The program by Tom Ray called Tierra is also well-known. It starts with a species that originally has 80 instructions. The creatures multiply and evolve until the computer s storage capacity is full. From then on the population is controlled by killing off creatures ranking lower on a fitness scale. One common outcome is the evolution of parasitism.
Parasitism is known to be important in biological evolution.
But the evolution of parasitism does not necessarily require any new genes the genes of the parasites and hosts already exist beforehand. True, biological genomes that become related in this way may in fact require new genes to make them compatible with each other. But in Tierra, nothing suggests that anything analogous to a new gene is ever created. John Koza s models of evolution, called Genetic Programming, start with selected algorithms that are shuffled and duplicated to create new subroutines. The subroutines are bred for their ability to solve a basic problem.