(b. Ichenheim, Germany, 16 April 1875; d. Berlin, Germany, 2 December 1933)
botany, genetics, applied genetics, population genetics.
Life . Born into a family of distinguished amateur botanists, Baur was elder of the two sons of Wilhelm Baur, a pharmacist, and Anna Siefert Baur, an innkeeper’s daughter. The father was a founding member of the Baden Botanical Society (1981) and an authority on the mosses of the Black Forest region. He played a significant role in shaping Baur’s early interest in botany by including him on numerous walking tours and field studies. This youthful interest was reinforced and cultivated to a passion In an uncle, Ludwig Leiner of Constance, with whom Baur lived during the first three years of gymnasium study (1885–1888). In 1888 Baur’s family moved from the small rural town of Ichenheim lo Karlsruhe, where both sons attended the gymnasium. Although not an outstanding student, Baur thrived in the company of amateur and professional botanists he met through his father. By the age of seventeen he was an accomplished amateur botanist.
When Baur completed the Abitur in 1894, he was spiritually and intellectually prepared to study botany at the university. But at his father’s insistence he enrolled as a premedical student at the University in Heidelberg in the winter semester of 1894. After a few semesters he moved on to study at Freiburg in Breisgau, then Strassburg, settling finally in 1897 at the University of Kiel. Throughout his student years Baur faithfully attended lectures in botany and biology, coming under the influence of Friedrich Oltmanns, August Weismann, and Otto Reinke. But his awakened interest in theories of descent, inheritance, and development did not lessen the obligation to his father. At Kiel. Baur completed his medical studies, passed the medical Staatsexamen. and received the M.D. degree in March 1900. After a brief interlude as a ship’s doctor and as an assistant physician at psychiatric clinics in Kiel and Emmendingen, he abandoned medicine and psychiatry for doctored work in botany at Freiburg. Under the supervision of Oltmanns, he completed the doctorate in 1903 with a study of the developmental aspects of fructification in lichens.
In 1903 Baur became first assistant to Simon Schwendener at the University Botanical Institute in Berlin. He qualified as Privatdozent in 1904 with a work on the fungal bacteria, an area to which he never returned, having discovered by then the snapdragon Antirrhinum majus, his door to experimental genetics. The poor facilities and working conditions at Schwendener’s institute made a lasting impression on Baur and became a source of anxiety as he turned steadily toward the study of inheritance and variation. His position at the institute, moreover, was undermined by Schwendener’s retirement in 1910. With little prospect of obtaining a university chair, in 1911 Baur accepted a professorship in botany at the Landwirtschaftliche Hochschule at Berlin. In 1914 he opened its Institute for Genetic Research at Berlin-Friedrichshagen; this modest facility served as Germany’s first center for experimental and applied genetics. It also marked the beginning of an institutional campaign for Baur, whose massive and costly breeding studies precluded a return to the troubled bosom of the German universities.
World War I and its aftermath postponed Baur’s plan for a Kaiser Wilhelm Institute for Genetic Research distinct from the Kaiser Wilhelm Institute for Biology (headed by Carl Correns since its opening on 17 April 1915), The Kaiser-Wilhelm-Gesellschaft did, however, provide Baur with some assistance. As a result, in 1923, he opened a new Institute for Genetic Research at Berlin-Dahlem. Intended to narrow the existing gap between genetic research and its application to agriculture, the facility represented a major institutional breakthrough for Baur. At the same time, it enabled him to fill another important deficiency: With Paula Hertwig and Hans Nachtsheim, he galvanized at Dahlem a German research nucleus that utilized the principles and methods of classical genetics outlined by the Morgan school at Columbia. He remained at Dahlem until 1928, when, in response to his demand for a largescale program in applied genetics, he became director of the new Kaiser Wilhelm Institute for Plant Breeding and Genetic Research at Muncheberg. He headed the Müncheberg institute until his death.
