CHAPTER XI 



THE VALUE OF INBREEDING AND OUTBREED- 

 ING IN PLANT AND ANIMAL IMPROVEMENT 



THE origin of our more important domestic animals 

 and cultivated plants is a matter on which there is no 

 direct evidence. Among animals the ostrich is the only 

 example of modern domestication; among plants not a 

 single species of great economic worth has been brought 

 into cultivation within historic times. If one must have 

 a theory concerning their genesis, and what one of us 

 does not delight in theorizing, the weight of evidence is in 

 favor of a poly-phyletic origin in nearly every case. There 

 is more than one wild species related to our modern dogs, 

 cattle, swine and sheep, our wheats, barleys, apples and 

 grapes; and these species will cross together and yield 

 partially fertile hybrids. The wild relatives of the do- 

 mestic forms were variable, so variable that many species 

 were differentiated by natural causes ; yet these species 

 groups remained so well adapted to each other germinally 

 that their hybrids are not completely sterile. What seems 

 more reasonable than to suppose the original domestic 

 races to have been produced by uniting two or more wild 

 types and following this union of diverse germ plasms 

 with more or less close inbreeding and selection? 



Such procedure, at least, has been the method whereby 

 the clearly distinct and highly valuable breeds of the pres- 

 ent day have originated. Take the draft horses as an 

 example. In the early days of Europe native breeds were 

 developed in every country for military purposes. Just 

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