Development and natural kinds : some lessons from biology

While philosophers tend to consider a single type of causal history, biologists distinguish between two kinds of causal history: evolutionaryhistory and developmentalhistory. This essay studies the peculiarity of development as a criterion for the individuation of biological traits and its relation to form, function, and evolution. By focusing on examples involving serial homologies and genetic reprogramming, we argue that morphology (form) and function, even when supplemented with evolutionary history, are sometimes insufficient to individuate traits. Developmental mechanisms bring in a novel aspect to the business of classification—identity of process-type—according to which entities are type-identical across individuals and natural kinds in virtue of the fact that they form and develop through similar processes. These considerations bear important metaphysical implications and have potential applications in several areas of philosophy.