The 1948 International Congress of Genetics in Sweden: People and Politics
Bengt O. Bengtsson, Anna Tunlid


The International Congresses have played an important role in the history of genetics. The Eighth International Congress, which in 1948 was held in Sweden, celebrated the conclusion of the war against Nazism and many new decisive scientific advances. It also signaled a hardening of the fight against Lysenkoism, which was growing in strength in the Soviet Union. A rare document is available from the Congress—an amateur film made by a young delegate, Nils Nybom. With its help a living description can be given of the scientific and political melees in which the delegates were involved.

Anecdotal, Historical and Critical Commentaries on Genetics

The period immediately following a war is a most difficult one in which to organize an international congress. (M. Demerec, 1948, in Bonnier and Larsson 1949, p. 85)

THE Eighth International Congress of Genetics was held in 1948. After an ambitious pre-Congress visit to University of Lund and plant breeding stations in southern Sweden, the main proceedings took place in Stockholm on July 7–14. The delegates met at Medborgarhuset, a striking example of modern Swedish architecture with grandiose front steps on which the participants relaxed between talks. Excursions outside Stockholm were made to the royal mansion Drottningholm with its 18th-century opera house and to the University of Uppsala. The details of the Congress are recorded in the Proceedings that were published as a supplement to Hereditas (Bonnier and Larsson 1949).

During the Congress a young Swedish student, Nils Nybom (1925–1970), later a professor of horticultural genetics at the Swedish Agricultural University, filmed all outdoor events with his small hand-driven camera. He had a cinematographic talent, and the film that he produced (8 mm, black and white, no sound, ∼25 min long) is a valuable and moving document of the Congress and its participants. The single copy of the film is owned by the Mendelian Society in Lund, and it has now been cleaned, digitalized, and re-edited. For those with internet access of sufficient quality it can be seen at When specific participants are referred to in this text, the accompanying numbers indicate at what point in the film they can be seen.

The International Congresses of Genetics have been of great importance for the development of the discipline (Haynes 1998), and due to the centrality of genetics for all kinds of human affairs, they have often carried strong political undertones. The 1948 Congress was perhaps more political than any of the others, and to most of the participants it must have felt like a victory congress because it marked the commencement of normal scientific exchanges after the defeat of Nazi Germany and its allies in the Second World War. The ongoing growth of genetics as an academic and applied science must also have felt like an important achievement. Much had happened both internally and externally to the discipline since the preceding congress in Edinburgh in 1939, and genetics was on its way to become one of the most important sciences in the post-war world. The Congress marked, however, not only past victories but also an important coming fight, namely the fight against the Stalinist version of hereditary science, Lysenkoism. This hotchpotch of ideas in which the inheritance of acquired characteristics played an important part had been lying low since the beginning of the war but was now again raising its head. We consider the people and politics involved in these bellicose interactions and start by describing the misfortunes of the preceding International Congress of Genetics of 1939, which partly explain why Sweden was chosen to host the Congress in 1948.


The various misfortunes of the Seventh International Congress of Genetics can be followed in its Proceedings (Punnett 1941). It should have been held 1937 in Moscow, but the local organization committee ran into problems with the Lysenkoists and the political control over science (Soyfer 2003). An attempt to postpone the Congress for one year did not help, so the Permanent International Committee under its chairman Otto Mohr from Norway transferred the task to the British geneticists, who invited the Seventh International Congress of Genetics to meet in Edinburgh on August 23–30, 1939.

The organizational problems were many. The eminent Russian geneticist Nicolai Vavilov was forbidden by the Soviet authorities to attend, as were all other Soviet scientists. And just as the geneticists began to assemble in Edinburgh it became clear that the Second World War was imminent. Many participants were recalled to their countries and left in haste, sometimes even without having had time to register, while others decided to stay in Britain and/or claimed refugee status. “But amongst us there were some 150 Americans, Canadians, Australians, New Zealanders, South Africans and others for whom immediate departure was impracticable. These formed a most solid core of immovables, and as long as they remained the congress was in being” (Punnett 1941, p. 6). Thus, the Seventh International Congress kept on lecturing, demonstrating, and discussing genetics until the eve of war. As for the next congress, the Italians made an offer to hold it in Rome in 1942, but it was decided to give the Permanent International Committee, now with Congress President F. A. E. Crew as its chairman, full authority to decide where and when it should be held.

