1 86 THE MEANING OF EVOLUTION 



earth, the varieties of climate, the variation between 

 marsh and upland, between valley and plateau, furnish 

 a complexity of environment into each niche of which 

 a new form of animal fitted itself. 



With the increased complexity of mammals comes 

 the submergence of the reptiles and amphibians to- 

 day. In all sorts of situations we find mammals. The 

 old-fashioned continent of Australia is separated from 

 everything about it by deep water, impassable to any 

 animal which lives upon it. In this secluded country 

 evolution is very slow and animals are very anti- 

 quated. We still find there mammals with the ancient 

 habit of laying eggs in a hollow in the ground, though 

 after these eggs are hatched the young are nursed on 

 the milk of the mother. But on the great continental 

 stretches, where competition is keen, where the animal 

 must battle for his life against a wide field of other 

 animals, where migration into new situations is pos- 

 sible, the rapidity of the development has been very 

 much greater. 



It is in such a situation that man has arisen. In 

 the extreme southeastern portion of Asia, and on the 

 islands lying close to the coast, his highest non-human 

 relatives, members of the ape family, have reached 

 their best development. These, of course, are not 

 man's ancestors. They are the less progressive mem- 

 bers who are left behind entirely in the race. 