Baur preferred rugged outdoor activity and rustic environs to urban life. After his marriage in 1905 to Elizabeth Venedey, they and their son and daughter lived on a small farm on the outskirts of Berlin. The family later settled on a larger farm at Muncheberg. Baur’s zeal for fieldwork took him to three continents and led to his mastery of a halfdozen languages. Although self-contained and somewhat of a loner, he bridged the distance between himself and others with his optimism, equity, and complete lack of vanity.
Professional Career . A relentless advocate of the intellectual and practical value of genetics, Baur was the first to offer, at a German university, lectures on Mendelian inheritance in conjunction with a practicum in experimental breeding. Thenovel program he developed while a Privatdozent at Berlin led in 1911 to the publication of an immensely influential textbook, Einführung in die experimentelle Vererbungslehre. An innovative and much beloved teacher, he was also the principal architect and editor of Zeitschrift für induktive Abstammungsund Vererbungslehre, the first scientific journal devoted to genetics, from its beginning in 1908. In 1911 Baur represented Germany at the Fourth International Congress of Genetics in Paris. That same year the newly established Kaiser-Wilhelm-Gesellschaft iur Förderung der Wissenschaften (Berlin) decreed the construction of the first of its scientific research institutes. Within a decade this scientific funding agency became the principal patron of new specialties and fields, including genetics. Accordingly, geneticists such as Baur. Carl Correns, and Richard Goldschmidt found a permanent home outside the traditional German university system.
World War I not only radically affected Baur’s scientific and institutional activities, it also disrupted his plan for a Berlin meeting of the Fifth International Congress of Genetics in 1916. He also was prevented from serving as exchange professor at the University of Wisconsin at Madison for the academic year 1914–1915. But although he suffered profound difficulties and disappointments, Baur was not a spiritual casualty of the war. Optimistic rather than disillusioned, he expanded both his scientific program and his professional activities, most notably in applied genetics. During the Weimar period he trained as many as thirty students a year, published a major textbook in applied genetics. Die wissenschaftlichen Grundlagen der Pflanzenzüchtung (1921). and established the first German journal for theoretical and applied genetics, Der Züchter (1929). He also attended, and frequently headed, the meetings of the three major German agricultural and breeding societies, and he served on numerous national and international agricultural planning committees.
Baur was honored in Germany as the founder of applied genetics, but he performed yet another important service for his science. On behalf of the Deutsche Gesellschaft für Vererbungswissenschaft (1921), a society he founded in concert with Correns and Goldschmidt, Baur resumed responsibility for planning the Fifth International Congress of Genetics. For six years he acted as goodwill ambassador of the scientifically isolated postwar German genetics community. When the congress met at Berlin in 1927, Baur served as its president. Two years later he attended the All-Russian Congress of Genetics and Breeding, where he met many of the Russian population geneticists. In 1931 he delivered lectures in London, Sweden, and South America, speaking on evolution, applied genetics, and eugenics. That same year he organized and presided at the Berlin meeting of the Congress of the International Plant Breeders Association. Baur remained professionally active until his death from heart failure.
Scientific Work . Baur’s memorable caveat to students and co-workers was “More experimentation, less speculation!” No crude empiricist, he saw in Mendelian principles the surest bridge between heredity and evolution, but for Baur surety entailed rigorous experimentation. Unlike William Bateson, who shared his view, Baur was a supremely pragmatic experimentalist. Gifted with an uncanny ability to recognize theoretical problems amenable to experimental testing, he exploited any discovery, idea, or method likely to yield concrete results; yet he was laboriously thorough and cautious of overinterpreting evidence. In this sense he strongly resembled Thomas H. Morgan. But whereas Morgan concentrated on the mechanisms of Mendelian inheritance, Baur focused increasingly on the genetic mechanisms of speciation.
