Fig. 6

Even technological, design-driven change can be strongly constrained by tinkered evolution. Software engineering illustrates this point very clearly. Software systems can be seen as complex networks of interacting blocks (a) describing given structures or functions. These networks are scale free and also display modularity (indicated by different colors). In b (upper plot), we show a small piece of a computer program for playing chess. Basic nodes include the location of each chessman, its definition and identity, and the movement. Although each chessman is a different component, the logic of relations is conserved when a code duplication is performed (b, lower) to generate a new element from a previous one. These duplication events (followed by rewire) are widespread