INTRODUCTION 33 



spicuous shade of colour, otherwise the animals would 

 show themselves against the grey soil, and would be 

 more easily found and captured. 



All these characteristics of the hare are continually 

 improved by natural selection, as only those can escape 

 their enemies that are best qualified to do so. But 

 as their enemies also are subjected to an improving 

 selection, higher qualifications will be required in the 

 next generation, and so on. In other words, the hares 

 will advance in each generation. It is true that we do 

 not directly observe this progress, but that is only 

 because our life is too short to appreciate the changes 

 brought about by natural selection, which require long 

 periods of time. Natural selection cannot act with the 

 same intensity as artificial selection. In the case of 

 the hare, for instance, not only two or three of the 

 swiftest survive, but a large number, and amongst 

 these many slow ones that have managed to escape 

 destruction by a favourable accident. It is only on the 

 average that the speediest survive, and, in fact, when 

 we take an average of many years, so that it will be 

 thousands of years before any appreciable result can 

 be seen. We do not see the grass growing, but we 

 can prove that it is longer to-day than it was yesterday. 

 So, if we could raise from the dead a man who had seen 

 a hare thousands of years ago, he would find a difference 

 in the hare of to-day. In point of fact, the skeletons of 

 animals belonging to earlier ages prove that they were 

 different then from what they are in our time. 



But we should greatly underrate the power of natural 

 selection if we attributed to it only the capacity to 



