Spanning a period of several millennia, the game's story involves Gaia, daughter of the sun and mystical embodiment of the Earth, guiding the player through five distinct geological periods of the planet's history. Beginning the game as a simple fish, the player must travel across the planet defeating enemies and gaining the strength to evolve into more powerful and complex organisms before eventually reaching earning a chance to enter the paradise realm of Eden, becoming Gaia's immortal partner. However, strange crystals with the ability to influence evolution are laden throughout the player's quest, with the mystery of their origin becoming a secondary factor to the story.
Source: Wikipedia, E.V.O.: Search for Eden , available under the CC-BY-SA License.