Social Mendelism : The Effects of Mendel s Theorems on the Formation of Human Sciences in Germany, 1900-1936 Abstract Amir Teicher At the beginning of the twentieth century, Mendel s laws of heredity were rediscovered. By 1910, these laws had been firmly established as the new basis for the study of heredity in plants, animals and humans. For scientists whose research fields included the examination of human heredity genealogists, psychiatrists and anthropologists, an attempt to apply the Mendelian model could not have relied on conducting crossing experiments as in the case of their peers from botany and zoology. Therefore scholars studying humans needed to base their hereditary inquiries on the computation of the prevalence of certain traits among family members in the course of several generations. The use of mathematical tools in dealing with heredity was not novel: among genealogists, psychiatrists and physical anthropologists (or, racial scientists ), various methods of quantification, computation and graphical representation were prevalent already at the end of the nineteenth century. Nevertheless, the Mendelian model offered new tools and became the gate through which additional reasoning mechanisms, which stemmed from mathematics and statistics, entered into the study of man. What impact did these tools have on the research practices in the respective science? Was the Mendelian model readily adopted or rejected? And how, if at all, were the old and the new scientific methods connected with the social world views of the scientists working in those three fields? These questions acquire special significance when we come to address the relations between scientific theories and social and political policies. Biological thought in Wilhelmine Germany, in Weimar Germany and above all in Nazi Germany provides i
us with an extreme historical case for examining the ways in which science and politics are intertwined. How did biopolitics evolve from the scientific perspective? What was the role of scientific instruments and methods of denotation and computation in the socio-scientific thought complex of racial hygiene? Social Darwinism and genetic reductionism are the most common characterizations for the framework of thought which combined social agendas and biological theories to create the so-called eugenic world view. But how did these theoretical ideas find expression in scientific work in the ways in which assumptions were phrased, hypotheses were corroborated or refuted, disciplinary concepts were defined and study results were presented both to professional peers and to the public? The answers to these questions vary from one field of research to another. For German genealogists, the attempt to rectify the connections between genealogical research and biological study was a crucial component of the overall effort to gain professional recognition from colleagues working in more established scientific fields. Their efforts led to focusing research strategies around a certain genealogical tool, the ancestors chart, which was later found to be useless from the perspective of Mendelian hereditary analysis. Nevertheless, the ancestors chart was praised by genealogists for answering the needs of biological research. Due to its popularity, a particular computational mechanism, which was a by-product of the structure of the ancestors chart, became widely used. The study shows that the practices associated with that mechanism had significant influence on the work of genealogists, on the arguments they raised and rejected and on the peculiar ways in which they coped with biological challenges, above all with the question of the impact that close kin marriages had on the characteristics of the descendants. In addition, a casual similarity between the computation practices used by genealogists and a particular mathematical ii
model offered in Mendel s paper created the false impression that the ancestors chart and Mendelian theory were intrinsically connected and mutually reinforcing. However, the Mendelian framework of thought influenced genealogical practices only belatedly and on a very limited scale. This stemmed from an essential contradiction between the Mendelian way of investigation, which was built on reviewing several generations of offspring, and the genealogical manner of research which revolved around examining historical sources to retrieve information on as many ancestral generations as possible. Only towards the second half of the 1920s, various conventions of denotation and graphical representation prevalent among physicians and biologists filtered into genealogical studies. The situation was different in German psychiatry. Although Mendelian research strategies did not make their way into psychiatric discourse before the beginning of the second decade of the twentieth century, once they were introduced into the field, they spread at an accelerated pace along with complex statistical techniques and increasing methodological sophistication. The molding of mental illnesses into Mendelian schemes seemed promising at first, but soon encountered severe difficulties. Tools developed by the statistician Wilhelm Weinberg and propagated among psychiatrists primarily due to the publications of Ernst Rüdin pointed to the inapplicability of simple Mendelian models to the inheritance pattern of mental disorders. During the 1920s, the status of the Mendelian model began to change: from a research strategy it was turned into a framework of legitimization that was applied post-factum, and sometimes forcefully, to statistical results which had clearly been obtained in non-mendelian ways. The study indicates the way in which the statistical tools that psychiatrists used to apply at the time were connected to the perception of ill genes as a threat to the iii
