Man in the Light of Evolution 



in a single generation is usually slight. Only as 

 these slight variations are accumulated from 

 year to year, is any marked change or improve- 

 ment perceptible. 



Thirdly, the success of the breeder in accumu- 

 lating these slight variations depends upon his 

 skill in selecting those individuals which have 

 the desired characteristics most marked, and al- 

 lowing only these to breed. This process of 

 selection must be kept up for years. But, if 

 skillfully applied under favorable conditions, 

 excellent results are almost sure to follow. The 

 superiority of the Saxon wool was due very 

 largely to the careful examination and selection 

 of the sheep by trained experts. The size of 

 fruits, the speed of the trotting horse, the amount 

 of milk or cream produced by cows, the number 

 of eggs laid by fowls, the value, the beauty, and 

 in some cases the ugliness, of dogs — all these 

 characteristics have been marvelously increased 

 by the same process. 



The laws of heredity and of variation apply 

 equally well to domesticated and to wild ani- 

 mals. Wild animals probably vary somewhat 

 less than domestic. But even here variations are 

 more frequent and often more marked than many 



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