BASIS OF THE PKOBLEM 63 



is considerably greater than that which would enable a sufficient 

 number of young to escape the unavoidable dangers. But the 

 ancestors of man must once have been subject to the same con- 

 ditions as those to which species in a state of nature are now 

 subject, and it will be into the causes and results of this pro- 

 gressive divergence from the former conditions that we shall look 

 in the first part of this book. 



