Tierra (computer simulation)

In this context, the computer programs in Tierra are considered to be evolvable and can mutate, self-replicate and recombine.

Tierra's virtual machine is written in C.[1] It operates on a custom instruction set designed to facilitate code changes and reordering, including features such as jump to template[2] (as opposed to the relative or absolute jumps common to most instruction sets).

Processes such as the dynamics of punctuated equilibrium, host-parasite co-evolution and density-dependent natural selection are amenable to investigation within the Tierra framework.

According to Thomas S. Ray and others, this may allow for more "open-ended" evolution, in which the dynamics of the feedback between evolutionary and ecological processes can itself change over time (see evolvability), although this claim has not been realized – like other digital evolution systems, it eventually reaches a point where novelty ceases to be created, and the system at large begins either looping or ceases to 'evolve'.

[3] Mark Bedau and Norman Packard developed a statistical method of classifying evolutionary systems and in 1997, Bedau et al. applied these statistics to Evita, an Artificial life model similar to Tierra and Avida, but with limited organism interaction and no parasitism, and concluded that Tierra-like systems do not exhibit the open-ended evolutionary signatures of naturally evolving systems.