Abstract Asimplemolecular system (“autocell”) is described consisting of the reciprocal linkage between an autocatalytic cycle and a self-assembling encapsulation process where the molecular constituents for the capsule are products of the autocatalysis. In a molecular environment sufficiently rich in the substrates, capsule growthwill also occur with high predictability.Growth to closure will be most probable in the vicinity of themost prolific autocatalysis and will thus tend to spontaneously enclose supportive catalysts within the capsule interior. If subsequently disrupted in the presence of new substrates, the released components will initiate production of additional catalytic and capsule components that will spontaneously re-assemble into one or more autocell replicas, thereby reconstituting and sometimes reproducing the original. In a diverse molecular environment, cycles of disruption and enclosure will cause autocells to incidentally encapsulate other molecules as well as reactive substrates. To the extent that any captured molecule can be incorporated into the autocatalytic process by virtue of structural degeneracy of the catalytic binding sites, the altered autocell will incorporate the new type of component into subsequent replications. Such altered autocells will be progenitors of “lineages” with variant characteristics that will differentially propagate with respect to the availability of commonly required substrates. Autocells are susceptible to a limited form of evolution, capable of leading to more efficient, more environmentally fitted, and more complex forms. This provides a simple demonstration of the plausibility of open ended reproduction and evolvability without self-replicating template molecules (e.g., nucleic acids) or maintenance of persistent nonequilibrium chemistry. This model identifies an intermediate domain between prebiotic and biotic systems and bridges the gap from nonequilibrium thermodynamics to life.