PERSPECTIVES EST EVOLUTION — RITCHIE 263 



formations are practically confined to the last 300 years. That is 

 a period infinitesimally short compared with the ages during which 

 the aboriginal faunas into which he was launched had been differ- 

 entiating, redistributing, and establishing themselves in a natural 

 balance. Wliat transformations has he wrought in so short a time? 

 The lengthening perspective of life upon the earth gives new sig- 

 nificance to the extent of man's interference. 



I do not propose here to examine in detail the magnitude of this 

 new world factor in the evolution of faunas and floras. That is 

 best shown in a limited area which can be intensively studied, and 

 I have elsewhere described with reasonable thoroughness the stages 

 and sum total of this process in Scotland, the recent geologic history 

 of which makes it particularly suited for such an analysis (Kitchie, 

 1919, 1920, 1923). I may, however, indicate the depth of penetra- 

 tion of this new faunistic factor by pointing out how superficial is 

 the view that regards man merely or mainly as a destroyer. He has 

 indeed deliberately reduced numbers or extirpated animals for his 

 own protection or for that of his flocks and crops, for food and 

 other necessities, for sport, and to satisfy the whims of luxury; and 

 without intention his cultivation of plains and marshes and destruc- 

 tion of primeval forest have destroyed feeding grounds and banished 

 their former tenants. Yet his addition to numbers far outweighs 

 his destruction. Intensive cultivation has added a stock of domestic 

 animals far beyond the bearing capacity of wild country, besides 

 increasing the numbers of wild creatures which also benefit from 

 his crops. Deliberate protection of animals, for sport, for utility, 

 for esthetic reasons, and on account of popular superstition, has 

 also multiplied nmnbers. Furthermore, apart from numerical 

 changes within the aboriginal faunas, man has changed their quali- 

 tative composition by introducing foreign animals deliberately (here 

 we must include domestic animals) , and unintentionally through the 

 ramifications of international commerce. 



These are simple primary effects of man's interference ; secondary 

 and remote consequences are even more impressive in their ultimate 

 issues. In general it may be said that wherever civilization has 

 made itself felt three main faunal changes are noticeable: The 

 largest animals tend to be reduced in numbers and eventually to 

 disappear; smaller creatures, dependent upon cultivation and human 

 habitations, multiply far beyond aboriginal numbers ; and the delib- 

 erate or accidental spread of "foreign" creatures is creating a degree 

 of cosmopolitanism throughout the world's faunas. 



How do these changes brought about by man stand, viewed in the 

 perspective of the long evolution of faunas upon the earth? There 

 are two types of cha;nge in progress in tlie natural assemblage of 



