PIV PACE 
THE past history of our race 1s far too vast and complex a 
subject to be surveyed adequately by any one individual. 
Hence this book is the result of cooperative effort on the 
part of workers in several different fields, all, however, 
with a direct bearing on the subject. 
Dr. Charles G. Abbot, Secretary of the Smithsonian 
Institution and Editor-in-Chief of the present Serres, has 
assumed the task of writing the first three chapters. In 
the first two of these he has described the setting of the 
cosmic stage upon which the human race is playing its 
part; while in the third he has told of the prenatal life of 
the individual, which so strikingly recapitulates the de- 
velopment of the species in many ways. 
The portions of the book dealing with the physical 
characteristics of prehistoric man have been based very 
largely upon the work of Dr. AleS Hrdlitka, of the Na- 
tional Museum, Chapters VII and VIII in particular hav- 
ing been taken almost verbatim from a technical mono- 
graph specially prepared by him for the Smithsonian 
Institution. 
For the remaining chapters and especially for those 
dealing with man’s cultural progress, the writer is re- 
sponsible. 
In order to avoid confusing the reader, the distinction 
between man’s physical development and his progress in 
civilization has been carefully maintained. In discussing 
the former, the plan has been followed of working back 
from the recent to the more remote past—from familiar 
types to those less well known. This method enables us 
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