I08. DARWINISM AND THE PROBLEMS OF LIFE 



At first the route was comparatively easy to find ; 



but the fijrther north they spread the more intricate it 



would become, the more strength it would require to 



traverse it, and the earlier the start would have to be 



made. But as they only spread gradually, this advance 



would be quite possible, as only the strongest would be 



able to meet the demands of the longer flight, and 



amongst their progeny, which would go still further 



north, again only the strongest would survive ; so that 



the power of covering long distances in the shortest 



To this theory we may object, in the first place, that there is no 

 proof whatever of the earlier condition of the earth compelling the 

 birds to cover wide stretches. In fact, it is not at all clear that steppes 

 and forests would afford no food and shelter to them. It is just the 

 opposite. It is not sufficiently borne in mind by the author that the 

 migratory birds live on insects, and that the migration is precisely 

 regulated by the alternate abundance of insects in the north and 

 south, and that the use of this rich provision of sustenance is an 

 admirable adaption. It would be a curious retrogression for the 

 migratory birds to adapt themselves to food that is already so much 

 sought by other animals. And to adapt themselves to privation! 

 Further, the basis of selection, the over-production of progeny, is lost 

 sight of, yet this is the principal ground of the migration. In the 

 author's opinion instincts are inherited habits. We shall refute this 

 theory in the sixth chapter ; but even if we admitted it, what was the 

 origin of the habit of the primitive birds to fly over the earth ? Among 

 the unconvincing objections that the author raises against other 

 theories of flight we find the following : " The birds could not know 

 that there was food for them in the south." But this difficulty only 

 exists in the author's own theory, and for this it is formidable. How 

 could the primitive birds know that they would find plenty of food if 

 they made long and rapid flight over desert wastes ? Finally, the whole 

 theory is impossible because a simple reflection tells us that the first 

 birds cannot have been migratory. The birds must have evolved from 

 creeping animals; their ancestors were reptiles, something like the 

 present lizards. It must have taken an enormous period of time for 

 their flying organs to have become powerful wings; only after vast 

 numbers of generations would they be sufficiently advanced to attempt 

 long flights without resting. 



