Spontaneous Generation and Colony Formation in the Amoeba World

The Amoeba world is a Tierra-like system that explores the spontaneous generation, and subsequent evolution, of self-replicating digital organisms. We present results on the spontaneous generation of self-replicators (SRs) in a version of Amoeba that uses a basis set containing 32 distinct opcodes (machine instructions). These opcodes were chosen in such a way that a randomly generated sequence would require 9 essential instructions in order to be a SR. Surprisingly, we observed that self-replicating colonies were generated containing members with only 7 essential instructions. Such colonies can exist because their members share instruction pointers with their neighbors. Therefore, each member does not need to possess the machinery for retaining its pointer. The spontaneous generation of these colonies is combinatorially favored because the probability is higher that a randomly generated sequence gives rise to a SR if fewer essential instructions are required. Also, selection favors the evolution of colonies whose members minimize their code length. These colonies typically contain about 200 self-replicating members. We have investigated the colony structure but have not observed differentiation within a colony. Viruses are randomly distributed