Cellular Automata Models of Self-Replicating Systems

Since von Neumann's seminal work around 1950, computer scientists and others have studied the algorithms needed to support self-replicating systems. Much of this work has focused on abstract logical machines (automata) embedded in two-dimensional cellular spaces. This research has been motivated by the desire to understand the basic information-processing principles underlying self-replica-tion, the potential long term applications of programmable self-replicating machines, and the possibility of gaining insight into biological replication and the origins of life. Here we briefly summarize the historical development of work on artificial self-replicating structures in cellular spaces, and then describe some recent advances in this area. Past research is viewed as taking three main directions: early complex universal computer-constructors modeled after Turing machines, qualitatively simpler self-replicating loops, and efforts to view self- replication as an emergent phenomenon. We discuss our own recent studies showing that self-replicating structures can emerge from non-replicating compo-nents and that genetic algorithms can be applied to automatically program simple but arbitrary structures to replicate. We also describe recent work in which self-replicating structures are successfully programmed to do useful problem solving as they replicate. We conclude by identifying some implications and important research directions for the future.