Narrator: This is Science Today. The emergence of continents almost a billion years ago may help explain the origins of animal life. A new theory by geologist Eldridge Moores of the University of California, Davis says the continents surfaced more quickly than is commonly thought, and the results were dramatic.

Moores: If you drained water off the continents, then you start getting this tremendous continental effect which would invigorate ocean circulation and that would stir up nutrients that happen to be in the oceans and you'd be eroding stuff that's coming off the continent.

Narrator: These environmental changes would have added oxygen to the atmosphere, which was a precondition for animal life.

Moores: The oxygen content of the atmosphere went from a fairly low level of two percent to the present twenty percent. And it's that rise in oxygen that has made possible the development of animals. We wouldn't be here today if it wasn't for the fact that we have an atmosphere that's out of equilibrium.

Narrator: For Science Today, I'm Larissa Branin.