178 ANIMALS OF THE PAST 



have taken place in the world's flora and fauna during 

 recent times, his influence, as a whole, has been insig- 

 nificant. Thus, while man exterminated the great 

 northern sea-cow, Rytina, and Pallas's cormorant on 

 the Commander Islands, these animals were already 

 restricted to this circumscribed area^ by natural causes, 

 so that man but finished what nature had begun. The 

 extermination of the great auk in European waters was 

 somewhat similar. There is, however, this unfortunate 

 difference between extermination wrought by man and 

 that brought about by natural causes: the extermina- 

 tion of species by nature is ordinarily slow, and the 

 place of one is taken by another, while the destruction 

 wrought by man is rapid, and the gaps he creates re- 

 main unfilled. 



Not so very long ago it was customary to account for 

 changes in the past life of the globe by earthquakes, 

 volcanic outbursts, or cataclysms of such appalling 

 magnitude that the whole face of nature was changed, 

 and entire races of living beings swept out of exist- 

 ence at once. But it is now generally conceded that 

 while castatrophes have occurred, yet, vast as they may 

 have been, their effects were comparatively local, and, 

 while the life of a limited region may have been ruth- 

 lessly blotted out, life as a whole was but little affected. 

 The eruption of Krakatoa shook the earth to its centre 

 and was felt for hundreds of miles around, yet, while it 

 caused the death of thousands of living beings, it re- 

 mains to be shown that it produced any effect on the 

 life of the region taken in its entirety. 



Changes in the life of the globe have been in the main 

 slow and gradual, and in response to correspondingly 



'It is possible that the cormorant may always have been confined to 

 this one spot, but this is probably not the case with the sea-cow. 



