186 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. Inall 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, 
