To prevent his digital organisms from running rampant in the real world as computer viruses or worms, Ray sets up his artificial-life scenarios within a software program that acts as a virtual computer. Outside the program, the computer creatures and their environment are simply innocuous streams of data that are no more risky than a text file on a word processor. No other attempts to create artificial life have been this successful, according to Ray. In simulations, everything is predefined. But, if you set up preconditions ahead of time, you only get back what you set up.
Evolution is more freewheeling.
Nature starts out with molecules that stumble onto innovations, and they get ahead when they make these innovations. Ray's only requirements were that the creatures could reproduce and were capable of open-ended evolution. Several necessary mechanisms were built into the program. These digital organisms could be inserted in subsequent experiments. Spontaneous diversification occurs rapidly, Ray says.