Dig through AltaVista or your favourite web skimmer and look for
references to "ALife" and to "Tierra." Related pages should swamp you
in references; the Nova Genetica page is chok full of goodness.
Ah yes, Life, one of the early cellular automata. It might amuse you
to know that the environment that amused a 12yr old boy, as you put
it, is the target of heavy research. Simple CAs like Life can host
very complex interacting entities, made up of nothing but cells that
blink on and off.
> Could you have moved your virtual people into other "worlds"? Does the
> world have to be specifically geared to support them, or can it be totally
> alien, like dropping them into a game of Sonic the Hedgehog :0
Like most life, if you take them out of an environment which supports
the physics their biologies depend on, they die quickly. In the case
of Tierran organisms, they are nothing but strings of assembly-like
code. Without an interpreter, they're just lumps of data like we're
just lumps of matter without consciousness.