Obligate Synchrony is a work of speculative science fiction presented entirely as a recovered archival record of a long-term evolutionary experiment.Within two isolated systems, the same pair of interdependent species are observed over successive generations. Each species produces a single resource essential to the survival of the other. Neither can evolve independence. From identical beginnings, the systems diverge under pressure, mutation, and selection.The narrative unfolds through timestamped logs, statistical summaries, internal reviews, and ethical annotations authored by the experiment's observers. There are no scenes, no dialogue, and no omniscient explanation. Meaning emerges instead from what is recorded, what is abstracted into data, and what quietly disappears from the archive altogether.As environmental conditions destabilize both systems, the observers are forced to confront the consequences of sustained non-intervention. The resulting record becomes not only a chronicle of evolutionary outcomes, but a study of observation itself: its limits, its costs, and the moral weight carried by those who claim neutrality.Blending evolutionary theory, systems analysis, and philosophical inquiry, Obligate Synchrony examines the tension between dominance and cooperation, survivability and dignity, and whether the act of understanding confers responsibility. It is a formally experimental novel for readers drawn to idea-driven speculative fiction, ethical science fiction, and works that challenge the boundary between documentation and narrative.