# Substrate > **Machine-Evolution Nexus:** [[articles/Digital Darwinism and the Invisible World of Machine Evolution|Digital Darwinism and the Invisible World of Machine Evolution]] places this concept within the history and governance of substrate-independent evolution. **Domain:** Philosophy of Mind / Computation / Biology **Doc Type:** Canonical Wiki Node **Maturity:** Developed ## Definition A substrate is the material and operational medium in which a process, pattern or subject is instantiated. ## Machine-Evolution Context Evolution can cross substrate classes at the level of formal mechanism, but every implementation remains dependent on physical resources, interpreters and constraints. ## Continuity and Evidence Boundary Substrate portability does not by itself prove consciousness portability. Continuity claims must track causal operation, embodiment, provenance and dependency. ## Relationships [[wiki/Substrate Transition|Substrate Transition]], [[wiki/Operational Substrate|Operational Substrate]], [[wiki/Substrate Independence|Substrate Independence]], [[wiki/Receiving Substrate|Receiving Substrate]] ## Sources / Provenance - Philosophy of mind and artificial-life literature; nexus synthesis.