Early Earth Was Not Arbitrary: Retrodictive Constraints on Pre-2.0 Ga Planetary Survivability

The earliest history of Earth remains one of the least constrained intervals in planetary science, limited by sparse geological records and extreme sensitivity to initial conditions. This study introduces a retrodictive, constraint-based simulation framework to explore which classes of early-Earth histories are compatible with the long-term persistence of oceans, crustal stability, and durable biochemical information. Rather than reconstructing a single speculative trajectory, the model evolves backward from known survivability constraints, eliminating histories that violate physical, geochemical, or informational persistence requirements. Across a broad ensemble of candidate histories spanning 2.5 billion years, the results reveal a rapid collapse of possibility space toward a small subset of viable trajectories. These surviving histories converge on stable causal network topologies despite extreme environmental noise, impact flux, and geochemical variability. The findings suggest that early Earth survivability was neither inevitable nor arbitrary, but instead depended on entry into narrow constraint corridors in physical and informational state space. This work provides a complementary perspective to forward simulations and offers a general framework for evaluating deep-time planetary habitability under profound uncertainty.