Although hypothesised there has been little investigation into how complex gene regulatory networks can evolve from simple regulatory motifs through modularisation, duplication and specialisation processes. In order to simulate natural evolution in a computational environment we evolve the connection between a genetic oscillator and a toggle switch motif using an evolutionary algorithm. We observe a connectivity preference between the motifs that is dependent on the coupling arrangement rather than on objective set-up. In addition, our results indicate the existence of a threshold in the connection parameters for the resulting dynamics for a specific coupling arrangement and objective set-up. We demonstrate that simple motifs can successfully be coupled through artificial evolution to form more complex, modular regulatory networks. These findings support, in principle, the above-mentioned hypothesis on evolutionary mechanisms in biological systems.