According to Kuhn's speciation analogy, scientific specialisation is fundamentally analogous to biological speciation. In this paper, we extend Kuhn's original language-centred formulation of the speciation analogy, to account for episodes of scientific specialisation centred around methodological differences. Building upon recent views in evolutionary biology about the process of speciation by genetic divergence, we will show how these methodology-centred episodes of scientific specialisation can be understood as cases of specialisation driven by value divergence. We will apply our model of specialisation by (...) value divergence to an episode of methodology-centred scientific specialisation: the emergence of molecular biology. (shrink)