Is Morphogenesis an Intrinsically Robust Process?

Because morphogenesis is dynamically complex, involving many processes operating over different spatial and temporal scales, it is generally assumed that the stability and repeatability of development depends primarily upon accurate control over parameter values i.e. a precise genetic program. However, it is possible that the dynamic coupling between the different mechanisms involved in development reduces the choices available to the system because of bias in successive symmetry-breaking events. Evidence for such stable cascades in morphogenetic processes is described, and a general argument is presented for morphogenesis as an intrinsically robust process. The evolutionary implications of the hypothesis are considerable.