  The Gray-Scott model can be thought of as an effective theory at large
spatiotemporal scales coming from a more fundamental theory valid at shorter
spatiotemporal scales. The more fundamental theory includes a composite
molecule which is trilinear in the molecules of the Gray-Scott model as was
shown in the recent derivation of the Gray-Scott model from the master
equation. Here we show that at a classical level, ignoring the fluctuations
describable in a Langevin description, the late time dynamics of the more
fundamental theory leads to the same pattern formation as found in the
Gray-Scott model with suitable choices of the parameters describing the
diffusion of the composite molecule.