Because of his methodological flexibility and his interest in the species question, Baur worked with equal ease and success in every major problem area of classical genetics. His diagnostic ability and investigative skill were evident at the outset of his career, soon after his arrival at Schwendener’s institute in 1903. While engaged in a study of the viral and bacterial causes of leaf mottling, he discovered a type of leaf variegation that seemed to be inherited rather than microbially induced. In 1905 he began to study inherited variegation in the aurea variety of Antirrhinum. Unaware of the irony of following rather too closely in the footsteps of Hugo de Vries (Oenothera) and Carl Correns (Mirabilis jalapa), Baur likewise fixed on an organism whose abnormal genetic mechanisms played havoc with Mendel’s laws. Over the next five years his work on Antirrhinum closely paralleled Correns’study of non-Mendelian inheritance in Mirabilis.
But Baur’s investigation of variegation was far more exhaustive than Correns’, encompassing plant chimeras and mosaic oddities in general Surpassing the earlier work of the botanists Hans Winkler and Hermann V öchting, Baur distinguished clearly among the four principal categories and causes of mosaic variegation: diseased plants, somatic mutation, graft hybrids, and hybrid seedlings. Only after extensive breeding experiments with hybrid seedlings and comparative cytological studies did Baur explain inherited variegation in terms of his theory of extranuclear plastid inheritance. Fully elaborated in his Untersuchungen über die Vererbung von Chromatophorenmerkmalen bei Melandrium, Antirrhinum und Aquilefiia (1910), the’ Plastom theory,’ as it was called, argued for the presence of individual hereditary particles, the plastids, in the cytoplasm of germ cells. These were of two types: normal color-bearing and mutant color-deficient Because of their random location in the cytoplasm, plastids could not pair (fertilization) or segregate (cell division) in the manner of nuclear chromosomes, but were passed on individually to the cytoplasm of daughter cells in a random, non-Mendelian fashion.
The clarification of plastid inheritance was subsequently regarded by many botanists as Baur’s most significant contribution to genetics. In contrast with Correns’ interpretation of the same phenomenon, Baur did not attribute a crucial role in the hereditary process to the cytoplasm as a whole. Moreover, he suggested that mutant plastids resulted from a nuclear, chromosomal mutation, chromosomes being the true arbiters of inheritance.
The relationship among heredity, variation, and speciation had preoccupied Baur’s thoughts since 1908, the year he established contact with William Bateson, Wilhelm Johannsen and Herman Nilsson-Ehle. To a large extent Baur modeled his hybridization experiments on those of these three earliest and most influential acquaintances. He had long since established that with the exception of leaf coloration. Antirrhinum’s traits Mendelized, In 1908 he provided the first clear demonstration of a lethal gene, and in the following years he corroborated the phenomena of linkage, multiple alleles, and reversion. With the move to the Landwirtschaftliche Hochschule in 1911, Baur turned permanently to the problem of speciation. In particular he was on the alert for any evidence suggesting the inheritance of acquired traits.
Baur’s prewar hybridization experiments led him to conclude that chromosomal mutations alone provided the material for evolution through natural selection. Accordingly, he directed his inquiries to the nature and transmission process of mutations. But it was not until the opening of the Institute for Genetics at Dahlem in 1923 that he had both the facilities and the theoretical framework needed to attack the mutation problem at the chromosomal level. Whereas Correns and Goldschmidt openly challenged the monopoly of nuclear chromosomes in inheritance, Baur not only adopted Morgan’s gene theory of inheritance and the experimental methodology of the Drosophila school but also engaged in much the same work. Employing Antirrhinum majus, as the botanical counte)t of Drosophila, he and his co-workers mapped chromosomes, studied the rearrangement of the chromosomal material, and identified the loci of genic mutations. Baur’s group also pioneered research on X-ray-induced mutations; success came some years later, largely through the efforts of his students Emmy Stein and Hans Stubbe.
