Others would be connected only intermittently. Each would have its own speed, its own operating system, its own quirks. Each program is 32 instructions long, and each instruction is a five-bit number. For each generation, the operating system runs these tiny programs once, performing the commands as it comes to them. This creates variation, the first of the two drivers of evolution.
Many mutations make no difference.
But others do. Through the Tierra operating system, the human operators have Godlike control. They can define how fast the creatures will mutate and specify how much time they get on the central processor to reproduce. Ray hopes that Tierra will answer a number of questions that have remained unanswered up to now. In the real world, species rely on an ecological niche created by differences as slight as a change in the colour of tree bark.