Tom Ray was a tropical biologist who conducted research in the Costa Rican rain forest from 1974 to 1989. His research focused on the ecologies and evolution of various species living there. Eventually he realized he there was a problem with studying evolution in the wild: it occurs far too slowly to actually observe it. He decided therefore to study evolution in a much faster medium, the digital computer. In 1991, he joined forces with the Santa Fe Institute in New Mexico to develop an evolutionary software platform called Tierra.
Genetic Algorithms, programs that simulate evolution to solve a specific problem, had already been well established, but Tierra was different. It wasn’t optimizing anything in particular. Small chunks of machine code were simply left on their own to replicate and compete for access to the CPU, and that was all. Occasional mutations in the copying process allowed evolution to take place. But, this wasn’t a simulation of evolution, these entities were actually evolving. What emerged from Tierra surprised Tom and most of the Santa Fe research team.
The first thing Tom noticed was that these replicating programs became smaller and smaller. A smaller program could replicate faster and so had an advantage over others. Some became so small that they evolved into parasites, tricking other programs into doing the copying for them. The hosts then evolved mechanisms to resist parasites. Some of the host programs were even able to trick the parasites into helping them. Eventually, a form of cooperation emerged where programs helped each other replicate. Then, free-riders emerged who took advantage of this group trust. All of this robust behavior, previously only observed in nature, emerged from Tierra automatically.
Tierra was groundbreaking for the field of Artificial Life, and inspired many systems like it afterwards, including the very robust evolutionary platform, Avida. Most importantly, it gave a demonstration of real evolution occuring in a medium other than nature.
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