Beyond the Darwinian Individual: An Evo-Devo Perspective on the Regulation of Individuality
1 : Departments of Philosophy and Biology, Duke University
Recent work on natural selection and evolutionary transitions in hierarchy highlights the central role of Darwinian populations, collections of (Darwinian) individuals with heritable variation and differing reproductive rates (Godfrey-Smith 2009). I expand this framework based on research on the role of individuality in the evolutionary development (evo-devo) of fungi and slime molds. I assess models using four concepts of individuality: history, function, development, and unit of evolution (Wilson 1999). According to the Darwinian population account, a key process in the evo-devo of a new kind of Darwinian population is the integration of Darwinian individuals into a whole and the de-Darwinization of those parts through reduction of heritable variation and/or dependence of reproductive fitness on intrinsic characters. This framework fits the majority of plants and animals but it does not work for filamentous fungi or plasmodial slime molds, which evolve and develop hierarchy not through integration of individual parts but through individuation of an integrated whole. This mode of evo-devo demonstrates the biological regulation of individuality not only in Darwinian terms but also in more general part-boundary terms of history, function, and development, and suggests the renewed relevance of broader metaphysical notions of individuality for philosophy of biology.