The purpose of this chapter is to put all the other chapters into perspective. Students are often confused about the spans of time—both absolute and relative—that are involved in the history of the earth, not to mention the history of the universe. In one profound sense, none of the rest of this book makes sense without understanding where our species fits into the bigger picture, both in time and in the fact that we are part of all the processes that have been in operation since the very beginning, whenever that was.
The first part of the chapter tells the history of the universe, focusing, of course, on the earth. It tells, simply, what happened when and in what order, and gives, albeit briefly, some sense of how these things happened and how we know.
The second part returns to the discussion from Chapter 2 about the pace of geological and biological evolution, looking at the process and results of plate tectonics—a rather uniformitarian process—and the catastrophic punctuations that resulted in mass extinctions that radically altered the nature of evolution.
The summary introduces the idea of evolution (indeed, of history in general) as a series of contingent events.
