequencies of dominant and recessive mutations, and their rate of change in generations.

From the table Chetverikov drew three important conclusions. First, any advantageous mutation entering such a population will not be swamped, but has a definite chance of spreading throughout the population: hence, “Darwinism, in so far as natural selection and the struggle for existence are its characteristic features, received a completely unexpected and powerful ally in Mendelism” (1961, p. 183). Second, all other things being equal, the advantageous mutant will eventually be present in all the members of the species—hence, in the absence of isolation, never “does the species give rise to a new species, never will there be a subdivision of the species into two, never will speciation occur” (1961, p. 184). Chetverikov documented actual cases of this replacement, drawing principally on his own knowledge of Lepidoptera systematics. If isolation occurs or selection ceases, he noted, the species will remain polymorphic. Third, because Norton’s table showed that dominant mutations are eliminated or incorporated much more quickly than recessives, Chetverikov concluded that natural selection promotes the accumulation of recessive genes in the population.

Chetverikov used these conclusions to address two central evolutionary problems: adaptation and speciation. Nonadaptive evolutionary processes, he argued, are possible in nature: “Systematics knows thousands of examples where the species are distinguished not by adaptive but rather by neutral (in the biological sense) characters, and to try to ascribe adaptive significance to all of them is work which is as little productive as it is unrewarding.” The actual process of speciation, in Chetverikov’s view, may be such a process, since “Not selection, butisolation is the actual source, the real cause of the origin of species” (1961, p. 188). For Chetverikov, evolution consists of two processes: “the process of differentiation, of splitting-up, leading in the end to speciation—isolation is its basis; the other leads to adaptation, to the progressive evolution of organic life, and its cause lies in the struggle for existence and the resulting natural selection” (1961, p. 189).

The fourth section of the paper, “Genotypic Milieu,” emphasizes the creative role of natural selection in the evolutionary process. On the basis of data on gene interaction, expression, and pleiotropy de veloped by the Morgan school and also during the period 1922–1925 by N. V. Timoféeff-Ressovsky, a member of the So-or, Chetverikov argued that all traits are “a complex result of the manifold interaction of all the genes comprising the genotype of the organism” (1961, p. 189), and that’ The very same gene will manifest itself differently, depending on the complex of the other genes in which it finds itself’ (1961, p. 190). From this Chetverikov concluded that there is no difference in principle between qualitative and quantitative variation; that observed “correlative variability” is a result of gene inter action; and that In selecting one trait, one gene, selection indirectly also selects a definite genolypic milieu, a genotype, most favorable for the manifestation of the given character….Selection results in the enhancement of the trait, and in this sense it actively participates in the evolutionary process’ (1961, p. 191).

Chetverikov’s paper closes with an agenda for the future:

… it is still too early to speak of a synthetic formulation of the evolutionary process. Only after we have disentangled the basic principles and regularities underlying the evolution of organisms in the widest sense of the word, as well as the phenomena of speciation, only then will we finally be able to attempt a reconstruction of the definitive structure of evolution and a consideration of its separate parts and finer details. (1961, p. 193)

This view of a coming evolutionary synthesis proved prophetic, and Chetverikov’s paper helped to bring it about. By establishing the relevance of genetics to the problem of the origin and evolution of species in nature, he helped to transform population genetics into evolutionary genetics.

Genetics of Natural Populations . The logic of Chetverikov’s 1926 paper led to the prediction that, despite their apparent phenotypic uniformity, natural populations should contain large numbers of hidden recessive mutants that can be revealed by genetic analysis. In the summer of 1925, members of Chetverikov’s group conducted the first studies of natural populations of Drosophila. In exchange for his help in the posthumous study of Lenin’s brain, the director of the Kaiser Wilhelm Institute for Brain Research, Oscar Vogt, had requested that a young Soviet geneticist be sent to help establish a genetics laboratory at his institute. Kol’tsov recommended Nikolai Timoféeff-Ressovsky and in 1925 he and his wife, Helena, were posted to Buch, near Berlin. Late that summer they collected seventy-eight pregnant female Drosophila melanogaster on the grounds of the Buch research station and mated the F₁s brother x sister. Such inbreeding revealed in the F₂s the presence of a number of mutations that had been hidden in heterozygous condition.

