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Séminaire doctoral Philsci - Felix Walpole et Nicolas Pastor
Felix Walpole (University of Toronto) - What is the challenge of epigenetics?
Epigenetic processes (methylation, histone marking) continue to be the subject of vigorous debate amongst philosophers of biology despite years of sustained discussion. In this paper, I argue that epigenetics has been so contentious because it poses a dilemma—it forces a choice between two supposedly objectional conclusions. By and large, most evolutionists contend that all adaptive evolution is variational in type; adaptation is the result of a sorting amongst variants (Lewontin, 1982). This conception holds two central commitments: i. the evolutionary process of inheritance is fundamentally conservative, i.e., what is inherited is random (unbiased) in regards to its effect., and ii. developmental processes, even when perhaps plastically "adaptive" within the lifetime of the individual, refrain from constituting true adaptive evolution until the process is co-opted by a genuine evolutionary process (i.e., the Baldwin Effect). Epigenetic processes display two fundamental features that make them difficult to accommodate viz these two commitments: they introduce adaptive bias, and they are trans-generationally stable. Thus, the strict variationalist must choose between two objectional conclusions— either epigenetic processes must be considered as genuinely adaptive, or they must be folded into the process of inheritance. Both strategies prove to complicate the variationalist position. The fall-out appears to be that if an evolutionary theory is to cover all cases of adaptive evolution, it will not be solely variational.