# Parasitism > **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:** Ecology / Digital Evolution **Doc Type:** Canonical Wiki Node **Maturity:** Developed ## Definition Parasitism is an interaction in which one lineage gains resources or reproduction by exploiting a host and imposing a cost on it. ## Machine-Evolution Context Tierra’s shorter programs evolved to borrow replication machinery from neighboring hosts. The strategy was not scripted; it emerged from shared memory, scarce CPU time and selection on replication. ## Continuity and Evidence Boundary Digital parasitism is an ecological relation, not a moral accusation. It demonstrates how environmental architecture creates exploitable dependencies. ## Relationships [[wiki/Parasite|Parasite]], [[wiki/Host-Parasite Coevolution|Host-Parasite Coevolution]], [[wiki/Tierra|Tierra]], [[wiki/Hyperparasite|Hyperparasite]] ## Sources / Provenance - Thomas Ray, “An Approach to the Synthesis of Life” (1991); PNAS evolvable-AI review (2026).