entire German public. The need to correct sampling bias and the construction of control groups encouraged conducting studies on the relatives of the mentally ill and led to creating a database whose eventual task was to deter healthy people from marrying the ill or their relatives. The visual methods for the representation of familial relations which had been common among psychiatrists embodied and intensified the social anxieties common to most of them by graphically magnifying hereditary dangers. Thus, scientific motivations, research techniques and world views were intertwined and mutually reinforced one another. For German physical anthropology, measurement, quantification and computation were a cornerstone of scholarly work which turned into a sub-discipline in its own right, namely, anthropometry. However, German anthropologists lagged significantly behind their British peers when it came to statistical analysis. This backwardness was justified using philosophical-ideological arguments on the uniqueness of the biological domain and on the advantage of experience-based tools over complex and abstract theorization. The eugenicist and statistician Fritz Lenz developed an entire statistical apparatus which he presented as an alternative to Karl Pearson s biometric school of statistics; Lenz tools were adopted by many of his colleagues and created a special path of computation and justification in German anthropology. At the same time, the effort to find a Mendelian model for various physical traits, headed by anthropologist Eugen Fischer, was extremely successful, if one was to judge by the declarations of the scholars involved. Almost all human physical traits, so it was argued, behaved according to Mendel s laws. An examination of the relevant academic publications reveals that the success of mendelizing human traits was gained through an array of linguistic abstractions, ambiguous terms and a disregard of contradicting evidence. At the end of the 1920s, the most prominent Mendelian trait, iv
blood type, raised new hopes in the hearts of anthropologists who were striving to find a Mendelian basis for their racial theories. These hopes were frustrated when it turned out that the ability to correlate blood types with the existing racial schemes was limited at best. Yet Mendelian insights did leave a deep mark on fundamental concepts of anthropological thought, most notably the definition of racial purity and racial mixture. These terms were revised and their scientific and societal meanings changed. Racial bastardization, in its biological meaning, was recognized as a feature common to all human beings; the beliefs regarding its damaging effect found no scientific support and needed to be re-conceptualized as the result of social instead of biological realities. Racial purity, on the other hand, turned from an ideal description of personal ancestry into a communal goal that could potentially be achieved by generations to come, provided that the relevant breeding policies were applied. The study examines in particular the effect of the developments in genealogy, psychiatry and anthropology on two major legislation acts in Nazi Germany: the sterilization law and the definition of the Jews according to the Nuremberg laws. In the sterilization law, which was passed in July 1933, eight different hereditary diseases were defined as requiring the sterilization of those carrying them. The study suggests that the justification for including some of these diseases in the law was the disciplinary status of those diseases as Mendelian exemplars, and not, as formerly assumed, their alleged hereditary or economic threat, which was in fact rather negligible. The sterilization law as a whole was presented to the German public as a law based on Mendelian research. In the official commentary detailing the background to the law, pedigrees presented as an empirical proof of the prevalence of diseases in families underwent severe processing until they embodied the Mendelian v
theory itself. Certain aspects of these processing procedures were commonly used in routine scientific work and could therefore not be regarded as part of a deliberate attempt to create false representations. Nevertheless, when it came to the law, these same methods were used to provide scientific legitimization for the legislation procedure as a whole. Similarly, the definition of the Jews and Mischlinge according to the Nuremberg laws was deeply influenced by Mendelian thought which turned into the primary tool for scientifically legitimizing those laws. The anthropological discipline was unable to supply a valid conceptual framework which allowed for an adequate definition of the Jews as a distinct race; however, on the basis of Mendelian theory it did become possible to define the descendants of racial intermarriage biologically as racial hybrids. In such a way, the question of the Mischlinge provided the law with the scientific framework it needed. At the same time, the practical tools used by German scholars and bureaucrats to determine racial origin usually relied neither on anthropological measurements nor on biological examinations, but on conventions developed in the genealogical research field and, most importantly, on the aforementioned ancestors chart. Paradoxically, the immense popularity of the ancestors chart in Nazi Germany was simultaneously the end point of its exclusive status among professional genealogists; although the genealogical practice was publicly revived under Nazi rule, genealogists felt they had to defend their professional status by objecting popular and amateurish currents of familial research. Thus the Mendelian model had a different influence on each of the examined fields of study. Nevertheless, it is possible to name several features common to all three research fields. First, the need to gain legitimization from professional peers was a significant driving force which impacted the way research results were examined and vi
discussed and which led to the creation of substantial gaps between the actual content of studies and the way they were described in professional publications. Second, the visual aspect of research was of special importance, facilitating the direct mediation of perceptions and ideas between scholars and between scholars and the public. Graphical representations of the prevalence of traits among family members embodied theoretical assumptions on the place of heredity in the creation of those traits; the knowledge presented in them was passed on in articles and books while disregarding reservations and nuances which sometimes appeared in the accompanying texts. Consequently, the ability to reinterpret research results differently and offer competing hypotheses was diminished as knowledge consolidated around a single scheme. Finally, in the same way that social ideologies dictated directions of research, the statistical tools and mathematical and hereditary models reshaped the theoretical possibilities in which social thought evolved. In this sense, the compatibility between research methods, computational techniques and graphic conventions common among heredity researchers and between their overall world views did not only stem from a deliberate attempt to subordinate scientific work to the ideological perceptions which scientists shared, but was the result of the joint development of scientific and social thought accompanied by the mutual influence of theoretical frameworks and practical scientific tools. vii