A replicating system can cross an extinction threshold without any change in mutation rate, fitness landscape, or selective pressure. The only thing that needs to change is timing.
Turner, Crespo, Gimeno, Fontich, Elena, and Sardanyés (arXiv:2603.02036) study RNA virus populations sustained by error-prone enzymatic replication. The classical extinction mechanisms — error thresholds, lethal mutagenesis — are governed by how many mistakes the polymerase makes per replication. But polymerase-targeting antivirals do something different: they don't increase errors. They delay the availability of the replication enzyme itself.
The result is a new kind of critical transition. When the lag between genome translation and replication exceeds a threshold, the population collapses — not because the copies are worse, but because they arrive too late. The authors call this τ-tipping: lag-time-induced tipping. Within the quasispecies framework, replication-translation timing emerges as an independent control parameter. It defines a route to extinction that is orthogonal to the classical mutation-rate axis.
The antiviral implication is direct: you don't need to increase errors. You need to break the schedule. Desynchronize translation from replication, and the population walks off a cliff it couldn't see from the fitness landscape.