As one recall's the Cretaceous period of the Tertiary marked the extinction of the dinosaurs. The Earth is approximately 4.55 billion years old and the first life dates to 3.5 billion years ago. The first primates appeared nearly 60 million years ago; this was after the dinosaurs had become extinct. Primate creatures were beginning to evolve by the end of the Mesozoic Era (ca. 65 m.y.a). Over millions of years, the continents have drifted to their present locations, carried along by the shifting plates of the earth's surface. During the Cenozoic era, most land masses had tropical or subtropical climates. Also during this time, Mammals were replaced by reptiles as the dominant large land animals.

In the Cenozoic era there are two periods: Tertiary and Quaternary. Each period is subdivided into epochs. The Tertiary had five epochs: Paleocene, Eocene, Oligocene, Miocene, and Pliocene...