From the game guide

Procedural Generation

Unlike most games on the market today, Spore will rely on procedural generation to deliver its content rather than hiring hoardes of artists to generate gigabytes of artwork. The premise is simple: use programatic methods to generate artwork rather than creating millions of textures, shapes, and behaviours by hand.

The old way and the “Mountain of content” problem

Traditionally, video games hire several artists to individually create the content for the game. Each building, each person, each texture you see in the game is usually created by an artist. This content is then saved into individual files and loaded up each time you start the game.

The problem becomes when the scope of the game increases. As levels start expanding, more and more content is required. In order for players to have a seamless experience, hundreds — maybe even thousands of similar objects need to be created. Some games have thousands of trees for example. So, how do you create enough content to fill up a Sim-Everything? Do you hire thousands of artists to construct the universe from hand? It becomes clear that there has to be a better way.

Enter procedural generation

The premise of procedural methods is built on the simple idea to use programatic methods to generate content. Instead of hiring an artist to design 10,000 trees, an algorithm could be developed to create 10,000 trees based upon the surroundings and random defects.

Procedural generation also gives Spore the power to bring creatures made in the creature editor to life. The game will analyze the bone structure and body shape of your creature and figure out how your creature will walk, play, eat, and sound like.

Procedural generation coupled with content sharing allows Spore to encompass everything from individual cells to the Universe itself.