In Moscow, parallel studies using the same technique began in the summer of 1925 on populations of four Drosophila species found in the environs of the Zvenigorod station. Beliaev studied twenty-two inbred lines of Drosophila phalerata Meig.; Astaurov studied twenty-seven lines of Drosophila phalerata Meig. and twenty-two lines of Drosophila transversa Fall.; Balkashina studied the nine lines of Drosophila vibrissina Duda: Gershenzon studied nineteen lines of Drosophila obscura Fall. However, these four species proved difficult to cultivate in the laboratory, so in 1926 the work at Zvenigorod continued on Drosophila melanogaster.

The use of this species involved advantages and drawbacks. It was easy to cultivate and study in the laboratory, and its genes had been thoroughly mapped and studied by the Morgan school. However, the appearance of a recognizable mutant in wild populations might be interpreted as the result of their contamination by laboratory stocks. For this reason, in 1926 Gershenzon and Rokitskii captured over 300 fertilized females in Gelendzhik, a remote mountainous region in the Caucasus. From them 239 inbred lines were established and studied, and 32 clearly identifiable mutations were discovered in their progeny. Surprisingly, the polychaeta recessive appeared in approximately 50 percent of the lines. Chetverikov reported preliminary results from the Berlin and the Gelendzhik populations at the Fifth International Congress of Genetics (Berlin, September 1927), and his German summary was published in 1928.

By 1929 Chetverikov was preparing to publish his results more widely. In 1928 the journal Nauchnoe slovo announced the forthcoming publication of an article by Chetverikov titled “The Role of Mutations in the Evolution of Organisms.” Most significantly, in the Chetverikov archives are two handwritten versions of an English text of his 1926 paper, probably dating from early 1929, with additional sections discussing the discovery of the mutagenic effect of X rays (1927) and summarizing his group’s studies of natural populations.

This English version was never sent abroad, however, and some of the investigations of the Chetverikov group were not published until the mid 1930’s (Gershenson, 1934; Balkashina and Romashov 1935). According to Astaurov,’ By far the most abundant material was collected on Drosophila melanogaster in 1926, and to this very day it has not been published in any complete form’ (1974, p. 64). The principal reason was Chetverikov’s arrest.

Arrest and Exile . In the spring of 1929 Chetverikov was detained by agents of the secret police (OGPU) and spent several months in its Butyrka prison in Moscow, after which he was sent into exile for six years by administrative order. No formal charges were ever brought against him and there was no trial. Chetverikov never learned the exact reason for his arrest.

Two related scenarios have been suggested. The first concerns the “Kammereraffair.” In the mid 1920’s there was strong support for the inheritance of acquired characteristics in the Communist Academy, which invited Paul Kammerer to Moscow to head a laboratory. A famous Viennese biologist and an outspoken socialist, Kammerer claimed to have demonstrated Lamarckian inheritance in salamanders. After articles by G. K. Noble and Hans Przibram in the 7 August 1926 issue of Nature suggested that his results were fraudulent, Kammerer killed himself. His obituary in Izvestiia (7 October 1926) mentioned a postcard, apparently sent by a Professor Chetverikov, “congratulating the Academy on Kammerer’s suicide” and castigated Chetverikovas “one of the reactionary obscurantists left behind in the U.S.S.R.” The next day Izvestiia published a letter from Chetverikov stating that he had sent no such postcard and that it was a malicious forgery. Chetverikov later conjectured that the same person who had forged his signature on the postcard in 1926 might have denounced him in 1929.

Second, Chetverikov’s arrest may have had something to do with the Droz-So-or. In a letter dated 28 July 1929 to Maxim Gorky seeking aid in obtaining Chetverikov’s release, Kol’tsov explained:

Early this year at the time of my stay in Paris, a stupid incident occurred among the graduate students at my Institute…. Tempers flared, and some of the students took it all out on S. S. Chetverikov. At the University they drew up an indictment of him consisting of ten charges…. The charges were published, and several days later Chetverikov was arrested…. (Shvarts, 1975, p. 256)

The nature of the “stupid incident” remains unclear. Chetverikov may have been denounced by a student who had been refused admission to the Dro-So-or; or by a member of the group whose wife had been blackballed: or by a colleague or rival who was envious of his popularity and influence. Until his secret police dossier is examined. we cannot know.

