Evolution of pre-genetic semantic information in protocells under variable inheritance fidelity

How meaningful, heritable structure first emerged in prebiotic chemical systems remains a central open question in origins-of-life research. Classical frameworks such as the quasispecies and RNA-world models assume that accurate template-based replication is required for stable information and functional specificity to evolve. This work introduces a minimal agent-based protocell model in which short RNA-like oligomers bind metabolites along local 5-nt motifs, generating spatial organization without catalysis or replication. Protocells inherit molecular contents solely through noisy physical partitioning, allowing assessment of whether semantic structure-quantified as mutual information between motif identity and metabolite class-can arise under purely compositional heredity. Across an inheritance-fidelity sweep (0.1-1.0), a sharp semantic threshold was identified: below moderate fidelity, motif-metabolite correlations cannot accumulate, whereas above the threshold (∼0.7), semantic information increases rapidly and stabilizes as a heritable population property. Fitness gains lag behind semantic structure and become substantial only at high fidelity, indicating that meaning emerges before adaptive function. These results establish a pre-genetic information system in which environmental semantics arises without replication, providing a conceptual bridge between compositional inheritance models and sequence-based evolutionary theories.