Life Is a Percolation Threshold

01The evidence

• Bifurcations and phase transitions have been analysed as the mathematical structure of the origin of life, with self-sustaining reaction sets treated as a collective property of a network rather than of a molecule.Philosophical Transactions B, 2025
• Thresholds of this kind have been catalogued across origin-of-life scenarios, which shows the field already suspects that the transition is collective but has not agreed on the order parameter.Thresholds in origin-of-life scenarios

02The tension

The two dominant programmes disagree about whether RNA or metabolism came first, and each has a plausible chemistry and an implausible step. Neither explains why the transition appears to have happened quickly and, as far as we know, once. A chemistry-specific account has to explain a singular event; a network account does not.

03The theory

Model the prebiotic soup as a graph: molecules are nodes, reactions are edges, and catalysis is a property that lets certain nodes accelerate certain edges. As diversity rises, the number of potential catalytic interactions rises faster than the number of molecules, and at some density a connected autocatalytic set spans the graph.

That is a percolation transition, and percolation transitions have a characteristic structure: a critical point, a diverging correlation length, and a sharp change in the size of the largest connected component. None of those features depends on which molecules are involved.

The consequence is that the origin of life is a phase transition in diversity, not a sequence of chemical lucky breaks. The soup reaches a critical number of distinct species and the network becomes self-sustaining. The specific chemistry determines which set percolates first, not whether percolation happens.

The theory is testable in two directions. In simulation, the critical diversity should scale with network degree in the way percolation theory predicts. In the lab, mixtures near the threshold should show bistability, flipping between quiescent and autocatalytic states with small changes in composition.

04What this is not

05Predictions

• P1There should be a critical molecular diversity for sustained autocatalysis, and it should scale with network degree as percolation theory predicts.
• P2Mixtures near the threshold should show bistability and hysteresis, switching states with small composition changes.
• P3The threshold should be largely independent of which molecular families are used, provided diversity and reactivity are matched.

06What would refute it

Autocatalysis that requires specific catalysts at every level of diversity, with no threshold behaviour, would leave the network account without a phenomenon.

07What it would change

It would reframe origin-of-life experiments as threshold measurements rather than molecule hunts, and give the field a shared order parameter.