Many private and official contacts and conflicts preceded the decision to ask Sweden to hold the Eighth International Congress of Genetics (Bonnier and Larsson 1949; Tunlid 2004). Important of course was the high international standing of the Swedish genetics community; with 18 participants, Sweden constituted the sixth largest contingent to the Edinburgh Congress after Great Britain and Northern Ireland (229), the United States (131), Germany (42), France (29), and India (21). The fact that, as a neutral country, Sweden had escaped the war and could offer the delegates some relative prosperity also played a role. As did the fact that the leading Swedish geneticists were well known and easily accepted by their victorious British and American colleagues. Many of them had traveled extensively in the United States in the 1930s with the aid of Rockefeller grants, and both F. A. E. Crew and Cyril Darlington (20:25) from Britain had made successful visits to Sweden during the war [where the latter for intelligence purposes noted the political sentiments among the younger scientists (Hagberg 2006, p. 101)].

Finally, the close contacts, often personal, between Swedish and Russian geneticists were very important. There was a strong sentiment in the genetics community that as much help as possible should be given to the embattled geneticists in the USSR (Krementsov 1996). And if they could not organize an International Congress themselves, perhaps they would at least be allowed to visit such an event in Sweden, a country with which the USSR had good contacts?

After some discussions about organizing a congress jointly with Denmark in 1947, which failed primarily because the International Microbiological Congress was held in Copenhagen that year, Crew, on behalf of the Permanent International Committee, decided to hold the Congress in Stockholm in July 1948. An organization committee was formed, which was headed by the human geneticist Gunnar Dahlberg, with plant geneticist Arne Müntzing (2:45) as vice chairman and drosophilist Gert Bonnier as general secretary. They all belonged to a young generation of internationally minded geneticists known for their critique of anti-Semitism. They represented the three main centers of genetic research in Sweden: Uppsala, Lund, and Stockholm. However, during the preparations for the Congress, Dahlberg fell seriously ill and could not take part in the event.

The organizing committee tried hard but was unable to solve its primary problem: it could not establish direct contact with the geneticists in the USSR to make it possible for them to attend the conference. Even worse, the fate of many of the Russian colleagues remained completely unknown. Did Vavilov live? [No, we know today. He had died in prison already in 1943 (Crow 1993).] And what about Timoféeff-Ressovsky, who for decades had worked in Berlin but had chosen to surrender to the Red Army? (Yes, he survived, but had to do top-secret radiation research in prison-like circumstances; his fate did not become known until many years later.)


The politics in the organization of the 1948 Congress to a large extent thus came to turn around questions of who was allowed and who was not allowed or in various ways discouraged from attending the Congress (Figure 1). All Soviet geneticists were warmly welcome, but they were not permitted by their authorities to come. What about the geneticists in various ways associated with Nazism or with any of the defeated countries? Were they welcome to attend?

Figure 1.—

The 1948 International Congress of Genetics in Stockholm. Courtesy of Nils-Olof Bosemark.

The question was sensitive, and it led to extensive discussions and frank exchanges among the organizers. It appears that the Swedish geneticists saw the Congress as a possibility for reconciliation, where geneticists from countries recently separated by war should be able to meet and (re)establish contacts. The decision, taken by the organizers of an earlier international congress on cell biology in Stockholm, to exclude German and Japanese scientists was thus deemed unacceptable to the geneticists. One understood, however, that respect must be shown to those who strongly reacted to the atrocities that had been committed during the war and who perhaps themselves had been exiled, detained, or imprisoned. The compromise found was to invite to the Congress only those Germans who could be regarded as generally acceptable. The German geneticist Hans Nachtsheim, who was considered “clean” in these matters (although see Paul and Falk 1999), provided a list of 18 “good” Germans who were all invited. Twelve of them, including Nachtsheim himself, attended the Congress, coming from all four postwar occupation zones. [They would soon find themselves in yet another conflict-laden situation, leaving, for example, Hans Stubbe (2:45) and Georg Melchers (8.54) in separate scientific communities in East and West Germany, respectively.] No particular restrictions were put on nationals from any other country, at least from the organizers' side. Referring to the handling of these questions, Milislav Demerec (7:21), from the United States but representing the Permanent International Committee, said that “courage and tact are required to handle the delicate situations that arise in preparing for an international meeting [immediately following a war]. Our Swedish colleagues are to be congratulated for the splendid work they have done. It is entirely to their credit that we are having a truly international congress” [Bonnier and Larsson (1949), p. 85; see also his positive description of the Congress in Science (Demerec 1948)].

