Current research on the origin of life aims at finding the simplest entity that can undergo spontaneous Darwinian evolution toward increasing replication efficiency. Here I consider some of the models of self-replicating molecular systems, and I show that they exhibit a distinct feature, namely, an infinity of stationary states forming a continuous curve; i.e., they are only marginally stable. I show that, in marginally stable chemical systems, thermodynamic fluctuations induce a drift directed toward increasing replication efficiency. This drift represents a form of evolution, taking place slowly, cooperatively, in macroscopic volumes of water.

• Received 13 May 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.058102