Duplication of modules facilitates the evolution of functional specialization

The evolution of simulated robots with three different architectures is stu died in this article. We compare a nonmodular feed-forward network, a hardw ired modular, and a duplication-based modular motor control network. We con clude that both modular architectures outperform the non-modular architectu re, both in terms of rate of adaptation as well as the level of adaptation achieved. The main difference between the hardwired and duplication-based m odular architectures is that in the latter the modules reached a much highe r degree of functional specialization of their motor control units with reg ard to high-level behavioral Functions. The hardwired architectures reach t he same level of performance, but have a more distributed assignment of Fun ctional tasks to the motor control units. We conclude that the mechanism th rough which functional specialization is achieved is similar to the mechani sm proposed for the evolution of duplicated genes. It is found that the dup lication of multifunctional modules first leads to a change in the regulati on of the module, leading to a differentiation of the functional context in which the module is used. Then the module adapts to the new functional con text. After this second step the system is locked into a functionally speci alized state. We suggest that functional specialization may be an evolution ary absorption state.