Whatever the cause of Chetverikov’s arrest, its consequences are clear. Within a year his entire group had been dispersed. Beliaev left in 1929 to work at the Central Asian Silkworm Breeding Institute in Tashkent; Astaurov joined him in 1930; Gershenzon accepted posts at the Zoological Institute of Moscow University and in Serebrovskii’s laboratory at the Timiriazev Institute in 1930; Promptov joined the staff on the Second Moscow Medical Institute; Rokitskii joined the Institute of Animal Breeding of the newly created Lenin All-Union Academy of Agricultural Sciences. Chetverikov’s wife stayed in Moscow but ceased to work at the IEB. Only Balkashina and Romashov remained. In the words of Astaurov (1974), “by 1930 the laboratory had effectively ceased to exist”.

By administrative order of the OGPU. Chetverikov was exiled to Sverdlovsk in the Urals for three years (1929–1932). During the first year and a half he was unemployed. In 1931 he became a scientific consultant to Gorkomkhoz on the planning and organization of a zoo at Sverdlovsk’s Park of Culture and Recreation. On 12 April 1932 his period of internal exile was extended for three years. In 1932 he moved to Vladimir, where he worked from 1 October as a teacher of entomology and biometrics at the Ministry of Agricultures Uchkombov (the scientific collective for the fight against agricultural and forest pests). After it closed in the fall of 1934, he taught mathematics at the ministry’s agricultural technikum in Vladimir.

Gorki and Silkworms . Following the expiration of his term of exile in 1935, Chetverikov reestablished a biological career in the city of Gorki. In 1933 I. I. Puzanov, who had known Chetverikov at Moscow University, accepted the chair in vertebrate zoology at Gorki University and became dean of its biological faculty; his assistant was Zoia Safronovna Nikoro, a docent in genetics. In 1935, on the initiative of Nikoro, Puzanov invited Chetverikov to head the genetics department of Gorki University beginning that fall. He accepted, and lived in a dormitory in Gorki until 1936, when he obtained an apartment. Thereupon his wife joined him, bringing his enormous butterfly collection.

As head of the genetics department, Chetverikov gave a course in entomology and a course in genetics (1935–1948). He also gave popular lectures; one of them, on developments in cytogenetics during the previous decade, was issued as a pamphlet (1936). In 1936 Puzanov was replaced as dean by A. D. Nekrasov (1874–1960) who, like Puzanov, was a friend of Chetverikov’s from Moscow University. The three Muscovites formed a Gorki branch of the Moscow Society of Naturalists. In the late 1930’s despite Chetverikov’s open opposition to the views of Lysenko, he was strongly supported at the university by Puzanov, Nekrasov, Nikoro, the botanist S. S. Stankov, and others.

In 1938 Chetverikov was awarded the degree of Candidate of Biological Sciences without a dissertation and was made a full professor. In April 1940 he took over from Nekrasov as dean of the biological faculty, serving in that post through 1947. He was nominated for a doctorate of biological sciences and was awarded the degree in June 1945.

While in Gorki, Chetverikov devoted himself to research on silkworms. In the winter of 1937 he was approached by the scientific secretary of the Ministry of Agriculture with the proposal that he engage in breeding the silkworm for Russian conditions: silk was needed for parachutes, and Japan was no longer regarded as a reliable supplier. A small experimental base for this work was built outside of Gorki. The saturnid silkworm (Antherea pernyi Guér.-Mén.) is bivoltine, with two generations per year, the second hatching in late autumn. In its native habitat, October is mild; in Russia, the silkworms emerging in the fall freeze before they can spin cocoons. Chetverikov set about trying to develop a monovoltine strain.

In early 1940 Chetverikov reported on his progress at a conference on sericulture and published a preliminary account in its proceedings (1941). By 1944, at a scientific conference at Gorki University and at the seventh plenary meeting of the sericulture commission of the Lenin All-Union Academy of Agricultural Sciences, he could proudly report that his strain “Gorki Monovoltine No. 1” was under trials and produced silk of superior quality. In 1944 a monograph summarizing his six years of research was sent to the agriculture academy for publication. On 4 November of that year, the presidium of the Supreme Soviet awarded him a medal of excellence for his work.

