The player is basically given control of one of the earliest animals to walk the planet and is charged with helping the creature to survive, spread and ultimately evolve into something more than it started out as.

It plays out a little like a mixture of Civilization and SimEarth so if you're into either of these games, you might want to take a look here. This is rather an abstract little game but one which is quite intriguing, if a little pointless in the end, and which makes for an entertaining time waster.