246 THE WORLD OF LIFE 



CHAP. 



That this is a true cause of the more frequent passing 

 away of the largest animal types in all geological epochs 

 there can be no doubt, but it certainly will not alone explain 

 the dying out of so many of the very largest Mammalia and 

 birds during a period of such limited duration as is the 

 Pleistocene (or Quaternary) age, and under conditions which 

 were certainly not very different from those under which 

 they had been developed and had lived in many cases down 

 to the historical period. 



What we are seeking for is a cause which has been in 

 action over the whole earth during the period in question, 

 and which was adequate to produce the observed result. 

 When the problem is stated in this way the answer is very 

 obvious. It is, moreover, a solution which has often been 

 suggested, though generally to be rejected as inadequate. 

 It has been so with myself, but why I can hardly say. 

 In his Antiquity of Man (4th ed., 1873, P- 4 I 8), Sir Charles 

 Lyell says : 



" That the growing power of man may have lent its aid as the 

 destroying cause of many Pleistocene species must, however, be 

 granted ; yet, before the introduction of fire-arms, or even the use 

 of improved weapons of stone, it seems more wonderful that the 

 aborigines were able to hold their own against the cave-lion, hyena, 

 and wild bull, and to cope with such enemies, than that they failed 

 to bring about their extinction." 



Looking at the whole subject again, with the much 

 larger body of facts at our command, I am convinced that 

 the above somewhat enigmatic passage really gives the 

 clue to the whole problem, and that the rapidity of the 

 extinction of so many large Mammalia is actually due to 

 man's agency, acting in co-operation with those general causes 

 which at the culmination of each geological era has led to 

 the extinction of the larger, the most specialised, or the most 

 strangely modified forms. The reason why this has not been 

 seen to be a sufficient explanation of the phenomena is, I 

 think, due to two circumstances. Ever since the fact of the 

 antiquity of man was first accepted by European geologists 

 only half a century ago, each fresh discovery tending to 

 extend that antiquity has been met with the same incredulity 

 and opposition as did the first discovery of flint weapons by 