Final Years . In the late 1940’s Chetverikov’s life became difficult for both personal and political reasons. On 2 July 1947 his wife died. Soon thereafter Chetverikov developed serious heart problems, leading him to resign as dean. The triumph of Lysenkoism in August 1948 led to Chetverikov’s separation from the university and the loss of his pension: on 13 August 1948 the Minister of Higher Education issued an order demanding “the dismissal of incorrigible Mendelist-Morganists” that mentioned Chetverikov by name. Although it was in press, Chetverikov’s silkworm monograph was never published and the manuscript may no longer exist. His’ Gorki Monovoltine No. 1’ was mixed with normal stock and the breed was lost.

After suffering a heart attack in September 1948, Chetverikov spent four months bedridden. He became partially blind, and by 1950 could not distinguish yellow from brown or gray from green. This made work with butterflies very difficult, so he gave his collection of more than 300, 000 specimens to the Zoological Museum of the Zoological Institute of the U.S.S.R. Academy of Sciences in Leningrad. In 1956 Chetverikov published his last scientific article, a description of a new species of Cucullia. That year he was visited by two former students whom he had not seen in thirty years, Helena and Nikolai Timoféeff-Ressovsky, the latter just emerging from the Gulag after a decade of imprisonment and exile.

An invalid during his final years, Chetverikov was looked after by his brother Nikolai, friends, and students. With their help he managed an active correspondence. Around 1958 he dictated his memoirs, dealing mainly with his student days, to Valery N. Soyfer. In 1959 he received word that he was to be a recipient of the Darwin Medal of the (East) German Academy of Sciences (Leopoldina), one of twenty-eight awarded to those who had made major contributions to the development of Darwinism and evolutionary theory. Because of ill health, however, he was unable to attend the award ceremonies.

On 13 June 1959 Chetverikov suffered a stroke and lapsed into a coma. He died during the night of 2 July, on the twelfth anniversary of his wife’s death.

Historical Significance . Immediately after Chetverikov’s death, his historical significance began to be recognized. In 1959 Theodosius Dobzhansky published an abbreviated English translation of Chetverikov’s classic paper: a full translation was published in 1961 by I. Michael Lerner, a Berkeley geneticist of Russian extraction. Thanks to these and other works, Chetverikov has come to be regarded, together with Haldane. Fisher, and Wright, as a founder of population genetics and the evolutionary synthesis.

Cheterikov’s evolutionary approach stands apart from that of his three cofounders. Unlike them, he had not been involved in agricultural breeding or eugenics; he did not begin with genetics and biometrics and deductively extrapolate their implications for evolution, given certain unrealistic, but mathematically necessary, assumptions. Rather, he began with a systematist’s concrete knowledge of natural populations and species, and sought to determine how recent findings in genetics and biometrics could illuminate their evolution in nature. Chetverikov used far less sophisticated mathematics than did Fisher, Haldane, and Wright, of course, but he spoke more directly to the concerns of practicing zoologists and naturalists.

In this sense, Chetverikov’s 1926 paper set the agenda for the second phase of the evolutionary synthesis (1935–1950). His treatment of the genetic dimension of interspecific variation, speciation, the role of isolation, and the implications of population size anticipated later works by Timoféeff-Ressovsky, Dobzhansky, Julian Huxley, and Ernst Mayr. His discussion of the genetic implications of small colonies and the evolutionary significance of the genotypic milieu foreshadowed the “founder principle” and the concept of the “good mixer” developed by Mayr and others in the 1940’s and 1950’s. His views on the selective neutrality of many genes and his critique of adaptationism anticipated the “neutral gene hypothesis” and the “punctuated equilibrium” theories of the 1970’s.