According to the Proceedings, 610 geneticists from 41 countries registered with the Congress. By far the largest delegations came from Sweden (139), Great Britain (112), and the United States (100), while a number of nations contributed a substantial number of delegates, such as France (27), Italy (22), Portugal (19), and Denmark (18). A single geneticist came from, for example, Japan (H. Kihara; 16:51) and China (C. C. Li; 16:59). In the film, the delegates can be seen shaking hands, studying experimental fields, chatting between sessions, or just enjoying the sun. They were the victors: they had survived the war and were back in science.

The positive ambiance in the film should not, however, let us forget those who did not attend the Congress: the dead, the lost, those forbidden to attend, or those just not welcome. Next to Vavilov, the second most notable absentee was actually a Swede, Herman Nilsson-Ehle, the Nestor among Scandinavian geneticists (Bengtsson 1999; Tunlid 2004). At the beginning of the Mendelian era, he had performed world-famous research on quantitative variation, and as the head of the Svalöf plant breeding institute and one of the world's first professors in “ärftlighetslära,” he had incessantly promoted the development of genetics. For Nilsson-Ehle, it was a science of utmost importance for society, and he initiated the creation of Swedish research institutes for race biology (later human genetics), animal breeding, horticulture, and forestry research. Politically, he was a stern anti-Bolshevist and a staunch supporter of Germany. The geneticists from southern Sweden saw in him the obvious president for an international congress to be held in Sweden, just as his friend Erwin Bauer had been the president of the 1927 Congress in Berlin. But the times were different and the international colleagues protested against the suggestion. To Otto Mohr, the Norwegian geneticist with extensive international experience but also with the experience of having been interned during the German occupation, it was totally unacceptable to appoint Nilsson-Ehle to the presidency. In a letter to the General Secretary of the Organizing Committee, Gert Bonnier, Mohr wrote: “We mustn't forget that distorted genetics and race-swindle formed one of the founding stones of the despicable ideology of the Nazi. And here a man like Nilsson-Ehle should have had special talents to judge. That's why we expected more from him.” (Tunlid 2004, p. 244; our translation from Norwegian).

Thus, Nilsson-Ehle was never made president of the 1948 Congress, and he did not attend it either. Instead, Herman Muller (14:13), world-famous drosophilist who in 1946 had been awarded the Nobel Prize in Medicine for his work on radiation-induced mutations, was chosen, with the Finnish Lepidoptera geneticist Harry Federley (14:34) as vice president.


On Wednesday, July 7, the Congress started with a plenary session at which Muller gave his presidential address, “Genetics in the Scheme of Things” (Bonnier and Larsson 1949, pp. 96–127). Known to the audience not only for his scientific achievements but also for his strong philosophical and political views, the listeners were probably nevertheless surprised by the briefness of Muller's reference to the victory over Nazism. It would have been natural if he had dwelled on the atrocities performed by the defeated powers, often in the name of hereditary theories. But this he did not do. His presentation is of ∼11,500 words in its printed version and of these only 132 are devoted to Nazi policy. It obviously sufficed to him, since “this monster overreached himself so suicidally, and his psychoses are now sufficiently well understood, to require no further comment here” (p. 105). A certain vigilance, however, was still called for since “this danger is by no means entirely past, as is shown, for example, by the increasing influence of ex- and not-so-ex-Nazis among the staffs of the German universities in the Western zones.”

Muller's talk was divided into seven parts covering topics such as the origin of life, the mutational decay of humankind, and the disastrous effects of Lysenkoism. The fifth topic was “Present and Potential Victories of Genetics.” Here Muller made his personal comments on what was going to be presented in Stockholm and where the field of genetics was moving in general. Today it serves as a brief guide to the scientific content of the Congress.

