ABSTRACT
One of the most characteristic properties of the developmental process is that it is stable. From Darwin to the present, most evolutionists have insisted that evolution is gradual. An embryo does not need an absolutely perfect environment and it can survive many small disturbances and even some large ones. C. H. Waddington arrived at his view from his experience in embryology. Dynamical systems typically have more parameters than are necessary to produce the entire range of behavior of the system. Biologists, faced with the immense complexity of organisms, have naturally tended to look at the three time scales separately, and physiology, developmental biology, and volution exist as separate disciplines. The epigenetic landscape illustrates remarkably well some important properties of developmental systems. Development is part of the medium time scale and interacts both with the short-term physiological processes that bring it about and also with the long-term process of evolution.