Although Chetverikov never resumed research in population genetics after his arrest in 1930, his work in the 1920’s exerted a powerful formative influence over its subsequent development. Romashov and Dubinin established a new group in population genetics at the Kol’tsov institute in 1932, and its internationally renowned research constituted a conscious extension of Chetverikov’s program. In Europe, population genetics and the evolutionary synthesis developed around Chetverikov’s students H. A. and N. V. Timoféeff-Ressovsky, who worked in Germany from 1925 to 1945. Dobzhansky had obtained Drosophila stocks from Chetverikov before he left Russia for the United States in 1927; a decade later, he drew upon Chetverikov’s perspective and reasoning in Genetics and the Origin of Species (1937), from which the evolutionary synthesis in the West is often dated. The same year, following Chetverikov’s lead, Dobzhansky began his series of forty-six articles on the genetics of natural populations that would form the core of American population genetics.

BIBLIOGRAPHY

I. Original Works. Chetverikov’s surviving papers (including lecture outlines, notebooks, typescripts, and manuscripts) are collected in fund 1650 of the Moscow branch of the Archive of the U.S.S.R. Academy of Sciences. In German his name is usually spelled Tschetwerikoff; in French, Tshetverikov, Tshetverikoff, or Tchetverikoff. During his lifetime he published more than thirty works. Ten have been republished in his Problemy obshchei biologii i genetiki (vospominaniia, stat’i, lektsii) (Problems of general biology and genetics [memoirs, ar ticles, lectures]). Z. S. Nikoro, ed. (Novosibirsk, 1983). Nine others are in his Fauna i biologiia cheshuekrylykh (Fauna and biology of butterflies and moths). G. S. Zolotarenko and Z. S. Nikoro, eds. (Novosibirsk, 1984).

Chetverikov’s earliest publication, and two others, are handbooks on how to collect insects: “Rukovodstvo k kollektsionirovaniiu cheshueskrylylskk (Lepidoptera)” (How to collect butterflies and moths [Lepidoptera]), in G. A. Kozhevnikov, ed., Rukovodstvo k zoologicheskim ekskursiiam i sobiraniiu zoologicheskikth kollektsii (Handbook for zoological expeditions and making zoological collections; Moscow, 1902); Kratkoe nastavlenie k sobiraniiu nasekomykh (Manual on collecting insects; Moscow, 1919); and Sbor i prigotovlenie zoologicheskikh kollektsii (Collecting and preparing zoological collections: Moscow and Leningrad, 1925), written with N. A. Bobrinskii. In addition, he published some twenty notes on butterfly systematics.

His three most important prerevolutionary works were’ Volny zhizni (Iz lepidopterologicheskikh nabliudenii za leto 1903 goda), (Waves of life [Observations of Lepidoptera in the summer of 1903]), in Izvestiia Imperatorskogo obshchestva liubitelei estestvoznaniia, antropologii i etnografii, 98 , Dnevnik zoologicheskogo otdeleniia, 3 , no. 6 (1905), 1–5 (106–110), republished in Chetverikov, 1983, 76–83; his dissertation. “Beiträge zur Anatomie der Wasserassel (Asellus aquaticus L.).” in Biulleten’ Moskovskogo obshchestva ispytatelei prirody, 1910, no. 4, 377–509; and “Osnovnoi faktor evoliutsii nasekomykh,” in Izvestiia Moskovskogo entomologicheskogo obshchestva, 1 (1915), 14–24, published in English as “The Fundamental Factor of Insect Evolution,” in Smithsonian Report for 1918, no 2566 (Washington, 1920), 441–449 After the revolution he published two articles for Bol’shaia sovetskaia entsiklopedia (Great Soviet encyclopedia): “Babochki” (Butterflies), in IV (Moscow, 1926), 264–275, and’ Biometriia’ (Biometry), in VI (Moscow, 1927), 338–344. See also his letter to the editor of the newspaper Izvestiia, 8 October 1926.

