This letter presents a new, artificial-life-based view of the Collatz problem, a well-known mathematical problem about the behavior of a series of positive integers generated by a simple arithmetical rule. The Collatz conjecture asserts that this series always falls into a 4 → 2 → 1 cycle regardless of its initial values. No formal proof has been given yet. In this letter, the behavior of the series is considered an ecological process of artificial organisms (1s in bit strings). The Collatz conjecture is then reinterpreted as the competition between population growth and extinction. This new interpretation has made it possible to analytically calculate the growth and extinction speeds of bit strings. The results indicate that the extinction is always faster than the growth, providing an ecological explanation for the conjecture. Future research directions are also suggested.

Symbiosis is the phenomenon in which organisms of different species live together in close association. Symbiogenesis is the name given to the process by which symbiotic partners combine and unify. This letter reconsiders previous work using the NKCS model of coevolution to explore symbiogenesis. In particular, the role of different replication rates between the coevolving partners is considered. This is shown to provide a broader scope for the emergence of endosymbioses and subsequent horizontal gene transfers.

We propose a self-replicating machine that is embedded in a two-dimensional asynchronous cellular automaton with von Neumann neighborhood. The machine dynamically encodes its shape into description signals, and despite the randomness of cell updating, it is able to successfully construct copies of itself according to the description signals. Self-replication on asynchronously updated cellular automata may find application in nanocomputers, where reconfigurability is an essential property, since it allows avoidance of defective parts and simplifies programming of such computers.

A simple abstract model is presented to show that a species with a favorable global effect on the whole biota (for example, by generating a moderate temperature range) can be selected through evolution. In the model, fluctuation in the growth rate among species leads to selection. The accompanying fluctuations in the quantity of resources, which return by circulation with a certain time lag, are likely to cause this selection. Different functions and various parameters are applied to the equations to monitor their effects on the whole system. In nature, producers satisfy the theoretical conditions of the model, implying the reality of the selection described by the mechanism presented here, during the history of the biota.

In a traditional cellular automaton (CA) a cell is implemented by a rule table defining its state at the next time step, given its present state and those of its neighbors. The cell thus deals only with states. We present a novel CA where the cell handles data and signals. The cell is designed as a digital system comprising a processing unit and a control unit. This allows the realization of various growing structures, including self-replicating loops and biomorphs. We also describe the hardware implementation of these structures within our electronic wall for bio-inspired applications, the BioWall.

The concept of self-protection , a capability of an organism to protect itself from exogenous attacks, is introduced into the design of artificial evolutionary systems as a possible method to create and maintain diversity in the population. Three different mechanisms of self-protection are considered and implemented on a cellular-automaton-based evolutionary system, the evoloop . Simulation results imply a positive effect of those mechanisms on diversity maintenance, especially when the self-protection is moderate so that it conserves both the attacker and the attacked. This letter briefly reports the models and the simulation results obtained using those models.

This letter describes an evolutionary system for creating lifelike three-dimensional plants and flowers, our main goal being the facilitation of producing realistic plant imagery. With these two goals in mind—ease of generation and realism—we designed the plant genotype and the genotype-to-phenotype mapping. Diversity in our system comes about through two distinct processes—evolution and randomization—allowing the creation not only of single plants but of entire gardens and forests. Thus, we are able to readily produce natural-looking artificial scenes.

“Strong artificial life” refers to the thesis that a sufficiently sophisticated computer simulation of a life form is a life form in its own right. Can John Searle's Chinese room argument [12]—originally intended by him to show that the thesis he dubs “strong AI” is false—be deployed against strong ALife? We have often encountered the suggestion that it can be (even in print; see Harnad [8]). We do our best to transfer the argument from the domain of AI to that of ALife. We do so in order to show once and for all that the Chinese room argument proves nothing about ALife. There may indeed be powerful philosophical objections to the thesis of strong ALife, but the Chinese room argument is not among them.

Self-replicating loops presented to date are essentially worlds unto themselves, inaccessible to the observer once the replication process is launched. In this article we present the design of an interactive self-replicating loop of arbitrary size, wherein the user can physically control the loop's replication and induce its destruction. After introducing the BioWall, a reconfigurable electronic wall for bio-inspired applications, we describe the design of our novel loop and delineate its hardware implementation in the wall.