This article reviews the growing body of scientific work in Artificial Chemistry. First, common motivations and fundamental concepts are introduced. Second, current research activities are discussed along three application dimensions: modelling, information processing and optimization. Finally, common phenomena among the different systems are summarized. It is argued here that Artificial Chemistries are "the right stuff" for the study of pre-biotic and bio-chemical evolution, and they provide a productive framework for questions regarding the origin and evolution of organizations in general. Furthermore, Artificial Chemistries have a broad application range to practical problems as shown in this review.

Self-reproducing, cellular automata-based systems developed to date broadly fall under two categories; the first consists of machines which are capable of performing elaborate tasks, yet are too complex to simulate, while the second consists of extremely simple machines which can be entirely implemented, yet lack any additional functionality aside from self-reproduction. In this paper we present a self-reproducing system which is completely realizable, while capable of executing any desired program, thereby exhibiting universal computation. Our starting point is a simple self-reproducing loop structure onto which we "attach" an executable program (Turing machine) along with its data. The three parts of our system (loop, program, data) are all reproduced, after which the program is run on the given data. The system reported in this paper has been simulated in its entirety; thus, we attain a viable, self-reproducing machine with programmable capabilities. 1 Introduction The study of art...

Building on the work of Von Neumann, Langton, and Sayama among others, we introduce the rst examples of evolution in populations of self-reproducing con gurations in asynchronous cellular automata. Reliance on a global synchronous update signal has been a limitation of all solutions since the problem of achieving self-production in cellular automata was rst attacked by Von Neumann half a century ago. Results of the author obviate the need for this restriction.

. Von Neumann's architecture for self-reproducing, evolvable machines is described. From this starting point, a number of issues relating to self-reproduction and evolution are discussed. A summary is given of various arguments which have been put forward regarding the superiority of genetic reproduction over self-inspection methods. It is argued that programs in artificial life platforms such as Tierra reproduce genetically rather than by self-inspection (as has previously been claimed). However, the distinction is blurred because significant parts of the reproduction process in Tierran programs are implicitly encoded in the Tierran operating system. The desirable features of a structure suitable for acting as a seed for an open-ended evolutionary process are discussed. It is found that the properties of such a structure are somewhat different to those of programs in Tierra-like platforms. These analyses suggest ways in which the evolvability of individuals in artificial ...

A new self-replicating cellular automata (CA) model is proposed as a latest effort toward the realization of an artificial evolutionary system on CA where structural complexity of self-replicators can increase in some cases. I utilize the idea of `shape encoding' proposed by Morita and Imai (Morita & Imai 1996b) and make the state-transition rules of the model allow organisms to transmit genetic information to others when colliding against each other. Simulations with random initial configuration demonstrate that it is possible that the average length of organisms and the average frequency of brancing per organism both increase, with decreasing self-replication fidelity, and saturate at some constant level. The saturation is caused in part by the fixation of place and shape of organisms onto particular sites. This implies the necessity of introducing some fluidity of site arrangements into the model for further development of evolutionary models using CA-like artificial medi...

Abstract. We consider temporal aspects of self-replication and evolvability – in particular, the massively asynchronous parallel and distributed nature of living systems. Formal views of self-reproduction and time are surveyed, and a general asynchronization construction for automata networks is presented. Evolution and evolvability are distinguished, and the evolvability characteristics of natural and artificial examples are overviewed. Minimal implemented evolvable systems achieving (1) asynchronous self-replication and evolution, as well as (2) protocultural transmission and evolution, are presented and analyzed for evolvability. Developmental genetic regulatory networks (DGRNs) are suggested as a novel paradigm for massive asynchronous computation and evolvability. An appendix classifies modes of life (with different degrees of aliveness) for natural and artificial living systems and possible transitions between them. 1 Models of Time: Logical vs. Physical Time We consider time in discrete dynamical systems. St. Augustine considered time as something intuitively graspable yet ineffable. Varshavsky distinguished two kinds of time: Time as a logical variable in a system defined by events vs. time as an independent physical variable [96], and studied self-timing and asynchrony theory for computing devices as the problem of reconciling the two types of time via design of system timing for the appropriate functioning asynchronous devices interacting with external environments. For a single observer or location, we can consider three main views of the (logical) time:

This chapter reports on the spontaneous emergence of computer programs exhibiting the ability to asexually reproduce, to reproduce by combining parts from two parents, and to improve their performance through evolution from a primordial ooze of primitive computational elements. The computational elements are a computationally complete set and compositions of them are capable of agglomerating themselves to one another.

We describe a multi-cellular shape replication mechanism implemented in a sensing and communication network, motivated by robust self-monitoring and self-repairing aerospace vehicles. In particular, we propose a self-referential representation (a “genome”), enabling self-inspection and selfrepair; an algorithm solving the problem for connected and disconnected shapes; and a robust algorithm recovering from possible errors in the “genome”. The presented mechanism can replicate combinations of predefined shapes and arbitrary shapes that self-organise in response to occurring damage.

Introduction Writing the natural history of agents poses a double challenge. Not only is it unclear (despite recent interest in agent based software technology) what should we understand under the term 'agent'. It is also a question, what natural history has to offer to the study of agents. One property the software objects called 'agents' have in common is that they show (are expected to show, believed to show, promised to show in return for the next budget...) a certain kind of intelligence. "An agent is a software thing that knows how to do things that you could probably do yourself if you had the time", says Ted Selker of the IBM Almaden Research Centre (quoted from Janca 1995). They are like us, and we are like them. So is an agent a little software person, and if yes/no, how can we tell? In this paper we briefly review the psychological and philosophical origins of some key concepts of "intelligence" which contribute to what is called agent thinking today

In this paper, we investigate and discuss the problem how the abilities of computing and self-reproduction can be realized in a "reversible" environment, especially in reversible cellular automata (RCA). An RCA is a "backward deterministic" CA in which every configuration of the cellular space has at most one predecessor. Such systems have a close connection to physical reversibility, and have been known to play an important role in the problem of inevitable power dissipation in computing systems. This problem will become much more important when one tries to construct nano-scaled functional objects based on microscopic physical law. We first discuss how computation-universality can be obtained under the reversibility constraint, and show our models of one- and two-dimensional universal RCAs. Next, we explain a self-reproducing model on a two-dimensional RCA and its mechanism. Our new attempt of creating a three-dimensional self-reproducing RCA is also stated. 1 Introduction Cellular ...