Raffaele Calabretta, Stefano Nolfi, Domenico Parisi and Günter P.
Abstract. The origin and structural and functional significance of
modular design in organisms represent an important issue debated in many
different disciplines. To be eventually successful in clarifying the
evolutionary mechanisms underpinning the emergence of modular design in complex
organisms, one should be able to cover all different levels of biological
hierarchy. Specifically, one should be able to investigate modularity at the
behavioral level - the level on which natural selection operates - and
understand how this level is related to the genetic level – the level at which
natural selection works through mutation and recombination. We describe a
simulation of the evolution of a population of robots that must execute a
complex behavioral task to reproduce. During evolution modular neural networks,
which control the robots’ behavior, emerge as a result of genetic duplications.
Simulation results show that the stepwise addition of structural units, in this
case genetic and neural 'modules', can lead to a matching between specific
behaviors and their structural representation, i.e., to functional