194 The Outline of Science 



stroyed the forests, he cultivated the wild, he made bridges, he 

 allowed aliens, like rats and cockroaches, to get in unawares. Of 

 course, he often did good, as when he drained swamps and got 

 rid of the mosquitoes which once made malaria rife in Scotland. 

 What has been the net result? Not, as one might think for 

 a moment, a reduction in the number of different kinds of ani- 

 mals. Fourteen or so species of birds and beasts have been ban- 

 ished from Scotland since man interfered, but as far as numbers 

 go they have been more than replaced by deliberate introductions 

 like fallow deer, rabbit, squirrel, and pheasant, and by accidental 

 introductions like rats and cockroaches. But the change is 

 rather in quality than in quantity; the smaller have taken the 

 place of the larger, rather paltry pigmies of noble giants. Thus 

 we get a vivid idea that evolution, especially when man interferes, 

 is not necessarily progressive. That depends on the nature of 

 the sieves with which the living materials are sifted. As Dr. 

 Ritchie well says, the standard of the wild fauna as regards size 

 has fallen and is falling, and it is not in size only that there is loss, 

 there is a deterioration of quality. "For how can the increase of 

 Rabbits and Sparrows and Earthworms and Caterpillars, and 

 the addition of millions of Rats and Cochroaches and Crickets 

 and Bugs, ever take the place of those fine creatures round the 

 memories of which the glamour of Scotland's past still plays 

 the Reindeer and the Elk, the Wolf, the Brown Bear, the Lynx, 

 and the Beaver, the Bustard, the Crane, the Bumbling Bittern, 

 and many another, lost or disappearing." Thus we see again 

 that evolution is going on. 



8 



The Adventurers 



All through the millions of years during which animals 

 have tenanted the earth and the waters under the earth, there has 

 been a search for new kingdoms to conquer, for new corners in 

 which to make a home. And this still goes on. It has been and 



