In 1907, German anthropologist Theodor Mollison invented a unique method for racial differentiation, called ‘deviation curves’. By transforming anthropometric data matrices into graphs, Mollison’s method enabled the simultaneous comparison of a large number of physical attributes of individuals and groups. However, the construction of deviation curves had been highly desultory, and their interpretation had been prone to various visual misjudgements. Despite their methodological shortcomings, deviation curves became very popular among racial anthropologists. This positive reception not only stemmed from the method’s (...) utilities, but was related to additional interests of its protagonists which the method helped promote. Deviation curves provided a unique solution to the holistic–atomistic controversy in German anthropology. By giving separate measurements a consolidated visual form, they substantiated the idea that the attributes of certain social groups were part of distinct racial compounds. Deviation curves thus reinforced racial suppositions, in face of severe criticism on the ontological reality of race itself. Finally, deviation curves emphasized the biological singularity of disadvantaged human groups – Jews, Africans and also women – and of their divergence from ideologically defined physical norms. Disciplinary and social interests thus became intertwined in the formation of a scientific method, which is used to this day in physical anthropology. (shrink)

This article offers a close examination of a small selection of pedigrees taken from German Mendelian and eugenic scholarship of the 1920s and 1930s. It examines the procedures that became customary for presenting data on human inherited pathologies, as well as the frequent changes in the information content of those charts. Relevant biographical and genealogical data was removed, and important indications regarding the diagnostic methods applied by the investigating scholar were lost, as soon as a pedigree was charted or reproduced. (...) Data on healthy individuals was condensed, leading to an emphasis on the hereditary burden of pathological traits. At times, healthy individuals were entirely omitted, as were exogenous martial partners. These modifications paved the way for further theoretical amendments, including the addition of ‘carrier’ status to chosen individuals along the pedigree. With this addition, these pedigrees changed their ontological status, from empirical records of human reproduction to partially hypothetical illustrations of Mendelian theory itself. This process was complemented by the representation of theoretical genetic models in the format of a human pedigree. A comparison to practices of charting pedigrees still common today suggests that the processes hereby revealed are far from exceptional. In line with the ideas put forward by Ludwik Fleck, they are interpreted as germane to the way scientific ideas are communicated and propagated and to the scientific culture of genetics. The article also offers a refinement to Fleck’s analysis of textbook construction, which highlights the extent to which textbook examples differ from the original data on which they are based. (shrink)