Science has an uncomfortable way of pushing human beings from center stage. In our prescientific stories, humans began as the focal point of Nature, living on an Earth that was the center of the universe. As the origins of the Earth and of mankind were investigated more carefully, it became clear that Nature had other interests beyond people, and the Earth was less central than previously hoped. Humankind was just one branch of the great family of life, and the Earth is a smallish planet orbiting an unexceptional sun quite far out on one arm of a run-of-the-mill spiral galaxy.