Kauffman's model: above a critical connectivity threshold, catalytic closure emerges spontaneously
Kauffman (1971): given N chemical species and reactions catalyzed by other species, a catalytic closure — a self-sustaining set — emerges above a critical connectivity threshold.
Food set = externally supplied molecules. Closure = a set S where every reaction producing a member of S is catalyzed by some member of S.
The transition resembles a phase transition: above critical p×q, large autocatalytic sets spontaneously appear. This may explain abiogenesis.