Taking an evo-devo approach to the living world changes our views of both of biology’s great creative processes – evolution and development. However, this is not a symmetrical change. Evolutionary biology is a more theory-driven discipline than developmental biology. Why this is so is itself an interesting question, but perhaps more one for philosophers and historians of biology than for biologists themselves. Anyhow, this difference between the disciplines means that our altered view of development is easier to adopt than our altered view of evolution – in the sense that it causes less tension in a pre-existing theoretical framework. Because of this fact, I will start with the simpler case (development, this section) but will spend longer on the more complex one (evolution, the other sections).