244 



THE WORLD OF LIFE 



CHAP. 



which was probably larger than the largest of the Moas, and 

 whose egg, frequently found in sand-hills, sometimes measures 

 3 feet by 2^- feet in circumference, and will hold more than 

 two gallons. It is almost certain that these huge birds were 

 all coeval with early man, and in the case of the Moas this 

 has been completely proved by finding their bones in ancient 

 native cooking ovens. It is probable, therefore, that their 

 final extinction was due to human agency. 



Probable Cause of Extinction of the Pleistocene Mammalia 



The complete extinction of many of the largest Mam- 

 malia, which were abundant in almost all parts of the world 

 in Pleistocene times, has not yet received a wholly satis- 

 factory explanation. The fact that the phenomenon is so 

 near to our own era renders it more striking than similar 

 occurrences in remote ages. With the one exception of the 

 glacial epoch, there has been very little modification of the 

 earth's surface since the close of the Tertiary era ; and 

 in several cases species which undoubtedly survived that 

 event have since become extinct. This great climatic catas- 

 trophe did undoubtedly produce extensive migration of 

 Mammalia ; but, owing to the fact that the ice-sheet had 

 very definite limits, and that numbers of large mammals 

 were merely driven southward, it is not held to be a sufficient 

 cause for so general a destruction of the larger forms of life. 



Another circumstance that puts the glacial epoch out of 

 court as a sufficient explanation of the widespread extinction 

 is that in two very remote parts of the earth, both enjoying 

 a warm or even a sub-tropical climate — Australia on the one 

 hand, and Brazil to Argentina on the other, — exactly the 

 same phenomena have occurred, and, so far as all the geo- 

 logical evidence shows, within the same general limits of time. 



It is no doubt the case that at each of the dividing lines 

 of the Tertiary era — that is, in passing from the Eocene to 

 the Miocene, or from the latter to the Pliocene, and thence 

 to the Pleistocene — many large Mammalia have also become 

 extinct. But in these cases a much greater lapse of time 

 can be assumed, as well as larger changes in the physical 

 conditions, such as extension of land or water, climate, vege- 

 tation, etc., which, combined with the special disabilities of 1 



