Evolution produces inherited responses to arbitrary messages in an artificial ecology

Can agents evolve responses to messages when communication is neither assigned a purpose nor directly rewarded? We evolved sexually reproducing neural agents in an artificial ecology where all agents could emit and receive four arbitrary symbols. The world provided no communication task, assigned speakers or listeners, predefined meanings, or direct reward for messaging. We ran three banks of 24 worlds under a protocol fixed in advance. Ten populations met activity and identity-count requirements set before their response effects were measured. Replaying natural interactions with messages removed or replaced revealed causal effects on evolved receiver-controller outputs; matched founders showed no detectable effects after correction. To test inheritance, we developed newborn agents from evolved genomes in matched founder worlds, without transferring adult memories or acquired state. In all 10 populations, newborn response patterns were more similar to evolved adult patterns than founder patterns were. Mean improvements in cosine similarity were +0.849 with equal weight per sender and +0.729 with equal weight per receiver; each exact population-level sign-flip test gave p = 0.0009766. These populations were nested within three banks. Both banks eligible for a separate, predefined directional safeguard passed. A second endpoint, inheritance of population-specific symbol frequencies, did not pass. Evolution thus produced genome-mediated responses to arbitrary messages without a communication-specific objective. The finding establishes inherited causal receiver sensitivity; message meaning, ecological benefit, and evolutionary adaptation of senders remain separate questions. This upload contains the paper and its supplementary information. The simulation code, analysis code, and raw data are not publicly available.