Chapter 7

The title of this chapter is the history of life. This is a chapter with the most gorgeous words I have ever read. Let me just copy some beautiful paragraphs down from the book. I know I cannot write so well as the book.

One of the most important achievements of science has been the discovery of change, the discovery that everything in the universe, from the scenery outside the window to the stars in the sky, has always been changing. Hills are worn down into plains; rocks crumble into soil. New mountains rise from the earth; sea bottoms become dry land; continents break up and drift apart. The face of the earth changes and with it the kinds of animals and plants that live on it. So slowly do these changes occur that our memory, even when aided by written records, can scarcely be expected to encompass them. The few thousand years of civilization are but a fleeting moment in the giant calendar of earth events. Indeed, only in the last century have we understood the meaning of the evidence that lies around us, the evidence that says: the earth is very old; the earth is ever-changing. Animals and plants of the past have recorded their own history in a number of different ways. Let us consider some of these.

One of the records left by ancient plants and animals is fossils. Here is what the book depicts. Ancient life has left us a monumental library inscribed in stone, in which the rocky books are stacked one on top of the other. The oldest volumes in this picture-book library are on the bottom of the pile and the most recent acquisitions are on top. The library of stacked volumes is made of the layers of sedimentary rocks that have accumulated down through the ages. These rocks and the fossils in them were formed underwater from soft mud and sand that later hardened into stone. Layer upon layer of rocks was built in this way. In a later period the whole mass might have been elevated by a great earth movement or the sea may have receded, making the rock a part of our visible landscape.

There is a chart in the book that illustrates the progress of lives through eras. According to the chart, some of the lives appearing in chronological order were bacteria, worms, amphibians, reptiles, dinosaurs, and mammals. Humans are newcomers. If all earth time were compressed into one year, human beings would come on the scene on December 31 just a few hours before midnight. With the coming of humans to earth anew force has been added-intelligence. With this intelligence humans have the power to change the earth in many ways/ for the first time a species existing that can deliberately and consciously influence its own future evolution-or its own extinction.

From our knowledge of the past there is every reason to believe that change will go on. The geologic forces that have been shaping the earth for billions of years will continue to be active. New forms of life will emerge.