| This study of the changing meanings of “Darwinism” from the 1860s through the 1920s focuses on Ernst Haeckel (1834–1919), Paul Kammerer (1880–1926) and other German and Austrian Darwinians. It challenges the prevailing view that Darwinism was “eclipsed” by other theories of evolution in the decades around the turn of the twentieth century, on the grounds that that view is based on an anachronistic definition of Darwinism that recasts avowed Darwinians like Haeckel and Kammerer as its opponents.; Haeckel's anti-clericalism and opposition to divine providence, God-given law, and teleology led him to embrace Darwinism for its promise of naturalistic, historical explanations in all of biology. Minimizing the possibilities for plan and purpose, Haeckel's Darwinism emphasized unpredictable environmental influences as the driving force behind organic change. The environment caused individual organisms to vary by acquiring new, more-or-less adaptive, characteristics, natural selection would see to it that the fittest variants would survive, and the acquired characteristics would be perpetuated through heredity. Haeckel spent most of his career combating any theory that would substitute internal causes of change, generated within the organism, for external ones. Internal causes, Haeckel argued, were too easily interpreted as manifestations of will, plan, or purpose. Haeckel's abhorrence of internal causes explains his opposition to pre-Darwinian “developmentalist” thinking, the embryology of Wilhelm His, the germplasm theories of August Weismann, and experimental embryology.; At the start of the twentieth century, younger Darwinians in Haeckel's orbit, including Richard Semon, Ludwig Plate, and Paul Kammerer adapted Haeckel's Darwinism to changes in the field of biology, wrought by the rise of Mendelian genetics and experimental methodology. The second half of this dissertation is devoted to Kammerer, who once described himself as one of the many pebbles moving under Haeckel's planet-sized gravitational influence. It shows how Kammerer tried to bring Haeckel's conception up to date by demonstrating the heritability of environmental effects in the laboratory and reconciling the results with genetics. Kammerer's experiments and contemporary reactions to them are analyzed, as are the circumstances leading to the scandal that ended Kammerer's career and might have prompted his suicide. |