While he was at Dahlem, Baur’s findings on mutations compared in quality and significance with those of his American contemporary and admirer. Hermann J. Muller. Baur was one of the first geneticists to determine the frequency of small pointmutations and to note the occurrence of the same mutation in individuals of the same race. After extensive study of both lethal and nonlethal mutations, he concluded that most dominant mutations were adverse but infrequent, while the recessive small point-mutations were of neutral survival value but relatively frequent. He also investigated polyploidy and other nonlethal mutations affecting the reproductive capacity of closely related individuals.
Baur concentrated on mutation research and genetic analysis of inheritance in Antirrhinum until his move to Müncheberg in 1928. The vastly improved facilities at the new institute allowed him to take the final step in an experimental study of evolution begun twenty years earlier. It was a step that brought him full circle, back to the naturalist tradition and training of his youth. In 1928 and 1929 he studied and collected specimens of geographic populations of snapdragon in Spain, Portugal, and France. His collection included thousands of domestic and wild varieties, and with these he began large-scale breeding of interspecific populations of the genus Antirrhinum. The work of the Müncheberg period represents one of the earliest major genetic studies of geographic populations known.
After successful breeding of fertile species crosses and detection of multiple alleles responsible for small specific differences in Antirrhinum, Baur synthesized the whole of his genetic and mutation research into a theory of progressive evolution. In the articles’ Evolution’ (1931) and’ Artumgrenzung und Artbildung in der Gattung Antirrhinum’ (1932), he argued that small point-mutations are the material for evolution. Of negligible selective value on their own. these relatively frequent mutations accumulate and combine through interbreeding to yield and enhance several new characters in individuals of a certain population. Selective pressure, which acts on all members of the population, may or may not favor those individuals carrying combinations of multiple alleles controlling new characters. The stability of environmental conditions, he added, is a critical factor in the evolutionary process.
Baur died before completing a massive breeding experiment involving more than 50, 000 second— and third-generation crosses of Antirrhinum; his records, too, remained incomplete and fragmented. It was known, however, that he was attempting to effect speciation through increased isolation of successive groups of related individuals, Whether Baur began to think in’ populationist’ terms has not been determined, but his work on small mutations and his interpretation of their significance for evolution did not escape the notice of evolutionary biologists working in the 1930’s and 1940’s.
Applied Genetics. As a close friend of the agricultural geneticist Herman Nilsson-Ehle, Baur was well aware of the discoveries and advances yielded by applied research. It was this awareness, as much as his social conscience, that enabled him to synthesize genetics and practical life into a new field. During the war years, when he first engaged in applied research, Baur mastered breeding methods that served him for the rest of his life. These combined the massive cultivation of crops, methodical measurement of the botanical characters of population and individual, establishment of pure lines (constant pedigrees) through self-fertilization, and cross-breeding of pure lines, with the application of Mendelian principles, pure-line theory, and evolution theory to practical and experimental breeding problems. Like Mendelian principles, however, these methods were largely ignored or unknown in the conservative German agricultural community. Confronting the need for education and reform in this quarter, Baur provided the rational basis of practical breeding in Die wissenschaftlichen Grundlagen der Pflanzenzüchtung (1921). He then proceeded to demonstrate the utility of the principles and methods outlined in his book through his work at Dahlem and Müncheberg.
Baur dealt with virtually eveny type of economically important plant. Among the most vital and threatened crop plants he worked on were grapes, which were struck in 1925 by an epidemic of yeast infection. At Dahlem he began hybridization experiments that by the time of his death yielded more than seven million disease-resistant varieties of grape. These were subsequently cultivated in the Rhine and Moselle regions. Baur’s success with grapes guaranteed the survival of German viticulture, but no less vital to German agricultural productivity was his work on grains, potatoes, and lupines. Here his approach truly complemented and reflected his experimental and theoretical interests.
