A Science Odyssey

1900: As the twentieth century dawns, scientists have few hard facts about the origins of Earth, humans, or life itself. Most believe the Earth was formed from material torn from the sun, and that as it cooled, its surface contracted, buckled, and cracked, creating mountains and oceans and causing earthquakes and volcanoes. We know little about our prehistoric ancestors. Our best clues are in the few ancient fossils recovered in Europe and Asia. The mechanism of evolution, by which physical traits are passed from one generation to the next, is unknown. Today: Our planet is not a static platform for life. The Earth is dynamic and unpredictable. Its surface is composed of large moving plates that consist of both the continents and oceanic crust. The movement is only a few centimeters a year, but it's enough to reshape the Earth, build mountains, spawn earthquakes, and create volcanoes. The accumulation of fossil finds has shown that the birthplace of the human species is in Africa. With the discovery of the structure of DNA has come an understanding of the mechanism by which chemical molecules pass on the code of heredity, creating the basis for evolution and the diversity of life.