xii Introduction 



daily cycle and the seasonal cycle may limit for many people 

 the span of attention and the range of imagination. From 

 earliest times, however, close observers have noted much 

 more. The actual composition of the living world is chang- 

 ing although it is at this stage impossible to go farther back 

 than the memory of a life-time. Well on into the Christian 

 era the thoughtful observers and the meditative minds were 

 " evolutionists." That is, those who thought at all took it 

 for granted that plants and animals changed not only in 

 the course of each individual's development, but also in 

 the course of time from one type to another. The existing 

 population^ it was assumed, is descended froTU its ancestors 

 with constant change. i 



From the time of St. Augustine in the Fifth Century 

 both the theologians and the lay scholars accepted as a mat- 

 ter of course the descent of living forms of the present from 

 more primitive ancestors as part of the historical view that 

 everything which has come to pass is part of the unrolling 

 of the scroll of the universe. This general theory of evolu- 

 tion was colored at one time by Greek speculation about the 

 nature of the world and of matter. At another time it was 

 colored by theological speculations of the church fathers, 

 yet it was a part of the intellectual equipment of western 

 civilization through many centuries. 



There is no essential difference between the evolution 

 of modern biologists and the evolution of Saint Augustine, 

 except perhaps in the former's search for mechanisms and 

 in the latter's assumption of an ultimate act of creation. 

 The scientist does not pretend to know what the beginnings 

 of life were. For his purposes, the study begins with things 

 as found. However far our speculations may lead us, he 

 considers the ultimate questions of origins, purpose and des- 

 tinies as outside his special province. 



A middle-aged person who Is told for the first time 

 that the world is round would find It difficult to assimilate 

 the Idea to his previous experience and thinking. It Is not 

 stupidity that makes one ask how the inhabitants of the an- 



