CHAPTER ONE Nothing But Time Just about everybody enjoys a birthday party After all birthday parties are fun They involve friends presents and a cake More than anything birthday parties mark a year's passage of time in the life of one human being
But marking time's passage for all the living things on planet Earth isn't quite so easy Marking time for all living things in the planet's entire history is even harder That's partly because one year in the life of a person is less than a split second when compared to the life of the planet Earth itself Earth has been around far longer than human beings In other words the planet has had many birthdays before there were people living on it to help celebrate
So how can we know things about Earth from the time before there were people The answers lay in the discovery and study of fossils Fossils represent time lots and lots of time They are snapshots that we can look at to learn about prehistoric life that existed an incredibly long time ago Some fossils are the remains of ancient plants or animals Some fossils are of plants or animals that still exist today
While Earth's exact age is impossible to know with certainty scientific dating methods used on rocks show the Earth to be about four and a half billion years old By contrast the fossils of modern humans date back merely thousands of years That leaves billions of prehistoric years with no human witnesses It's difficult to understand just how much time that is The noted scientist and fossil expert Stephen Jay Gould once said that if the timeline of life's history on Earth were represented by a person's arm the part of the arm occupied by human beings would amount to no more than a single fingernail clipping The rest of the finger hand and arm all the way back to the shoulder would Stephen Jay Gould represent prehistory Almost all of what we know about prehistoric life comes from fossils
