  Open-ended evolutionary dynamics remains an elusive goal for artificial
evolutionary systems. Many ideas exist in the biological literature beyond the
basic Darwinian requirements of variation, differential reproduction and
inheritance. I argue that these ideas can be seen as aspects of five
fundamental requirements for open-ended evolution: (1) robustly reproductive
individuals, (2) a medium allowing the possible existence of a practically
unlimited diversity of individuals and interactions, (3) individuals capable of
producing more complex offspring, (4) mutational pathways to other viable
individuals, and (5) drive for continued evolution. I briefly discuss
implications of this view for the design of artificial systems with greater
evolutionary potential.
