there were quite a few approaches (more or less accurate) to society simulators. i can't provide you with links but just type AI in google and after a while of search you should find many virtual lakes, anthills etc.

my suggestion is to gather as many AI gurus as possible and create some well-developed engine that would control a society of species with some possibility of interfering in the world. the AI engine would react naturally to the changes made.

the goals of the game aren't that important in my opinion. people could have missions or scenarios (like in many other strategy games) but the main fun would focus on building and developing society just like in sim city etc.

that's just my suggestion

take care all