As early as 1913 Baur had proposed the study and utilization of wild types of grains, potatoes, and other food crops. After 1918 he amassed large collections of specimens from as far afield as Asia Minor (1926) and the Andes of Peru and Chile (1931). As in the case of Antirrhinum, he studied regional populations, appraised environmental conditions, and collected samples for genetic analysis and hybridization experiments. His methods of testing the viability of new varieties in large and small populations, by allowing environmental conditions to weed out weak members of successive generations, were likewise employed with Antirrhinum. After comparative analysis of genotypic composition and experiments with interspecific crosses, Baur successfully bred a wheat-rye hybrid suited to cultivation in light, sandy soils and a wild-domestic cross of potato that was both disease— and cold-resistant Toward the end of his career he also began to study the effects of X-ray–induced mutations in wheat, hoping to produce new, improved strains of this staple.
Baur’s most noteworthy agricultural triumph, and one that attracted a great deal of scientific attention, was his discovery in 1930 of a sweet, nonalkaline variety of lupine, a wild member of the bean family. Some years earlier, when he first considered lupines as a possible source of fodder, he had predicted the appearance and immediate consumption by wild animals of a sweet, mutant variety of this otherwise very bitter plant. Certain of his instincts, he bred more than two million wild lupines and found the anticipated mutants; their descendants were cultivated thereafter as fodder crops. While not a test of progressive evolution, the lupine experiment provides an apt illustration of Baur’s readiness and ability to put theory into practice.
Eugenics. In 1907, while still a relatively new convert to the study of inheritance, Baur joined the Gesellschaft für Rassenhygiene, a eugenic society founded in 1905 by the physician Alfred Ploetz. For the remainder of his life Baur was an active member of this society and a regular contributor to its journal, Archivfür Rassen- und Gesellschaftsbiologie. Like most eugenicists of the period, Baur was not indifferent to the issue of hereditary racial differences. On the contrary, his interest in the evolution and genetic composition of the races of man led him to publish jointly with Eugen Fisher and Fritz Lenz the extremely popular but controversial Grundlagen der menschtichen Erblichkeitslehre und Rassenhygiene (1921).
From the beginning of his involvement with the German eugenics movement, however, Baur regarded the application of genetics to human heredity largely from the standpoint of medical science. Formerly a physician, he saw in eugenics the means for controlling and eradicating human hereditary defects and diseases. Optimism rather than morbid anxiety lay at the heart of his commitment to rational human breeding. Responding to the cultural pessimism of Oswald Spengler’s Decline of the West (1918), Baur argued that disease was the primary cause of the degeneration of human society. Through a process he called’ reversed selection,’ human culture interferes with the weeding-out function of natural selection to promote the spread of inherited debility. He maintained that genetics, medicine, and science in general could unite to overcome the degenerative effects of reversed selection.
Given the relatively new and unexplored status of human genetics, Baur cautioned against immediate widespread implementation of eugenic programs. He repeatedly emphasized the need for more research, especially of the type conducted by Agnes Blühm and others at the Kaiser Wilhelm Institute for Biology at Dahlem, Throughout the Weimar era Blühm investigated the teratogenic and mutagenic effects of alcohol and other chemicals on living organisms. Toward the end of his life Baur conducted similar investigations, convinced of their medical value—others, however, were skeptical. In 1931 Hermann J. Muller severely criticized Baur’s position concerning the possible mutagenic effects of chemical agents. But in this very novel area of research, Baur’s instincts proved once again to have been correct. They failed him, however, in one important respect. Although science continued to serve the practical needs of society, it did not guide society in the pursuit of rational humanitarian policies. In his last years at Müncheberg, the institute experienced serious financial difficulties. These were overcome soon after his death, but not without a change in the character and function of both his institute and other Kaiser Wilhelm Institutes when ihey came under the jurisdiction of the National Socialist government.
