I call an experiment “crucial” when it makes possible a decisive choice between conflicting hypotheses. Joharmsen's selection for size and weight within pure lines of beans played a central role in the controversy over continuity or discontinuity in hereditary change, often known as the Biometrician-Mendelian controversy. The “crucial” effect of this experiment was not an instantaneous event, but an extended process of repeating similar experiments and discussing possible objections. It took years before Johannsen's claim about the genetic stability of pure (...) lines was accepted as conclusively demonstrated by the community of geneticists. The paper also argues that crucial experiments thus interpreted contradict certain ideas about the underdetermination of theories by facts and the theory-ladenness of facts which have been influential in recent history and sociology of science. The acceptance of stability in the pure lines did not rest on prior preference for continuity or discontinuity. And this fact permitted a final choice between the two theories. When such choice is characterized as “decisive” or “final”, this is not meant in an absolute philosophical sense. What we achive in these cases is highly reliable empirical knowledge. The philosophical possibility of drawing (almost) any conclusion in doubt should be distinguished from reasonable doubt in empirical science. (shrink)

In 1920, Eugen Steinach and Paul Kammerer reported experiments showing that exposure to high temperatures altered the structure of the gonad and produced hyper-sexuality in "heat rats," presumably as a result of the increased production of sex hormones. Using Steinach's evidence that the gonad is a double gland with distinct sexual and generative functions, they used their findings to explain "racial" differences in the sexuality of indigenous tropical peoples and Europeans. The authors also reported that heat induced anatomical changes in (...) the interstitial cells of the gonad were inherited by the heat rats' descendants. Kammerer used this finding to link endocrinology to his long-standing interest in the inheritance of acquired characteristics. The heat rats supported his hypothesis that the interstitial cells of the double gland were the mechanism of somatic induction in the inheritance of acquired characteristics. The Steinach-Kammerer collaboration, Kammerer's use of Steinach's "puberty gland" to explain somatic induction, and his endocrine analysis of symbiosis reveal Paul Kammerer's late career attempt to integrate endocrinology and genetics with the political ideals of Austrian socialism. With them he developed a bioethics that challenged the growing reliance on race in eugenics and instead promoted cooperation over competition in evolution. I relate his attempt to the controversies surrounding the interstitial cells, to the status of extra-nuclear theories of heredity, and to Kammerer's commitment to Austromarxist social reforms during the interwar period. (shrink)

One area of genetics particularly dominated by German-speaking geneticists (Brücher, Correns, Lehmann, Michaelis, Oehlkers, Renner, von Wettstein) during the interwar period was research in the field of cytoplasmic inheritance (Plasmon-Theory). The controversy between the botanists Lehmann (Tübingen) and Brücher (Jena, Tübingen) about the function of “supressor genes” in Epilobium cell division was central to debates about cytoplasmic inheritance. The failure of Brücher, Michaelis and Oehlkers to replicate Lehmann's Epilobium experiments ultimately forced Lehmann to admit his error.

Bernard Norton's friends in the history of science have had many reasons for commemorating, with admiration and affection, not only his research and teaching but no less his conversation and his company. One of his most estimable traits was his refusal to beat about the bush in raising the questions he thought worthwhile pursuing. I still remember discoursing at Pittsburgh on Darwin's route to his theory of natural selection, and being asked at the end by Bernard what were Darwin's views (...) on heredity. I answered with the conventional waffle to the effect that the theory concerned the populational fate rather than the individual production and transmission of heritable variation, so that whatever views Darwin had on heredity had only a subsidiary place in his theorizing. Bernard was not fooled. ‘I would have thought’, he said, ‘that in order to understand anyone's theorising about evolution it would be necessary to look at his views on heredity’. (shrink)

The 1920-1960 period saw the creation of the conditions for a unification of disciplines in the area of evolutionary biology under a limited number of theoretical prescriptions: the evolutionary synthesis. Whereas the sociological dimension of this synthesis was fairly successful, it was surprisingly loose when it came to the interpretation of the evolutionary mechanisms per se, and completely lacking at the level of the foundational epistemological and metaphysical commitments. Key figures such as Huxley, Simpson, Dobzhansky, and Rensch only paid lip (...) service to the conceptual dimension of the evolutionary synthesis, as they eventually realized that a number of evolutionary phenomena could not be explained by its narrow theoretical corpus. Apparently, the evolutionary synthesis constituted a premature event in the development of evolutionary biology. Not only are the real achievements of the evolutionary synthesis in need of reevaluation, but this reassessment also has important implications for the historiography of Darwinism and the current debates about the darwinian movement. (shrink)