His classic theoretical paper was “O nekotorykh momentakh evoliutsionogo protsessa s tochki zreniia sovremennoi genetiki,” in Zhurnal eksperimental’ noi bioloii. ser. A, 2, no. 1 (1926), 3–54; summary in German, ibid., no. 4 (1926), 237–240; excerpts translated by Theodosius Dobzhansky in Cold Spring Harbor Symposia in Quantitative Biology, 24 (1959), 27–30; complete English trans by Malina Barker, ed. by 1. Michael Lerner, “On Certain Aspects of the Evolutionary Process from the Standpoint of Modern Genetics,” in Proceedings of the American Philosophical Society, 105 , no. 2 (April 1961), 167–195. The Russian original was republished, with notes dictated by Chetverikov to Valery Soyfer, in the mid 1950’s, in Biulleten’ Moskovskogo obshchestva ispytatelei prirody, Otdel biologi, 70 , no. 4 (1965), 33–74, and in Klassiki sovetskoi genetiki 1920–1940 (Classic of Soviet genetics 1920–1940; Leningrad, 1968), 133–170. A French translation was published as Les Lois de l’Hérédité (Mont-Pelerin, Switzerland, 1970).

The work of Chetverikov and his group on the genetics of natural populations was published only in abbreviated form. Before his arrest Chetverikov published only résumés of three conference papers: “Teoreticheskaia predposylka geneticheskogo analiza vidov roda Drosophila” (The theoretical premise of genetic analysis of Drosophila species). in Trudy Vtorogo S’ ezda Zoologov, Anatomov i Gistologov SSR v Moskve 4–10 maia 1925 g. (Proceedings of the Second Congress of Zoologists, Anatomists, and Histologists of the U.S.S.R., at Moscow, 4–10 May 1925 Moscow, 1927), 163–164;’ Eksperimental’noe reshenie odnoi evoliutsionnoi problemy’ (Experimental solution of one evolutionary problem), in Trudy Tret’ego Vserossiiskogo S’ ezda Zoologov, Anatomov i Gistologov v Leningrade 14–20 dekabria 1927 g. (Proceedings of the Third All-Russian Congress of Zoologists, Anatomists, and Histologists at Leningrad, 14–20 December 1927; Leningrad, 1928), 52–54; and’ Über die genetische Beschaffenheit wilder Populationen,’ in Verhandlungen des Fünften internationalen Kongresses fü Vererbungswissenschaft, Berlin, 1927, II (Leipzig, 1928), 1499–1500, repr. in Zeitschrift fü induktive Abstammungsund Vererbungslehre, 46 (1928), 38–39.

Due to Chetverikov’s arrest in 1929, all the longer treatments, though still partial, were by his students; H.A. Timoféeff-Ressovsky and N. W. Timoféeff-Ressovsky, “Genetische Analyse einer freilebenden Drosophila melanogaster population,” in Wilhelm Roux’ Archiv für Entwicklungsmechanik der Organismen, 109 (1927), 70–109; S. M. Gershenson.’ Mutant Genes in a Wild Population of Drosophila obscura Fall.,’ in American Naturalist, 68 , no. 719 (1934), 569–571; and E. I. Balkashina and D. D. Romashov, “Geneticheskoe stroenie populiatsii Drosophila. I. Geneticheskii analiz zvenigorodskikh (Moskovskoi oblasti) populiatsii Drosophila phalerata Meig., transversa Fall. i vibrissina Duda’ (The genetic structure of Drosophila populations. I. Genetical analysis of populations of Drosophila phalerata Meig,. transversa Fall. and vibrissina Duda of Zvenigorod, Moscow Province), in Biologicheskii zhurnal, 4 , no. 1 (1935), 81–106.

After 1930 Chetverikov published only three works: Tsitologiia nasledstvennosti za poslednie desiat’ let (The cytology of inheritance during the last decade; Gorki, 1936); “Selektsiia na monovol’tinnost’ u Kitaiskogo dubovogo shelkopriada Antherea pernyi Guer.-Mén.” (Selection for monovoltinism in the Chinese saturnid silkworm Antherea pernyi Guér.-Mén.), in Selektsiia i akklimatizutsiia dubovykh shelkopriadov (Selection and acclimatization of the silkworm; Moscow, 1941), 16–22; and “Novyi vid roda Cucullia Schrk, (Lepidoptera, Noctuidae) iz luzhnogo Priural”ia’ (A new species of the genus Cucullia Schrk. [Lepidoptera, Noctuidae] from the foothills of the southern Urals), in Russkoe entomologicheskoe obozrenie, 35 , no. 4 (1956), 927–928.

