524 



THE THEORY OF EVOLUTION 



plants under domestication, and in the experiments conducted by 

 breeders and scientists. Domestic animals must have originated 

 from wild ancestors that were gradually tamed by man, although 

 in most instances there is no historic record of the original domes- 

 tication. Some forms are still in the preliminary stages. The 



Indian elephant, for ex- 

 ample, is not reared in 

 captivity, but caught when 

 nearly full-grown and 

 trained. The attempts to 

 domesticate the few sur- 

 viving bison of the North 

 American continent and 

 the rearing of certain fur- 

 bearing animals in cap- 

 tivity illustrate possible 

 beginnings of domestica- 

 tion in the present. In 

 the great majority of 

 cases, however, the origi- 

 nal domestication occurred 

 before the period of the 

 earliest historic records. 



In some instances, like 

 those of the domestic fowl 

 (Fig. 281) and the pig 

 (Fig. 282), the original 

 wild species, from which 

 all the domestic breeds 

 seem to have descended, 

 can be determined with 

 reasonable certainty. In 

 other cases, like that of 

 the dog, there is no single 

 wild species that can be so identified. The argument regarding 

 evolution in all these cases is that many types, so different 

 that they would be called species if found in nature, have actu- 

 ally originated under the eyes of man without his appreciating 

 what was taking place. Thus, there has been an " origin of 

 species " among domesticated animals. From this, one may argue, 



Fig. 282. — Evolution of domestic swine. 



Above, the wild boar Sus scrofa and its young; 

 below, a prize-winning Duroc Jersey barrow on a 

 somewhat smaller scale. The domestic pig of 

 Europe and America has descended from the wild 

 boar of Europe, Sus scrofa, with some admixture 

 from the wild hoar of Asia, Sus vitatus. (Above, 

 from Flower and Lydekker, " Mammals Living and 

 Extinct," copyright, 1891, by A. and C. Black, 

 reprinted by permission; below, courtesy College of 

 Agriculture, University of Missouri.) 