I. Original Works. Baur produced a total of 109 scientific publications in his lifetime. These covered problems ranging from bacterial infections in plants to the emergence of new species. The most important of his publications are’ Untersuchungen über die Vererbung von chromatophoren Merkmalen bei Melandrium, Antirrhinum und Aquilegia,’ in Zeitschrift für induktive Abstammungs- und Vererbungslehre, 4 (1910) 81–102;Einführung in die experimentelle Vererbungslehre (Berlin, 1911); Grundlagen der mensechlichen Erblichkeitslehre und Rassenhygiene (Munich, 1921), with Eugen Fischer and Fritz Lenz: Die wissenschaftlichen Grundlagen der Pflanzenzüchtung: ein Lehrbuch für Landwirte, Gärtner und Forstleute (Berlin, 1921);’ Die Bedeutung der Mutation für das Evolutions— problem,’ in Zeitschrift für induktive Abstammungs-und Verebungslehre, 37 (1925), 107–115;’ Untersuchungen über Faktormutationen. I. Antirrhinum majus mut, phantastica,’ ibid., 41 (1926), 47–53;’ Untersuchungen über Faktormutationen. II. Die Häufigkeit von Faktormutationen in verschiedenen Sippen von Antirrhinum majus, III. Über das gehäufte Vorkommen einer Faktormutation in einer bestimmten Sippe von A. majus,’ ibid., 251–258; Menstchliche Erblichkeitslehre und Rassenhygiene (Munich. 1928), with Eugen Fischer and Fritz Lenz; Handbucn der Vererbungswissenschaft (Berlin, 1928), with Max Hartmann;’ I, Evolution, II. Scope and Methods of Plant Breeding Work in Müncheberg,’ in Journal of the Royal Horticultural Societ, 56 (1931), 176–190:’ Artumgrenzung und Artbildung in der Gattung Antirrhinum, Sektion Antirrhinastrum,’ in Zeitschrift für induktive Abstammungs— und Verer-bungslehre, 63 (1932), 256–302.
A complete chronological bibliography of Baur’s works, including articles written for newspapers and a list of the scientific journals that he edited, is available in Elisabeth Schiemann s’ Nachrufe Erwin Baur’ (see below).
The Erwin Baur papers are located at the Bibliothek und Archiv zur Geschichte der Max-Planck-Gesellschaft in West Berlin. A description of the contents of the collection is provided in Jonathan Harwood.’ The History of Genetics in Germany,’ in Mendel Newsletter, 24 (October 1984), 1–3. The collection consists primarily of documents and papers pertaining to the establishment of Baur’s Kaiser Wilhelm institutes at Dahlem and M uumlncheberg; it does, however, include the manuscript of Karl von Rauch’s 300-page unpublished biography of Baur as well as biographical material from other sources, Little of Baur’s correspondence with other botanists and geneticists survives, but a number of very important letters are available in two archival collections, Nachlass Carl Steinbrink and Sammlung Ludwig Darmstaedler, at the Staatsbibliothek Preussischer Kulturbesitz in West Berlin.
II. Secondary Sources. The most comprehensive treatment of Baur’s life and career is Elisabeth Schiemann,’ Nachrufe Erwin Baur,’ in Berichte der Deutschen botanischen Gesellshaft, 52 (1934), 4–114, Additional perspective on institutional developments that had an impact on Baur’s career can be gained from Lothar Burchardt. Wissenschaftspolitik im Wilhelminischen Deulschland (Göllingen, 1975); and Günther Wendel, Die Kaiser-Wilhelm-Gesellschaft 1911–1914 (Berlin, 1975). Three works reviewing the development of genetics in Germany during Baur’s lifetime are H. Friedrich-Freska,’ Genetik und biochemische Genetik in den Institulen der Kaiser-Wilhelm-Gesellschaft und der Max-Planck-Gesellschaft,’ in Naturwissenschaften, 48 (1961), 10–22; Jonathan Harwood,’ The Reception of Morgan’s Chromosome Theory in Germany: Inter-war Debate over Cytoplasmic Inheritance,’ in Medizin historisches Journal, 19 (1984), 3–31; and Hans Nachtsheim,’ Die Entwicklung der Genetik in Deutschland von der Jahrhundertwende bis zum Atomzeitalter.’ in Hans Leussink, ed., Studium Berolinense (Berlin, 1960), 858–867.
Natasha X. Jacobs