EVOLUTION 



711 



history, and perhaps often involves hybridisation which would 

 not occur in nature, but there can be no doubt that within 

 historic times changes have been produced simply by selection. 

 The peculiar appearance of the dogs and cattle in seventeenth- 

 and eighteenth-century pictures cannot be ascribed to the poor 



Fig. 546. — The bones of the forefoot of a horse compared with those of earher 



members of its family. — From Swinnerton. 



(a) Eohipptis {Hyracotherium) (Lower Eocene) : {b) Orohippus (Middle Eocene) ; (c) Mesokippus (Lower 

 Oligocene) ; (d) Hypohippus (Lower Pliocene) ; [e) Equus (Upper Pliocene to Present). 



draughtsmanship of the artists, for the men and women in them 

 differ only in clothes from those of the present day. We know 

 that in cattle there has been 

 conscious selection for 

 certain valuable qualities of 

 beef and milk yield, and 

 also for certain colour types 

 such as the red-bodied white- 

 faced Herefords, and there 

 has probably been uncon- 

 scious selection in other 

 directions as well. This 

 selection has changed the 

 type, and it was a great part 

 of Darwin's argument that 

 what man could do in a short time nature could do in unlimited 

 centuries. 



3. In Darwin's time palaeontology, the study of fossils, was 

 little developed, but he realised that, if evolution had occurred, 



Fig. 547. — The gradual transition between 

 Paludina neumayri (a) the oldest form, 

 and Paludina hcernesi (j). — From 

 Neumayr. 



