Right Wing Professor's thoughts have me musing on the significance of the development control genes. Perhaps they represent the limits for new body plans, i.e. must be allowed by the control genes.
For instance, "eyeness" which had been thought to have evolved separately among the various phyla now is speculated to be facilitated by the development control genes of a common ancestor. Anyway, that's my layman's lingo for this article: How the Eye Got its Brain
If true, that would support autonomous self organizing complexity - over the more disorganized process of random mutation and natural selection, though it would not preclude it as factor.
However, it brings the question back to the point raised by VadeRetro, whatever caused the Cambrian explosion is unique and the subject of much speculation - creating a menu of body plans with a survival interest. By my gross estimate, the survival rate was about 60% - mighty impressive if the development control genes were randomly created! (I believe there were about 50 in the Cambrian Explosion and about 30 survived.)
Finally, if the real cause for so few new body plans (2 or 3) is that the Cambrian explosion gave us development control genes – then I’m still in a quandary as to why such an event has not since recurred, unless of course the regulatory control genes are self-correcting to avoid those kinds of adaptations.
I suspect that the events that took place before the Cambrian were unique. History doesn't exactly repeat itself. Time doesn't move backwards.