Reciprocal Linkage between Self-organizing Processes is Sufficient for Self-reproduction and Evolvability Terrence W. Deacon Department of Anthropology and Helen Wills Neuroscience Institute University of California, Berkeley, CA, USA deacon@berkeley.edu Abstract A simple molecular 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 growth will also occur with high predictability. Growth to closure will be most probable in the vicinity of the most pro- lific 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 com- ponents will initiate production of additional catalytic and cap- sule components that will spontaneously re-assemble into one or more autocell replicas, thereby reconstituting and some- times reproducing the original. In a diverse molecular envi- ronment, cycles of disruption and enclosure will cause auto- cells 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 al- tered 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 com- monly required substrates. Autocells are susceptible to a lim- ited 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. Keywords artificial life, autocatalysis, nonequilibrium, origins of life, protocell, replicator, self-assembly January 7, 2006; accepted March 30, 2006 136 Biological Theory 1(2) 2006, 136–149. c 2006 Konrad Lorenz Institute for Evolution and Cognition Research