154 ANIMALS OF THE PAST 
climate with their accompanying variations in 4 
the supply of food, and, to a lesser extent, 
against their various enemies, including man. — 
This power of flight, acquired early in 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 wingless 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 inher- 
ited 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 carni- 
vores and where the dense vegetation is some — 
safeguard against man; the emu comes from _ 
the Australian plains, where also there are no 
four-footed enemies * and where his ancesto 
* The dingo, or native dog, is not forgotten, but, like ma % 
it ts a comparatively recent animal. 
