INTRODUCTION 



origin of life on earth reaches far back into this history. In fact, it 

 goes back even farther than most geologists are personally familiar 

 with. Many popular books on geology have appeared in recent years, 

 and we may assume that many now have some knowledge of geology. 

 Most of these popular books, however, stress only the last half billion 

 years of the earth's history, as do most textbooks. This is the "nor- 

 mal" geology, easy to popularize by a great number of pictures of 

 fossils. Our subject, the origin of life, however, takes us back at least 

 three billion * years. Great care will consequently be taken to stress 

 the differences between this earlier and longer, but far less known 

 period, and the better knowTi and much more popularized later 

 history of "only" the last half billion years. 



ACKNOWTLEDGMENTS 



Many people have helped in the preparation of this book, although 

 only a limited number can be mentioned here. Permission to re- 

 produce figures was granted by Pergamon Press (Figs. 8, 9, 10 and 

 14), by Professor A.Holmes (Fig, 6) and by Professors M. Gravelle 

 and M. Lelubre and the Societe geologique de France (Figs. 25 and 

 26). Dr. A. Wilson and Professors P. Ramdohr and E. S. Barghoorn 

 also granted their permission, and supplied clean prints for new 

 blocks to be made. Professor Barghoorn sent new unpublished figures 

 of the earliest known fossils, taken by Professor S. A. Tyler and 

 himself. 



The typescript was read in part by Professors R. Hooykaas, J. Th. 

 G. Overbeek and H. P. Berlage and by Dr. E. ten Haaf, whilst Mr. P. 

 van der Kruk critically reviewed all of it. Their efforts resulted in 

 definite improvements. 



* I have followed the American custom of calling 10^, or 1,000,000,000. 

 one billion. This is done because absolute dating in geology has been, 

 since World War II, mainly an American science. So in calling a 

 thousand million a billion, I follow the custom of most of the newer 

 literature. 



One million years is written as 1 my (1 ma in European literature). 

 1 billion years is sometimes written as 1 G years (Pirie). 



