ABSTRACT
The story of life on the Earth is there for us to read. It is written in the rocks in the form of fossils. Indeed, scientists have been analyzing such rocks for more than a century, and now, we have a pretty good idea of when and how life advanced from microorganisms into plants and animals. We know because they left images of themselves, in the form of fossils. They are the preserved forms of plant and animal remains, sometimes many millions of years old. They progressively record the first fishes, the first amphibians, the first reptiles, and the first mammals. We are particularly interested in the mammals because we humans are mammals and this book is about our evolutionary story. This chapter introduces the concept of rocky strata as a chronological record of life evolution. It also discusses fossils, what they are, and how they form.