A brief autobiography by Chetverikov, in German, appears in Nova acta Leopoldina, n.s.21 , no. 143 (1959), 308–310. His memoirs, dictated to Valery Soyfer in 1958, have been published as’ Iz vospominanii’ (From the memoirs), in Priroda, 1974, no. 2, 68–69; Pervyi god v Moskovskom universitete’ (First year at Moscow University). ibid., 1980, no. 5, 50–55; and “Vospominaniia” (Memoirs), ibid., 1980, no. 11, 88–94, and no. 12. 76–85, and reprinted in Chetverikov (1983), 41–75.

II. Secondary Literature. For discussions in English specifically devoted to Chetverikov, see the articles by Mark B. Adams, “The Founding of Population Genetics: Contributions of the Chetverikov School, 1924–1934,” in Journal of the History of Biology, 1 , no. 1 (1968), 23–39. “Towards a Synthesis: Population Concepts in Russian Evolutionary Thought, 1925–1935,” ibid., 3, no. 1 (1970), 107–129, and “Sergei Chetverikov, the Kol’tsov Institute, and the Evolutionary Synthesis,” in Ernst Mayr and William B. Provine, eds., The Evolutionary Synthesis (Cambridge, Mass., 1980), 242–278; by Theodosius Duzhansky. “Evolution of Genes and Genes in Evolution.” in Cold Spring Harbor Symposia on Quantitative Biology, 24 (1959), 15–30, and’ Sergei Sergeevich Tshetverikov 1880–1959,’ in Genetics, 55 , no. 1 (January 1967), 1–3; by Hisao Kaneko and Kuniyoshi Ohta. “The Case of a Biologist: The Life of S. S. Chetverikov,” in Journal of the Humanities and Natural Sciences (Tokyo Keizai University), no. 60 (1982), 1–50, and “Supplement.” ibid., no. 62 (1982), 209–229 (in Japanese, summaries in English); and by I. Michael Lerner. “Introductory Note,” in Proceedings of the American Philosophical Society, 105 , no. 2 (April 1961), 167–169.

For sources in Russian, see the articles by B. L. Astaurov. “Dve vekhi v razvitii geneticheskikh predstavlenii” (Two landmarks in the development of genetic concepts), in Biulleten’ Moskovskogo obshchestva ispytatelei prirody, Otdel biologi, 1965, no. 4, 25–32, and “Zhizn” S. S. Chetverikova’ (The life of S. S. Chetverikov), in Priroda, 1974, no. 2, 57–67, and its revised version.’ Sergei Sergeevich Chetverikov (6 maia 1880–2 iiulia 1959): Zhizn “tvorchestvo” (… Life and work), in Chetverikov (1984), 78–98; by V. V. Babkov, “Tsentral”naia problema genetiki populiatsii” (The central problem of population genetics), in Chetverikov (1983), 6–40, and Moskovskaia shkola evoliutsionnoi genetiki (The Moscow school of evolutionary genetics: Moscow, 1985); by P. F. Rokitskii.’ S. S. Chetverikov i evoliutsionnaia genetika” (S. S. Chetverikov and evolutionary genetics), in Prioda, 1974, no. 2, 70–74, and “S. S. Chetverikovirazvitie evoliutsionnoi genetiki” (S. S. Chetverikov and the development of evolutionary genetics, in Izistorii biologii (From the history of biology), no. 5 (Moscow, 1975), 63–75; by V. N. Soyfer.” Neizvestnaia rabota S. S. Chetverikova po populiatsionnoi genetike” (An unknown work of S. S. Chetverikov on population genetics), in Iz istorii biologii (From the history of biology), no, 3 (Moscow, 1971), 177–192; by Anatolii Shvarts. “Dve sud”by’ (Two fates), in Novyizhurnal (New York), no. 121 (December 1975) 248–269; by N. V. Timoféeff-Ressovsky and N. V. Glotov, “Sergei Sergeevich Chetverikov, 1880–1959,” in Vydaiushchiesia sovetskie genetiki (Leading Soviet geneticists; Moscow, 1980) 69–76; and by G. S. Zolotarenko, “Posleslovo” (Afterword), in Chetverikov (1984), 71–77.

Mark B. Adams