Fig. 5From: Convergent Evolutionary Paths in Biological and Technological NetworksStarting from a basic logic block, such as a NAND gate (a), a combination algorithm allows generating more complex gates which can themselves be used to build further gates. The two circuits shown in b and c are examples of these evolved circuits (redrawn from Polak and Arthur 2006). The basic result of this combinatorial evolution is that more and more complex computational blocks (indicated as XOR, EQUIV, IMPLY, etc.) are generated, thus defining a variety of modules. Such modular organization is a characteristic feature of electronic designs, where integrated circuits (such as the one shown in d–e) are fixed combinations of simpler gatesBack to article page