For Muller, the main presentation was to be Charlotte Auerbach's description of “Chemical Induction of Mutations.” Auerbach (17:45) had worked on chemical mutagenesis during the war as a refugee in Edinburgh in collaboration with J. M. Robson, and in the film she is seen together with another brilliant Edinburgh geneticist refugee, Guido Pontecorvo (21:40). The topic of chemical mutagenesis that Auerbach, Demerec, and many others approached in the Congress was, of course, of great interest to Muller with his own background in radiation genetics. It was also an important step forward for genetics whose task it was “to bring us nearer to those elusive ultimate objects of our study, the genes.” Today, some 60 years later, it is difficult to comprehend how very much the participants in Stockholm knew about genetics, and how very little they understood about the structure and function of the gene. It is easy to follow Muller when he concluded that “we have good reasons to believe that … all … genes … have the same essential composition, inasmuch as they require a combination of some kind of nucleic acid or nucleic acid prototype with some kind of protein or protein prototype” (p. 108). But when the famous cytologist Cyril Darlington (Figure 2) ended his plenary presentation on “The Working Units of Heredity” by saying that the gene “is biologically adjustable in both length and breadth,” the statement probably made more sense in 1948 than it does today.

Figure 2.—

C. D. Darlington and R. A. Fisher in discussion during a break in the program. Courtesy of Nils-Olof Bosemark.

As a way to develop the understanding of genes, Muller mentioned the working out of “semi-allele (repeat) differences,” particularly the Rh system in man. In the film, R. A. Fisher (6:17), the theoretical originator of this work (Edwards 2007), can be seen marching between plant breeding plots in the almost only known footage of him. His own presentation to the Congress concerned tetrasomic inheritance in Lythrum, while it was up to his friend R. R. Race to describe their C, D, E–c, d, e interpretation of the Rhesus factor. From the Proceedings, one can understand that a heated discussion took place around this interpretation of the antigenic system.

Muller also showed special interest in studies on the “significance of various kinds of breeding systems” and made explicit references to the work by Cyril Darlington (20:25), Kenneth Mather (16:11), Ledyard Stebbins (10:38), and Ralph Erskine Cleland (18:07). Cleland is seen in the film in deep discussion with Gunnar Östergren (18:07), the Swedish geneticist who, by comparing B chromosomes to “genetic parasites,” had just cast doubt on the interpretations of genetic systems that assumed that they always evolve adaptively (Hurst et al. 1996).

The empirical and mathematical population geneticists were given their proper due by Muller, and at the end of the film a sequence is seen where Theodosius Dobzhansky and J. B. S. Haldane exchange pleasantries (23:45). Of the three founding fathers of theoretical population genetics—R. A. Fisher, J. B. S. Haldane, and Sewal Wright—the latter did not attend the Congress.

Muller, who liked to regard all questions from a higher perspective, found it easy to praise the evolutionary synthesis that was under development at the time, aiming to join genetics with other biological fields, including paleontology. In the relevant books by Dobzhansky and Stebbins, an important role is played by empirical examples taken from the Swedish plant geneticists who in the film are seen demonstrating field experiments: Göte Turesson (22:28), Arne Müntzing (5:12), Åke Gustafsson (8:14), Olof Tedin (5:48), and Albert Levan [who later became one of the pioneers of human cytogenetics (9:47)]. To this group of empirical evolutionists should be added the Dane Jens Clausen (11:08), who at this time worked on plant variation in California. In addition, the father of ecological genetics, E. B. Ford, who presented results on industrial melanism to the Congress, can be seen in the film (23:37), as can the heretic evolutionary geneticist Richard Goldschmidt (3:30), a refugee from Germany now at the University of California at Berkeley.

So far we have discussed Muller's views on the results from higher organisms. He was, however, adamant on how important research on microorganism was going to be in the future, now that genetics “has literally blasted its way into the core of bacteria and viruses.” Salvador Luria, who did not attend the conference, was acknowledged for his work on phages, and results on them were presented by Max Delbrück in his talk on “Genetic Experiments with Bacteriophages.” Georg Melchers (10:37) and German colleagues described their war-time research on viruses in Nicotiana. And a special indirect reference was given by Muller to Philip L'Héritier for his work on the inheritance of virus-like elements in Drosophila.

