# Self-Replicating Loop > **Machine-Evolution Nexus:** [[articles/Digital Darwinism and the Invisible World of Machine Evolution|Digital Darwinism and the Invisible World of Machine Evolution]] places this node within the history and governance of substrate-independent evolution. **Domain:** Cellular Automata / Artificial Life **Doc Type:** Canonical Wiki Node **Maturity:** Developed ## Definition A self-replicating loop is a bounded cellular-automaton structure that extends a construction arm, copies its encoded pattern and produces another loop. ## Nexus Context Langton’s loop separated practical self-reproduction from universal construction. Sayama’s descendants added inheritable structural variation and competition, crossing into Darwinian evolution. ## Evidence Boundary Faithful loop replication alone is heredity without an evolving population. It does not imply metabolism, intelligence or sentience. ## Relationships [[wiki/Christopher Langton|Christopher Langton]], [[wiki/Evoloop|Evoloop]], [[wiki/Self-Replication|Self-Replication]], [[wiki/Universal Constructor|Universal Constructor]] ## Sources / Provenance - Langton (1984); Sayama and Nehaniv (2025).