Fig. 1

Overview of the model. a The developing organisms live on a 2D lattice. Each individual organism consists of a row of cells, of which the posterior-most cell divides at regular intervals. Within the growth zone, the morphogen (in blue) is maintained at a high concentration; it decays in cells outside of this zone. The genome of the organism codes for a network of regulatory interactions, which determines the spatio-temporal dynamics of the proteins within each cell (see d). b The gradients resulting from the different morphogen decay rates (d) used in our simulations. The lambda indicates the position (or time) at which the morphogen concentration is half-maximal, i.e. 50: \(\lambda ={\mathrm{ln}}(2)/d\). c The initial conditions for each new individual at the start of its development. There is a growth zone with high morphogen, and a “head” region without morphogen. d At the end of development, the expression of the segmentation gene is averaged over a number of time steps, and from this the segment boundaries are determined. e The mutational operators acting on the genome