128 ANIMALS OF THE PAST 



their geological history, has enabled birds to spread 

 over the length and breadth of the globe as no other 

 group of animals has done, and to thrive under the most 

 varying conditions, and it would seem that if this power 

 were lost it must sooner or later work harm. Now to- 

 day we find no great flightless birds in thickly populated 

 regions, or where beasts of prey abound; the ostriches 

 roam the desert wastes of Arabia, Africa and South 

 America where men are few and savage beasts scarce, 

 and against these is placed a fleetness of foot inherited 

 from ancestors who acquired it before man was. The 

 heavy cassowaries dwell in the thinly inhabited, 

 thickly wooded islands of Malaysia, where again there 

 are no large carnivores and where the dense vegeta- 

 tion is some safeguard against man; the emu comes 

 from the Australian plains, where also there are no 

 four-footed enemies 1 and where his ancestors dwelt in 

 peace before the advent of man. And the same things 

 are true of the Moas, the ^Epyornithes, the flightless 

 birds of Patagonia, the recent dodo of Mauritius and the 

 solitaire of Rodriguez, each and all of which flourished 

 in places where there were no men and practically no 

 other enemies. Hence we deduce that absence of 

 enemies is the prime factor in the existence of flightless 

 birds, 2 although presence of food is an essential, while 

 isolation, or restriction to a limited area, plays an im- 

 portant part by keeping together those birds, or that 

 race of birds, whose members show a tendency to dis- 

 use their wings. It will be seen that such combinations 



ir The dingo, or native dog, is not forgotten, but, like man, it is a com- 

 paratively recent animal. 



2 Note that in Tasmania, which is very near Australia, both in space 

 and in the character of its animals, there are two carnivorous mammals, 

 the Tasmanian "Wolf" and the Tasmanian Devil, and no flightless 

 birds. 