With respect to bacteria, Muller pointed to the fact that their “genetic material, or parts of it, can now be actually extracted and handled in vitro without loss of its viability—a possibility opening up remarkable opportunities for studies of the chemistry of the gene and of mutation” (p. 116). He was right, but not many concrete results were reported at the time. Luca Cavalli (his name then) presented data on chemical mutagenesis in Escherichia coli, as did Milislav Demerec, who referred to the work by Joshua Lederberg that made it possible to talk about “linkages” and “crossing over” also in bacteria. (Neither Joshua nor Esther Lederberg attended the Congress.)

Muller knew that “a rapidly growing group of fundamental biochemical reactions” was on its way to being unraveled in bacteria and “moulds.” With respect to the last group of organisms, the fungi, the Congress heard presentations by, among others, Boris Ephrussi (18:25), Guido Pontecorvo (21:40), and Laura Garnjobst (describing work done by Raymond W. Barratt, Edward Tatum, and herself). A second open scientific conflict in the Congress, in addition to the one concerning the inheritance of the Rhesus factor, was obviously played out between the well-known Danish yeast geneticist Øyvind Winge (18:34) and Carl Lindegren, who presented results on the “conversion of genes” that he claimed broke Mendel's rules and in which Winge did not believe. Winge's sensitivity can be partly explained by a heightened feeling of how important it was to defend genetics from all kinds of revisionist attempts now when Lysenkoism was threatening to make a comeback.


The largest parts of Muller's presidential address “Genetics in the Scheme of Things” were devoted to the genetics of humans and the necessity to fight against Lysenkoism. The questions are related, but we start with the first.

Not only some geneticists, but also some topics were notably absent from the Stockholm Congress. The Congress marked the end of a bloody world war, but it also marked the end of unbelievable atrocities performed in the name of hereditary science. However, as far as can be judged from the Proceedings, the topic of racism and fascist biological theory was never explicitly tackled in any presentation, except for some brief references at the opening of the Congress. J. B. S. Haldane (23:21) gave a technical plenary talk on “The Rate of Mutation of Human Genes,” while most of the presentations in the sessions devoted to human genetics concerned details of different hereditary diseases. The Dane Tage Kemp, newly appointed professor of genetics and eugenics in Copenhagen, had been invited to give a plenary presentation on “The Rise of Human Genetics,” but to judge from the Proceedings he gave a poor performance. The paper appears hastily written and may have been acceptable in the 1930s when Kemp was strongly supported by the Rockefeller Foundation (Koch 1996). In 1948, his advocacy for collecting and keeping a national register with detailed information on all asocial, handicapped, mentally deficient, and genetically ill individuals in Denmark must have sounded uncomfortable and out of date. The decade after the war saw a restructuring of the field of human genetics with old concerns shifting out of focus and new priorities developing (Kevles 1985). However, in Kemp's presentation to the Congress, not much of this was to be heard, with his insistence on eugenics being right and acceptable if performed with “trained medical knowledge” (as if lack of proper medical knowledge was the main problem with Nazi eugenic practices!). More in line with future trends was probably the presentation by Luisa Gianferrari on “The Genetics Consultory Board of Milan University” describing a free genetic counseling service, which indicated a move away from direct societal control over reproduction.

Muller's own contribution to the problem of human genetics consisted of his principled insistence on the need for human genetic improvement (or at least a fight against mutational deterioration). In this he continued his pre-World War II crusade for a “left-wing eugenics,” argued in the name of human rationality and expressed, for example, in the “Geneticists' Manifesto” (Crew et al. 1939). Unlike Kemp, who saw questions on human reproduction from a very narrow medical-governmental viewpoint, Muller regarded humankind from a lofty and abstract perspective and argued for the necessity that it rationally guide its own biological future. What he now in 1948 bitterly recognized was that not even in the most fully rational socialist or communist society could sound eugenic practices evolve spontaneously.

