Evolution acts on the body shape of animals but also on the neural configuration. So there has to have been a natural selection for huge frog legs, so the frog can jump. But also a selection for the neuronal circuits which control the legs.

In which order do these traits evolve? It is possible that (pre-)frogs with bigger legs survive for some reason and the circuits evolve later. This would correspond with my intuition which stems from the Darwin finch example. However, it could also be possible that the neural circuits change first and produce (pre-)frogs which show the behaviour of jumping around. If this trait is established in a population, frogs with bigger legs would have a survival benefit.

Is there a theory which describes behavioural selection followed by morphological selection? I would love to read something about this.