THE CAUSES OF EXTINCTION OF MAM:MALIA 



HENRY FAIRFIELD OSBORN 



In studying the past history^ of the Mammalia we find that in 

 some cases the causes of the extinction are as obscure as in other 

 cases they are obvious. I have thus been led to review the subject 

 very carefully, gathering opinions and observations from various 

 sources. I especially desire to arouse discussion and to receive 

 -criticisms and suggestions which will be warmly welcomed.^ 



History of Opinion 



We find that while the main trend of present inquiry- as to the 

 external causes of extinction had been suggested by the middle of 

 the nineteenth century, subsequent discoveries and observations 

 furnish new and exact materials for induction both as to external 

 and internal causes. 



Cuvier, Lyell, Darwin. — The 'cataclysmal' views of Cuvier,^ 

 of wholesale destructions brought about by sudden and great 

 geological changes, naturally gave way to the ' uniformita,rian ' 

 views gradually developed from the time of Buffon to that of Dar- 

 win. The notions of the similarity of past and present causes, 

 of the survival of the fittest, of internal causes of variation, devel- 

 opment, and decline, gradually took their modern form. Whewell * 

 clearly sets forth the opinions which developed between 1796 and 



1 Especially in connection with a monograph for the U. S. Geological Survey, 

 entitled "The Titanothercs." which has been in preparation since 1900. This 

 series of articles in the Naturalist will be embodied in somewhat modified 

 form in the monograph. 



* Address, Professor Henrv Fairfield Osborn, American Museum of Natural 

 History, New York. 



* Whewell, — . Histoi-y of the Inductive Sriemrs, vol. 3. 1S37. 



