410 HEREDITY AND ENVIRONMENT 



Lectures on Contemporary Evolution in 

 Man," but the species has remained relatively 

 stable during the historic epoch as compared 

 with the much longer prehistoric period. 



The past history of man has been a long one, 

 no one can say how long, but probably not less 

 than half a million years have passed since the 

 genus Homo appeared, and not less than one 

 hundred thousand years since the present 

 species arose. There is every reason to believe 

 that the future history of man will be even 

 longer. Barring great secular changes, catas- 

 trophes or cataclysms, which cannot be fore- 

 seen nor provided against, man controls his 

 own destiny on this planet. 



It is a curious fact that in prescientific times 

 the instability of nature especially appealed to 

 men. How often in the past have men looked 

 forward to a "speedy end of the world"! It 

 may well have seemed to our ancestors a use- 

 less thing to take any thought for the morrow 

 if very soon the heavens are to be rolled up as 

 a parchment and the elements dissolved in fer- 

 vent heat; it would be folly to plan for future 

 ages if the time is at hand when the angel 