Actually, according to Muller, the situation in the summer of 1948 was moving in exactly the wrong direction. In the Soviet Union, where earlier Muller had worked but from which he had left in dismay in the 1930s, all genetic knowledge on which sound eugenics should be based was on its way to being banned:In that country, unfortunately, it has come to pass that genetics as we know it no longer finds a place in the official curricula and that it is regarded by the dominant group of officials as a dire heresy. Most of the main geneticists are, as the case may be, broken, executed, disgraced, not to be located, fugitives, forced into other work or, in the mildest cases, driven to such a redirection of their lines of research and publication as to give the appearance of working somehow in support of the doctrines approved by the [political] officials (p. 106).

Muller's outburst against Lysenkoism and his description of the political repression of genetics in the USSR comprised a substantial part of his presidential address (∼15%), and he himself found it so out of order that he introduced it with a disclaimer saying that he did not speak “in the role of an official of this Congress,” but that he was “convinced that these things should be stated here.” And he obviously knew what he was talking about. Soon after the Congress the Lysenkoists, with the full support of Stalin, grabbed power over all biological research in the Soviet Union and Eastern Europe. Muller described the event in a footnote to his address as printed in the Proceedings: “Approximately one month after the above words were spoken, the Central Committee of the Communist Party of the USSR announced its approval of the doctrine of inheritance of acquired characters, and of the attack on genetics by the charlatan Lysenko” (p. 108).

All Congress delegates in Stockholm knew that Lysenko and his followers had fought genetics since the 1930s (although Trofim Lysenko himself participated in the Ithaca Congress in 1932), but probably few expected that the Soviet Union would break with its positive image as an ally in the defeat of Nazi Germany by proclaiming there to be “bourgeois sciences” and forbidding all its communist supporters to adhere to genetics. The political situation in the world was, however, under rapid change: the Berlin blockade had started just days before the Congress began, and by the end of the year the Cold War was a somber reality.

A sign of the bitter and conflict-laden times ahead appeared at the plenary session that ended the Congress. Here 11 delegates from Bulgaria, Czechoslovakia, Poland, and Yugoslavia wanted to register their disagreement with “some of the statements made in the address of the President,” which they did not believe would “contribute to international scientific collaboration.” The motion was not discussed, but the petitioners were promised that their statement would be included in the Proceedings. International politics was more important than ever in the debate on inheritance (Krementsov 1996).


Some of the geneticists attending (Figure 3) the Congress in Stockholm are still professionally active, and they provide the rest of us with a link to the event. They also help make contemporary the entire history of genetics, since some of the delegates whom they met in 1948 at the Congress had themselves experienced the start of genetics in 1900. Foremost among these early geneticists was Erich Tschermak von Seysenegg (6:50), one of the rediscovers of Mendel's laws. In the film, he is seen happily smiling during his visit to the Svalöf plant breeding institute, a true link to the origin of genetics.

Figure 3.—

One of the lecture theaters before the start of the session. Courtesy of Nils-Olof Bosemark.

The Stockholm Congress was also the event where a woman, Charlotte Auerbach, played the leading scientific role, albeit in an environment dominated by men, although perhaps less so than expected. The number of women studying the plant breeding fields during the pre-Congress is high and, for example, at Uppsala Hedda Nordenskiöld (22:21) was one of the demonstrators. Attending the Congress were also some women who later would make contributions to the development of genetics, for example, Mary Lyon and Salome Gluecksohn-Schoenheimer (later Gluecksohn-Waelsh). One of the early leading Mendelian geneticist, Kristine Bonnevie from Norway, was registered to attend the Congress to talk about one of her mouse mutants, but died before its start.

Thus, with the aid of the Congress Proceedings and the remarkable film that Nils Nybom produced, it is possible even today to obtain an inkling of the many exciting and tension-laden dimensions that structured those summer days in Sweden. The genetic congresses that followed—from Bellagio in Italy 1953 to Berlin in 2008—would of course also carry political undertones and have exciting delegates, although probably somewhat less so than the Eighth Congress in Stockholm 1948.


Nils-Olof Bosemark, Arne Hagberg, Antonio Lima-de-Faria, and Udda Lundqvist all attended the 1948 Congress and have been most helpful in recognizing delegates in the film. We are also grateful for comments from audiences in Lund, Sweden; Cambridge, United Kingdom; and Berlin, Germany. Staffan Lindström helped with the re-editing of the film, and we owe him many thanks. The photographs have been kindly provided by Nils-Olof Bosemark. Part of this work was supported by the Mendelian Society in Lund.


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