Download Abstract

‘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