Heredity III, 19th to Early 20th Century: Heredity Theorized

organized by Staffan Müller-Wille and Hans-Jörg Rheinberger

Max-Planck-Institute for the History of Science, Berlin, Germany

Report

This workshop was the third in a series of workshops dedicated to the social practices and institutions in which the knowledge of heredity was materially entrenched and in which it unfolded its effects in various social arenas, science as a matter of course, but also medicine, jurisdiction, technology, notably breeding, literature and art (see general description of our project ‘A Cultural History of Heredity’). Like the two previous workshops “Heredity in the Seventeenth and Eighteenth Centuries” and “Heredity in the Late Eighteenth and Nineteenth Centuries”, this workshop was devoted to a historical ‘epoch’ characterized by a decisive trend in the development of hereditary thought, namely the theorizing of heredity, and demarcated by two seminal publications: Francis Galton’s Hereditary Talent and Character (1865) and Wilhelm Johannsen’s Über Erblichkeit in Populationen und in reinen Linien (1903). The first two workshops had dealt with the longue durée processes which resulted in heredity occupying the centre of biological thought from the mid nineteenth century onward. While no general concept of heredity had been underlying the discourse of the life sciences (including medicine, anthropology and the moral sciences) in the eighteenth century, such a concept was slowly emerging in the first half of the nineteenth century, at the expense of a set of ancient distinctions in regard to observed similarities between parents and offspring: the distinctions of specific vs. individual, paternal vs. maternal, normal vs. pathological similarities, all gave gradually way to a generalised notion of heredity capturing relations among traits regardless of the particular life forms they were part of. Contributions to the first two workshops have been documented in nos. 222 and 247 of the preprint series of the Max-Planck-Institute for the History of Science. A summary of the results has been published as preprint no. 276 (download or order preprints here). The main outcome of the third workshop, which took place at the Max-Planck-Institute for the History of Science January 13 to 16, 2005, is that the two dichotomies developed by historians so far with respect to late nineteenth-century theories of heredity, namely soft vs. hard (Ernst Mayr, The Growth of Biological Thought , 1982: ch. 16) and blending vs. non-blending inheritance (Robert C. Olby, Origins of Mendelism , 1985: ch. 3) do not seem to work well to fully capture the variety of theoretical approaches in that time period. There are two reasons for this: (1) It became apparent during the conference that up until the very end of the nineteenth century speculations into heredity either conflated these oppositions, or remained rather indifferent with respect to them. Within the medical community, for example, the belief was widespread that diseases leave their “stamp” upon offspring or that substances like alcohol “poison” the germinal substances. This position reflects a conception of heredity both “soft” and “hard” at the same time -- soft, in as much as environmental factors induce change in the hereditary substance; hard, in as much as this change, once it has occurred, is irrevocably passed on in the germinal line (in obvious analogy to original sin). Likewise, the “blending” of parental forms in offspring was often seen as compatible with a view of the hereditary substance as being composed of “non-blending”, particulate elements, as notably in Darwin’s theory of pangenesis and Galton’s theory of the stirp. Both oppositions, “soft” vs. “hard” and “blending” vs. “non-blending” seem to have become serious issues of dispute and dissent only after the onset of Mendelism in 1900. (2) The oppositions of “soft” vs “hard” and “blending” vs “non-blending” heredity cover up or cut across more fundamental, and more hotly debated, oppositions with regard to the material make-up and causal agency of hereditary material. Was heredity to be conceived as a natural force or as an organic structure? What was the source of the hereditary material, the ancestral organism itself or something passed on independently. Was there a particular substance that formed the germ plasm, and where was it possibly located? And could it be related to particular cellular structures? What, if any, were the elements of the hereditary material, and how did these elements relate to each other? Did they fuse, or just mix? And in what manner did they determine the future organism, directly throughout the individual life-span, or only by determining the first steps of development? Finally, what, if any, where the distinct roles the two sexes played in inheritance? The nineteenth century did not come up with concluding answers to these questions, as is well known, and the contributions to the workshop showed the considerable breadth of positions with respect to inheritance that persisted well into the first decade of the twentieth century. Yet the very nature of these questions points to a decisive trend in the period studied by the workshop. Inheritance was increasingly seen not as a relation between individual organisms – ancestors and descendents – but as a relation of populations to their shared, germinal substrate. Various contributions pointed to two important, but until now under-researched sources of models that shaped representations of this substrate: genealogy and epidemiology. Genealogy developed in the late nineteenth century into a tool for analysing populations rather than individual ancestry, and brought to the fore both the openness of family relations and the quasi-mathematical closure of genetic relationships. In epidemiology, heredity, infection, and vaccination intersected to produce what Jean-Paul Gaudiellière and Ilana Löwy have called the “impossible separation” of horizontal and vertical dimensions in the transmission of diseases (Gaudiellière & Löwy ed. 2001). The reason for the “devaluation of ancestry” in favour of (cultural as well as biological) inheritance seen as a common stock of dispositions seems to lie in the association of heredity with the future rather than the past, with projection rather than with legitimization, that occurred in the context of the all-pervading late-nineteenth century theme of progress. Even where the past entered hereditary discourse, it did so either as a threat to the present, in form of “atavisms”, “throw-backs” and “degeneration”, or as a “heritage”, “stock”, or “capital” to be appropriated anew by each generation. Breeding plants and animals provides the obvious model here, and Mendelism with its close connection to the breeding industry took the decisive step to attack hereditary phenomena by “deducing forward”, as Raphael Falk put it during the workshop. Studying the development of Mendelism against the background explored by this workshop will be the agenda for the next workshop, which is planned to take place at the University of Exeter in autumn 2006.

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