Self-Reproduction and Evolution in Cellular Automata: 25 Years after Evoloops

TL;DR

The paper surveys 25 years of progress on self-reproduction and evolution in cellular automata, clarifying foundational concepts like Moore's criterion, Langton's criterion, and von Neumann's problem, and distinguishing self-replication from self-reproduction. It chronicles the rise of evoloops as the first CA system to exhibit Darwinian evolution through inheritable variation, and recounts subsequent extensions (asynchronous updates, self-protection, sex, dynamic environments) that broaden the evolutionary dynamics. The review then covers contemporary trends toward open-ended evolution and continuous CA (e.g., Lenia), highlighting work that pushes from self-replication toward true self-reproduction and evolving ecosystems, including neural CA and diffusion-based parameter mutations. It also outlines major open problems—robustness, open-endedness, autopoiesis, and the integration of space-based versus region-based genetics—along with directions for future research in continuous, distributed, and autopoietic CA models. Collectively, the article clarifies how Darwinian evolution can emerge in spatial computation and points toward design principles for long-term, open-ended artificial life in CA-inspired media.

Abstract

The year of 2024 marks the 25th anniversary of the publication of evoloops, an evolutionary variant of Chris Langton's self-reproducing loops which proved constructively that Darwinian evolution of self-reproducing organisms by variation and natural selection is possible within deterministic cellular automata. Over the last few decades, this line of Artificial Life research has since undergone several important developments. Although it experienced a relative dormancy of activities for a while, the recent rise of interest in open-ended evolution and the success of continuous cellular automata models have brought researchers' attention back to how to make spatio-temporal patterns self-reproduce and evolve within spatially distributed computational media. This article provides a review of the relevant literature on this topic over the past 25 years and highlights the major accomplishments made so far, the challenges being faced, and promising future research directions.

Figures (2)

• Figure 1: Spontaneous evolution of evoloops (image from Sayama1999a). Time indicates the number of updates applied.
• Figure 2: Various patterns evolved within Evolutionary Lenia (images courtesy of Bert Chan; from Chan2023).